Precise Synthesis of Poly(silphenylenesiloxane)s with Epoxy Side Functional Groups by Tris(pentafluorophenyl)borane as a Catalyst

Abstract

ABSTRACT:1,!-Dimethylhydroxysilyl, -dimethylhydrosilyl, -dimethylmethoxysilyl -terminated tetramethylsilphenylenesiloxane prepolymers were prepared by sequential palladium-catalyzed dehydrocoupling polymerization of 1,4-bis(dimethylsilyl)benzene with water, reduction with lithium aluminium hydride, and palladium-catalyzed methanolysis. 1,4-Bis[(glycidyl-or cyclohexene oxide-functionalized alkyl)methylhydrosilyl]benzene and methyldimethoxysilanes with the same epoxy groups were synthesized by hydrosilylation of 1,4-bis(methyldihydrosilyl)benzene and methyldimethoxysilane with (terminal olefin-functionalized alkyl) substituted epoxides in the presence of platinum catalyst. 1,4-Bis[(glycidyl-or cyclohexene oxide-functionalized alkyl)methyl(hydroxy or methoxy)silyl]benzenes were obtained by hydrolysis and methanolysis of the hydrosilyl derivatives. Poly(silphenylenesiloxane)s with epoxy side groups were synthesized by hetero-polycondensation of the hydrosilane, hydroxysilane and methoxysilane functional groups in the prepolymer and 1,4-bis[(epoxy-functionalized alkyl)methylsilyl]benzene, or 1,1-dimethoxy(epoxy-functionalized alkyl)methylsilane in the presence of a catalyst. Tris(pentafluorophenyl)borane was found to be an excellent catalyst for the polymerization. Cross-linking a polymer with 1,4-diaminobenzene gave stretchable polymer film by solution cast method. Modern technologies have continuous demands on development of high-temperature elastomeric materials. Polysiloxanes are a kind of good candidates as high-temperature elastomer because of the property originated from flexible and heat-resistant Si-O-Si backbone, which is also the origin of good dielectric and surface properties, and so on. 1-3However, some thermal degradation reaction of polysiloxanes was noticed at high temperature. Corriu 4 elucidated that the main course of degradation of polysiloxane is the intermolecular exchanges of Si-O bonds, followed by intramolecular exchanges of Si-O bonds to depolymerize. Incorporation of rigid aromatic units into the siloxane backbone generally interrupts the siloxane redistribution reaction at high temperature, and improves both mechanical and thermal properties without simultaneous loss of other good features of polysiloxanes. Thus, polysilarylenesiloxanes, derivatives of polysiloxanes by partially replacing -O-by arylene groups, show better thermal and mechanical property than polysiloxanes. 2,3,5,6 Polysilphenylenesiloxanes, a class of typical polysilarylenesiloxane, were intensively reported as materials possessing thermal stability and satisfying low temperature elasticity, although their crystallinity is usually higher than polysiloxanes, which is a possible obstacle in various applications, for instance, application in electronic device materials as a thin film. One of the attractive aspects of these polymers is the easiness of introducing variety of functional substituents, such as vinyl, phenyl, hydrido, flouroalkyl, etc. 7-11These functional groups were found to significantly affect the thermal p...

An Approach to Epoxy Resins: Oxysilylation of Epoxides

“…However, the “hardener” consists of compounds containing two or more Si–H groups, and the reaction is affected using catalytic amounts of B­(C 6 F 5 ) 3 . The curing reaction adds Si–H across one epoxide C–O bond to form new Si–O and C–H bonds coincident with ring opening. − We term this reaction oxysilylation, as suggested in Scheme .…”

Metal-Free Room-Temperature Vulcanization of Silicones via Borane Hydrosilylation

“…Originally developed by Piers and Parks for the hydrosilylation of aldehydes, ketones, and esters, 20 it has been further extended to amides, 21 olefins, 22,23 quinolines, 24 and nitriles. 25 While previous work has focused on small-molecule transformations, B(C 6 F 5 ) 3 -catalyzed hydrosilylation has been employed in polymer chemistry to produce a variety of Si−O-containing polymers, including polysiloxanes via the oligomerization of dihydrosilanes, 26,27 poly-(silphenylenesiloxane)s via the polycondensation of dihydrosilanes and dialkoxysilanes or dihydroxysilanes, 28,29 and poly(silyl ethers) via the polycondensation of dihydrosilanes and dihydroxysilanes, 30 dienes, 31 or diketones. 32 The use of B(C 6 F 5 ) 3 in vulcanization, however, has been limited because previous examples are based on the reaction of hydrosilanes with alkoxysilanes or other nonatom-efficient partners, 33−37 with the evolved gaseous byproducts used to produce foams or removed prior to full cure.…”

“…Originally developed by Piers and Parks for the hydrosilylation of aldehydes, ketones, and esters, it has been further extended to amides, olefins, , quinolines, and nitriles . While previous work has focused on small-molecule transformations, B­(C 6 F 5 ) 3 -catalyzed hydrosilylation has been employed in polymer chemistry to produce a variety of Si–O-containing polymers, including polysiloxanes via the oligomerization of dihydrosilanes, , poly­(silphenylenesiloxane)­s via the polycondensation of dihydrosilanes and dialkoxysilanes or dihydroxysilanes, , and poly­(silyl ethers) via the polycondensation of dihydrosilanes and dihydroxysilanes, dienes, or diketones …”

Synthesis and Properties of Silphenylene-containing Epoxy Resins with High UV-stability

“…For instance, the incorporation of silarylene units like silphenylene and silnaphthylene into the polysiloxane backbone significantly enhances its thermal stability under oxidative and inert atmospheres. There are a few reports of silarylene-containing epoxy resins (13), and to our knowledge, there is none about utilizing them for LED encapsulation. We considered that the d-p π coordinate bonds between silicon atoms and aryl groups can effectively decrease the electron cloud density of the aryl, and thus endowed the silarylene-containing epoxy resin with high stability to heat and ultraviolet irradiation.…”