三嵌段共聚物刷诱导乳液自组装制备响应性多孔结构色微球

Preparation of Stimuli-responsive Structural Colored Porous Microspheres via Emulsion Self-assembly Induced by Bottlebrush Triblock Copolymers

我们近期报道了两亲性嵌段共聚物刷(聚降冰片烯-g-聚苯乙烯)-b-(聚降冰片烯-g-聚环氧乙烷)(PS-b-PEO)诱导的“有序自发乳化机制”,简便地制备了多孔结构色微球.在此基础上,本工作中设计合成了含聚丙烯酸叔丁酯(PtBA)中间嵌段的三嵌段共聚物刷,探究其对界面自组装行为的影响规律.实验结果表明,PtBA嵌段会使水-油界面过渡层厚度增加,而显著影响聚合物刷在W/O界面上的排列方式.此外,PtBA可在酸性条件下水解生成聚丙烯酸(PAA),与有机碱作用后成盐,使孔内壁亲水性增加、微球体积膨胀、结构色红移,从而制备出刺激响应性结构色微球.

Our recent work showed that amphiphilic bottlebrush block copolymer(polynorbornene-graft-polystyrene)-block-(polynorbornene-graft-poly(ethylene oxide))(PS-b-PEO)could induce organized spontaneous emulsification,yielding structural colored porous microspheres templated by ordered water-in-oil-in-water(W/O/W)double emulsion droplets.Herein,we demonstrate the design and synthesis of a series of triblock copolymers with a poly(tert-butylacrylate)(PtBA)block between PS and PEO blocks,and disclose the influence of the middle block on interfacial self-assembly.It turned out that the transition layer at W/O interface becomes thicker in the presence of PtBA block,leading to great influence on packing parameters of the bottlebrush amphiphiles.Even though decreased ordering of nanopore arrays is observed relative to that of diblock copolymers,the middle block enables the wide tuning of reflection across the whole visible spectrum(471-717 nm)simply through variation of droplet evaporation time.Moreover,stimuli-responsive structural colored microspheres are obtained via hydrolysis of PtBA to poly(acrylic acid)(PAA)which can react with organic bases and form organic salts,leading to enhanced hydrophilicity of the microspheres,swelling of the photonic structure,and red-shift of structural color.A large increase of reflection maximum of up to 50 nm is achieved in the presence of arginine at a low concentration of 10-3 mol/L.Such a color change can be completed within 4 min,providing an effective method for fast and sensitive detection.This work not only provides useful fundamental knowledge regarding the interfacial self-assembly of triblock copolymers,but also demonstrates an effective strategy for making stimuli responsive photonic structures.