Fine‐tuning of phase behavior of oxazoline copolymer‐based organic–inorganic hybrids as solid‐supported sol–gel materials

Abstract

Silica-supported organic-inorganic polymer hybrids were synthesized via in situ sol-gel condensation of silica monomer in the presence of oxazoline copolymer. A stable copolymer of 2-ethyl-2-oxaoline and 2-isopropyl-2-oxazoline was prepared using methyl p-tosylate as the living polymerization initiator with molecular mass of 4200 g mol −1 . Lower critical solution temperature (LCST) of this copolymer was thermally found to be at 77 C. The copolymer was mixed with tetramethoxysilane (TMOS) in different amounts (0.039:1 to 0.158:1 weight ratios) via in situ sol-gel condensation to produce organic-inorganic hybrids including thermosensitive copolymer. Tuning of these solid-supported materials showed sharp phase transitions changes in a temperature range from 42 to 58 C, which was confirmed using differential scanning calorimetry. Enthalpy of the phase transition was also calculated using the area above the endothermic peak. A typical concave curve was obtained for LCST-type phase diagram suggesting the dependence of phase transition temperature on the concentration of the copolymer in the hybrid.