Ultra-Extensible Solvent-Free Elastomers Based On Nanocomposite Poly(2-Methoxyethylacrylate)/Clay Xerogels

Physically cross-linked solvent-free supramolecularly assembled nanocomposite elastomers were prepared, which displayed exceptionally high extensibility (up to 6000%), besides generally high mechanical properties (G' in rubber region between 1.5 and 40 MPa). The nanocomposites are based on linear poly(2-methoxyethylacrylate) (polyMEA) and montmorillonite clay (physical cross-linker), and were obtained via free-radical polymerization of the monomer in the presence of the exfoliated nanofiller dispersed in water. The mechanical properties of the studied products were varied in a very wide range by changing the concentrations of the radical redox co-initiator pair, at given constant nanofiller loadings. The latter in turn also strongly altered the product properties. This applied synthesis approach, aimed at obtaining longer elastic chains, made possible to increase the elongation at break up to six times, and also to tremendously and simultaneously increase the toughness (effect of entanglements), as well as to shift the tensile curves between "plastic-like elastomer" and "simple elastomer." In all cases, however, the nanocomposite samples displayed a highly efficient recovery, even after very high deformations. The structure-property relationships were deeper elucidated by thermo-mechanical analysis (DMTA), TGA (thermal stability, elastic chains' immobilization), TEM and X-ray diffraction.