title: The first example of main-chain cyclic azobenzene polymers.
abstract: A novel main-chain azobenzene cyclic polymer, cyclic-PEHPA, has been successfully synthesized by 'click' cyclization of the α-alkyne-ω-azido hetero-difunctional linear precursors (linear-PEHPA), which is synthesized by a step-growth polymerization of the 3'-ethynylphenyl[4-hexyl-(2-azido-2-methyl- propionate) phenyl] azobenzene (EHPA). Gel permeation chromatography, and (1) H NMR and FT-IR spectra confirmed the complete transformation of linear-PEHPA into cyclic-PEHPA. With the same molecular weights, the cyclic-PEHPAs are found to have higher glass transition temperatures than the linear-PEHPAs, but almost the same decomposition temperatures. In addition, the obtained cyclic azobenzene polymer with lower molar mass shows a slightly better trans-cis-trans photoisomerization ability than the corresponding linear-PEHPA.
authors.affiliation: Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science of Soochow University, Suzhou 215123, P. R. China.
authors.forename: Xu
authors.initials: X
authors.lastname: Xu
authors.forename: Nianchen
authors.initials: N
authors.lastname: Zhou
authors.forename: Jian
authors.initials: J
authors.lastname: Zhu
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Tu
authors.forename: Zhengbiao
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zhenping
authors.initials: Z
authors.lastname: Cheng
authors.forename: Xiulin
authors.initials: X
authors.lastname: Zhu