P(NIPAm-co-TMSPMA)/Silica hybrid microgels: Structures, swelling properties and applications in fabricating macroporous silica

P(NIPAm-co-TMSPMA)/Silica hybrid microgels were prepared by in-situ sol–gel process of tetraethyl orthosilicate (TEOS) in the presence of thermo-sensitive P(NIPAm-co-TMSPMA) microgels, which were synthesized via surfactant-free emulsion copolymerization (SFEP) of N-isopropylacrylamide (NIPAm) and 3-(trimethoxysilyl)propylmethacrylate (TMSPMA). At preparation temperature above the volume phase transition temperatures (VPTT) of P(NIPAm-co-TMSPMA) microgels, i.e. 50 °C, the silica nanoparticles could not penetrate into the collapsed microgels but uniformly covered on the surface of microgels and the obtained P(NIPAm-co-TMSPMA)/Silica hybrid microgels had the raspberry-like structures. Whereas, at preparation temperature below the VPTT, i.e. 25 °C, the silica nanoparticles were uniformly distributed inside the swelled microgels and the resultant P(NIPAm-co-TMSPMA)/Silica hybrid microgels exhibited uniform organic–inorganic hybrid structures. The presence of silica nanoparticles restricted the swelling–deswelling capability of P(NIPAm-co-TMSPMA)/Silica hybrid microgels and also prevented the merging of hybrid microgels during drying. Macroporous silica with ordered macropores could be easily fabricated by selectively calcinating the organic microgel component after the assembly of the P(NIPAm-co-TMSPMA)/Silica hybrid microgels.