Polyphosphazenes

Vol. 7

POLYPHOSPHAZENES

603

POLYPHOSPHAZENES

Introduction

Polyphosphazenes (1–9) belong to the class of inorganic polymers (qv). They have a
heteroatomic backbone consisting of alternating phosphorus and nitrogen atoms,
with two side groups attached to each phosphorus atom (Fig. 1). The side groups
can be organic, inorganic, or organometallic. Perhaps the most attractive feature
of polyphosphazene chemistry is the very broad range of groups that can be easily
incorporated into the macromolecular chain, which opens up unlimited possibili-
ties for derivatization. The number of different polyphosphazenes that have been
synthesized will soon approach 1000; no other polymer synthesis has been studied
so extensively. The ability to control the macromolecular architecture and to ﬁne-
tune properties of the resultant polymer has attracted the attention of many re-
search groups throughout the world. The initial application of polyphosphazenes
as high performance elastomers has expanded into solid polymer electrolytes,
membranes for gas and liquid separations, optically active polymers, biomateri-
als, and proton-exchange membranes for fuel cells. Polyphosphazenes are strong
competitors for their isoelectronic analogues, polysiloxanes, which are considered
the most important of all inorganic polymers with regard to commercial applica-
tions (see S

ILICONES

History.

The history of polyphosphazenes dates back to 1897, when Stokes

(8) reported that phosphonitrilic chlorides could be converted by heating into “the
rubber-like polyphosphonitrilic chloride.” He described it as a “body, or a mixture
of bodies, of very high molecular weight, that is highly elastic and insoluble in all
neutral solvents, but which swells enormously in benzene”. Since then there have
been a number of studies devoted to polymerization of phosphonitrilic chlorides.
Attempts to carry out the polymerization in organic solvents containing hydrogen

604

POLYPHOSPHAZENES

Vol. 7

NHCH

(a)

(b)

(c)

(d)

Fig. 1.

General formula (a) and three examples of polyorganophosphazenes with phenoxy

(b), methylamino (c), and methyl/phenyl (d) substituents.

were unsuccessful. Later studies performed in halogenated solvents showed some
moderate success: a soluble fraction of 18–50% with a polymerization degree of
300 was reported (11). Any effort to increase the molecular weight of the polymer
resulted in formation of cross-linked, insoluble “inorganic rubber”. To overcome
the problem of cross-linking, Kauth (12) proposed a two-step synthesis. In the ﬁrst
step the monomer was heated for

1
2

h at 150–200

◦

C, which resulted in a partially

polymerized oil that could be dissolved in a suitable solvent. This solution was
used to “saturate some material,” and the ﬁnal polymerization was accomplished
by an additional heating step. The struggle to obtain a soluble, long-chain polymer
continued until the mid-1960s when Allcock and Kugel (13) reported that linear
polydichlorophosphazene could be obtained. Optimization of the polymerization
conditions and macromolecular substitution of chlorines with organic nucleophiles
led to hydrolytically stable polyorganophosphazenes. Since then, interest by the
military and polymer industries has led to an enormous growth in polyphosp-
hazene science.

Nomenclature.

Of the several naming systems related to phosphorus–

nitrogen

compounds:

phosphonitrile

(the

oldest

one),

azaphosphorine,

phosphorus-

µ-nitrido, nitrilo-phosphoranylidyne, and phosphazene (14), only

the last one has been generally accepted and adopted by the macromolecular
research community. To comply with IUPAC nomenclature, a polyphosphazene
with the common name poly(diphenoxyphosphazene) should be named catena-
poly[(diphenoxyphosphorus)-

µ-nitrido], if rules for “inorganic and coordination

polymers” (15) were applied. If on the other hand, rules for “organic polymers” (16)
were used, then the preferred constitutional repeating unit should be reoriented
and the polymer should be named poly[nitrilo(diphenoxyphosphoranylidyne)].

Synthesis

There are three general methods to synthesize polyphosphazenes. One is the ring-
opening polymerization of hexachlorocyclotriphosphazene, followed by a macro-
molecular substitution of chlorine atoms with a desired nucleophile or a combina-
tion of nucleophiles. As a result, the side groups are bonded to phosphorus through
oxygen or nitrogen linkages. This is the primary method for polyphosphazene syn-
thesis. The second method, called a “single-pot synthesis,” is based on direct reac-
tion of ammonium and phosphorus salts. The product, poly(dichlorophosphazene),
then reacts with an appropriate nucleophile to give a poly(organophosphazene). It
is claimed that production costs for this second method are low. The third method
is condensation polymerization of phosphoranimines. Here the substituents are

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POLYPHOSPHAZENES

605

PCl

250

°C

−

(a)

(b)

(c)

Fig. 2.

(a) Trimer synthesis, (b) the ring-opening polymerization, and (c) the macromolec-

ular substitution.

usually attached to phosphorus atoms prior to the polymerization. Very high
molecular weights (M

= 10

) can be reached with ring-opening polymerization

but the molecular weight distribution is very broad. Only moderate molecular
weights (M

= 10

–10

) are accessible via the condensation method; however,

polydipersity in this case is usually

<2.

Ring-Opening Polymerization.

There are two variants of the method:

melt polymerization and solution polymerization. The ﬁrst method was devel-
oped by Allcock (13,17,18) and is shown schematically in Figure 2. It starts with
the reaction of phosphorus pentachloride and ammonium chloride that leads to
hexachlorocyclotriphosphazene. Following a multistep puriﬁcation involving sub-
limation, this compound is polymerized by heating at 250

◦

C in an evacuated

and sealed glass tube for 24–48 h. After termination of the reaction, the lin-
ear poly(dichlorophosphazene) is isolated, by either sublimation or extraction of
low molecular weight species, or by dissolution and precipitation. The molecu-
lar weight of the polymer is often very high, M

∼10

, but the molecular weight

distribution is very broad. In the ﬁnal step, the polydichlorophosphazene, dis-
solved in an inert solvent, is added to a suitable nucleophilic reagent. The product,
usually polyorganophosphazene, is isolated by multiple precipitations. There are
variants of the above method where partially substituted trimer is polymerized
(Fig. 3) (19). Here a nucleophilic substitution is carried out on cyclochlorophos-
phazene and then the substituted trimer undergoes thermal ring-opening poly-
merization. This approach allows for the preparation of polyphosphazenes with
substituents that cannot be incorporated through a classical macromolecular sub-
stitution route. There are, however, limitations imposed by both steric and mech-
anistic factors on the extent of substitution that makes the trimer polymerizable.
Unless the substituted ring is highly strained as, for example, in the presence of
transannular ferrocenyl (20), polymerization is generally feasible when no more
than three nongeminal chlorines in hexachlorocyclophospazene are substituted.
Fully methyl- or phenyl-substituted trimers undergo ring–ring equilibration but
no polymers are formed (21,22). Ring-opening polymerization of some mixed ring

250

°C

−

Fig. 3.

Trimer substitution and the ring-opening polymerization of the substituted trimer.

606

POLYPHOSPHAZENES

Vol. 7

systems, eg, (NPCl

)

NSCl, (NPCl

)

NSOCl, and (NPCl

)

NSOF, has been re-

ported (23–25). These polymerizations were carried out at much lower temper-
atures 90–180

◦

C) than that required for (NPCl

)

alone.

The alternative method, solution ring-opening polymerization, was de-

veloped by several researchers (26–29), but most of the work is by Mag-
ill and co-workers (30). The polymerization of (NPCl

)

is carried out

in 1,2,4-trichlorobenzene using sulfamic or toluenesulfonic acid as a cata-
lyst and CaSO

· 2H

O as a promoter. The reaction is fast and yields

poly(dichlorophosphazene) of high molecular weight with narrow and monomodal
molecular weight distribution. From the poly(dichlorophosphazene) precursor, the
desired poly(organophosphazene) is obtained by reaction with a suitable nucle-
ophile. This last step is common to both the melt polymerization and the solution
polymerization methods.

“Single-Pot”

Synthesis.

order

simplify

the

synthesis

poly(dichlorophosphazene), Allen and co-workers (31,32) developed a method
based on “two-step, single-pot” reaction of ammonium sulfate with phospho-
rus pentachloride (PCl

). Both reactants are heated until a liquid monomer,

P-trichloro-N-(dichlorophosphoryl)monophosphazene, is formed, which is then
bulk-polymerized by further heating under inert atmosphere. After distilling off
oxyphosphoryl chloride, the product, poly(dichlorophosphazene), is isolated. The
authors claim that the method offers good yields, short reaction time, elimination
of halogenated solvents, and leads to a polyphosphazene of high molecular weight
and lower polydispersity.

Another method of direct synthesis of poly(dichlorophosphazene) developed

by Carriedo and co-workers (33) has been disclosed. NH

Cl and PCl

react in the

presence of CaSO

·H

O and NH

HSO

as promoters, leading to polyphosphazenes

of molecular weight on the order of 2

× 10

. The yields are 30–40% on the basis

of PCl

Condensation Polymerization.

Several procedures for the condensa-

tion polymerization of polyphosphazenes are known. In 1982, De Jaeger and co-
workers (34) published an alternate synthetic route to poly(dichlorophosphazene)
on the basis of thermal elimination of phosphoryl chloride from a P N P precur-
sor. Important advantages of the reaction, as compared to the ring-opening poly-
merization, were the possibility to control the molecular weight of the polymer
and to reduce the amount of cyclic oligomers in the product. The ﬁrst success-
ful condensation polymerization of substituted polyphosphazene was reported by
Neilson and Wisian-Neilson (35–37). The reaction scheme is shown in Figure 4.
The sequence begins with the synthesis of a N-silylphosphoranimine monomer
containing the desired side groups and two leaving groups (trimethylsilyl and tri-
ﬂuoroethoxy). The product is isolated by a fractional distillation with an overall
yield of ca 75%. The monomer is then polymerized by heating in a sealed glass

200

°C

SiMe

Fig. 4.

