Liao Chuyi, Hsu Chungen, Wang Xiaogong
Department of Chemical Engineering, Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing 100084, P. R. China.
Langmuir. 2020 Dec 1;36(47):14372-14385. doi: 10.1021/acs.langmuir.0c02733. Epub 2020 Nov 16.
This study focused on mussel-like surface adhesion and photoinduced cooperative deformation of a unique type of Janus particles (JPs), composed of an isosorbide-based molecular glass bearing push-pull type azo chromophore (IAC-4) and a 2,6-pyridinedicarboxamide-containing poly(dimethylsiloxane) oligomer (Hpdca-PDMS). The JPs were obtained by the solvent evaporation method in an aqueous medium with the dispersed phase of a solution of IAC-4 and Hpdca-PDMS in dichloromethane (DCM). The JP formation and its mechanism were investigated by electron microscopy, in situ optical microscopy, and theoretical analysis. The results showed that the Janus structures form through gradual segregation between the two components in the droplets induced by the evaporation of DCM, which follows the ternary phase diagrams calculated according to Flory-Huggins theory. In the following stage, the gradual coalescence of small domains in droplets is controlled by dynamic factors. After being deposited on a substrate, the JPs exhibit unidirectional adhesion with the Hpdca-PDMS parts spreading on the substrate, while the IAC-4 parts orientate away from the substrate. The mussel-like adhesion is caused by the interfacial interaction of Hpdca-PDMS with the hard surfaces (i.e., glass and silicon substrates) and its strong ability to spread and wet the surfaces to increase the contact area with the surfaces. Upon irradiation with linearly and circularly polarized laser beams at 488 nm, respectively, a series of unique surface morphologies are observed because of the photoinduced deformation of the IAC-4 parts along the electric vibration direction of the polarized light and the cooperative deformation of the Hpdca-PDMS parts of the JPs. The cooperative deformation reveals the strong interfacial interaction and cohesiveness between the IAC-4 and the Hpdca-PDMS phases in JPs. No peeling-off from the substrate is observed after the large-scale deformation, which also indicates the strong adhesion of the JPs on the substrate surfaces. This study not only demonstrates the mussel-like adhesion and unique cooperative deformation behavior but also supplies new insights into the interfacial interaction in JPs as well as that with hard surfaces, thus opening a new avenue for surface modification and functionalization.
本研究聚焦于一种独特类型的 Janus 粒子（JPs）的类贻贝表面粘附和光致协同变形，该粒子由含推拉型偶氮发色团的异山梨醇基分子玻璃（IAC - 4）和含 2,6 - 吡啶二甲酰胺的聚二甲基硅氧烷低聚物（Hpdca - PDMS）组成。通过在水介质中采用溶剂蒸发法，以 IAC - 4 和 Hpdca - PDMS 在二氯甲烷（DCM）中的溶液作为分散相来制备 JPs。通过电子显微镜、原位光学显微镜和理论分析研究了 JP 的形成及其机制。结果表明，Janus 结构是通过 DCM 蒸发诱导液滴中两种组分的逐渐分离形成的，这遵循根据 Flory - Huggins 理论计算的三元相图。在接下来的阶段，液滴中小区域的逐渐聚结受动力学因素控制。沉积在基材上后，JPs 表现出单向粘附，Hpdca - PDMS 部分铺展在基材上，而 IAC - 4 部分远离基材取向。类贻贝粘附是由 Hpdca - PDMS 与硬表面（即玻璃和硅基材）的界面相互作用以及其在表面铺展和润湿以增加与表面接触面积的强大能力引起的。分别用 488 nm 的线偏振和圆偏振激光束照射时，由于 IAC - 4 部分沿偏振光的电振动方向发生光致变形以及 JPs 的 Hpdca - PDMS 部分的协同变形，观察到一系列独特的表面形态。协同变形揭示了 JPs 中 IAC - 4 和 Hpdca - PDMS 相之间强烈的界面相互作用和内聚性。在大规模变形后未观察到从基材上剥离，这也表明 JPs 在基材表面具有很强的粘附力。本研究不仅展示了类贻贝粘附和独特的协同变形行为，还为 JPs 中的界面相互作用以及与硬表面的界面相互作用提供了新的见解，从而为表面改性和功能化开辟了一条新途径。
