Synthesis and characterization of two shape-memory polymers containing short aramid hard segments and poly(ε-caprolactone) soft segments

A number of segmented copolymers were synthesized by reacting 4-aminobenzoyl end-functionalized poly(ε-caprolactone)s of Mn 2000, 3000 and 4000 g mol−1 with three aromatic diacid dichlorides in the presence of chlorotrimethylsilane. Polymer purity, molar mass, thermal and mechanical properties were characterized by NMR, MALDI-TOF mass spectrometry, GPC, DSC, and DMTA. Promising shape-memory properties were observed for two polymers that contained comparatively short, semicrystalline poly(ε-caprolactone) soft segments of molecular weight 3000 g mol−1 and either terephthalamide or 2,6-naphthalenedicarboxyamide hard segments. Cast films of these polymers were soft and elastomer-like at room temperature. Loading could be conveniently achieved by cold-drawing at room temperature and strain recovery took place upon heating above the melting temperature of the soft segment (35 °C). Cast films reached uniform deformation properties with strain recovery rates as high as 99% and strain fixity values of 78% after passing through only one or two training cycles.