Investigating the Phase-Morphology of PLLA-PCL Multiblock Copolymer / PDLA Blends Cross-linked Using Stereocomplexation
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.465
Investigating the Phase-Morphology of PLLA-PCL Multiblock Copolymer / PDLA Blends Cross-linked Using Stereocomplexation Victor Izraylit1,2, Oliver E. C. Gould1, Karl Kratz1, Andreas Lendlein1,2* 1
Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, HelmholtzZentrum Geesthacht, Kantstrasse 55, 14513 Teltow, Germany 2 Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
ABSTRACT The macroscale function of multicomponent polymeric materials is dependent on their phasemorphology. Here, we investigate the morphological structure of a multiblock copolymer consisting of poly(L-lactide) and poly(ε-caprolactone) segments (PLLA-PCL), physically cross-linked by stereocomplexation with a low molecular weight poly(D-lactide) oligomer (PDLA). The effects of blend composition and PLLA-PCL molecular structure on the morphology are elucidated by AFM, TEM and SAXS. We identify the formation of a lattice pattern, composed of PLA domains within a PCL matrix, with an average domain spacing d0 = 12 – 19 nm. The size of the PLA domains were found to be proportional to the block length of the PCL segment of the copolymer and inversely proportional to the PDLA content of the blend. Changing the PLLA-PCL / PDLA ratio caused a shift in the melt transition Tm attributed to the PLA stereocomplex crystallites, indicating partial amorphous phase dilution of the PLA and PCL components within the semicrystalline material. By elucidating the phase structure and thermal character of multifunctional PLLA-PCL / PDLA blends, we illustrate how composition affects the internal structure and thermal properties of multicomponent polymeric materials. This study should facilitate the more effective incorporation of a variety of polymeric structural units capable of stimuli responsive phase transitions, where an understanding the phase-morphology of each component will enable the production of multifunctional soft-actuators with enhanced performance.
INTRODUCTION Biodegradable polymers such as polylactones [1] and their blends are highly desirable for the creation of degradable implants [2, 3], drug delivery systems [4, 5] and sustainable packaging solutions [6]. The synthetic alteration of lactide-based copolyesters and their combination with other polymeric segments has led to the
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determination of a structure-property relationship and enabled tailoring of their bulk properties [7, 8], with the realization of emergent behavior unseen in homopolymer materials [9-11]. However, the combination of multiple chemically distinct entities (e.g. segments in block copolymers or blend components) must overcome issues with their compatibility to control the resulting matrix
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