Characterizations of Multiphase Biogenic Polymer Blends from Poly(L-lactide) and Poly(methyl methacrylate)
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0897-J08-09.1
Characterization of Multiphase Biogenic Polymer Blends from Poly(L-lactide) and Poly(methyl methacrylate) Kim-Phuong Le1, Richard Lehman1, Kenneth VanNess2, and James D. Idol1 1 AMIPP Advanced Polymer Center, Rutgers University, Piscataway, NJ, USA 2 Department of Physics, Washington and Lee University, Lexington, VA, USA ABSTRACT Melt processing of binary immiscible polymer systems has been a focus of our group as an economical and scalable route to achieve synergistic or superior mechanical properties at and around the co-continuous region without the need of compatibilization. System of poly(Llactide) (PLLA) and poly(methyl methacrylate) (PMMA) was selected to target bio-related applications, including bone fillers and scaffolds, where the biodegradability of PLLA will enable the integration of native tissue into the material over time. Tunable properties such as morphology, interconnectivity, resorbability and interfacial bonding control the long-term integrity of the new material and influence the interaction and integration of new tissue. Binary blends of PLLA and PMMA has been prepared and characterized over a large range of compositions in which regions of co-continuity are of special interest. Such regions exhibit a well interconnected structure that ensures controlled release of resorbable PLLA. Modulated differential scanning calorimetry (MDSC) detected a broad and unexpected transition between 70 oC and 100 oC. The magnitude of this transition is greatest within co-continuous regions, suggesting the presence of a complex or other derivative of the two primary phases. This complex appears to provide a degree of compatibilization between the phases, thus inducing mechanical property synergism which has been confirmed by flexural and nano-indentation analyses. INTRODUCTION Thermo-mechanical mixing of two or more polymers is a preferred method for new material development since it does not involve costly synthesis while process scale-up can be achieved quickly and inexpensively. Under optimal processing conditions, thermal polymer blends may exhibit synergistic and advantageous properties [1]. Miscible blends and/or compatibilized immiscible blends are the main objectives for thermal blending, but uncompatibilized immiscible blends have recently gained significant attention [2] due to their ability to provide unexpected properties. Studies have shown that for certain applications such as bone fillers and tissue scaffolds, immiscible blends have specific advantages in morphological and mechanical properties. Presently, it is believed that co-continuous nature of certain immiscible compositions gives rise to the synergistic properties due to the intimate interaction between the components. Multiphase polymer blends in which one phase is transient and another phase is persistent can provide the ideal balance of phases with the ratio modified to meet the specific application and to produce the desired results [3]. The initial processing of the blend is important and numerous physical properties of
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