The synthesis and characterization of multiarm star-shaped graft copolymers of polycaprolactone and hyperbranched polyester

[Display omitted] •Synthesis of block copolymers of polycaprolactone without drying of ε-CL.•Synthesis of block copolymers of polycaprolactone without addition of catalyst.•Thorough analysis of graft copolymers.•Tuning of graft copolymer’s thermal properties. Simple and efficient method for the synthesis of multiarm star-shaped graft copolymers of polycaprolactone (PCL) and hyperbranched polyester Boltorn H40 (BH40) is presented. Grafting of ε-caprolactone (CL) from BH40 proceeds without the addition of a catalyst, and without drying of CL. p-Toluenesulfonic acid, which is added as a catalyst during the synthesis of BH40, acts also as a catalyst for CL grafting. Terminal –OH groups of BH40 react with CL, while the linear ones remain almost intact, except at high reactant ratio and prolonged reaction time. The presence of water changes the copolymer structure and properties, but the influence is minor. Star-shaped copolymers were prepared in a mass ratio of BH40:CL 1:1 to 1:10 and characterized. Glass transition temperature is decreasing while the degree of crystallinity is increasing with the increasing reactant ratio.