Nano-gel containing thermo-responsive microspheres with fast response rate owing to hierarchical phase-transition mechanism

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• 作者：Li-Li Yue ; Rui Xie ; ^{xierui@scu.edu.cn} ; Jie Wei ; Xiao-Jie Ju ; Wei Wang ; Liang-Yin Chu ; ^{chuly@scu.edu.cn}
• 关键词：Thermo-responsive microspheres ; Rapid response ; Composite structure ; Hierarchical phase-transition ; Poly(N-isopropylacrylamide)
• 刊名：Journal of Colloid and Interface Science
• 出版年：2012
• 期刊代码：125_00219797
• 类别：ch
• 出版时间：1 July, 2012
• 卷：377
• 期：1
• 页码：137-144
• 文件大小：908 K

摘要

A new strategy is developed in this study to achieve thermo-responsive microspheres with fast response rates by designing a hierarchical phase-transition mechanism. The proposed thermo-responsive microspheres are composed of poly(N-isopropylacrylamide-co-acrylic acid) (PNA) microsphere matrixes and embedded poly(N-isopropylacrylamide) (PNIPAM) nano-gels, which have different volume phase-transition temperatures (VPTTs). The VPTT of PNIPAM nano-gels (VPTT₁) is lower than that of PNA microsphere matrixes (VPTT₂). Upon heating-up, the temperature increases across the VPTT₁ first and then the VPTT₂, as a result the PNIPAM nano-gels shrink earlier than the PNA microsphere matrixes. Upon cooling-down, the temperature decreases across the VPTT₂ first and then the VPTT₁, as a result the PNA microsphere matrixes swell earlier than the PNIPAM nano-gels. Consequently, large amounts of voids and channels form around the nano-gels inside the microsphere matrixes when the temperature changes across the range between VPTT₁ and VPTT₂, which are beneficial to the enhancement of water transport rate inside the microsphere matrixes. The experimental results show that, compared with normal homogeneous PNA (N-PNA) microspheres, the nano-gel containing PNA (C-PNA) microspheres exhibit remarkably fast response rate due to the hierarchical phase-transition mechanism attributed to different VPTT values of the embedded nano-gels and the microsphere matrixes.