Mixed micelles from synergistic self-assembly of hybrid copolymers with charge difference electrostatic interaction indu
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ng Cao, Jianjie Xie, Qi Li, and Xianming Chen Fujian Provincial Key Laboratory of Fire Retardant Materials, College of Materials, Xiamen University, Xiamen
Shiao-Wei Kuo Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
Lizong Dai Fujian Provincial Key Laboratory of Fire Retardant Materials, College of Materials, Xiamen University, Xiamen (Received 31 January 2016; accepted 26 May 2016)
Novel mixed micelle was successfully fabricated by the synergistic self-assembly of poly(methacrylate isobutyl polyhedral oligomeric silsesquioxane (POSS)-co-Nisopropylacrylamide-co-oligo(ethylene glycol)methyl ether methacrylate-co-acrylic acid) (P(methacrylate isobutyl (MAPOSS)-co-NIPAM-co-OEGMA-co-AA)) and poly(methacrylate isobutyl POSS-co-N-isopropylacrylamide-co-oligo(ethylene glycol) methyl ether methacrylate-co-2-vinylpyridine) (P(MAPOSS-co-NIPAM-co-OEGMA-co-2VP)). Dynamic light scattering (DLS) and transmission electron microscopy characterizations demonstrate that the formation of mixed micelles is driven by electrostatic interaction. The formation of the mixed micelles was further implied by a simple fluorescence resonance energy transfer based technique. The mixed micelle possesses the biggest size at pH 5 7.0, which is attributed to the strongest electrostatic interaction between the two kinds of micelles. The zeta potential under different pH was detected to further investigate the surface charges corroborating the discussions. DLS and UV-vis indicate that the lower critical solution temperature (LCST) is pH dependent. The mixed micelles reach the highest LCST at pH 7.0. The LCST of the mixed micelle can be tuned by adjusting the volume ratio of the two kinds of micelles as well. Moreover, the thermo-responsive behavior of the mixed micelle is absolutely reversible.
I. INTRODUCTION
An amphiphilic polymer usually contains both hydrophilic and hydrophobic chains.1 Their self-assembly behavior can be attributed to the microphase separation,2 competing hydrophilic and hydrophobic interactions, and complementary physical interactions. Normally, solution self-assembly of amphiphilic polymers can afford structural hierarchies and various nanostructured phases, such as layered, core–shelled, cylindered ones, and so on.3 5 Sensitive polymers can change their structures and properties according to external stimuli.6 They have been extensively investigated recently as smart materials for various applications such as biomedicine, optics, Contributing Editor: Tao Xie a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.226
electronics, and so on.7 Most of the stimuli-responsive systems are driven by four fundamental forces, namely ionic, hydrophobic, hydrogen bonding, and van der Waals interactions.8 All of these forces are responsible for the ability of smart system to interconvert between two phases. In one case, the environmental stimulus enhances the attractive forces and the system col
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