The thermal condensation polymerization of phosphoranimine.

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POLYPHOSPHAZENES

607

°C

SiMe

PCl

Fig. 5.

The “living” cationic condensation polymerization of phosphoranimine.

ampule at 180–200

◦

C for 7–12 days. This method allows for the synthesis of sym-

metrical and unsymmetrical homopolymers as well as random copolymers, but
selection of the monomers is limited to either dialkyl- or alkyl–aryl-substituted.
An improvement over the thermal process was proposed by Matyjaszewski’s group
(38,39). They prepared homo- and copolymers by tetrabutylammonium ﬂuoride
(TBAF) catalyzed anionic polymerization of phosphoranimines bearing triﬂuo-
roethoxy and alkoxyalkoxy substituents. The conditions of the reactions were rel-
atively mild (100

◦

C for 3–4 h) and it was possible to quantitatively produce lin-

ear polyphosphazenes with a narrow molecular weight distribution. The method,
however, could be used in a very limited number of cases. The most promis-
ing condensation route was reported by Allcock and co-workers (40–43). It was
based on PCl

-induced, room temperature “living” cationic polymerization of N-

(trimethylsilyl)-phosphoranimine. The reaction scheme is presented in Figure 5.
For example, polymerization of N-(trimethylsilyl)-trichlorophosphoranimine
leads to poly(dichlorophosphazene). Generally, if the monomer contained less
then two organic substituents at the phosphorus, then an additional step, namely
macromolecular nucleophilic substitution of the remaining chlorines, was neces-
sary. The potential advantage of the method is that it allows for the synthesis of
polyphosphazenes with controlled molecular weight and low polydispersity, with
sophisticated architectures (eg block copolymers, hybrid organic/phosphazene
copolymers, or star-branched polymers).

Polymeric Material Types

Phosphazene

Homopolymers.

Macromolecular

substitution

poly(dichlorophosphazene) with use of a single kind of nucleophile leads to
a symmetrical homopolymer. Symmetrical or unsymmetrical phosphazene
homopolymers can also be obtained by condensation methods. If the bulkiness
of the substituents do not impose any sterical constraints, then the resultant
polyphosphazene is a crystalline material. Otherwise, glasses are obtained with
a T

of 150–250

◦

C, as is the case for poly(spirophosphazenes) (44,45).

Copolymers.

When two or more nucleophiles are used during the macro-

molecular substitution of poly(dichlorophosphazene), a mixed substituent sys-
tem (46), ie a random copolymer, is obtained. There exists numerous data on
the preparation and characterization of various random copolymers (47–53).
To synthesize a block copolymer (or unsymmetrical homopolymer) condensation
polymerization needs to be employed. Matyjaszewski and co-workers (54) syn-
thesized block copolymers bearing various combinations of triﬂuoroethoxy and
alkoxyalkoxy groups, by adding a second phosphoranimine after the ﬁrst con-
verted completely. Signiﬁcant differences were found between random and block

608

POLYPHOSPHAZENES

Vol. 7

copolymers with respect to their thermal properties and morphology. The T(1)
transition of the random materials decreased dramatically when the fraction of
units bearing alkoxyalkoxy groups increased, while the T(1) of the block copolymer
was unaffected by the composition. Also, densities of the random copolymers de-
creased more rapidly than densities of the block materials when the fraction of the
alkoxyalkoxy-bearing units was increased. Allcock and co-workers (55–57) syn-
thesized copolymers with controlled molecular weights through a PCl

-catalyzed

cationic polymerization. First a N-(trimethylsilyl)-trichlorophosphoranimine was
polymerized into a “living” poly(dichlorophosphazene). Next a second phospho-
ranimine, eg N-(trimethylsilyl)dichlorophenyl phosphoranimine was copolymer-
ized using the “living” terminus. Subsequent replacement of the chlorine atoms
with an appropriate side group resulted in a hydrolytically stable copolymer. A
similar method was used to prepare a hybrid di- and triblock poly(phosphazene–
ethylene oxide) and poly(phosphazene-siloxane) copolymers (58–61). Amphiphilic
diblock copolyphosphazene with methoxyethoxyethoxy/methoxyethoxyethoxy and
methoxyethoxyethoxy/phenyl units was synthesized by Chang and co-workers
(62) and its micellar characterization was examined. The most voluminous lit-
erature on polyphosphazene copolymers relates to grafting. Wisian-Neilson and
co-workers (63) prepared copolymers of poly(methylphenylphosphazene) with
polystyrene, polymethylmethacrylate and with silicone grafts using anionic poly-
merizations. Chang and co-workers (64) grafted poly(2-methyl-2-oxazoline) onto
partially brominated poly[bis(4-methylphenoxy)phosphazene] of low molecular
weight (M

= 6200) via cationic polymerization. When a high molecular weight

polyphosphazene was used (M

> 10

), severe gelation resulted and the copolymer

was insoluble in available solvents. Gleria and co-workers (65) synthesized several
copolymers by thermal or photochemical grafting of various vinyl polymers onto
polyphosphazene matrices. The free-radical process was initiated by hydrogen
abstraction from a primary, secondary, or tertiary carbon of the alkylphenoxy sub-
stituent. Monomers such as maleic anhidride (66), methylmethacrylate (67), N,N

dimethyl-acrylamide (68), meth(acrylic) acid (69), styrene (70), and vinyl acetate
or alcohol (71,72) were used. Welker and co-workers (73,74) studied radiation-
induced grafting onto allylamino-substituted polyphosphazenes and Prange and
co-workers (75) prepared graft copolymers from polyphosphazene and polystyrene
macromonomers.

An interesting example of a phosphazene random copolymer containing thio-

phenoxy groups was synthesized by Carriedo and co-workers (76). Although very
long reaction times were required and low yields (ca 25%) were observed, it was
the ﬁrst time that a thiophenoxy-substituted poly(phosphazene) was obtained.

Polyphosphazene

Blends.

Polyphosphazene blends were investi-

gated for thermal stabilization of organic polymers, biochemical applica-
tions, and membrane preparation. Poly[bis(carboxylatophenoxy)phosphazene]–
polyurethane blends (77) were prepared through reactive mixing of the polyphos-
phazene with diisocyanate and diol prepolymers, and their ﬂame-retarding poten-
tial was analyzed. Chen-Yang and co-workers (78) prepared blends of poly[bis(p-
chlorophenoxy)phosphazene] and polystyrene, and studied their morphology, ther-
mal properties, and ﬂammability. Partial compatibility was observed when the
polyphosphazene content was less than 50%. Ambrosio and co-workers (79) stud-
ied degradable polyphosphazene/polyester blends with self-neutralizing potential.

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POLYPHOSPHAZENES

609

Herrero and Acosta (80) investigated the microstructure of poly(ethylene oxide)–
poly[(octaﬂuoropentoxy)(triﬂuoroethoxy)phosphazene] blends. Limited miscibil-
ity of both components was inferred, based on the observed shift of the compo-
nents’ glass-transition temperatures. Wycisk and co-workers (81) prepared mem-
branes from blends of sulfonated poly[bis(3-methylphenoxy)phosphazene] with
polyimides, polyacrylonitrile, and Kynar FLEX PVDF. Morphology, electrochemi-
cal performance, and methanol permeabilities of the membranes were then evalu-
ated as part of a program to investigate such blends in direct methanol fuel cells.
The polymers were immiscible and a domain-type structure was observed. The
best compatibility resulted when the tetrabutylammonium or sodium salt of the
polyphosphazene was used (82).

Cross-Linked Polyphosphazenes.

Many applications require some

level of cross-linking to be incorporated into the polymer to obtain an elastomer
or to make it stronger, insoluble, or more thermally/chemically stable (83). Three
kinds of cross-links are generally distinguished: physical (through crystallites
or glassy microdomains), ionic complexes, and ﬁnally, covalent cross-links. The
most stable are covalent bonds and these are of utmost importance. Two gen-
eral methods, both of the radical nature, were generally used to induce covalent
cross-linking in polyphosphazenes. One was based on incorporating some num-
ber of unsaturated functions like vinyl or allyl groups into the polyphosphazenes.
This approach was generally adopted for vulcanization of polyphosphazene elas-
tomers (84,85). The second method relied on labile hydrogen abstraction from sec-
ondary or tertiary carbons in the side groups (86–89). In Figure 6, an example is
presented of photo-cross-linking of poly[(4-ethylphenoxy)(phenoxy)phosphazene]
(90). Here, irradiation with UV light of wavelength 340 nm causes excitation of
the benzophenone photoinitiator, which then abstracts hydrogen from a benzylic
carbon of the polyphosphazene side groups. As a result, a macroradical is formed,
where recombination of two macroradicals results in formation of a covalent cross-
link. Electron beam irradiation or

γ -ray exposure was also used to induce cross-

linking of alkylaryloxy- or oligoethoxy-substituted polyphosphazenes (74,91–95).
Interesting results were obtained with ionic cross-links. Allcock described the
use of poly[bis(carboxylatophenoxy)phosphazene] for a microencapsulation of

340 nm

Fig. 6.

