Photomechanical Effects in Azo-Polymers Studied by Neutron Reflectometry

Abstract

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Synthesis and photochromic behavior of some azo-polysiloxanes modified with nucleobases or donor-acceptor groups

“…• C), that can be attributed to a melting process of the ordering phase that appear at 54 • C. Aggregation and crystallization processes above 50 • C, due to azobenzene association dipoles, were reported recently by Yager et al [20]. Probably, a similar association process takes place for our azo-polysiloxanes, accentuated by the presence of the nucleobases.…”

Volume generation towards dynamic surface morphing in liquid crystal polymer networks

“…So it is postulated that the reduction of molecular order is accompanied with the density decrease (and corresponding volume increase), which is independent from the molecular alignment configurations [28]. Free volume formation in azobenzene side-chain polymers by photoactuation have been published earlier [45,46]. Barrett and co-workers reported even a volume increase of 17% at room temperature, measurements that were supported by neutron reflectometry.…”

Surface properties, thermal behavior, and molecular simulations of azo-polysiloxanes under light stimuli. Insight into the relaxation

“…These endotherms may be ascribed to the melting of an ordered phase involving either the trans and cis azo side-chains, or both the main chain and the side groups. It has been recently reported by Yager et al 33 and by our group 34 that crystalline domains could be attributed to azobenzene dipoles association that could generate crystalline domains. Two hours after UV irradiation the endotherm at 60 o C disappears (Figure 4(c)) and five hours after irradiation no melting endotherm remains, the glass transition being the only signal still observable (Figure 4(d)), the polymer so recovering its fully amorphous state.…”