Amphiphilic Graft Copolymers of Hydroxypropyl Cellulose Backbone with Nonpolar Polyisobutylene Branches

The novel amphiphilic graft copolymers with hydrophilic hard polar hydroxypropyl cellulose (HPC) backbone and hydrophobic soft nonpolar polyisobutylene (PIB) branches have been successfully synthesized through nucleophilic substitution reaction of living PIB chains carrying oxonium ions with the −OH groups along HPC backbone. The PIB branch length in the graft copolymers could be designed by living cationic polymerization and the grafting density could be adjusted by PIB+/−OH molar ratio. The living PIB chains carrying oxonium ion were prepared by transformation of allyl bromide end groups in the presence of AgClO4 and silver nanoparticles (3.2±0.3 nm, 0.7 wt%–1.8 wt%) generated in situ from AgBr. The phase-separation morphology was formed in the graft copolymers due to their incompatibility between backbone and branches. The hydrophilicity on the surface of graft copolymer films could be turned to hydrophobicity by increasing grafting density or/and length of PIB branches. The soft PIB segments in graft copolymers provided an unique surface via self-assembly for anti-protein adsorption against bovine serum albumin. A small amount of Ag nanoparticles in the copolymers contributed to good antibacterial activities against Staphylococcus aureus or Escherichia coli.