Crystalline and micellar properties of amphiphilic biodegradable chitooligosaccharide-graft-poly(ε-caprolactone) copolymers

Amphiphilic chitooligosaccharide-graft-poly(ε-caprolactone) (COS-g-PCL) copolymers were controllably synthesized using protection/deprotection technique of COS via trimethylsilyl groups and ring-opening polymerization of ε-caprolactone. Their crystalline properties were investigated with differential scanning calorimetry. With the increase of PCL content in graft copolymer, the values of ΔH and Xc became enhanced, and Tm shifted to higher temperatures. Micellar properties of amphiphilic graft copolymers were studied. Spherical micelles from COS11-g-PCL132 were prepared. However, due to the higher PCL content, the spherical micelles from COS11-g-PCL520 easily confused together so that the complicated network morphology was formed. Interestingly, hierarchical structure was observed in the formed network morphology, as being driven by the crystallization of PCL segments in micelles. Using pyrene as a model compound, the micelles from COS11-g-PCL132 copolymers can be loaded by hydrophobic therapeutic agent, potentially offering an appropriate vehicle for drug delivery.