Liao Chuyi, Huang Hao, Liang Chenxi, Wang Xiaogong
Department of Chemical Engineering, Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing 100084, P. R. China.
Langmuir. 2020 Mar 31;36(12):3159-3173. doi: 10.1021/acs.langmuir.9b03628. Epub 2020 Mar 17.
This study investigated Janus particles (JPs) composed of an azo polymer and a pyrene-containing polymer, focusing on preparation, formation mechanism, photoinduced deformation behavior, and fluorescent properties as well as tunable colors of the dispersions. A methacrylate-based copolymer containing pyrenyl groups (P(MMA--PyMA)) and two azo polymers, i.e., a methacrylate-based polymer (PCNAZO) and an epoxy-based polymer (CH-TZ-NT) both bearing push-pull-type azo chromophores, were synthesized for this purpose. Two types of Janus particles, P(MMA--PyMA)/PCNAZO JPs and P(MMA--PyMA)/CH-TZ-NT JPs, were fabricated through microphase separation of the components in the droplets dispersed in aqueous media, induced by the evaporation of the organic solvent. The process of JP formation was thoroughly investigated by exploiting the function of pyrene moieties as a molecular probe through measuring the fluorescence emission spectra at different times during the structure evolution. The photoluminescent (PL) intensity, excimer emission, and vibrational fine structure of the fluorescence spectra were observed to give information about phase separation and solidification occurred in the dispersed droplets. The observations were rationalized by analysis with ternary phase diagrams calculated on the basis of the Flory-Huggins theory. Upon irradiation with a linearly polarized laser beam at 488 nm, the azo polymer parts in the P(MMA--PyMA)/PCNAZO JPs were observed to be elongated along the electric vibration direction of the polarized light and transformed into particles with unique morphologies. The dispersions of JPs with different compositions of the two types of the polymers showed highly tunable color changes originating from both fluorescence of the pyrenyl fluorophores and light absorption of the azo chromophores.
本研究调查了由偶氮聚合物和含芘聚合物组成的双面粒子（JPs），重点关注其制备、形成机制、光致变形行为、荧光特性以及分散体的颜色可调性。为此合成了一种含芘基的甲基丙烯酸酯类共聚物（P(MMA - PyMA)）以及两种偶氮聚合物，即均带有推挽型偶氮发色团的甲基丙烯酸酯类聚合物（PCNAZO）和环氧类聚合物（CH - TZ - NT）。通过有机溶剂蒸发诱导分散在水介质中的液滴内各组分的微相分离，制备了两种类型的双面粒子，即P(MMA - PyMA)/PCNAZO JPs和P(MMA - PyMA)/CH - TZ - NT JPs。利用芘部分作为分子探针的功能，通过测量结构演化过程中不同时间的荧光发射光谱，深入研究了双面粒子的形成过程。观察到荧光光谱的光致发光（PL）强度、准分子发射和振动精细结构，以获取有关分散液滴中发生的相分离和固化的信息。通过基于弗洛里 - 哈金斯理论计算的三元相图分析，对这些观察结果进行了合理解释。在用488 nm的线偏振激光束照射时，观察到P(MMA - PyMA)/PCNAZO JPs中的偶氮聚合物部分沿偏振光的电振动方向伸长，并转变为具有独特形态的粒子。两种聚合物不同组成的双面粒子分散体显示出高度可调的颜色变化源于芘荧光团的荧光和偶氮发色团的光吸收。
