%0 journal article
%@ 0014-3057
%A Noechel, U., Reddy, C.S., Uttamchand, N.K., Kratz, K., Behl, M., Lendlein, A.

%D 2013
%J European Polymer Journal
%N 9
%P 2457-2466 
%R doi:10.1016/j.eurpolymj.2013.01.022
%T Shape-memory properties of hydrogels having a poly(Epsilon-caprolactone) crosslinker and switching segment in an aqueous environment
%U https://doi.org/10.1016/j.eurpolymj.2013.01.022
9 
%X Here we study the thermomechanical properties as well as the shape-memory behavior of a series of CLEG copolymer networks in an aqueous environment. The mechanical properties of the networks at 25 °C in aqueous environment were found to increase from 4 MPa to 77 MPa with increasing crosslink density. The shape-memory properties of the copolymer networks were examined in an aqueous environment by both bending as well as uniaxial elongation experiments. Excellent dual-shape properties with high shape fixity ratios around Rf = 79–100% and shape recovery ratios in the range of Rr = 59% to Rr = 100% were obtained for copolymers with a PCLDIMA weight fraction ⩾50 wt% in the starting composition. The swelling of CLEG in H2O resulted in a reduction of the switching temperature. Furthermore the structural changes during programming of CLEG were assessed in situ by small and wide angle X-ray scattering (SAXS, WAXS) experiments, which confirmed that the overall degree of crystallinity as well as the orientation of the crystalline domains controlled the dual-shape performance. We have found that an appropriate switching segment should result in a degree of crystallinity higher than 10–20% to enable high strain fixity ratios. Furthermore, hydrogels having dual shape-memory capability could be created by using semi-crystalline crosslinker simultaneously acting as the switching segment.