Synthesis and characterization of resorcinarene-centered eight-arm poly(ε-caprolactone) stars catalyzed by yttrium complex
2008
Gou, Peng-Fei | Zhu, Wei-Pu | Shen, Zhi-Quan
Two novel multifunctional precursors with eight alcoholic hydroxyls were synthesized by derivatization of resorcinarene. Well-defined eight-arm star-shaped poly(ε-caprolactone)s (SPCLs) with reasonably narrow molecular weight distributions have been successfully prepared using the precursors as macro-initiators and yttrium tris(2,6-di-tert-butyl-4-methylphenolate) [Y(DBMP)₃] as catalyst at 40 °C. The molecular weight of SPCLs was characterized by end group ¹H NMR analyses and size-exclusion chromatography, which could be well controlled by the molar ratio of the monomer to the precursor. The polymerization is more controllable with the precursor holding longer hydrocarbon chains as R groups. Differential scanning calorimetry analyses suggested that the maximal melting point, the crystallization temperature, and the degree of crystallinities of SPCLs increased with the increasing of the molecular weight, and were significantly lower than that of the counterpart linear poly(ε-caprolactone) (LPCL). Furthermore, polarized optical microscopy indicated that LPCL showed fast crystallization rate with apparent Maltese cross pattern, whereas SPCL exhibited irregular spherulite and apparently slower crystallization rate.
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