Siloxane-containing block copolymers polymerization

Siloxane-containing block copolymers are often prepared by step-growth or condensation polymerization of preformed diftmctionalized siloxane oligomers with other diftmctionalized monomers or oligomers. Our current work (3, 4, 6-8) on siloxane chemistry includes the preparation of a number of functionalized oligomers, with emphasis on equilibration processes with the commonly available cyclic tetramer, octamethylcyclotetrasiloxane (D4), in the presence of a functionalized disiloxane or end blocker. 

Siloxane containing block or segmented copolymers can be synthesized either by living anionic polymerization of the cyclic organosiloxane trimers with appropriate vinyl monomer(, 4 ) or by step-growth or condensation copolymerization of preformed a,w-difunctional siloxane oligomers with conventional difunctional... 

Si NMR of siloxane systems has been used in studying organosilicone containing block copolymers to determine block length and chemical redistribution during polymerization. (85) Block copolymers of bisphenol A polycarbonate (BPAP) and polydimethyl-siloxane (PDMS) [20] were studied by both and Si NMR to determine a variety of structural parameters. 

Block copolymers containing polysiloxane segments are of great interest as polymeric surfactants and elastomers. Polycondensation and polyaddition reactions of functionally ended prepolymers are usually employed to prepare well-defined block copolymers. The living polystyrene anion reacts with a,co-dichloropoly(dimethyl-siloxane) to form multiblock copolymers398. ... 

One of the most important uses of end-functionalized polymers is the preparation of block copolymers.73,74 The reactions are identical to the chain extensions already mentioned, except that the sequences being joined are chemically different. In the case of the -OSilCR Y chain ends mentioned above, R is typically (CH2)3 5 and Y can be NH2, OH, COOH, CH=CH2, and so on The siloxane sequences containing these ends have been joined to other polymeric sequences such as carbonates, ureas, urethanes, amides, and imides. 

Tphe surface activity of block copolymers containing dimethylsiloxane units as one component has received considerable attention. Silicone-poly ether block copolymers (1,2,3) have found commercial application, especially as surfactants in polyurethane foam manufacture. Silicone-polycarbonate (4, 5), -polystyrene (6, 7), -polyamide (8), -polymethyl methacrylate (9), and -polyphenylene ether (10) block copolymers all have surface-modifying effects, especially as additives in other polymeric systems. The behavior of several dimethylsiloxane-bisphenol A carbonate block copolymers spread at the air—water interface was described in a previous report from this laboratory (11). Noll et al. (12) have described the characteristics of spread films of some polyether—siloxane block co-... 

Summary Well-defined amphiphilic block copolymers containing a poly(dimethyl siloxane) (PDMS) and a poly(ethylene oxide) (PEO) block were synthesized by ringopening polymerization of hexamethylcyclotrisiloxane, followed by chain extension with a PEO block of a defined length. These amphiphilic molecules were used as structure-directing agents in a solvent evaporation-driven synthesis approach to self-assembled mesostructured silica films. In addition, a general theoretical approach for an understanding and ultimately a prediction of the phase behaviour of block copolymers is presented. 

As with other classes of polymers considered above, ring-opening polymerization has also been employed as the basis of another general approach to the synthesis of siloxane block copolymers— in this case by the anionic polymerization of cyclopolysiloxanes in ways which yield either polysiloxane-b/ock-polysiloxane products or those containing polysiloxane and other structural classes of blocks. 

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