Synthesis of ladder-like polysilsesquioxane with well-defined graft polymers

Well-defined hybrid polymers consisting of organic polymers grafted from inorganic backbone were synthesized by atom transfer radical polymerization (ATRP). Ladder-like structured polysilsesquioxane functioned as both ATRP initiator and hard inorganic backbone, while the organic polymers grafted were hard styrene and soft n-butyl acrylate. Ladder-like structured poly(chloromethylphenylsilsesquioxane) (LCMPSQ) was synthesized using sequential two-step reactions with (-chloromethyl)phenyltrimethxysilane as a monomer in one bath in the presence of K₂CO₃ as a base catalyst (M_w=6,000). Obtained LCMPSQ was then used as a multi-functional macroinitiator for graft polymerization of styrene (St) or/and n-butyl acrylate (nBA) monomers via ATRP using a CuCl catalyzed system, which gave three types of hybrid graft polymers: poly(styrene-g-silsesquioxane) (PS-g-PSQ), poly(nBA-g-silsesquioxane) (PnBA-g-PSQ) and poly(styrene-ran-nBA-g- silsesquioxane) (PS/nBA-g-PSQ). The hybrid graft polymers were prepared with various organic/inorganic weight fractions by changing the molecular weights of the organic graft polymers, which showed narrow molecular weight distributions (PDI < 1.4) on less than 50% of the polymerization conversion.