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J. Chruściel


Progress in the chemistry of polymethylhydrosiloxanes

Polimery 1999, No 7-8, 462


DOI: dx.doi.org/10.14314/polimery.1999.462


Summary

Syntheses and practical applications of polymethylhydroxysiloxanes (PMHS) are reviewed. Synthesis of new block PMHS containing single (isolated) MeHSiO units (PDMS-b-PMHS) is described, viz., Me3SiO[(Me2SiO)mMeHSiO]n (Me2SiO)mSiMe3 (m = 2, 6,1 0 ,1 4 , ~ 50; n = 5, 10 or 15) where n is the average number of Si-H groups in the macromolecule. These new PMHS were prepared by heteropolycondensation of dimethylsiloxanediols HO(Me2SiO)mH (m = 2, 6, 10, 14, ~ 50) with methyldichlorosilane MeHSiCl2 in diethyl ether as solvent in the presence of Et3N and (4-dimethylamino)pyridine (DMAP), and in the case of tetramethyldisiloxane-l,3-diol, in the presence of pyridine only. The block structure of PMHS was confirmed by IR and NMR spectral methods and by elementary analyses. Four new compounds were isolated: Me3Si[(Me2SiO)mMeHSiO]n(Me2SiO)mSiMe3 (m = 2, n = 1, 2; m = 6, n = 1) and c-[(Me2SiO)2MeHSiO]2 and their chemical structures were established by spectral methods (29Si-NMR) (Table 4), whereby the block microstructure of PDMS-b-PMHS was confirmed. Seven homologous series of PMHS were synthesized, endowed with statistical chain structures and molecular compositions identical with those of block PMHS and their microstructure was determined by 2


Keywords: polymethylhydrosiloxanes, block and random polysiloxanes, synthesis, microstructure, 29Si-NMR, heteropolycondensation, hydrolytic polycondensation, cationic polymerization

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