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Synthesis and Characterization of a Series of Star-Branched Poly(epsilon-caprolactone)s with Nanoscale Molecular Architectural Variation

J. Choi, H.J. Song and S-Y Kwak
Seoul National University, KR

Keywords:
star-branched polymer, poly(epsilon-caprolactone), branching ratio, thermal property, crystallinity

Abstract:
In this study, a series of star-branched poly(epsilon-caprolactone)s (SPCLs) was synthesized with nanoscale molecular architectural variation in arm numbers and lengths by ring-opening polymerization under bulk condition. Arm numbers were varied to be 3, 4, and 6 by the use of multifunctional initiating cores. The lengths of poly(epsilon-caprolactone) arms were varied by controlling molar ratio of monomer-to-initiating hydroxyl group molar ratio being 5, 10, 15. Molecular weights were determined by both 1H NMR end-group analysis and MALDI-TOF mass spectrometry, which gave the reasonably consistent values. The branching architecture was evaluated by the branching ratio, g, the ratio of mean-square radius of SPCL to that of liner counterpart of the same chemistry and equivalent molecular weight. The radii of gyration were determined using SAXS. The g values were observed to decrease with increase in arm numbers, indicating more compact molecular structure for SPCLs with higher arm numbers, while no such effect was found for arm length variation. The melting and degradation temperatures were observed to increase with increasing arm lengths when arm number being constant. For the SPCLs with the equivalent molecular weights, the degree of crystallinity was found to decrease with increasing arm numbers.

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