Polyphosphazenes and Polysiloxanes

Polymer 69 was prepared by following two different routes in the first, Cgo was incorporated directly to a suitably functionalized polymer (68) by the o-quinodimethane method [15]. The second strategy deals with the incorporation of a C6o-derivative (70) directly into an amino-functionalized polysiloxane (67). In both cases, the polymers show identical M values and a remarkable content in [60]fullerene as high as 30wt%. This new material displayed a Mw analogue to those of 69 (-35 000) as well as a high thermal stability of up to 435 °C. 

Cgo was loaded into the polymer by means of pendant aminofishing groups, giving rise to low weight macromolecules with moderate C6o-contents 

Recently, Manners, Sargent et al. have reported the synthesis of a series of polyferrocenylsilane random copolymers containing covalently bound pendant [60]fullerene cages [71]. 

On the other hand, polymers 89a and b were obtained in high yields and high My, (66000 and 70000, respectively) [75]. Polymer 89a was blended together with MDMO-PPV and spin-coated to prepare organic solar cells. However, 

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This review deals with several types of polymer hosts that have been investigated. These include polyethylene oxide and its several modified forms, comb like polymers such as polyacrylates and inorganic polymers such as polyphosphazenes and polysiloxanes. Various instrumental techniques have been employed in the structural characterization of polymer electrolytes. The structural information obtained from methods such as Extended X-ray Absorption Fine Structure (EXAFS), X-ray diffraction methods, vibrational spectroscopy and nuclear magnetic resonance (NMR) have also been discussed. 

It should be noted that, in addition to their use as electronic conductors, polymers can also function as ionic conductors. Materials such as poly(ethylene oxide) and certain oligoethyleneoxy-substituted polyphosphazenes and polysiloxanes, which conduct Li" ions, are used in this regard as polymeric electrolytes for battery applications (9]. 

Cyclophosphazenes are a fascinating group of inorganic heterocyclic compounds whose chemistry is multi-faceted, well developed and reasonably well understood. They are closely related to the linear poly-phosphazenes this relationship is unlike any other existing between ring-polymer systems. Although cyclic siloxanes and polysiloxanes have a close interrelationship, the number and types of cyclophospha-zene derivatives that are known, together with their exact counterparts in polyphosphazenes, underscore the utility of cyclophosphazenes as models for the more complex polyphosphazenes. The literature on cyclophosphazenes has appeared earlier in the form of books (1,2), chapters of books (3-5), authoritative compilations of data (6,7), and several reviews (8-21). The current literature on this subject is reported annually in the Specialist Periodic Reports published by the Royal Society of chemistry (22). This review deals mostly with chlorocyclo-... 

It should be noted that inorganic rings play a crucial role as monomers for the preparation of both polysiloxanes and polyphosphazenes and they are also utilised for making polysilanes. Inorganic rings have also been used as key precursors to several other inorganic polymer systems [e.g. poly(sulfur nitride) and polythionylphosphazenes]. 

Many examples of inorganic polymers with metallocene-containing side-groups also exist. Most of the polymers prepared have been based on main chains of polyphosphazenes, polysilanes, polysiloxanes, and polycarbosilanes. These materials are surveyed in the following sections. 

SPh determination of silicon and phosphorus in form of Si-Mo and P-Mo heteropolyacids are used successfully for series determination of these heteroelements in OEC and polymers (polysiloxanes, polyphosphazenes, etc.). 

The design of functionalized polymers with a specific utilization is seen in new polysiloxanes used by Zeldin (p. 199) as phase transfer catalysts. Novel functional polyphosphazenes have been reported as well by Allcock (p. 250). The introduction of transition metal cyclopentadienyl, metal carbonyl and carborane moieties into polyphosphazene macromolecules is representative of truly novel chemistry achieved after careful model studies with corresponding molecular systems. 

A number of polyphosphazenes of repeat unit [-PRR N-] also exhibit liquid-crystalline phases [166-168]. It is certainly intriguing that apparently the only classes of flexible chains that extensively exhibit liquid-crystalline phases are the polysiloxane and polyphosphazene semi-inorganic polymers. 

Amorphous comb polymers, with short-chain polyethers attached to a polyphosphazene backbone (Blonsky, Shriver, Austin and Allcock, 1984), Fig. 5.15, or a polysiloxane backbone (Xia, Soltz and Smid, 1984), Fig. 5.16, have been found to be excellent hosts for alkali metal salts. The PN... 

