An efficient route to synthesize thermoresponsive molecular bottlebrushes of poly[o-aminobenzyl alcohol-graft-poly(N-isopropylacrylamide)]

A new strategy to prepare thermoresponsive molecular bottlebrushes of poly[o-aminobenzyl alcohol-graft-poly(N-isopropylacrylamide)] [P(oABA-g-PNIPAM)] via the grafting-through approach by combination of the RAFT polymerization and acid-catalyzed polymerization of aniline derivatives is proposed. Ascribed to the efficient acid-catalyzed polymerization, the present strategy affords the convenient synthesis of the thermoresponsive molecular bottlebrushes of P(oABA-g-PNIPAM). In the molecular bottlebrushes of P(oABA-g-PNIPAM), the thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) chains are densely grafted to the poly(o-aminobenzyl alcohol) backbone, which leads to strong steric repulsion among the side chains of PNIPAM and therefore retards the soluble-to-insoluble phase transition of the tethered PNIPAM chains. It is found that the soluble-to-insoluble phase transition of P(oABA-g-PNIPAM) takes place at a higher lower critical solution temperature (LCST) than that of the linear PNIPAM counterparts, and the PNIPAM side chains in P(oABA-g-PNIPAM) are just partly dehydrated even at the temperature above LCST, which is different from the linear PNIPAM counterparts.