Synthesis And Properties Of Benzocyclobutene-introduced Polycarbosilanes

BCB have been considered as one of the most promising low-dielectric materials owing to their superior thermal, film-forming, low dissipation factor and low dielectric properties. However, BCB-based structures alone are difficult to meet the performance requirement of next-generation low-dielectric materials. Thus, it is needed to utilize the structure features of high performance polymers. In general, high performance polymers possess main-chain rigid or cross-linked structures. In this work, based on this rule, BCB units were introduced into the organosilicon polymers to synthesize a series of novel alternating copolymers containing BCB units. The thermal and dielectric properties of polymers and curing behavior were investigated systematically.In this work, a kind of benzocyclobutene/vinylphenyl-introduced polycarbosilanes(PVBCS) were synthesized by H2PtCl6 catalyzed ring-opening copolymerization of 4-(1-methylsilacyclobutyl) benzocyclobutene(4-MSCBBCB) and 1-methyl-1-(4-vinylphenyl) silacyclobutane(1-MVPSCB). By directly introducing photo-active groups on the pendants of polycarbosilanes, the PVBCS was endowed with photopatternability without additionally using any photo-initiators or photo-crosslinkers. DSC and FTIR characterization demonstrated that the PVBCS was UV&thermally curable. The UV curing was conducted at ambient temperature and the thermally curing was performed above 200 oC. TGA curves of the cured PVBCS indicated that the 5% weight loss temperature is 473 oC, which is above the required temperature limit. The cured PVBCS also has low dielectric constant of 2.32-2.40 in the range of 1 k~1 MHz. The high temperature performance and low-dielectric constant could be attributed to the polycarbosilane main-chain structure and the benzocyclobutene-based cross-linked structure.A kind of benzocyclobutene-introduced polycarbosilane-block-polylactic acid diblock copolymer(PSB-b-PLA) were synthesized by SnOct2 catalyzed ring-opening copolymerization of lactide and macromolecular initiator(PSB-OH) which wassynthesized by s-Bu Li catalyzed ring-opening polymerization of 4-(1-methylsilacyclobutyl) benzocyclobutene(4-MSCBBCB) and then end group modified with 1,2-epoxypropane. PSB-b-PLA structure were characterized by NMR and FT-IR, the direct introduction of low temperature degradation of poly lactic acid(PLA), the formation of porous polymer film with low dielectric constant(k=2.1 in the range of 1 k~1 MHz) by self-assembly after curing and degradation of PLA segment.