Optically driven mechanical softening in polymers containing azobenzene and alkyl chains

DANIELA GARCÍA NÚÑEZ; PATRICIA OYANGUREN; MARIA J. GALANTE; DIANA P. FASCE

Mar del Plata

Simposio; XVI Latin-American Polymer Symposium, XIV Iberoamican Polymer Congress; 2018

INTEMA

Epoxy linear polymers with azobenzene and alkyl side groups were prepared and their photoinduced optical response was investigated. The azobenzene groups contribute to light response while alkyl chains form strong physical crosslinks by tail-to-tail associations among them, and exhibit the behavior of a physical network.After being illuminated with linear polarized light at 488 nm (relaxed state) leads to a decrease in the slope of the loading curves, which is evidence of polymer softening. The diffusion of azobenzene material originates solely from photo-induced molecular motions and the resultant athermal photofluidization at room temperature. The different mechanical response between initial and relaxed states, asserts the irreversible character of the mechanical changes induced by the photoisomerization of azobenzene molecules. The association among dodecyl chains, physical gelation process, produced a small increase of the modulus before illumination. In the relaxed state, crosslinking restrains the mobility of oriented azo groups for randomization, thus providing stability to the photoinduced orientation and decreasing the photo-softening effect.