The photo-cross-linking of poly[(4-ethylphenoxy)(phenoxy)phosphazene] with ben-

zophenone photoinitiator.

610

POLYPHOSPHAZENES

Vol. 7

mammalian cells (96). Acid–base complexation was also employed for cross-
linking (97). In this way a poly[bis(3-methylphenoxy)phosphazene] sodium sul-
fonate was blended with polybenzimidazole into a membrane. Insoluble ﬁlms were
obtained after conversion of the sulfonate groups into sulfonic acid moieties and
heat treatment of the polymer (98). The cross-linking degree and water swelling
were controlled by adjusting the polybenzimidazole content.

Functional Polyphosphazenes.

Functionalization can be deﬁned as the

introduction of chemical groups into the polymer chain that exert a speciﬁc func-
tion (eg chemical, physical, or biological) (99). Introduction of reactive groups into
a polyphosphazene via the general macromolecular substitution route usually re-
quires use of protected reagents, otherwise cross-linking and precipitation of the
partially substituted polydichlorophosphazene may result (100,101). Derivatives
containing hydroxylic (102–104), amine (105–108), and carboxylic (109) groups
were prepared in this way.

Carriedo and co-workers (110,111) developed an interesting method of syn-

thesizing various poly(aryloxyphosphazenes) using K

or Cs

as pro-

ton abstractors to substitute for chlorine atoms in poly(dichlorophosphazene).
Even if bifunctional nucleophiles were used, no cross-linking was observed
when the carbonates were present and the resultant polyphosphazene was sol-
uble. Using this method, novel poly(spirophosphazenes) (112) and the chiral
poly(dioxybinaphtylphosphazenes) (45) were synthesized.

A signiﬁcant amount of research was devoted to post-functionalization of

aryloxy- or methyl-substituted polyphosphazenes. In the ﬁrst case, electrophilic
aromatic substitution reactions were used to obtain sulfonated (113–116), car-
boxylated (117) nitrated (aminated) (118,119) and phosphonated (120,121) prod-
ucts (Fig. 7a). Alternatively, methyl substituents were deprotonated with n-BuLi
and subsequently treated with a desired nucleophile (Fig. 7b). Using this method,
polyphosphazenes bearing carboxylic (122), alcohol (123,124), ester (125), and
other (63,126) groups became available. Numerous studies have been devoted

n-BuLi

−

COOH

(b)

(a)

Fig. 7.

(a) Sulfonation of the phenoxy substituents of the poly[bis(phenoxy)phosphazene]

and (b) lithiation/carboxylation of the methyl group of poly[(methyl)(phenyl)phosphazene].

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POLYPHOSPHAZENES

611

OCH

-m

-p

NHCH

NHC

-p

−100

−50

100

Glass-transition temperature,

°C

Fig. 8.

The dependence of glass-transition temperature on the type of side group R in

symmetrically substituted polyphosphazenes, [R

PN]

to a surface modiﬁcation of polyphosphazenes (98,100). The most important ob-
jectives were balancing hydrophobicity or hydrophilicity, and immobilization of
biologically active compounds (113,127–130).

Properties

Polyphosphazenes, owing to their inorganic backbone, are characterized by proper-
ties that are not common to organic polymers, namely low temperature ﬂexibility,
nonﬂammability, good thermal stability, and biocompatibility.

Backbone Flexibility.

A characteristic feature of all the polyphosp-

hazenes is their high skeletal ﬂexibility, which is reﬂected in their very low glass-
transition temperatures (Fig. 8). The high segmental mobility of the chain was
explained by Allcock (4) as originating from cylindrical symmetry of the P N
bond because of broad overlapping of the nitrogen p-orbital with any of the ﬁve
d-orbitals of the phosphorus (131). For example, the backbone torsional barrier in
poly(diﬂuorophosphazene) was found to be as low as 0.1 kcal per repeat unit (1). Al-
though the formal structure of the polymers comprised a system of alternating sin-
gle and double bonds, no electron delocalization was evidenced and an “island” pi-
bond structure was postulated. Structural studies on poly(dichlorophosphazene)
suggested a slight alternation in P N bond lengths in the polymer backbone with
values of 0.144 and 0.168 nm (132).

Crystallinity.

Polyphosphazenes with a single substituent that is either

small or rigid are semicrystalline. Their melting behavior consists of two ﬁrst-
order transitions, T(1) and T

, separated by a 150–200

◦

C gap. Optical microscopy

showed that the crystalline structure was not lost at T(1), but rather existed as
a mesophase until T

was reached (2). Most ﬂuoroalkoxy and aryloxy derivatives

exhibited very high thermal stability with decomposition temperatures of 300–
400

◦

Applications

Elastomers.

An elastomer is a material that can be stretched repeatedly to

a high extent (elongation greater than 200%) and always retracts to its original di-
mensions when the stress is released. Chain ﬂexibility resulting from a freedom of

612

POLYPHOSPHAZENES

Vol. 7

OCH

CHF

Fig. 9.

An example of a typical polyphosphazene elastomer (EYPEL-F).

bond rotation within the polymer backbone is the main prerequisite for achieving
elastomeric properties. Polyphosphazenes with low glass-transition temperatures
proved to be best suited as high performance elastomers (61,133,134), especially
for military applications. Substitution of two different types of ﬂuoroalkoxy side
groups on the same chain gave phosphazene polymers that were elastic at tem-
peratures as low as

−60

◦

C, nonﬂammable, and resistant to hydrocarbon solvents,

oils, and hydraulic ﬂuids. A representative structure is shown in Figure 9 (135).
Several polyphosphazene ﬂuoroelastomers were commercialized under the trade
name PNF or EYPEL-F. Polyphosphazenes were also used for toughening of ther-
mosetting resins (136). Polydialkoxyphosphazenes were tested as low temperature
greases and sealants (137). These materials proved to have high plasticity over
a wide temperature range (

−100

◦

C to

+100

◦

C) with a decrease in the compres-

sive/tensile modulus as the temperature was lowered.

Solid Polymer Electrolytes.

Poly(ethylene oxide) (PEO) doped with a

lithium salt has been used as the solid polymer electrolyte in rechargeable lithium
batteries. The oxygen atoms in the PEO backbone coordinate metal cations, thus
facilitating dissociation of the dissolved salts. However, because of its crystallinity,
high conductivity could only be achieved when heated above 65

◦

C. In 1984 Allcock

and co-workers (138) found that poly[bis(methoxyethoxyethoxy)phosphazene]
(MEEP, Fig. 10) doped with certain lithium and silver salts exhibited a room
temperature ionic conductivity that was 2–3 orders higher than that of doped
PEO. The repeat unit of MEEP has six oxygen atoms for cation coordination.
The side groups are very ﬂexible, which together with the inherent backbone
ﬂexibility, contributed to a glass-transition temperature being as low as

−84

◦

The polymer, however, was totally amorphous, which resulted in problems with
its dimensional stability (139). A signiﬁcant amount of research was directed
to overcome this disadvantage. There were reports on cross-linking (140–142),
blending with PEO (143,144), composites with silicates (145,146), and synthe-
sis of poly(phosphazene-ethylene oxide) block copolymers (59). A new mechani-
cal stabilization strategy, based on ceramic composites, was invented and devel-
oped at the Idaho National Engineering and Environmental Laboratory (147).
Polyphosphazenes bearing crown ethers (148), sulfone or sulfoxide (149), or sul-
fonate (150) groups were also tested as potential Li

ion conducting solid polymer

electrolytes.

OCH

Fig. 10.

Poly[bis(methoxyethoxyethoxy)phosphazene] (MEEP), a solid polymer elec-

trolyte that was studied for use in lithium batteries.

Vol. 7

POLYPHOSPHAZENES

613

Membranes for Gas Separation.

Many linear polyphosphazenes have

been tested as membranes for gas separation (151). Derivatives with phenoxy,
triﬂuoroethoxy, or n-alkoxy were of most interest. Some of the work focused on
O

and N

permeability (152–155) but other gases were also investigated (156–

160). The literature data show a wide scatter of measured permeabilities for the
same polymers. Most of the confusion can be attributed to the quality of the
polymer samples, their thermal history, and experimental factors. Nevertheless,
some trends are apparent. In general, low-T

polyphosphazenes with alkoxy sub-

stituents have very high oxygen permeabilities, comparable to those of siloxane
polymers, but with better selectivities (151). Also, polyphosphazenes showed a
very high permeability for CO

. Polyphosphazene membranes were applied to the

recovery of helium from natural gas (158). Poly[bis(phenoxy)phosphazenes] have
been tested in mixed gas separations where SO

separation factors as high as

17.2 were observed at 190

◦

C (161). The effect of trimethylsilyl substituents on the

gas transport properties of a series of polyphosphazenes has also been reported
(162). When substituted at the para position of the phenoxy side groups, the poly-
mers promoted an increase in selectivity accompanied by a decrease in gas per-
meability. Alternatively, incorporation of the trimethylsilyl group on the methyl
group of poly[(methyl)(phenyl)phosphazene] resulted in an increase of both per-
meability and selectivity. While searching for chemoselective membranes, Orme
and co-workers (163) incorporated three pendant groups into a polyphosphazene
chain: 2-(2-methoxyethoxy)ethanol, 4-methoxyphenol, and 2-allylphenol. The ﬁrst
group gave the polymer proper hydrophilic character, the second group provided
hydrophobic counterbalance and ﬁlm-forming abilities, and ﬁnally, the third group
enabled cross-linking (Fig. 11). The membranes showed some promise for CO

sep-

aration. The gas permeability of poly(organophosphazenes) was also the subject
of theoretical studies and atomistic simulations (164).

