Recently, thermoresponsive synthetic polymers, which have shown a reversible phase separation in an aqueous solution, have attracted much attention and their applications are presented in various material scenes.1, 2, 3, 4, 5, 6 A variety of investigations on thermoresponsive materials have been presented, especially, in the fields of microencapsulation, biosensors and drug delivery.7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 Owing to the interest in such utilities we have also initiated studies on thermoresponsive organic–inorganic hybrids based on polysilsesquioxane (PSQ). The combination of PSQ with functional polymers is expected to present useful and practical hybrid materials that maintain the essential characteristics of the inorganic polysiloxane structure, such as improved mechanical strength, weatherability and heat durability.18, 19, 20, 21 In fact, the modifications of PSQ or oligo-silsesquioxanes by grafting polymeric components have been reported by several groups.22, 23, 24, 25, 26 Our previous efforts, in which a polymer of N-isopropylacrylamide (NIPAM) was chosen and introduced as the graft chain into PSQ backbone, focused on thermoresponsive properties and were also examples of modified hybrids.27, 28 In the graftings from PSQ, one of the findings in the grafting of poly(NIPAM) was that at least 20 monomer units of NIPAM in a graft chain were necessary to maintain a good solubility in water. Consequently, the copolymerization of NIPAM with N,N-dimethylacrylamide was required when a small number of NIPAM monomer units in one graft chain were grafted. Consequently, copolymerization of NIPAM with N,N-dimethylacrylamide was required when a small number of NIPAM monomer units in one graft chain were grafted. This leads us to conclude that a more hydrophilic polymeric component is favorable for the efficient synthesis of thermoresponsive PSQ derivatives, which show reversible hydrophobic aggregation at the lowest critical solution temperature (LCST).

The typical structures that cause thermoresponsive property usually contain hydrophilic amide or ethylenedioxy groups with hydrophobic alkyl groups;29, 30, 31, 32, 33 therefore, we designed readily obtainable functional groups that were formed by the simple addition reaction of 2–alkoxyethylamines to the isocyanato group. The functional group, which consisted of 2-alkoxyethylamino groups and a urea bond, was introduced into PSQ as a substituent. The thermoresponsive properties of PSQ were examined in a previous report.34 On the basis of its properties, to expand applicability of the functional groups for providing the thermoresponsive property, methacrylate polymer was chosen as a versatile polymeric component in this report.

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