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. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48163.