Abstract
Well-defined 3-miktoarm star copolymer 3 mu-HBPE(PCL)(2)(HBPE: hyperbranched polyethylene, PCL: poly[epsilon-caprolactone]) was synthesized by combining chain walking polymerization (CWP), ring-opening polymerization (ROP), and "click" chemistry. The synthetic methodology includes the following steps: (a) synthesis of in-chain ethynyl-functionalized PCL, (PCL)(2)-C equivalent to CH by ROP of epsilon-caprolactone (CL) with ethylene-functionalized solketal (3-[prop-2-yn-1-yloxy] propane-1,2-diol) as difunctional initiator and phosphazene superbaset-BuP(2)as catalyst; (b) synthesis of azido-functionalized hyperbranched PE (HBPE-N-3) by CWP of ethylene with alpha-diimine-Pd(II) catalyst, followed by quenching with excess 4-vinylbenzyl chloride and transformation of chloro to azide group with sodium azide; and (c) "clicking" HBPE-N(3)and (PCL)(2)-C equivalent to CH using copper(I)-catalyzed azide-alkyne cycloaddition.H-1 NMR spectroscopy, gel permeation chromatography, Fourier-transform infrared spectroscopy, and differential scanning calorimetry were used to determine the molecular characteristics and thermal properties of the polymers. Self-assembly behavior of 3 mu-HBPE (PCL)(2)in petroleum ether, a selective solvent for HBPE, was investigated by dynamic light scattering, atomic force microscopy, and transmission electron microscopy. The in-chain alkyne-functionalized poly(epsilon-caprolactone) is a valuable precursor for PCL-based complex macromolecular architectures.