Synthesis and morphological characterization of miktoarm star copolymers (PCL)2(PS)2 of poly(ε‐caprolactone) and polystyrene |
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Authors: | Arnaldo T. Lorenzo Alejandro J. Müller Dimitrios Priftis Marinos Pitsikalis Nikos Hadjichristidis |
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Affiliation: | 1. Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080‐A, Venezuela;2. Alejandro J. Müller, Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080‐A, Venezuela;3. Nikos Hadjichristidis, Department of Chemistry, University of Athens, 15771 Panepistimiopolis, Zografou, Athens, Greece;4. Department of Chemistry, University of Athens, 15771 Panepistimiopolis, Zografou, Athens, Greece |
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Abstract: | An heterofunctional initiator combining two reactive sites for ring opening polymerization and two for atom transfer radical polymerization was used to prepare three A2B2 miktoarm star copolymers of poly(ε‐caprolactone) (PCL) and polystyrene (PS). The morphology and thermal properties were studied by transmission electron microscopy, polarized light optical microscopy, and differential scanning calorimetry. The (PCL)2(PS)2 72/28 (72 wt % PCL) sample was crystallized from a disordered melt. In this case, crystallization drove the structure formation and a lamellar morphology was obtained at the microdomain level, while spherulites were observed at a superstructural level. The other two samples, 39/61 and 27/73, with lower PCL content and higher total molecular weight, were not able to form spherulites. Surprisingly, these miktoarm star copolymers exhibited hexagonally packed cylinders and spheres morphologies, respectively, instead of lamellar and cylindrical morphology. Such unexpected and novel behavior was explained in terms of the higher resistance of the arms to be stretched in a miktoarm star copolymer when compared with the corresponding linear diblocks. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5387–5397, 2007 |
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Keywords: | crystallization differential scanning calorimetry (DSC) living radical polymerization miktoarm stars polarized optical microscopy ring‐opening polymerization TEM |
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