Trilayered Morphology of an ABC Triple Crystalline Triblock Terpolymer
AuthorsPalacios, Jordana K.
Müller, Alejandro J.
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AbstractTriple crystalline triblock terpolymers are materials with remarkable semicrystalline superstructures. In this work, we report for first time the alternating triple lamellar morphology that self-assembles inside spherulites of a triblock terpolymer composed of poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(l-lactide) (PLLA). The morphology of the PEO-b-PCL-b-PLLA triblock terpolymer is compared to an analogous PCL-b-PLLA diblock copolymer. Both diblock and triblock form a single phase in the melt. Two crystallization protocols were employed to create particular crystalline morphologies. In both cases, the isothermal crystallization of the PLA block is induced first (at 81 °C, a temperature above the melting points of both PCL and PEO blocks) and PLLA spherulites form a template, whereupon cooling the other two blocks can crystallize within the PLLA interlamellar spaces. WAXS analysis demonstrated the double crystalline and triple crystalline nature of the materials. The lamellar structure was evaluated by AFM observations and SAXS measurements. Moreover, theoretical SAXS curves of one-dimensional structural models were calculated. AFM micrographs of the triblock terpolymer evidenced the three different lamellae of PLLA, PCL and PEO that coexist together within the same spherulite. Three different lamellar thickness were determined, and their dimensions suggested that all blocks crystallized in chain-folded conformations. The evolution of the triple lamellar morphology during heating of tricrystalline samples was followed by in situ synchrotron SAXS measurements. The theoretical analysis of the SAXS curves of the triblock terpolymer allowed us to propose a stacking morphological model, in which a particular trilayer structure exists, where one lamella of PCL or one lamella of PEO is inserted randomly between two adjacent PLLA lamellae.
CitationPalacios JK, Tercjak A, Liu G, Wang D, Zhao J, et al. (2017) Trilayered Morphology of an ABC Triple Crystalline Triblock Terpolymer. Macromolecules 50: 7268–7281. Available: http://dx.doi.org/10.1021/acs.macromol.7b01576.
SponsorsThe authors acknowledge funding by ALBA project 2016091863 (2017). We also acknowledge staff from the BL11 beamline at ALBA synchrotron as well as travel funding by “Ministerio de Economía y Competitividad” and “Generalidad de Cataluña” (Grant No. 2016091863). We gratefully acknowledge funds received through the following projects: “Mineco MAT2014-53437-C2-P”. G.L. is grateful to the financial support from the National Natural Science Foundation of China (51203170) and from the Youth Innovation Promotion Association of CAS (2015026). We are also grateful to Dr. Eva Crosas at ALBA Synchrotron, Cerdanyola del Vallès, Barcelona, Spain, and Dr. Daniel Fulla at Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany, for their collaboration with the SAXS data treatment. Dr. Eva Crosas was supported by the Spanish Nuclear Safety Council (CSN).
PublisherAmerican Chemical Society (ACS)