Pervaporation.

Separation of water–organic and organic–organic solu-

tions by pervaporation is another area for potential applications of polyphos-
phazene membranes (151). Selectivities as high as 10

have been reported for

the separation of dichloromethane from water by pervaporation, using a mem-
brane prepared from poly[bis(triﬂuoroethoxy)phosphazene] (161,165). High se-
lectivities for the separation of toluene and heptane were observed with a simi-
lar membrane (166). Pervaporation of water and alcohols was also investigated
(167–169).

P N P

OCH

O(C

CH CH

Fig. 11.

Polyphosphazene with methoxyethoxyethoxy, 4-methoxyphenoxy and 2-

allylphenoxy substituents used by Orme and co-workers (144) for gas separation studies.

614

POLYPHOSPHAZENES

Vol. 7

Separation of Tritiated Water.

Aromatic polyphosphazene membranes

were investigated in the separation of tritiated water from normal water, because
of their excellent radiological, thermal, and chemical stability (170,171). For these
experiments carboxylated poly(diaryloxy)phospohazenes were used. A tritium de-
pletion as high as 33% was reported.

Proton-Exchange Membranes for Fuel Cells.

Fuel cells are a promis-

ing power source of the future. In current hydrogen/air PEM fuel cells, Naﬁon
perﬂuorinated membranes are used as the proton-conducting separator of the an-
ode and cathode half-cells. In addition to its high price, Naﬁon has two serious
drawbacks that limit its use: high methanol crossover in direct methanol fuel cells
(DMFC) and loss of conductivity (dehydration) at temperatures above 100

◦

C in hy-

drogen/air fuel cells. Polyphosphazenes are a serious alternative to Naﬁon. Prelim-
inary studies showed that ﬁlms from sulfonated and UV-cross-linked poly[bis(3-
methylphenoxy)phosphazene] possessed high proton conductivity, low methanol
diffusivity, and good thermo-oxidative stability (172–174). Blends of sulfonated
polyphosphazene and an inert organic polymer like a polyimide, poly(vinylidene
ﬂuoride), or polyacrylonitrile (PAN) were also investigated (175). The polyphosp-
hazene component of the blend was stabilized by UV or e-beam cross-linking. The
resultant membranes had conductivities from 0.01 to 0.06 S/cm (in water, 25

◦

and an equilibrium water swelling from 20 to 60% (25

◦

C). Direct methanol fuel cell

(DMFC) tests were performed using membrane-electrode assemblies (MEA) pre-
pared from SPOP/PAN and SPOP/Kynar FLEX (copolymer of vinylidene ﬂuoride
and hexaﬂuoropropylene) blends. With a three-layer composite MEA (a methanol
blocking ﬁlm sandwiched between two high-conductivity membranes), a signif-
icant reduction in methanol crossover was observed with a modest decrease in
current–voltage behavior, as compared to Naﬁon 117 (176). Phosphonated pol-
yaryloxyphosphazenes were synthesized by Alcock and co-workers (120,121) and
investigated as potential membrane materials for use in direct methanol fuel
cells. The membranes cast from N,N-dimethylformamide were found to have con-
ductivities between 0.01 and 0.1 S/cm and methanol diffusion coefﬁcients (in
3 M MeOH) between 0.14

× 10

− 6

and 0.27

× 10

− 6

/s. Phenyl phosphonic

acid functionalized poly[aryloxyphosphazenes] were prepared and evaluated as
proton-conducting membranes in DMFC tests (177). Sulfonated derivatives of
polyphosphazenes were also tested but their methanol barrier properties were
found to be less attractive (178). Polyphosphazenes bearing sulfonimide groups
were examined in a H

fuel cell at temperatures above 80

◦

C. Less deactiva-

tion of the membrane due to dehydration (as compared to Naﬁon) was observed
(179,180), which is a signiﬁcant ﬁnding if these polymers are to be used in high
temperature PEM fuel cells.

Biomedical Applications.

Biomedical applications were investigated

by a number of polyphosphazene research groups (181). The most impor-
tant studies concerned biocompatibility, biodegradation, enzyme immobiliza-
tion, and drug delivery (182,183). Polyphosphazene implants and prosthe-
ses were also examined. Biocompatibility through appropriate manipulation
of surface or bulk chemistry was studied extensively (184). Works on the
synthesis and cross-linking of amphiphilic polyphosphazenes (94), heparin
immobilization (185–187), and other surface functionalizations (4,101) were
reported.

Vol. 7

POLYPHOSPHAZENES

615

Trypsin and glucose-6-phosphate dehydrogenase were immobilized on

surface-aminated poly[bis(phenoxy)phosphazene] and successfully tested in
continuous-ﬂow reactors (130). Biodegradable polyphosphazene/poly(lactite-co-
glycolide) blends were tested for controlled drug delivery using p-nitroaniline
as a model release agent (188). Other polyphosphazenes that were suscepti-
ble to erosion under physiological conditions were also investigated; they con-
tained amino acid ester (189–193), imidazolyl (194,195), glyceryl (104), or glu-
cosyl (103) groups. In vivo performance under clinically relevant conditions
were planned for poly[(p-methylphenoxy)-co-(ethylglicinato)phosphazene] matri-
ces (196). Water-soluble methoxyethoxy–aminoaryloxy co-substituted polyphos-
phazenes were synthesized and tested as carriers for N-acetylglycine (106).
Synthetic vectors for gene delivery based on polyphosphazenes were also
reported (197). Song and co-workers (198,199) investigated the synthe-
sis and antitumor activity of poly(organophosphazene)/diamineplatinum and
poly(organophosphazene)/deoxorubicin conjugates. Only the ﬁrst conjugate ex-
hibited high antitumor activity due to controlled release of diamineplatinum(II).
Polyphosphazene membranes and microspheres were investigated for the treat-
ment of periodontal diseases (200). Antibacterial drugs, useful in periodontal tis-
sue regeneration, could be entrapped in the membranes and released at appropri-
ate rates to ensure therapeutic concentrations in the tissue. A hydroxyapatite–
polyphosphazene composite was tested as a possible artiﬁcial bone-replacement
material (201). Peripherial nerve regeneration with a poly[(organo)phosphazene]
tubular prosthesis was presented as an alternative to silicone tubes usage (30).
In other studies mammalian liver cells were encapsulated using calcium-cross-
linked polyphosphazene (96), and polyphosphazene microspheres for insulin de-
livery were prepared (203) and their release behavior were evaluated. The use
of polyphosphazenes as resilient denture liners and maxillofacial prostheses was
also reported (204). Water-soluble phosphazene polymers were used to enhance
the immunogenicity of HIV-1 secreted viral antigens (205). The system was found
to have potential as a new HIV-1 vaccine candidate for human trials.

Flame Retardants.

The high phosphorus and nitrogen content of

polyphosphazenes make them nonﬂammable (206). Their properties are charac-
terized by a high oxygen index (2), low smoke emission, noncorrosiveness, and low
toxicity of combustion gases. Several polyphosphazenes were tested as coatings,
foams, and coverings for electric cables. In ﬂaming combustion, a commercially
viable polyphosphazene exhibited a 75% reduction in heat release rate compared
to the polyurethane rubber currently used in ﬁre-blocked aircraft seat cushions
(207). Cyclic, oligomeric, and polymeric phosphazenes have been investigated as
ﬂame-retarding additives and blends for several commodity polymers. For exam-
ple, ﬂame retardation improvement of polyurethane has been achieved by the
use of aziridinyl substituted cyclotriphosphazene (208). The trimer served a dual
function as cross-linker and as ﬂame-retardant. Improvement of ﬂame resistancy
by incorporation of cyclic phosphazenes into organic polymers was the subject
of many studies (209–213). Chen-Yang and co-workers (78) showed that blends
of poly[bis(p-chlorophenoxy)phosphazene] and polystyrene had thermal stabil-
ity and ﬂame resistance signiﬁcantly better than those of a pure polystyrene.
Reed and co-workers (214) blended poly[bis(carboxylatophenoxy)-phosphazene]
with structural polyurethane using reactive mixing and analyzed the thermal

616

POLYPHOSPHAZENES

Vol. 7

stabilities of the resultant foams. An increase in ﬂame resistance at loadings equal
to or greater than 20 wt% was observed. Chen-Yang described the syntheses of
an epoxy resin (215) and polyimides (216) containing ﬂame-retarding cyclophos-
phazene.

Optical Devices.

Of most interest in this application are those stud-

ies related to the nonlinear optical effects in polyphosphazene derivatives bear-
ing aromatic azo units (217–219) and the photorefractive effect with polyphosp-
hazenes bearing carbazolyl substituents (220). Possible applications include opti-
cal switches, frequency doublers for lasers, holographic data storage, and real-time
image processing.

