Synthesis, thermal and mechanical properties of benzocyclobutene-functionalized siloxane thermosets with different geometric structures

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• 作者：Jun Yang ; Yuanrong Cheng ; Fei Xiao ; ^{feixiao@fudan.edu.cn}
• 关键词：Benzocyclobutene-functionalized resins ; Curing behaviors ; Mechanical properties ; Thermal properties
• 刊名：European Polymer Journal
• 出版年：2012
• 期刊代码：35_00143057
• 类别：ms
• 出版时间：April, 2012
• 卷：48
• 期：4
• 页码：751-760
• 文件大小：1152 K

摘要

A series of benzocyclobutene-functionalized siloxane thermosets were prepared to investigate the relationship between the monomer鈥檚 chemical structure and the properties of the corresponding polymer. Monomer 1,1,3,3-tetramethyl-1,3-bis[2鈥?(4鈥?benzocyclobutenyl)]vinyldisiloxane (DVS-BCB) and 1,3,5,7-tetramethyl-1,3,5,7-tetra[2鈥?(4鈥?benzocyclobutenyl)]vinylcyclotetrasiloxane (CYC-BCB) were synthesized by Heck reaction. Copolymer Poly(DVS-BCB-co-POSS) was obtained through incorporating octavinyl-T8-silsesquioxane (Vinyl-POSS) into DVS-BCB matrix via Diels-Alder reaction. The oligomers, P-DVS-BCB, P-CYC-BCB and P-Poly(DVS-BCB-co-POSS), were obtained by refluxing the mesitylene solution of the BCB monomers at the BCB ring opening temperature. The BCB monomers and oligomers showed a similar curing behavior with an exothermic peak temperature near 260 掳C. The curing kinetic parameters, the apparent activation energy (E_a), the frequency factor (A) and the reaction order (n), were obtained by non-isothermal DSC method. The BCB polymers possessed good thermal stability (T_d > 450 掳C in N₂). Due to the highly crosslinked network structure, CYC-BCB polymer exhibited higher glass transition temperature, higher modulus and lower coefficient of thermal expansion than DVS-BCB and Poly(DVS-BCB-co-POSS) polymers. Moreover, the BCB polymers also demonstrated low dielectric constants (<2.8 at 1 MHz) and low water absorptions. The films prepared from the BCB oligomer solution showed a well planarization (root-mean-square roughness <0.5 nm).