The immobilization of poly(N-isopropylacrylamide) (PNIPAM) onto the surface of silica beads via hyperbranched polysiloxysilane (HBPS) was studied to develop a new material for cell cultivation. HBPS terminated with a vinyl functional group was synthesized by self-polymerization of an AB 2 monomer. The terminal vinyl group was converted into a chain-transfer agent for reversible addition fragmentation chain transfer (RAFT) polymerization. The obtained HBPS was immobilized on the silica surface by mixing silica beads and HBPS in hexane. The graft polymerization of PNIPAM onto the silica surface was achieved using RAFT polymerization. The molecular weights of the grafted polymers obtained by cleavage from the surface of silica beads using NaOH aqueous solution were in the range of 6000-23 000 and the polydispersity index values were 1.4-1.6. The grafted silica beads have been tested for cell cultivation. Silica-HBPS-g-PNIPAM with a higher molecular weight (M n ) of PNIPAM (cleaved PNIPAM M n ¼ 14 800 and 23 700) showed a thermo-reversible phase transition at approximately 34 1C, and controlled cell adhesion and detachment was demonstrated with these beads.

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