Figure 8.

(a) Structural schematic of natural spider silk, which contains β-crystalline domains (green blocks) that act as heat-stable netpoints and hydrogen bonds (red dimer block) that act as moisture-sensitive netpoints, compared to (b) a synthetic bioinspired shape-memory polymer, which contains heat-stable silk-mimetic β-crystalline domains formed by oligoalanine and crystalline PCL domains (red rectangles) that act as heat-labile crosslinks. (c) The chemical structures of the PCL and oligoalanine-poly(propylene glycol) (PPG) segments of this bioinspired polymer are shown. While natural spider silk can undergo contraction and shape recovery when exposed to water or high humidity, these synthetic shape-memory polymers are temperature-sensitive, retaining a stretched state if cooled under tension and returning to their original shape upon re-heating. Copyright 2013 WILEY-VCH Verlag GmbH & Co, adapted with permission from [112].