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Photoresponsive thin films of well-synthesized azobenzene side-chain liquid crystalline polynorbornenes as command surface for patterned graphic writing

Year: 2021

Journal: Polymer, Volume 218, MAR 18

Authors: Chen, Jian; Xu, Tianchi; Zhao, Weiguang; Ma, Ling-Ling; Chen, Dongzhong; Lu, Yan-Qing

Organizations: National Natural Science Foundation of China [21875098, 21574062, 52003115]; Natural Science Foundation of Jiangsu Province [BK20200320]; Program for Changjiang Scholars and Innovative Research Team in University [IRT_16R38]; Fundamental Research Funds for the Central Universities; Scientific Research Foundation of Graduate School of Nanjing University [2017ZDL06]

Keywords: Azobenzene; Azopolymer; Command surface; Photoalignment; Ring-opening metathesis polymerization (ROMP)

Azobenzene-containing polymers (azopolymers) are a kind of intensively explored fascinating photoresponsive materials, liquid crystalline (LC) azopolymers with excellent film-forming, ordered structure and self-repairing capability are endowed with enhanced photoisomerization and photoalignment characteristics capable of developing into photo-modulated smart surfaces. Here in this work, two azobenzene side-chain LC polynorbornenes of PNB-Azo-n with different DP of n = 50 and 100 have been well synthesized through ring-opening metathesis polymerization (ROMP). The polynorbornene backbone of less flexibility with larger spacing between adjacent azobenzene side groups endows stronger inhibition for H-aggregation and better photoresponsiveness. The high-DP azopolynorbornene of PNB-Azo-100 thin films well behave as command surface for the upper layer nematic LC molecules thanks to their better performance in photoisomerization and photoalignment, together with their good compatibility and dissolution-resistance to the nematic LC mixture of E7. Selectively optically readable LC graphic writings at normal size through various photomasks have been demonstrated, and higher grid resolution up to sub-ten micrometer with a digital micromirror device (DMD) based dynamic photo patterning system has been achieved. Therefore, such kind of LC azopolynorbornenes demonstrate promising applications in LC photoalignment system and photoresponsive devices for potential anti-forgery document security and smart card technology.