Isothermal crystallization of poly(ε–caprolactone) pcl in three‐armed copolymers

Abstract

Branched copolymers are a special class of polymeric materials in which are reflected the combined effects of polymer segments and architectural constraints of the branched architecture. In this work, three-armed graft copolymers, poly (hydroxyethyl methacrylate-graft-poly(caprolactone), [P(HEMA-g-PCL)]3, are synthesized by combination of reversible addition-fragmentation chain-transfer (RAFT) and ring opening polymerization (ROP) mechanisms in a one-pot/one-step protocol. The resulting macromolecules are characterized by 1H Nuclear Magnetic Resonance (NMR), size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The preliminary results indicate the success of the methodology and are in agreement with literature reports. In addition, DSC isothermal crystallization are performed, and Avrami's theory is employed in order to obtain kinetics parameters of interest, such as the half-life for the crystallization process (t1/2), the bulk crystallization constant (k), and the Avrami's exponent (n). Thermal analysis evidences a noticeable reduction in the melting temperature compared with linear PCL homopolymer. However, the presence of branches does not modify the values of the maximum degradation temperatures significantly. Finally, the synthesized copolymers adopt a two-dimensional crystallization type (disk and cylindrical).