Linear polymers polysiloxanes

The most important silicon-oxygen systems of course, are the linear polysiloxane polymers. These important materials are resistant to heat or oxidation, exhibit little change in properties with temperature, are water repellent and biologically inert. The history of the discovery and development of silicones has been summarized172. 

While the basic chemistry and physical behavior of linear polysiloxane polymers is well studied and, generally speaking, well understood, simple unmodified polysiloxanes are rarely encountered in real world applications. The majority of commercial silicone products are complex multicomponent formulations which take the form of elastomeric rubbers, adhesives, sealants, coatings, fluids or gels. Silicone elastomers are chemically crosslinked networks of linear polysiloxanes which exhibit poor mechanical properties in their native, unmodified state [1]. In order to obtain the desired combinations of mechanical, physical and chemical properties for a specific application, commercial high-performance silicone elastomers... 

Chojnowski, J. Cypry k, M. Synthesis of Linear Polysiloxanes. In Silicon-Containing Polymers. The Science and Technology of Their Synthesis and Applications, Jones, R. G., Ando, W., Chojnowski, J., Eds. Kluwer Dordrecht, 2000 Chapter 1, pp 3—41. 

Chojnowski J, Cypryk M (2000) Synthesis of Linear Polysiloxanes. In Jones RG, Ando W, Chojnowski J, editors. Silicon-Containing Polymers. Dordrecht Kluwer Academic Publishers, pp. 3 1... 

Linear polysiloxanes having reactive terminal groups are often condensed with reactive orgaiuc polymers. For example, hydroxy-terminated siloxanes can be condensed with a carboxy-terminated polyester, as illustrated in equation (28). The resulting polymers behave as thermoplastic elastomers, having some of the desirable properties of both siloxanes and polyesters. Similar condensation reactions have been used to synthesize siloxane copolymers with polyamides, polyethers, polycarbonates, and so on. 

Ml he history OF LINEAR POLYSILOXANES dates back at least 116 years (i), and research activity in this area steadily accelerated during this period as synthetic methods improved and as the fundamental nature of polymers became clear. The industrial prominence of poly(dialkylsiloxane)s was a particularly strong impetus to the development of this field (2). Thus, a large body of literature has accumulated, which has been extensively reviewed. The reviews by Wright (3), Sigwalt (4), and Kendrick et al. (5) are excellent and current, whereas that by Voronkov et al. (6) covers the earlier literature. Siloxane polymerization has now become suflSciently commonplace, so that it is sometimes discussed in general textbooks on polymer chemistry (7). 

The polymerization reaction leads to an equilibrium mixture of linear polysiloxanes and cyclic siloxanes, wheras the equilibrium of the polycondensation reaction can be shifted to the polymer side by removing the condensation water. 

Silicone Polymers - Laser flash photolysis studies on poly(silylenes) generates radical cations along with silyl radicals and polysiloxane composities for the space shuttle have been found to be stable to far UV light exposure. Linear polysiloxanes have been found to be more unstable than branched or crosslinked polymers while the transparency of poly(methylphenylsilane) increases with light exposure. Photooxidised polysiloxanes doped with iodine are converted into semiconductors. ... 

Siloxane units making up linear polysiloxane molecules are designated "D" (difunctional), and are superscripted in the same fashion as above subscripts refer to chalnlength of linear polymers. 

Figure 2.11 Fluids, resins, and elastomers. Silicone fluids are linear chains where molecular weight determines viscosity, silicone resins are branched polymers and thus glass-like solids and silicone elastomers are composed of long, linear polysiloxane chains reinforced with an inorganic filler and cross-linked. (From Plastics Handbook, Modern Plastics Magazine, McGraw-Hill, New York, 1994, p. 86.)...

Ganicz, T. Pakula, T. Fortuniak, W. Bialecka-Florjanczyk, E., Linear and Hy-perbranched Liquid Crystalline Polysiloxanes. Polymer 2005, 46,11380-11388. 

Monosubstituted POSS have been incorporated into various elastomers such as linear polysiloxanes or hyperbranched polysiloxanes. POSS have also been grafted with other polymers or copolymers, for example, styrene-butadiene-styrene triblock copolymer, which influenced rheological and morphological properties of this copolymer (389). 

Silicone Resins. Silicone resins are an unusual class of organosiloxane polymers. Unlike linear polysiloxanes, the typical silicone resin has a highly... 

The linear polysiloxane (diphenylsilylene)oxy is represented by the structure shown as Figure 14. The lUPAC name also differs appreciably from the CAS name. According to the mles for linear organic polymers, this polymer would be oriented and named poly[oxy(diphenylsilylene)] (13). 

Radical addition of thiol or thiol-modified support to the vinyl group gives the respective thioether linkage 34 and represents one of the most convenient ways to immobilize Cinchona alkaloids [163, 172]. There are also few examples of platinum-catalyzed hydrosilylation of Cinchona alkaloids toward 11-silyl-substituted derivatives 35 with the use of monomeric silanes or polysiloxane polymers [173-175]. De Vries reported rhodium-catalyzed hydroformylation of the four main members of Cinchona alkaloids carried out on a hundred gram scale. Under optimized condition, linear aldehydes 36 were selectively obtained with the yield over 80% [176]. 

This paper will summarize work performed in our laboratory on the synthesis of hybrid materials using cyclic oligo- and linear polysiloxanes in conjunction with polystyrenes, acrylates and methacrylates synthesized by ATRP. Architectural variation will also be discussed including linear, graft and star polymers. 

Simultaneous and sequential IPNs based on various polymeric systems have been prepared using polydimethylsiloxane (PDMS) as the host network (3-8). These systems include poly(ether-urethane), polystyrene, poly(2,6-dimethyl-1,4-phenyleneoxide), polyacrylic acid, PDMS, polymethylmethacrylate, polyethylene oxide (PEO)... as the guest network. Some semi-interpenetrating networks (s-IPNs) based either on a linear polymer embedded in a polysiloxane network (5,9,10) or on a linear polysiloxane combined with a PEO network (8) have also been described. In some cases, PDMS has been replaced by polyaromatic siloxanes such as polydiphenyl or polymethylphenylsiloxanes (10-12). The focus of this paper concerns the preparation and properties of IPNs and s-IPNs based on polysiloxanes and poly(diethyleneglycol bis-allylcarbonate) (13,14). 

Separation of the two stages of polymerization is possible because the propagation of strained monomers is much faster than the backbiting and chain transfer. In contrast to the entropy-driven polymerizations of unstrained cydosiloxanes, the driving force for the polymerization of cydotrisiloxanes is the enthalpy of the ring-strain release. If the polymerization is quenched at a proper moment, a high yield of polymer maybe obtained even in the case when the equilibrium concentration of linear polysiloxane is very low. 

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