Smart Copolymers from vegetable oils and styrene obtained by cationic polymerization

M.I. ARANGUREN; MEIORIN, C; M. MOSIEWICKI

Pretoria

Conferencia; 11th International Conference on Frontiers of Polymers and Advanced Materials, XI ICFPAM; 2011

In this work, the preparation and characterization of smart copolymers based on highly unsaturated vegetable oils is reported. The carbon-carbon double bonds in oils are reactive in cationic polymerization reactions, which allows using them without chemical modification [1-3]. Different compositions of copolymers obtained by cationic polymerization with varying tung oil/styrene weight ratios lead to materials with a wide range of final properties. For some of the compositions the obtained materials present shape memory behavior. In those cases, the polymers are able of “remembering” their original shape after having been deformed above a switch temperature, which in these thermoset copolymers is the glass transition temperature. By further application of an external stimulus (in this case, temperature) the original shape is recovered [4]. The mechanical, dynamicmechanical properties, damping and shape memory behavior were analyzed. The glass transition temperatures were close to room temperature for all the copolymers, and generally decreased with the content of tung oil. Similar trend was observed for the elastic modulus. The glass transition temperatures, as well as the mechanical properties at room temperature were related to the crosslinking density and chain mobility in the network. The shape memory behavior was investigated by subjecting the films to cyclic thermal and tensile loads. These hard elastomers exhibited shape memory behavior with high recovery and fixity ratios for copolymers with at least 40 wt.% of styrene in a low temperature range. The copolymer with 30 wt.% tung oil reached an elongation of 100% and almost complete fixing of the transient shape (fixity ratio=100). Additionally, high damping factors (between 0.4 and 1.38) for the tung oil homopolymer and the copolymer with 70 wt.% styrene, respectively, were measured in a temperature range between 28.9 and 43.3°C. This damping capability under conditions close to room temperature could be potentially important for practical applications