In ABA triblock copolymers, the blocks can self-assemble via microphase segregation, leading to the formation of physical molecular networks that impact properties such as shape memory or elastic strength. We exploited this trait to produce intelligent shape memory polymer fibers (SMPFs) from ABA triblock copolymers comprised of glassy end-blocks and rubbery mid-blocks combined within a melt-spun bicomponent fiber with mid-block affinitive homopolymers in order to induce excellent interfacial adhesion. When subjected to mechanical loading at T &lt; Tg of the end-blocks, the copolymer retains its elasticity while the homopolymer undergoes plastic deformation, thus a stable temporary shape is locked in due to the reordering of the homopolymers. Heating the material beyond the homopolymer Tm allows the SMPFs to rapidly recover to the original dimensions. Our SMPFs possess excellent strain recovery ratios while being able to withstand multiple cycles of strain. In order to tune the desired properties of the SMPFs, we investigated the molecular details of the phase segregation, network formation, and interface integrity with dissipative particle dynamics (DPD) simulations. Since the identification of microdomains and chains conformations in molecular systems that do not segregate strongly poses a significant challenge, we developed an approach to post-process particle simulation data in order to quantify the molecular networks that are formed by the end-blocks in ABA triblock copolymer systems. Using this approach, we quantified the fractions of the ABA triblock copolymers that participate in bridging, looping, dangling, and unsegregated conformations within the molecular network as a function of the copolymer composition, copolymer chain length, incompatibility between the A and B blocks, simulation temperature, and in the presence of homopolymer interfaces. Our simulation results correlate well with experiments, and reveal the nature of copolymer chain conformations across a broad range of incompatibility strengths and in the presence of a mid-block compatible interface.

Molecular design of shape memory polymer fibers that are thermally responsive

250th National Meeting (2015)

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