Organosilicon hydrides in macromolecular design: Reactions of chain-transfer and hydrosilylation
Introduction
Earlier [1] on an example of polymerization MMA it has been shown that organohydrodisilanes are effective chain-transfer agents comparable to the strongest ones of the known molecular-weight regulators of polymers, e.g. mercaptans [2]. A special feature of these chain-transfer agents proved to be a strong influence of silicon atom sequences on their reactivity.
The goal of the present paper was the comparison of the reactivity of silicon hydrides as chain-transfer agents in the polymerization of monomers of a different polarity such as styrene and methyl methacrylate and the study of molecular weight characteristics of the polymers prepared in the presence of these compounds.
Section snippets
Materials
Fifteen organosilicon hydrides (OSH) containing of 98–99 % the basic substance were investigated in this work (Table 1). Pentamethyldisilane (1), 1,1,2,2-tetramethyldisilane (4), 1,2-dimethyldisilane (7), bis(trimethylsilyl)methylsilane (8), tris(trimethylsilyl)silane (9) were synthesized by the known methods described in Refs. [3], [4], while bis(trimethylsiloxy)methylsilane (13) and 1,2-bis(silyl)ethane (14) were prepared as demonstrated elsewhere [5], [6], respectively. The syntheses of
Reactivity of organosilicon hydrides as chain-transfer agents in radical polymerization of styrene and methyl methacrylate
The experimental values of the relative constants of the chain-transfer onto OSH in the polymerization of styrene and MMA up to 10 wt.% of conversion are given in Table 2. As the data in Table 2 show, the activity of OSH in the chain-transfer reaction in the radical polymerization depends on their chemical structure and the monomer nature. The influence of the chemical structure of OSH on their reactivity is mainly explained by the availability in their molecules of a sequence from two and more
Conclusions
Organosilicon hydrides as a new class of chain-transfer-agents in radical polymerization are investigated. We found that the reactivity of organosilicon hydrides depends on its chemical structure and activity of monomer. It is shown that the organosilicon hydrides may be used in macromolecular design. Block copolymer PMMA-polystyrene was prepared by means of combination of the chain-transfer reaction and the reaction of hydrosilylation.
Acknowledgements
The IR-spectra of the polymers were measured at the Analytical center of the Institute of Organometallic Chemistry of Russian Academy of Science with financial support of RFBR (Project 96-03-40-042). The authors express their sincere appreciation to S.Ya. Khorshev and T.G. Mushtina for the measurement of IR-spectra and M.A. Lopatin for the help rendered in the construction of correlation dependences.
References (17)
- et al.
Aliphatic organopolysilanes
Adv Organomet Chem
(1968) - et al.
Organodisilane hydrides: a promising new class of chain-transfer agents in free-radical polymerization
Polym Sci B
(1998) Free radicals in a solution
(1960)Properties and preparation of Si–Si linkages in inorganic and organic silicon compounds
Top Curr Chem
(1974)- et al.
The addition of silicon hydrides to olefinic double bonds. X. Addition to phenylalkenes. The nuclear magnetic resonance proton spectra of (phenylalkyl)silanes
J Org Chem
(1964) - et al.
Synthesis and properties of disilylmethane, 1,3-disilylpropane and 1,3,5-trisilen-2,4,6-trimethylencycloalkane
Dokl AN SSSR
(1953) - et al.
Reactions of methylchlorodisilanes with Grignard reagents
Izv Acad Nauk Ser Chem
(1995) - et al.
The methylsubstituted disilanylsesquioxanes and disilanylsiloxanes
J Obshch Khim
(1990)