Hybrid Polyphosphazenes

In the last decade a number of hybrid polyphosphazenes containing backbone
elements such as carbon, sulfur, or metal, in addition to phosphorus and nitro-
gen, have been synthesized and studied. Ring-opening polymerization of appro-
priate cyclic heterophosphazene has led to polymers like polycarbophosphazenes,
polythiophosphazenes and polythionylphosphazenes (Fig. 12). Several polycar-
bophosphazenes have been synthesized (221,222). The general observation is that
the polymers have a higher glass-transition temperature than the correspond-
ing polyphosphazenes, which attributed to the lower rotational freedom of the
C N bond as compared to P N. The ﬁrst well-characterized examples of polythio-
phosphazenes, were reported by Dodge and co-workers (223). The polymers were
moisture-sensitive and degradation was retarded only when bulky substituents
such as o-phenylphenoxy were present. It was found that the S Cl bond was more
reactive than the P Cl bond, which allowed for a regioselective substitution to
yield polythiophosphazenes with different aryloxy substituents at the sulfur and
phosphorus atoms. Synthesis of polythionylphosphazenes was reported by Liang
and Manners (224). The perchlorinated polymers were moisture-sensitive, but re-
actions with aryloxy nucleophiles or primary amines converted them into stable
poly(aryloxythionylphosphazenes) and poly(aminothionylphosphazenes), respec-
tively (225,226). The substitution with aryloxides was regioselective but, contrary
to the situation observed with polythiophosphazenes, only substitution of the P Cl
bonds was observed and the S Cl bonds were intact. On the other hand, amines

(b)

(a)

(c)

Fig. 12.

(a) Polycarbophosphazene, (b) polythionylphosphazene, and (c) polythionylphos-

phazene, as examples of hybrid polyphosphazenes.

Vol. 7

POLYPHOSPHAZENES

617

CH CH

2 n

(c)

(b)

(a)

Fig.

13.

Polymers

containing

cyclic

phosphazene

trimers:

(a)

poly(alkenyl-

cyclophosphazene), (b) cyclolinear polyphosphazene, and (c) cyclomatrix material.

substituted easily at both phosphorus and sulfur atoms. Depending on the type
of substituent, the polythionylphosphazenes showed properties typical of elas-
tomers or glasses. Condensation routes to sulfur–nitrogen–phosphorus polymers
were also reported (227,228).

Polymers Containing Cyclophosphazenes.

Besides linear polyphos-

phazenes, three other macromolecular structures can be obtained based on the
cyclic trimer: organic polymers with cyclophosphazene side groups, cyclolinear
polymers, and cyclomatrix materials (Fig. 13). Poly(alkenylcyclophosphazenes)
were studied in Allen’s group (210). His approach involved the synthesis of
cyclophosphazenes with an unsaturated group and subsequent radical copoly-
merization with various organic monomers, eg styrene or methyl methacry-
late (229–232). The polymers consisted of an organic backbone, with the phos-
phazene rings as side groups. Other approaches involved either incorporation
of phosphazene trimers into condensation polymers (233,234) or linkage to
preformed organic polymers (213,235). Lately, Allcock presented the synthe-
sis of cyclolinear-phosphazene-containing polymers via ADMET polymerization
(236,237). Phosphazene–triazine cyclomatrix polymers were prepared by Mathew
and co-workers (238). The group of Kumar and Gupta (239–241) developed sev-
eral cyclolinear and cyclomatrix derivatives of polyimides. These materials showed
good thermo-oxidative stability and a high char yield of 50–60% in air at 800

◦

BIBLIOGRAPHY

“Polyphosphonitrilic Polymers” under “Phosphorus-Containing Polymers” in EPST 1st ed.,
Vol. 10. pp. 139–144, by H. R. Allcock, The Pennsylvania State University; “Polyphosp-
hazenes” in EPSE 2nd ed., Vol. pp. 31–41, by H. R. Allcock, Pennsylvania State University.

1. H. R. Allcock, Phosphorus–Nitrogen Compounds, Academic Press, Inc., New York,

1972, p. 337.

2. R. E. Singler, N. S. Schneider, and G. L. Hagnauer, Polym. Eng. and Sci. 15, 321

(1975).

3. Ph. Potin and R. De, Jaeger, Eur. Polym. J. 27, 341 (1991).
4. H. R. Allcock, in J. E. Mark, H. R. Allcock, and R. West, eds., Inorganic Polymers,

Prentice Hall, Englewood Cliffs, 1992, p. 61.

5. H. R. Allcock, in P. Wisian-Neilson, H. R. Allcock and K. J. Wynne, eds., Inorganic

and Organometallic Polymers II (ACS Symposium Series 572), American Chemical

618

POLYPHOSPHAZENES

Vol. 7

Society, Washington, D.C., 1994, p. 208.

6. H. R. Allcock, in K. Hatada, T. Kitayama, and O. Vogl, eds., Macromolecular Design

of Polymeric Materials, Marcel Dekker, Inc., New York, 1997, p. 475.

7. M. Gleria and R. De Jaeger, J. Inorg. Organomet. Polym. 11, 1 (2001).
8. H. R. Allcock, Chemistry and Applications of Polyphosphazenes, John Willey & Sons,

Inc., Hoboken, N. J., 2002.

9. R. De Jaeger and M. Gleria, eds., Phosphazenes: A Worldwide Insight, NOVA Science

Publishers, Happauge, N. Y., 2002.

10. H. N. Stokes, Am. Chem. J. 19, 782 (1897).
11. E. L. Gefter, Organophosphorus Monomers and Polymers, Associated Technical Ser-

vices, Inc., Glen Ridge, 1962, p. 230.

12. U.S. Pat. 2,382,423 (Aug. 14, 1945), H. J. Kauth (to General Cable Corp.).
13. H. R. Allcock and R. L. Kugel, J. Am. Chem. Soc. 87, 4216 (1965).
14. K. Matyjaszewski and W. V. Metanomski, ACS Polym. Prepr. 43, 755 (2002).
15. IUPAC, Pure Appl. Chem. 57, 149 (1985).
16. IUPAC, Pure Appl. Chem. 48, 373 (1976).
17. H. R. Allcock, R. L. Kugel, and K. J. Valan, J. Inorg. Chem. 5, 1709 (1966).
18. H. R. Allcock and R. L. Kugel, Inorg. Chem. 5, 1716 (1966).
19. H. R. Allcock, Polymer 21, 673 (1980).
20. I. Manners, G. H. Riding, J. A. Dodge, and H. R. Allcock, J. Am. Chem. Soc. 111, 3067

(1989).

21. H. R. Allcock, G. H. Riding, I. Manners, J. A. Dodge, G. S. McDonnell, and J. L.

Desorcie, Polym. Prepr. 31, 48 (1990).

22. H. R. Allcock and D. B. Patterson, Inorg. Chem. 16, 197 (1977).
23. J. A. Dodge, I. Manners, H. R. Allcock, G. Renner, and O. Nuyken, J. Am. Chem. Soc.

112, 1268 (1990).

24. M. Liang and I. Manners, J. Am. Chem. Soc. 113, 4044 (1991).
25. M. Liang and I. Manners, Makromol. Chem., Rapid Commun. 12, 613 (1991).
26. U.S. Pat. 4,005,171 (Jan. 25, 1977), K. A. Reynard and A. H. Gerber (to Horizons Inc.).
27. U.S. Pat. 4,242,316 (Dec. 30, 1980), D. P. Sinclair (to Standard Oil Co.).
28. A. N. Mujumdar, S. G. Young, R. L. Merker, and J. H. Magill, Makromol. Chem. 190,

2293 (1989).

29. U.S. Pat. 4,946,938 (Aug. 7, 1990), J. H. Magill and R. L. Merker (to University of

Pittsburgh).

30. A. N. Mujumdar, S. G. Young, R. L. Merker and J. H. Magill, Macromolecules 23, 14

(1990).

31. C. W. Allen and A. S. Hneihem, Phosphorus, Sulfur and Silicon Relat. Elem. 144, 213

(1999).

32. U.S. Pat. 6,309,619 (Oct. 30, 2001), C. W. Allen, A. S. Hneihen, and E. S. Peterson (to

Bechtel BWXT Idaho, LLC).

33. Span. Pat. ES 2,166,272 (2002), G. A. Carriedo, F. J. Garcia Alonso, and P. Gomez

Elipe (to Universidad de Oviedo).

34. M. Helioui, R. De Jaeger, E. Puskaric, and J. Heubel, Makromol. Chem. 183, 1137

(1982).

35. P. Wisian-Neilson and R. H. Neilson, J. Am. Chem. Soc. 102, 2848 (1980).
36. R. H. Neilson and P. Wisian-Neilson, Chem. Rev. 88, 541 (1988).
37. R. H. Neilson, P. Wisian-Neilson, J. J. Meister, A. K. Roy, and G. L. Hagnauer, Macro-

molecules 20, 910 (1987).

38. K. Matyjaszewski, U. Franz, R. A. Montague, and M. L. White, Polymer 35, 5005

(1994).

39. M. L. White and K. Matyjaszewski, Macromol. Chem. Phys. 198, 665 (1997).
40. H. R. Allcock, C. A. Crane, C. T. Morrissey, J. M. Neilson, S. D. Reeves, C. H. Honeyman

Vol. 7

POLYPHOSPHAZENES

619

and I. Manners, Macromolecules 29, 7740 (1996).

41. J. M. Neilson and H. R. Allcock, Macromolecules 30, 1854 (1997).
42. H. R. Allcock, C. A. Crane, C. T. Morrissey, and M. A. Olshavsky, Inorg. Chem. 38,

280 (1999).

43. H. L. Allcock, S. D. Reeves, C. R. Denus, and C. A. Crane, Macromolecules 34, 748

(2001).

44. G. A. Carriedo, F. J. Garcia Alonso, P. A. Gonzales, and J. L. Garcia Alvarez, Macro-

molecules 31, 3189 (1998).

