Hybrid Colloids Composed of Two Amphiphilic Azo Polymers: Fabrication, Characterization, and Photoresponsive Properties

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• 作者：Yonghong Deng ; Nan Li ; Yaning He ; Xiaogong Wang
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：September 4, 2007
• 年：2007
• 卷：40
• 期：18
• 页码：6669 - 6678
• 全文大小：674K
• 年卷期：v.40,no.18(September 4, 2007)
• ISSN：1520-5835

文摘

This article reports the fabrication and characterization of a novel type photoresponsive colloidscomposed of two amphiphilic azo polymers. The colloids were built up by using an amphiphilic random azocopolymer (PEAPE) and a polydispersed azo homopolymer (BP-AZ-CA), which were functionalized withazobenzene type and pseudo-stilbene type chromophores, respectively. The colloids were prepared by graduallyadding deionized water into a THF solution containing both PEAPE and BP-AZ-CA. In order to study the influenceof the preparation conditions on the colloid composition and structure, the colloids were also prepared by mixingtwo THF-H₂O solutions or dispersions of the polymers with different initial water content (C_w0) and then addingwater into the mixture. When mixing the solutions with C_w0 below the critical water content (CWC), uniformcolloidal spheres composed of the two polymers could be obtained. Upon irradiation of a linearly polarized Ar⁺laser beam, the hybrid colloidal spheres were deformed to "tadpole-like", "spindle-like", and other nonsphericalstructures depending on the composition of the colloids. As only the BP-AZ-CA component could be driven bythe light irradiation, the photoinduced deformation degree increased with the increase of the active component inthe hybrid colloids. When mixing the dispersions with C_w0 above CWC, the colloids obtained were observed tobe a mixture of the hybrid colloids and monocomponent colloids. The photoisomerization study confirmed thatthe cores of the hybrid colloids were formed from the more hydrophobic PEAPE component, and the coronaswere rich in the BP-AZ-CA component. The colloidal structures were formed due to the gradual hydrophobicaggregation of the polymeric chains in the THF-H₂O media. In the forming process, the more hydrophobic PEAPEchains started to aggregate first and then BP-AZ-CA chains gradually assembled on the cores while the watercontent gradually increased. The understanding and methodology can be applied to construct colloids composedof two or more photoresponsive polymers or even other functional polymers.