Polymer hydrogels: heterogeneous structure and deformation behaviour

Title: Polymer hydrogels: heterogeneous structure and deformation behavior Author: Evgeny Karpushkin Department: Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University in Prague Supervisor: Miroslava Dušková-Smrčková Ing. Dr., Institute of Macromolecular Chemistry AS CR, Heyrovského náměstí 2, 162 06 Prague 6 Abstract: Model series of crosslinked poly(2-hydroxyethyl methacrylate) hydrogels differing in morphology were prepared by polymerization-induced phase separation. Morphology, swelling and dynamic mechanical properties in broad frequency range of the model gels were tested. The vitrification of gels was found sensitive to microstructure of polymer network and to solvent content and to polymer-solvent interaction, but not to the macroscopic morphology of the gel. The low-frequency mechanical response was found sensitive to both polymer network properties and hydrogel morphology. Lightly crosslinked hydrogels showed relatively high mechanical losses in the rubbery plateau region, due to physical association of chains. Fused-particles type hydrogels revealed a weak secondary relaxation at low frequency, ascribed to motion of the dangling particles aggregates. These aggregates, elastically inactive, along with inhomogeneous stress field arisen in porous material, were..