45. G. A. Carriedo, F. J. Garcia Alonso, P. Gomez Elipe, J. L. Garcia Alvarez, M. P. Tara-

zona, M. T. Rodriguez, E. Saiz, J. T. Vazquez, and J. I. Padron, Macromolecules 33,
3671 (2000).

46. S. H. Rose, J. Polym. Sci., Part B: Polym. Phys. 6, 837 (1968).
47. D. P. Tate, J. Polym. Sci., Polym. Symp. 48, 33 (1974).
48. R. E. Singler, G. L. Hagnauer, and R. W. Sicka, ACS Symp. Ser. 260, 143 (1984).
49. H. R. Penton, Kautch. Gummi, Kunstat. 39, 301 (1986).
50. M. Gleria, F. Minto, L. Flamigni, and P. Bortolus, J. Inorg. Organomet. Polym. 2, 329

(1992).

51. U.S. Pat. 5,260,103 (1993), M. Gleria, F. Minto, and L. Flamigni (to Consiglio Nazionale

delle Ricerche).

52. H. R. Allcock and Y. B. Kim, Macromolecules 27, 3933 (1994).
53. F. Minto, M. Gleria, A. Pegoretti, and L. Fambri, Macromolecules 33, 1173 (2000).
54. M. L. White and K. Matyjaszewski, Macromol. Chem. Phys. 198, 665 (1997).
55. H. R. Allcock, S. D. Reeves, J. M. Nelson, and C. A. Crane, Macromolecules 30, 2213

(1997).

56. J. M. Nelson and H. R. Allcock, Macromolecules 30, 1854 (1997).
57. H. R. Allcock, S. D. Reeves, J. M. Nelson, and I. Manners, Macromolecules 33, 3999

(2000).

58. J. M. Nelson, A. P. Primrose, T. J. Hartle, and H. R. Allcock, Macromolecules 31, 947

(1998).

59. H. R. Allcock, R. Prange, and T. J. Hartle, Macromolecules 34, 5463 (2001).
60. R. Prange and H. R. Allcock, Macromolecules 32, 6390 (1999).
61. H. R. Allcock and R. Prange, Macromolecules 34, 6858 (2001).
62. Y. Chang, S. C. Lee, K. T. Kim, C. Kim, S. D. Reeves, and H. R. Allcock, Macromolecules

34, 269 (2001).

63. P. Wisian-Neilson in P. Wisian-Neilson, H. R. Allcock, and K. J. Wynne, eds., Inorganic

and Organometallic Polymers II (ACS Symposium Series 572), American Chemical
Society, Washington, D.C., 1994 p. 246.

64. J. Y. Chang, P. J. Park, and M. J. Han, Macromolecules 33, 321 (2000).
65. M. Gleria, F. Minto, P. Bortolus, G. Facchin, and R. Bertani, in P. Wisian-Neilson,

H. R. Allcock and K. J. Wynne, eds., Inorganic and Organometallic Polymers II (ACS
Symposium Series 572), American Chemical Society, Washington, D. C., 1994, p. 279.

66. M. Gleria, F. Minto, M. Scoponi, F. Pradella, and V. Carassiti, Chem. Mater. 4, 1027

(1992).

67. F. Minto, M. Scoponi, L. Fambri, M. Gleria, P. Bortolus, and F. Pradella, Eur. Polym.

J. 28, 167 (1992).

68. F. Minto, M. Scoponi, M. Gleria, F. Pradella, and P. Bortolus, Eur. Polym. J. 30, 375

(1994).

69. F. Minto, M. Gleria, P. Bortolus, L. Fambri, and A. Pegoretti, J. Appl. Polym. Sci. 56,

747 (1995).

70. M. Gleria, A. Bolognesi, W. Porzio, M. Catellani, S. Destri, and G. Audisio, Macro-

molecules 29, 469 (1987).

71. F. Minto, L. Fambri, and M. Gleria, Macromol. Chem. Phys. 197, 3099 (1996).

620

POLYPHOSPHAZENES

Vol. 7

72. L. Fambri, F. Minto, and M. Gleria, J. Organomet. Polym. 6, 195 (1996).
73. M. F. Welker, H. R. Allcock, G. L. Grune, R. T. Chern, and V. T. Stannett, Polym. Mater.

Sci. Eng. 66, 259 (1992).

74. M. F. Welker, H. R. Allcock, G. L. Grune, R. T. Chern, and V. T. Stannett, in L. F. Thom-

son, C. G. Wilson, and S. Tagawa, eds., Polymers for Microelectronics (ACS Symposium
Series 537), American Chemical Society, Washington, D. C., 1994, p. 293.

75. R. Prange, S. D. Reeves, and H. R. Allcock, Macromolecules 33, 5763 (2000).
76. G. A. Carriedo, J. Jimenez, P. Gomez-Elipe, and F. J. Garcia Alonso, Macromol. Rapid

Commun. 22, 444 (2001).

77. C. S. Reed, J. P. Taylor, K. S. Guigley, M. M. Coleman, and H. R. Allcock, Polym. Eng.

Sci. 40, 465 (2000).

78. Y. W. Chen-Yang, H. F. Lee, and T. T. Wu, in P. Wisian-Neilson, H. R. Allcock and K.

J. Wynne, eds., Inorganic and Organometallic Polymers II (ACS Symposium Series
572), American Chemical Society, Washington, D.C., 1994, p. 295.

79. A. M. A. Ambrosio, H. R. Allcock, and C. T. Laurencin, Proc. Soc. Biomater. 25, 9 (1999).
80. C. R. Herrero and J. L. Acosta, Polym. Int. 32, 349 (1993).
81. R. Wycisk, R. Carter, and P. Pintauro, in 12th Annual Meeting of the North American

Membrane Society, Lexington, May 15–20, 2001.

82. R. Wycisk, R. Carter, P. N. Pintauro, and C. Byrne, in ACS 222nd National Meeting,

Chicago, August 26–30, 2001.

83. R. A. Dickie, R. S. Bauer, and S. S. Labana, eds., Cross Linked Polymers Chemistry,

Properties, and Applications (ACS Symposium Series 367), American Chemical Soci-
ety, Washington, D. C., 1988.

84. U.S. Pat. 3,702,833 (1972), S. H. Rose and K. A. Reynard (to Horigons, Inc.).
85. H. R. Penton, Kautsch. Gummi, Kunstst. 39, 301 (1986).
86. M. Gleria, F. Minto, L. Flamigni, and P. Bortolus, J. Inorg. Organomet. Polym. 2, 329

(1992).

87. M. Gleria, F. Minto, L. Fambri, and A. Pegoretti, Eur. Polym. J. 31, 791 (1995).
88. F. Minto, M. Gleria, A. Pegoretti, and L. Fambri, Macromolecules 33, 1173 (2000).
89. R. Graves and P. N. Pintauro, J. Appl. Polym. Sci. 68, 827 (1998).
90. R. Wycisk, P. N. Pintauro, W. Wang, and S. O’Connor, J. Appl. Polym. Sci. 59, 1607

(1996).

91. D. Babic, D. M. Souverain, V. T. Stannett, D. R. Squire, G. L. Hagnauer, and R. E.

Singler, Radiat. Phys. Chem. 28, 169 (1986).

92. H. R. Allcock, S. Kwon, G. H. Riding, R. J. Fitzpatrick, and J. L. Bennett, Biomaterials

19, 509 (1988).

93. V. T. Stannett, G. L. Grune, R. T. Chern, and H. R. Allcock, Polym. Prepr. (Am. Chem.

Soc., Div. Polym. Chem.) 35, 876 (1994).

94. H. R. Allcock, M. Gebura, S. Kwon, and T. X. Neenan, Biomaterials 9, 500 (1988).
95. F. F. Steward, R. E. Singler, M. K. Harrup, E. S. Peterson, and R. P. Lash, J. Appl.

Polym. Sci. 76, 55 (2000).

96. S. Cohen, M. C. Bano, K. B. Visscher, M. Chow, H. R. Allcock, and R. Langer, J. Am.

Chem. Soc. 112, 7832 (1990).

97. J. Kerres, A. Ullrich, F. Meier, and T. Haring, Solid State Ionics 125, 243 (1999).
98. R. Wycisk, R. Carter, and P. N. Pintauro, unpublished results (2001).
99. H. R. Allcock, in A. O. Patil, D. N. Schulz, and B. M. Novak, eds., Functional Polymers

(ACS Symposium Series 704), American Chemical Society, Washington, D. C., 1998,
p. 261.

100. H. R. Allcock, Chem. Mater. 6, 1476 (1994).
101. H. R. Allcock, Appl. Organomet. Chem. 12, 659 (1998).
102. M. A. Olshavsky and H. R. Allcock, Chem. Mater. 9, 1367 (1997).
103. H. R. Allcock and A. G. Scopelianos, Macromolecules 16, 715 (1983).

Vol. 7

POLYPHOSPHAZENES

621

104. H. R. Allcock and S. Kwon, Macromolecules 21, 1980 (1988).
105. H. R. Allcock, E. H. Klingenberg, and M. F. Welker, Macromolecules 26, 5512 (1993).
106. S. K. Kwon, Bull. Korean Chem. Soc. 21, 969 (2000).
107. S. K. Kwon, Bull. Korean Chem. Soc. 22, 1243 (2001).
108. G. A. Carriedo, J. I. F. Martinez, F. J. G. Alonso, E. R. Gonzalez, and A. P. Soto, Eur.

J. Inorg. Chem. 1502 (2002).

109. H. R. Allcock, S. Kwon, Macromolecules 22, 75 (1989).
110. G. A. Carriedo, F. J. Garcia Alonso, and P. A. Gonzalez, Macromol. Rapid. Commun.

