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Holographic Gratings in Diblock Copolymers with Azobenzene and Mesogenic Side Groups in the Photoaddressable Dispersed Phase

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  • This work was financially supported by the Deutsche Forschungsgemeinschaft, Collaborative Research Center (Sonderforschungsbereich) 481 “Complex Macromolecular and Hybrid Systems in Internal and External Fields” (Project B2). We thank Óscar Lafuente for his valuable assistance.

Abstract

Diblock copolymers, consisting of a photoaddressable mesogen-containing dispersed phase and a polystyrene matrix, have been synthesized and characterized as holographic data storage materials. The photoaddressable phase contains p-methoxy-substituted azobenzene side groups and benzoylbiphenyl mesogenic side groups in a statistical distribution. Three-ring mesogenic groups in combination with photoaddressable azobenzene side groups have been introduced for the first time in block copolymers in order to increase the local refractive-index difference between illuminated and non-illuminated volume elements, as well as to improve the stability of the orientation, while, at the same time, decreasing the optical density. To this end, a series of block copolymers with different azobenzene/mesogen ratios have been synthesized. The light-induced reorientation dynamics of the chromophores and mesogens and the long-term stability of the orientation have been studied with volume holographic measurements. A remarkable increase in stability of the holographic gratings has been achieved.

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