title: Azo-Polymer Janus Particles Assembled by Solvent-Induced Microphase Separation and Their Photoresponsive Behavior.
abstract: We report the successful fabrication of photoresponsive Janus particles (JPs) composed of an epoxy-based azo polymer and poly(methyl methacrylate) (PMMA). Two representative azo polymers, of which one polymer (BP-AZ-CN) has cyano groups as electron-withdrawing substituents on the azobenzene moieties and the other polymer (BP-AZ-CA) has carboxyl groups as the electron-withdrawing substituents, were adopted for the investigation. The nanoscaled JPs, with a narrow size distribution and different azo polymer/PMMA ratios, were fabricated through self-assembly in solution and as dispersions. Upon irradiation with linearly polarized light (λ=488 nm), two types of photoresponsive behavior were observed for JPs in the solid state. For JPs composed of BP-AZ-CN and PMMA, the light irradiation caused the azo-polymer component to be stretched along the light polarization direction. Conversely, for JPs composed of BP-AZ-CA and PMMA, the azo-polymer component became separated from PMMA component under the same irradiation conditions. These observations are valuable for a deeper understanding of the nature of self-assembly and photoinduced mass-transport at the nanometer scale.
authors.affiliation: Department of Chemical Engineering, Key Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing, 100084, People's Republic of China.
authors.forename: Xinran
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Chemical Engineering, Key Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing, 100084, People's Republic of China.
authors.forename: Shouping
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Chemical Engineering, Key Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing, 100084, People's Republic of China.
authors.forename: Bingyang
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Chemical Engineering, Key Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing, 100084, People's Republic of China.
authors.forename: Xiaogong
authors.identifier: http://orcid.org/0000-0002-8721-6976
authors.initials: X
authors.lastname: Wang
keywords: Janus particles; azo compounds; deformation; nanoparticles; self-assembly