Polycarbosilane-modified styrene-based polymers with ultra-low dielectric constant, greatly enhanced mechanical strength and thermal stability

Ultra-low dielectric constant (a) materials have aroused much attention in recent years. in this work, taking styrene polymers as an example which have low a but poor mechanical strength, we find a hopeful way to fulfill the task via graft copolymerization. The graft copolymerization was conducted by a reaction of silacyclobutene pendant groups on polystyrene polymer with disilacycobutene (DSCB) via ring-opening reaction, forming polystyrene with polycarbosilane structures on side chains. The curing of graft polystyrene via reaction of BCB results in the polycarbosilane-modified styrene resins. Cured graft polystyrene exhibited T-d around 460 degrees C, which is greatly higher than unmodified styrene resins. Nanoindentation measurement showed that as compared with unmodified styrene resins, the modulus of cured graft polystyrene was greatly increased from 0.18 to 8.1 GPa. More attractively, the graft polystyrenes also exhibit significantly low epsilon. The lowest value for as-prepared graft polystyrenes reaches to similar to 1.85, thus providing a new strategy to achieve ultra-low a via grafting technique.