Synthesis, Structure and Property of Shape Memory Polyurethane
Date Issued
2016
Date
2016
Author(s)
Wu, Chien-Hsin
Abstract
Shape memory polyurethanes (SMPUs) were prepared from similar chemistry but in different polymer architectures with crosslinkers. The dual functional building block 4-isocyanato-4’ (3,3-dimethyl-2,4 -dioxo-azetidino)diphenylmethane (IDD) was selected to prepare poly(urea/maloamid) and a chain extender of PUs under mild condition without resorting to painstaking protection-deprotection or activation methodology. A diol compound with reactive azetidine-2,4-dione group was prepared and introduced as side chain moieties of poly(ε-caprolactone) (PCL) based polyurethane (SPUs). The SPUs with reactive pendants were crosslinked by 1,6-diaminohexane, or modified by an alkoxysilane (3-aminopropyltriethoxysilane, APTS) followed by a sol-gel reaction to bring about crosslinked PUs for shape memory applications. Thermal and mechanical properties of the crosslinked SPUs are strongly dependent on the chemical structure of the interchain-linker between the polymer chains. In addition, SMPUs comprising dendritic (DG series) or linear (LG series) poly(urea/malonamide) hydrogen bond-rich side chains with uniform chain lengths, providing physical crosslinking interactions to PUs. With the reactive functional group, azetidine-2,4-dione as the side chain of SPU to be a crosslinking site, different grafting ratios with various chain lengths of poly(urea/malonamides) were incorporated onto SPU. Consequently the physical crosslinking density could be adjusted. Via NMR, IR, EA, Mass and GPC analysis, we were able to confirm that the precise control of the poly (urea/malonamide) chain lengths were obtained. Phase transition temperatures of SMPUs were observed via differential scanning calorimeter (DSC). By introducing the chemically crosslinked structures, the deformed samples completely recovered to their original shape in less than 3 second without any deficiency during shape recovery tests. Shape recovery went up to 99% during cyclic thermomechanical tensile tests, indicating that the polyurethanes with chemical crosslinking effects exhibited higher impact than did the linear and dendritic side-chain polyurethanes. Consequently, these novel crosslinked polyurethanes with excellent shape-memory effect have been successfully developed in this work.
Subjects
shape memory
polyurethane
drndron
organic/inorganic hybrid
iterative synthesis
adamantane
Type
thesis
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