Thermal Annealing of High cis-1,4-Polybutadiene/Octadecyl Acrylate Blends as a One-Step Process for Fabricating Shape Memory Polymers

Blending molecular crystals with a cross-linkable elastomerisan inexpensive, formulation- and processing-friendly route to developshape memory polymers (SMPs). In this work, a shape memory materialconsisting of thermally cross-linked, octadecyl acrylate (ODA)-graftedpolybutadiene (PB) and free octadecyl acrylate was prepared. High-temperature(175 degrees C) annealing of a melt-processable blend of PB and ODAresults in the ene grafting of a portion of the ODA onto the PB chainsproducing a side-chain crystalline polymer, while simultaneous cross-linkingof the PB produces a cross-linked network. At ODA loadings of 0.66ODA molecules:PB repeat unit (80 wt % ODA), materials with high shapefixity (>99%) and recovery (>99%) were prepared. Higher shaperecoverywas measured compared to previously reported peroxide cross-linkedPB/ODA blends. Limited blooming of the free ODA was found on storedsamples and during shape memory cycling, an improvement compared toother elastomer small molecule blends. These results are discussedin terms of the synthesis, structure, and physical properties of thisblend system.

Automated summary

Blending molecular crystals with a cross-linkable elastomer is a cost-effective and processing-friendly method to develop shape memory polymers (SMPs). In this study, a shape memory material composed of thermally cross-linked, octadecyl acrylate (ODA)-grafted polybutadiene (PB) and free octadecyl acrylate was prepared. By annealing a melt-processable blend of PB and ODA at high temperature (175 degrees C), a side-chain crystalline polymer and a cross-linked network were simultaneously formed. Materials with high shape fixity (>99%) and recovery (>99%) were obtained at ODA loadings of 0.66 ODA molecules: PB repeat unit (80 wt % ODA). Compared to previous peroxide cross-linked PB/ODA blends, higher shape recovery was achieved. Limited blooming of the free ODA was observed on stored samples and during shape memory cycling, indicating an improvement compared to other elastomer small molecule blends. The synthesis, structure, and physical properties of this blend system are discussed in this work.