Polypropylene-based graft copolymers via CuAAC click chemistry

Abstract

Graft copolymers from commercial chlorinated polypropylene (PP-Cl) possessing either poly(ethylene glycol) (PEG) or poly(epsilon-caprolactone) (PCL) grafts are synthesized by copper (I)-catalyzed azide-alkyne cycloaddition 'click' reaction (CuAAC). For this purpose, azido-functional polypropylene is prepared by nucleophilic substitution of chlorine groups of PP-Cl with azidotrimethylsilane-tetrabutylammonium fluoride. Whereas, the clickable alkyne end-functional PEG and PCL are independently synthesized by esterification reaction of poly(ethylene glycol) methyl ether with 4-pentyonic acid at room temperature and ring-opening polymerization of epsilon-caprolactone using stannous octoate as catalyst and propargyl alcohol as initiator. Finally, the corresponding graft copolymers, PP-g-PEG and PP-g-PCL, with different surface properties were successfully synthesized by CuAAC 'click' reaction under mild condition. Spectral, chromatographic and thermal analyses at various stages prove the formation of desired polypropylene-based graft copolymers with well-defined properties. Furthermore, the water contact angle values of PP-Cl, PP-g-PEG and PP-g-PCL are found as 90 +/- 1 degrees, 78 +/- 1.8 degrees and 83 +/- 2.1 degrees, respectively.