18, 371 (1997).

111. G. A. Carriedo, F. J. Garcia Alonso, P. A. Gonzalez, J. L. Garcia, and P. Gomez-Elipe,

Phosphorus, Sulfur Silicon Relat. Elem. 146, 73 (1999).

112. G. A. Carriedo, L. Fernandez-Catuxo, F. J. Garcia Alonso, P. Gomez-Elipe, and P. A.

Gonzalez, Macromolecules 29, 5320 (1996).

113. H. R. Allcock and R. J. Fitzpatrick, Chem. Mater. 3, 1120 (1991).
114. E. Montoneri, M. Gleria, G. Ricca, and G. C. Pappalardo, Makromol. Chem. 190, 191

(1989).

115. E. Montoneri, M. Gleria, G. Ricca, and G. C. Pappalardo, J. Macromol. Sci., Chem.

A26, 645 (1989).

116. R. Wycisk and P. N. Pintauro, J. Membr. Sci. 119, 155 (1996).
117. H. R. Allcock, R. J. Fitzpatrick, and L. Salvati, Chem. Mater. 4, 769 (1992).
118. H. R. Allcock, P. E. Austin, and T. F. Rakowsky, Macromolecules 14, 1622 (1981).
119. H. R. Allcock and J. Y. Chang, Macromolecules 24, 993 (1991).
120. H. R. Allcock, M. A. Hofmann, and R. M. Wood, Macromolecules 34, 6915 (2001).
121. H. R. Allcock, M. A. Hofmann, C. M. Ambler, and R. V. Morford, Macromolecules 35,

3484 (2002).

122. P. Wisian-Neilson, M. S. Islam, S. Ganapathiappan, D. L. Scott, K. S. Raghuveer, and

R. R. Ford, Macromolecules 22, 4382 (1989).

123. P. Wisian-Neilson and R. R. Ford, Organometallics 6, 2258 (1987).
124. P. Wisian-Neilson and R. R. Ford, Macromolecules 22, 72 (1989).
125. P. Wisian-Neilson, L. Huang, M. Q. Islam, and R. A. Crane, Polymer 35, 4985 (1994).
126. P. Wisian-Neilson, C. Zhang, K. A. Koch, and J. Gruneich, Phosphorus, Sulfur, Silicon

69, 144 (1999).

127. H. R. Allcock, J. S. Rutt, and R. J. Fitzpatrick, Chem. Mater. 3, 442 (1991).
128. H. R. Allcock, R. J. Fitzpatrick, and K. B. Visscher, Chem. Mater. 4, 775 (1992).
129. H. R. Allcock, C. T. Morrissey, W. K. Way, and N. Winograd, Chem. Mater. 8, 2730

(1996).

130. H. R. Allcock and S. Kwon, Macromolecules 19, 1502 (1986).
131. D. P. Craig and N. L. Paddock, Nature 181, 1052 (1958).
132. Y. Chatani and K. Yatsuyanagi, Macromolecules 20, 1042 (1987).
133. D. P. Tate, J. Polym. Sci., Symp. Ser. 48, 33 (1974).
134. H. R. Penton, in M. Zeldin, K. J. Wynne, and H. R. Allcock, eds., Inorganic and

Organometallic Polymers (ACS Symposium Series 360), American Chemical Society,
Washington, D. C., 1988, p. 277.

135. J. H. Magill, Polymer Data Handbook, Oxford University Press, Oxford, 1999, p. 750.
136. O. L. Abu-Shanab, C. P. Chang, and M. D. Soucek, High Perform. Polym. 8, 455 (1996).
137. V. S. Papkov, M. N. Ilina, V. P. Zhukov, D. J. Tsvankin, and D. R. Tur, Macromolecules

25, 2033 (1992).

138. P. M. Blonsky, D. F. Shriver, P. E. Austin, and H. R. Allcock, J. Am. Chem. Soc. 106,

6854 (1984).

139. H. R. Allcock, M. E. Napierala, D. L. Olmeijer, C. G. Cameron, S. E. Kuharcik, C. S.

Reed, and S. J. M. O’Connor, Electrochimica Acta 43, 1145 (1998).

140. J. S. Tonge and D. F. Shriver, J. Electrochem. Soc. 134, 269 (1987).

622

POLYPHOSPHAZENES

Vol. 7

141. J. L. Bennett, A. A. Dembek, H. R. Allcock, B. J. Heyen, and D. F. Shriver, Chem.

Mater. 1, 14 (1989).

142. G. A. Nazri and S. G. Meibuhr, J. Electrochem. Soc. 136, 2450 (1989).
143. K. M. Abraham and M. Alamgir, J. Power Source 195, 43 (1993).
144. K. M. Abraham, M. Alamgir, and R. K. Reynolds, J. Electrochem. Soc. 136, 3576 (1989).
145. B. K. Coltrain, W. T. Ferrar, C. J. T. Landry, T. R. Molaire, and N. Zumbulayadis,

Chem. Mater. 4, 358 (1992).

146. C. Kim, J. S. Kim, and M. H. Lee, Synth. Met. 98, 153 (1998).
147. J. DeGaspari, Mech. Eng. Mag. Online (Oct. 2002).
148. H. R. Allcock, D. L. Olmeijer, and S. J. M. O’Connor, Macromolecules 31, 753 (1998).
149. H. R. Allcock and D. L. Olmeijer, Macromolecules 31, 8036 (1998).
150. S. Ganapathiappan, H. C. Chen, and D. F. Shriver, Macromolecules 21, 2299 (1988).
151. G. Golemme and E. Drioli, J. Inorg. Organomet. Polym. 6, 341 (1996).
152. M. Kijiwara, in B. Sedlacek and J. Kahovec, eds., Synthetic Polymer Membranes, Wal-

ter de Gruyter, Berlin, 1987, p. 347.

153. M. Kijiwara, J. Mater. Sci. 23, 1360 (1988).
154. F. A. Bittirova, V. V. Kireev, and A. K. Mikitaev, Vysokomol. Seoedin. Ser. B 23, 30

(1981).

155. Jpn. Pat. 59154105 (1984), M. Yamabe, G. Kojima, and H. Wachi (to Asahi Glass Co.).
156. T. Hirose and K. Mizoguchi, J. Appl. Polym. Sci. 43, 891 (1991).
157. E. Drioli, S. M. Zhang, A. Basile, G. Golemme, S. N. Gaeta, and H. C. Zhang, Gas Sep.

Purif. 5, 252 (1991).

158. E. S. Peterson and M. L. Stone, J. Membr. Sci. 86, 57 (1994).
159. G. Golemme, E. Drioli, and F. Lufrano, Polym. Sci. 36, 1647 (1994).
160. P. Wisian-Neilsen and G. F. Xu, Macromolecules 29, 3457 (1996).
161. E. S. Peterson, M. L. Stone, R. R. McCaffrey, and D. G. Cummings, Sep. Sci. Technol.

28, 423 (1993).

162. H. R. Allcock, C. J. Neilson, W. D. Coggio, I. Manners, W. J. Koros, D. R. B. Walker,

and L. B. Pessan, Macromolecules 26, 1493 (1993).

163. C. J. Orme, M. K. Harrup, T. A. Luther, R. P. Lash, K. S. Houston, D. H. Weinkauf,

and F. F. Stewart, J. Membr. Sci. 186, 249 (2001).

164. J. R. Fried and P. Ren, Comput. Theor. Polym. Sci. 10, 447 (2000).
165. E. S. Peterson, M. L. Stone, W. F. Bowen, and A. K. Gianotto, Recents Prog. Genie Proc.

6, 381 (1992).

166. D. Roizard, M. Pineau, A. Bac, J. J. Cuny, and P. Lochon, in W. R. Bowen, R. W. Field,

and J. A. Howell, eds., Proceedings of the Euromembrane ’95 Conference Bath, U. K.,
Sept. 18–20, 1995, p. II–239.

167. F. Suzuki, K. Onozato, H. Yaegashi, and T. Masuko, J. Appl. Polym. Sci. 34, 2197

(1987).

168. Y. M. Sun, C. H. Wu, and C. L. Lin, J. Polym. Res. (Taiwan) 6, 91 (1999).
169. C. J. Orme, M. K. Harrup, J. D. McCoy, D. H. Weinkauf, and F. F. Stewart, J. Membr.

Sci. 197, 89 (2002).

170. D. A. Nelson, J. B. Duncan, G. A. Jensen, and S. D. Burton, Trans. Am. Nucl. Soc. 71,

82 (1994).

171. J. B. Duncan and D. A. Nelson, J. Membr. Sci. 157, 211 (1999).
172. H. Tang and P. N. Pintauro, J. Appl. Polym. Sci. 79, 49 (2000).
173. Q. H. Guo, P. N. Pintauro, H. Tang and S. O’Connor, J. Membr. Sci. 154, 175 (1999).
174. R. Carter, R. Evilia, and P. N. Pintauro, J. Phys. Chem. B 105, 2351 (2001).
175. R. Wycisk, R. Carter, H. Yoo, and P. N. Pintauro, NAMS 2002, 13th Annual Meeting,

Long Beach, Calif., May 11–15, 2002.

176. R. Carter, R. Wycisk, H. Yoo, and P. N. Pintauro, Electrochem. and Solid-State Lett.

5, A195 (2002).

