Thionylphosphazene

The polymerizations of other cyclic phosphazenes have also been studied, including car-bophosphazene, thiophosphazene, and thionylphosphazene [De Jaeger and Gleria, 1998 McWilliams et al., 2000]... 

In the case of some cyclics, such as the thionylphosphazene six-membered ring [NS(0)Cl(NPCl2)2], the small degree of ring-strain makes the favourable A/Zrop and unfavourable TAArop terms finely balanced. In the presence of a catalyst such as GaCls, ROP can be favoured at high concentrations and depolymerisation to the cyclic monomer at low concentrations [eqn (8.2)]. 

A third variant on the polyphosphazene skeletal structure is represented by the poly(thionylphosphazenes) (reactions (65) and (66)) in which every third phosphorus along the chain is replaced by a sulfur VI atom.266-272 These species are more hydrolytically stable than their sulfur IV analogues, probably because the presence of two side groups on sulfur provides additional protection for the main chain. 

Molecular dynamics calculations have been carried out to simulate a conformational model and vibrational spectra of poly(dichlorophospha-zenes). Molecular dynamics similations for [NP(OCH2CF3)2] and the isomers [NP(OBu")2] , [NP(OBu )2] and [NP(OBu )2] show a reasonable agreement between the calculated and experimental values of density and glass transition temperature as well as for gas transport parameters in these polymers.Small molecule models have been used for a theoretical approach of poly(thionylphosphazenes). ... 

Keywords. Phosphorus, Polymers, Heterophosphazenes, Thionylphosphazenes, Phosphino-boranes... 

One of the most well studied heterophosphazenes is the cyclic thionylphosphazene 18 which was first prepared in 1972 by two different low yield routes. Van de Grampel et al. reported the synthesis of small quantities of this species via the vacuum thermolysis of C13P=N-PC12=N-S02C1 [24]. An alternate, low yield route... 

In 1991, Liang and Manners reported that when the cyclic thionylphosphazene 18 is heated in the melt at 165°C, thermal ROP takes place to yield the poly-thionylphosphazene 19 with chlorine substituents at both sulfur and phosphorus [23] ... 

The fluorinated derivative 20 which can be prepared by reaction of the per-chlorinated thionylphosphazene with AgF2 [29], HgF2/AlCl3 [30], or alternatively with AgBF4 [31], also undergoes thermal ROP when heated in the melt at 180°C yielding 21 [32] ... 

Fig. 1. Molecular structures of a a 12-memberedthionylphosphazenering (22 a) b a24-mem-bered thionylphosphazene ring (23). Reproduced from [35] with permission...

In order to prepare hydrolytically stable polythionyiphosphazenes the perchlo-rinated polymers were reacted with nucleophiles to substitute the hydrolytically sensitive main group-element halogen bonds [2]. This type of post-polymerization structural modification is well-established in polyphosphazene chemistry [2,8]. Thus, aryloxide nucleophiles or primary amines were used to substitute the polymers leading to poly(aryloxythionylphosphazenes) 24 and poly(amino-thionylphosphazenes) 25 respectively [35,37] ... 

Two alkoxide nucleophiles trifluoroethoxide and butoxide were chosen to model the substitution pattern of 18 and 20. The reaction of cyclic thionylphosphazene with NaOBu was found to follow the same order of reactivity as NaOPh however, unlike NaOPh the substitution of the S-Cl bond was facile at room temperature and the substitution of the S-F bond required an excess of nucleophile. Interestingly, although the reaction of the cyclic thionylphosphazenes with the NaOCH2CF3 was found to follow the same general order of reactivity as NaOPh or NaOBu (PC12 > PCl(OPh) > S (O)X), a significant enhancement in reaction rate was detected with each equivalent of trifluoroethoxide added. 

Scheme 1. Proposed mechanism for the thermal ring-opening polymerization (ROP) of cyclic thionylphosphazenes (18 and 20)...

PROPERTIES OF SPECIAL INTEREST Film-forming elastomers, potential oxygen sensors for biomedical and aerospace are among this class of poly(thionylphosphazenes) depending upon substituents present. ... 

SYNTHESIS Poly[(M-butylamino)thionylphosphazene] can be prepared via the amino lysis of the chlorinated poly(thionylphosphazene) with butylamine. The chlorinated poly(thionylphosphazene) is synthesized via the thermal ring opening polymeriztion (ROP) of the corresponding cyclic thionylphosphazene... 

Professor Emeritus, Material Science and Engineering Department, University of Pittsburgh, Pennsylvania Poly(aryloxy)thionylphosphazenes Poly(phosphazene), bioerodible Poly(phosphazene) elastomer Poly(phosphazene), semicrystalline... 

Thionylphosphazene polymers can be obtained by condensation of linear compounds (112.252) [99]. Products include gums, glasses and elastomers. Polyphosphazenes containing carbon atoms in the main chain have also been made (12.253) [100,101]. 

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