基于温度/pH双响应的聚合物表面活性剂调控嵌段共聚物微球形貌

Morphology Switchable Block Copolymer Microparticles by Temperature/pH Dual Responsive Polymer Surfactant

研发响应多重外界刺激而改变形貌的嵌段共聚物微球对发展新型智能材料具有重要意义.本工作提出了一种温度/pH双响应嵌段共聚物微球形貌转变的策略.在利用乳液挥发法制备聚苯乙烯-b-聚(4-乙烯基吡啶)(PS-b-P4VP)微球时,引入温度/pH双响应的聚丙烯酸-b-聚(N-异丙基丙烯酰胺)(PAA-b-PNIPAM)作为表面活性剂,通过调控实验温度以及水相的pH值,实现了PS-b-P4VP微球在蚕蛹状、草莓状、洋葱状等形貌之间的转变.这种独特的形貌转变依赖于温度/pH调控的PAA-b-PNIPAM的亲疏水性转变,以及由此导致的表面活性剂在界面分布位置的改变,进而改变了油水界面的界面选择性以及微球的形貌.通过改变PAA-b-PNIPAM的质量分数、PAA和PNIPAM的嵌段比,系统地研究了温度/pH对PS-b-P4VP微球形貌转变机制的影响.提供了一种温度/pH双响应的微球形貌转变的策略,有望在药物释放、智能传感等领域发挥重要作用.

The preparation of block copolymer microparticles that change morphology in response to multiple external stimuli is of great significance for the development of new smart materials.This work proposes a new strategy to control the morphology transition of block copolymer microparticles by taking advantage of temperature/pH dual-responsive polymeric co-surfactant,poly(acrylic acid)-b-poly(N-isopropylacrylamide)(PAA-b-PNIPAM).The transformation of polystyrene-b-poly(4-vinylpyridine)(PS-b-P4VP)microparticles among pupa-like particles,strawberry-like particles,and onion-like particles could be realized by tuning the volatilization temperature and the pH value of the aqueous phase.This morphological transformation depended on the hydrophilic and hydrophobic transformation of PAA-b-PNIPAM regulated by temperature/pH,which changed the distribution of co-surfactant at the interface,resulting in the change of the interface selectivity of oil/water interface and the morphology of the microparticles.Moreover,the effects of temperature/pH on the morphology transition mechanism of PS-b-P4VP microparticles were systematically studied by means of changing the mass fraction of PAA-b-PNIPAM and the block ratio of PAA to PNIPAM.This work provides a new way for shaping the microparticle morphology of inert block copolymers via the introduction of temperature/pH dual-responsive co-surfactant.Such dual-responsive microparticles are expected to be used in drug release,smart delivery,and other areas.