Vol. 7

POLYPHOSPHAZENES

623

177. H. R. Allcock, M. A. Hofmann, C. M. Ambler, S. N. Lvov, X. Y. Zhou, E. Chalkova, and

J. Weston, J. Membr. Sci. 201, 47 (2002).

178. M. F. Fedkin, X. Zhou, M. A. Hofmann, E. Chalkova, J. A. Weston, H. R. Allcock, and

S. N. Lvov, Mater. Lett. 52, 192 (2002).

179. M. A. Hofmann, C. M. Ambler, A. E. Maher, E. Chalkova, X. Y. Zhou, S. N. Lvov, and

H. R. Allcock, Macromolecules 35, 6490 (2002).

180. S. N. Lvov, NAMS 2002, 13th Annual Meeting, Long Beach, Calif., May 11–15, 2002.
181. A. G. Scopelianos, in W. S. W. Shalaby, ed., Biomedical Polymers, Hanser, New York,

1994, p. 153.

182. S. M. Ibim, A. A. Ambrosio, D. Larrier, H. R. Allcock, and C. T. Laurencin, J. Controlled

Release 40, 31 (1996).

183. A. K. Andrianov and L. G. Payne, Adv. Drug Delivery Rev. 31, 185 (1998).
184. H. Kawakami, S. Kanezaki, M. Sudo, M. Kanno, S. Nagaoka, S. Kubota, Artif. Organs

26, 883 (2002).

185. T. X. Neenan and H. R. Allcock, Biomaterials 3, 78 (1982).
186. S. Lora, M. Carenza, G. Palma, G. Pezzin, P. Caliceti, P. Battaglia, and A. Lora, Bio-

materials 12, 275 (1991).

187. M. Carenza, S. Lora, G. Palma, G. Pezzin, and P. Caliceti, Radiat. Phys. Chem. 48,

231 (1996).

188. C. T. Laurencin, S. E. Ibim, H. R. Allcock, A. M. Ambrosio, S. El-Amin, and M. S.

Kwon, Bioact. Mater. 24, 971 (1997).

189. H. R. Allcock, T. J. Fuller, D. P. Mack, K. Matsumura, and K. M. Smeltz, Macro-

molecules 10, 824 (1977).

190. J. H. L. Crommen, E. H. Schacht, and E. H. G. Mense, Biomaterials 13, 511 (1992).
191. P. Caliceti, S. Lora, F. Marsilio, A. Guiotto, F. M. Veronese, Il Farmaco 49, 69

(1994).

192. H. R. Allcock, S. R. Pucher, and A. G. Scopelianos, Biomaterials 15, 563 (1994).
193. L. Y. Qiu and K. J. Zhu, J. Appl. Polym. Sci. 77, 2987 (2000).
194. H. R. Allcock, T. J. Fuller, and K. Matsumura, Inorg. Chem. 21, 515 (1982).
195. H. R. Allcock and T. J. Fuller, J. Am. Chem. Soc. 103, 2250 (1981).
196. J. H. Magill, Polymer Data Handbook, Oxford University Press, Oxford, 1999, p. 746.
197. J. Luten, J. H. van Steenis, N. M. E. Schuurmans-Nieuwenbroek, C. F. van Nostru-

mand, and W. E. Hennink, Spring Meeting of the Belgian-Dutch Biopharmaceutical
Society, Gorleus Laboratoria, Leiden, the Netherlands, May 31, 2002.

198. S. C. Song, C. O. Lee, and Y. S. Sohn, Bull. Korean Chem. Soc. 20, 250 (1999).
199. S. C. Song, C. O. Lee, and Y. S. Sohn, Polym. Int. 48, 627 (1999).
200. F. M. Veronese, F. Marsilio, S. Lora, P. Caliceti, P. Passi, and P. Orsolini, Biomaterials

20, 91 (1999).

201. K. A. Bernheim, C. S. Reed, and H. R. Allcock, J. Invest. Med. 47, 42A (1999).
202. F. Langone, S. Lora, F. M. Veronese, P. Caliceti, P. P. Parnigotto, F. Valenti, and G.

Palma, Biomaterials 16, 347 (1995).

203. P. Caliceti, F. M. Veronese, and S. Lora, Int. J. Pharm. 211, 57 (2000).
204. L. Gettleman, XIV International Conference on Phosphorus Chemistry, Cincinnati,

Ohio, July 12–17, 1998.

205. L. Yichen, N. Touzjian, N. Kushner, C. Chutkowski, H. Qian, and S. Jenkins, XI

International Conference on AIDS, Vancouver, Canada, July 7–12, 1996 (Abstract
Mo. A.520).

206. W. C. Kuryla and A. J. Papa, ed., Flame Retardancy of Polymeric Materials, Vol. I,

Marcel Dekker, Inc., New York, 1973.

207. R. E. Lyon, U. S. Department of Transportation, Federal Aviation Administra-

tion, Cabin and Fire Safety Reports, Fire-Resistant Elastomers, DOT/FAA/AR-TN01/
104.

624

POLYPHOSPHAZENES

Vol. 7

208. W. K. Huang, J. T. Yeh, K. J. Chen, and K. N. Chen, J. Appl. Polym. Sci. 79, 662

(2001).

209. K. Inoue, S. Kaneyuki, and T. Tanigaki, J. Polym. Sci., Part A: Polym. Chem. 30, 145

(1992).

210. C. W. Allen, Trends Polym. Sci. 2, 342 (1994).
211. I. I. Selveraj and V. Chandrasekhar, Polymer 38, 3617 (1997).
212. H. R. Allcock, W. R. Laredo, C. R. deDenus, and J. P. Taylor, Macromolecules 32, 7719

(1999).

213. H. R. Allcock, T. J. Hartle, J. P. Taylor, and N. J. Sunderland, Macromolecules 34, 3896

(2001).

214. C. S. Reed, J. P. Taylor, K. S. Guigley, M. M. Coleman, and H. R. Allcock, Polym. Eng.

Sci. 40, 465 (2000).

215. Y. W. Chen-Yang, H. F. Lee, and C. Y. Yuan, J. Polym. Sci., Part A: Polym. Chem. 38,

972 (2000).

216. Y. W. Chen-Yang, H. F. Le, and S. F. Chen, Phosphorus, Sulfur, Silicon Rel. Elem. 75,

109 (1996).

217. H. R. Allcock, C. G. Cameron, T. W. Skloss, S. Taylor-Meyers, and J. F. Haw, Macro-

molecules 29, 233 (1996).

218. G. Rojo, F. Agullo-Lopez, G. A. Carriedo, F. J. Garcia Alonso, and J. I. Fidalgo, Martinez,

Synth. Met. 115, 241 (2000).

219. G. Rojo, F. Agullo-Lopez, G. A. Carriedo, F. J. Garcia Alonso and J. I. Fidalgo, Martinez,

Polym. Bull. 45, 145 (2000).

220. Z. Li, J. Li, and J. Qin, React. Funct. Polym. 48, 113 (2001).
221. I. Manners, G. Renner, O. Nuyken, and H. R. Allcock, J. Am. Chem. Soc. 111, 5478

(1989).

222. H. R. Allcock, S. M. Coley, and C. T. Morrissey, Macromolecules 27, 2904

(1994).

223. J. A. Dodge, I. Manners, H. R. Allcock, G. Renner, and O. Nuyken, J. Am. Chem. Soc.

112, 1268 (1990).

224. M. Liang and I. Manners, J. Am. Chem. Soc. 113, 4044 (1991).
225. Y. Ni, A. J. Lough, A. L. Rheingold, and I. Manners, Angew. Chem., Int. Ed. 34, 998

(1995).

226. Y. Ni, A. Stammer, M. Liang, J. Massey, G. J. Vancso, and I. Manners, Macromolecules

25, 7119 (1992).

227. V. Chunechom, T. E. Vidal, and M. L. Turner, Proc. Partner. Polym. 50 (1996).
228. V. Chunechom, T. E. Vidal, H. Adams, and M. L. Turner, Angew. Chem., Int. Ed. 37,

1928 (1998).

229. J. G. DuPont and C. W. Allen, Macromolecules 12, 169 (1979).
230. C. W. Allen and R. P. Bright, Macromolecules 19, 571 (1986).
231. J. C. Shaw and C. W. Allen, Inorg. Chem. 25, 4632 (1986).
232. G. Bosscher and J. C. van de Grampel, J. Inorg. Organomet. Polym. 5, 209 (1995).
233. U. Tunca and G. Hizal, J. Polym. Sci., Part A: Polym. Chem. 36, 1227 (1998).
234. P. Radhakrishnan Nair, C. P. Reghunadhan Nair, and D. J. Francis, Eur. Polym. J. 32,

1415 (1996).

235. T. J. Hurtle, N. J. Sunderland, M. B. McIntosh, and H. R. Allcock, Macromolecules 33,

4307 (2000).

236. H. R. Allcock, E. C. Kellam III, and M. A. Hofmann, Macromolecules 34, 5140

(2001).

237. H. R. Allcock and E. C. Kellam III, Macromolecules 35, 40 (2002).
238. D. Mathew, C. P. R. Nair, and K. N. Ninan, Polym. Int. 49, 48 (2000).
239. D. Kumar, A. D. Gupta, and M. Khullar, J. Inorg. Organomet. Polym. 3, 259

(1993).

Vol. 7

POLYSILANES

625

240. D. Kumar, A. D. Gupta, and M. Khullar, J. Polym. Sci., Part A: Polym. Chem. 31, 2379

(1993).

241. D. Kumar and A. D. Gupta, Macromolecules 28, 6323 (1995).

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