One method of reducing crystallinity in PEO-based systems is to synthesize polymers in which the lengths of the oxyethylene sequences are relatively short, such as through copolymerization. The most notable hnear copolymer of this type is oxymethylene-linked poly(oxyethylene), commonly called amorphous PEO, or aPEO for short. Other notable polymer electrolytes are based upon polysiloxanes and polyphosphazenes. Polymer blends have also been used for these applications, such as PEO and poly (methyl methacrylate), PMMA. The general performance characteristics of the polymer electrolytes are to have ionic conductivities in the range of cm) or (S/cm). 

Applications. Polymers with small alkyl substituents, particularly (13), are ideal candidates for elastomer formulation because of quite low temperature flexibility, hydrolytic and chemical stability, and high temperature stability. The ability to readily incorporate other substituents (in addition to methyl), particularly vinyl groups, should provide for conventional cure sites. In light of the biocompatibility of polysiloxanes and P—O- and P—N-substituted polyphosphazenes, poly(alkyl/arylphosphazenes) are also likely to be biocompatible polymers. Therefore, biomedical applications can also be envisaged for (3). A third potential application is in the area of solid-state batteries. The first steps toward ionic conductivity have been observed with polymers (13) and (15) using lithium and silver salts (78). 

Specifically, the greatest emphasis in the following chapters is placed on polyphosphazenes (1.9), polysiloxanes (1.10), and polysilanes (1.11). Chapters 6 and 7 introduce a wide variety of other polymers that contain elements such as phosphorus, germanium, sulfur, boron, aluminum, and tin, and a variety of transition metals. These polymers are expected to provide the basis for many of the new advances of the future. Chapter 8... 

Two other families of polymers with fluorinated side groups have been investigated in the field of elastomers polysiloxanes and polyphosphazenes [394, 395]. These latter macromolecules, called NPF, have been obtained by chemical change of poly(dichlorophosphazene) as for classic phosphazenes ... 

The crystallization of 3D-ordered crystalline phases from thermotropic mesophases, envisaged as stable pre-crystalline partially ordered intermediates, is an additional interesting issue which should be considered with care experimentally, theoretically, and with appropriate simulation approaches. Depending upon the nature of the mesophase it can be seen as a crystal-crystal transition or, for conformationally disordered, columnar mesophases, it approaches a true crystallization process. It is quite clear that the preexisting order will play a major role for example if the mesophase is chain-extended, bundle equilibria and chain-folding should not play any role. Indeed available experimental evidence supports this idea. Mechanistic and kinetic features should in general differ widely from the standard chain-folded crystallization processes yielding thin lamellar structures. In a number of cases (polyphosphazenes, polysiloxanes, see below) the crystalline polymorphs obtained from the chain-extended precursor differ from those obtained from solution. 

For webs, the substrate electrode is usually a vapor-deposited, semitransparent metal layer (Ritchie and Fenn, 1987 Chen, 1993). Al, Ni, and Cr are commonly used. The use of semi-transparent electrodes permits the use of rear exposures for erase purposes. In the case of drums, the metal cylinder serves as the electrode. Usually, a thin, less than 1 pm, blocking layer is interposed between the electrode and the photoreceptor to prevent charge injection. This layer must not be so thick that a residual potential builds up during cycling. Many insulating polymers have been used acrylic polymers, epoxy resins, polyamides, polyesters, polyphosphazenes, polysiloxanes, polyurethanes, vinyl polymers, etc. 

In addition to the termination of living poly(dichlorophosphazene) with phos-phoranimine-terminated poly(dimethylsiloxane), another method has been presented to synthesize poly(phosphazene-siloxane) block copolymers. Hydrosilyla-tion reactions of hydride-terminated poly(dimethylsiloxane) and allyl-terminated polyphosphazenes (210a, 210b) have been shown to yield polyphos-phazene-h/ocfc-polysiloxane-h/oc/c-polyphosphazene polymers (21 la, 21 Ib). ... 

Species that combine the properties of organosilicon compounds and phos-phazenes are prepared by the linkage of organosilicon side groups to a small molecule cyclic or linear high polymeric phosphazene skeleton. This is particularly important for high polymeric derivatives in which hybrid properties typical of polysiloxanes (silicones) and polyphosphazenes - may be obtained. 

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