Park Ji Hoon, Han Nuri, Song Ji Eun, Cho Eun Chul
Department of Chemical Engineering, Hanyang University, Seoul, 04763, South Korea.
Macromol Rapid Commun. 2017 Feb;38(3). doi: 10.1002/marc.201600621. Epub 2016 Dec 22.
A surfactant-free approach is proposed to synthesize nonspherical Janus particles with temperature-dependent wettability on hydrophobic surfaces. Sub-micrometer-sized particles comprising poly(styrene-co-divinylbenzene) core and a thermally responsive poly(N-isopropylacrylamide-co-methacrylic acid) shell are first synthesized to stabilize styrene droplets in water, producing a Pickering emulsion. Upon heating to 80 °C and subsequent addition of initiators to the aqueous phase, styrene droplets are polymerized and combine with the core-shell particles to construct dumbbell-shaped nonspherical particles. The shape of the nonspherical particles is controllable by adjusting the equilibrium time of the Pickering emulsion at 80 °C, which is conducted prior to polymerization. The mechanism of formation is discussed in more detail. Since molecular surfactants or stabilizers are not used during the synthesis, the present nonspherical particles well exhibit their own temperature-dependent amphiphilic characteristics. The aqueous dispersion containing the dumbbell-shaped particles alters its wettability on hydrophobic polymer surfaces according to temperature changes, demonstrating its temperature-dependent amphiphilicity change.
提出了一种无表面活性剂的方法来合成在疏水表面具有温度依赖性润湿性的非球形Janus颗粒。首先合成由聚（苯乙烯-共-二乙烯基苯）核和热响应性聚（N-异丙基丙烯酰胺-共-甲基丙烯酸）壳组成的亚微米级颗粒，以稳定水中的苯乙烯液滴，从而产生Pickering乳液。加热至80°C并随后向水相中加入引发剂后，苯乙烯液滴聚合并与核壳颗粒结合，形成哑铃形非球形颗粒。通过调节在80°C下Pickering乳液的平衡时间（在聚合之前进行），可以控制非球形颗粒的形状。对形成机理进行了更详细的讨论。由于在合成过程中未使用分子表面活性剂或稳定剂，因此本非球形颗粒很好地展现了其自身的温度依赖性两亲特性。含有哑铃形颗粒的水分散体根据温度变化改变其在疏水聚合物表面的润湿性，证明了其温度依赖性两亲性变化。
