Clay Composites by In Situ Polymerization of Ionic Liquid-Based Dispersions

Flexible composite materials were prepared by in situ copolymerization of ionic liquid like monomers─namely 1-vinyl-3-ethyl imidazolium bis(trifluoromethane)sulfonimide (M1) and 1-(2-acryloyloxyundecyl)-3-methylimidazolium bis(trifluoromethane)sulfonimide (M2) that were cross-linked with 1,1′-octane-1,8-diylbis(3-vinyl imidazolium) di[bis(trifluoromethane)sulfonimide] (CL). Mixtures of polymerizable ionic liquids were used to disperse organo-modified montmorillonite clay as a filler. Polymerization of the mixtures resulted in copolymer composites. The glass transition temperature of the composites could be tuned in the range of −2–127 °C by varying the ratio of the ionic liquid monomers M1 and M2, which is presented in the article for the first time along with its homopolymer. The mechanical properties were significantly enhanced by using a copolymer matrix instead of either of the respective homopolymers. The toughest M1–M2 copolymer composite exhibited a toughness of 5.3 ± 1.4 MPa, while the toughnesses of corresponding poly(M1) and poly(M2) films were 0.6 ± 0.2 and 0.5 ± 0.003 MPa, respectively. The composite could be filled uniformly with large amounts of montmorillonite clay. The copolymer matrix was able to take up large amounts of clay while still exhibiting mechanical properties that surpassed the unfilled matrix.