Grafting thermosensitive PNIPAM onto the surface of carbon spheres

Abstract Thermosensitive polymer poly(N-isopropylacrylamine) (PNIPAM) grafted-carbon spheres (CSs) composites were synthesized and investigate the influence of synthesis parameters on phase transition temperature in order to produce thermosensitive composites with different phase transition temperatures, which may be applied to different application fields. First, vinyl groups were introduced onto the surface of CSs by mixed acid oxidation and reacting with 3-methacryloxypropyl trimethoxysilane. Then, PNIPAM was grafted onto the surface of CSs by surface free-radical polymerization. According to the differential scanning calorimetric analysis, the PNIPAM-grafted CSs composites are temperature responsive. The weight ratio of monomer to CSs and the initiator dosage had great influence on the polymer shell thickness and the lower critical solution temperature (LCST) of the composites determined by the number of grafted polymer chain, chain length and the cross-link degree. The polymer shell thickness and the LCST of the composites increased with the increase of the amount of monomer in proper range, however, first increase and then decrease with the increasing initiator dosage. The cross-linking agent content affects critically the cross-link degree, and then the LCST. Therefore, the LCST of the PNIPAM-grafted CSs composites was adjustable by changing the synthesis parameters, which lays the basis for CSs application in different fields.