Synthesis and properties of hyperbranched polymers by polymerization of an AB3-type incompletely condensed cage silsesquioxane (IC-POSS) monomer

An incompletely condensed cage silsesquioxane (IC-POSS)-based AB 3 -type monomer, tris(dimethylsilyl)-p-vinylhexaisobutyl-IC-POSS (3), was prepared by the corner-cleaved reaction of vinylheptaisobutyl-POSS (1) and subsequent capping reaction with chlorodimethylsilane. The structure of 3 was confirmed by FT-IR; H-1-, C-13-, and Si-29-NMR; and HR-FAB-MS analyses. These analyses also suggested 12.5 mol% contamination of tris(dimethylsilyl)-heptaisobutyl-IC-POSS (4). The hydrosilylation polymerization of 3 as an AB(3)-type IC-POSS monomer in the presence of Karstedt's catalyst in toluene at 80 degrees C overnight provided a soluble polymer with a number average molecular weight (M-n) and molecular weight distribution (M-w/M-n) of the polymer that are 3.9 x 10 3 and 1.39, respectively. The resulting hyperbranched polymer (HB) reacted with two molar equivalents of isoprenol or allylheptaisobutyl-POSS against the Si-H groups in the presence of Karstedt's catalyst in toluene at 80 degrees C for 7 h. The HB polymers before and after post functionalization with isoprenol or allylheptaisobutyl-POSS showed 1% weight loss at 298, 285, and 358 degrees C, respectively, under N-2. Introducing POSS units at the terminus significantly increased the thermal stability. The XRD pattern of the HB polymers showed a denser structure formed in the allylheptaisobutyl-POSS-terminated HB polymer. The refractive index of the HB polymer before post functionalization was 1.4376. Post functionalization with isoprenol and allylheptaisobutyl-POSS increased the refractive index to 1.4464 and 1.4573, respectively.