Designing Multiple-Shape Memory Polymers with Miscible Polymer Blends: Evidence and Origins of a Triple-Shape Memory Effect for Miscible PLLA/PMMA Blends

作者：Samuel Cedric^*; Barrau Sophie; Lefebvre Jean Marc; Raquez Jean Marie; Dubois Philippe

来源：Macromolecules, 2014, 47(19): 6791-6803.

DOI：10.1021/ma500846x

Shape memory properties of polymers represent one of the most expanding fields in polymer science related to numerous smart applications. Recently, multiple-shape memory polymers (multiple-SMPs) have attracted significant attention and can be achieved with complex polymer architectures. Here, miscible PLLA/PMMA blends with broad glass transitions are investigated as an alternative platform to design multiple-SMPs. Dual-shape memory experiments were first conducted at different stretching temperatures to identify the so-called %26quot;temperature memory effect%26quot;. The switch temperature of the symmetric 50% PLLA/50% PMMA blend smoothly shifted from 70 to 90 C for stretching temperatures increasing from 65 to 94 C, attesting for a significant %26quot;temperature memory effect%26quot;. Asymmetric formulations with 30% and 80% PMMA also present a %26quot;temperature memory effect%26quot;, but the symmetric blend clearly appeared as the most efficient formulation for multiple-shape memory applications. A programming step designed with two successive stretchings within the broad glass transition consequently afforded high triple-shape memory performances with tunable intermediate shapes, demonstrating that the symmetric blend could represent an interesting candidate for future developments. Advanced shape recovery processes are consistent with a selective activation of specific %26quot;soft domains%26quot; or nanodomains arising from the broad glass transition and the large distribution of relaxation time observed by DSC and dielectric spectroscopy. Polarized IR measurements pointed out that the composition of activated/oriented %26quot;soft domains%26quot; could vary with stretching temperature, giving rise to the %26quot;temperature-memory effect%26quot;. Consequently, from a polymer physics standpoint, nanoscale compositional heterogeneities within the symmetric blend could be suspected and discussed on the basis of available models for miscible blends and for multiple-SMPs.

• 出版日期2014-10-14