Synthesis of Thermo-Responsive Fluorinated Star-Shaped Polymers by Living Cationic Polymerization
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Synthesis of Thermo-Responsive Fluorinated Star-Shaped Polymers by Living Cationic Polymerization Tomomi Irita1, Katsuhiko Imoto1, Takabumi Nagai1 and Sadahito Aoshima2 e-mail address [email protected] 1
Chemical R&D Center, Daikin Industries, Ltd., 1-1 Nishi Hitotsuya, Settsu-shi, Osaka, 5668585, Japan 2 Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan ABSTRACT Well-controlled fluorinated star-shaped polymers with oxyethylene units were designed and synthesized by living cationic polymerization. These fluorinated star-shaped polymers were prepared using successive fluorinated initiators to generate fluorinated, end-functionalized and hydrophilic segments with oxyethylene. Poly(vinyl ether)s with oxyethylene units are known to be thermo-responsive polymers that exhibit a lower critical solution temperature (LCST) in aqueous solutions. These novel fluorine-containing star-shaped polymers with oxyethylene were also thermo-responsive, as expected. In addition, the hetero-fluorinated star-shaped polymers with oxyethylene segments and different fluorine compositions were synthesized with various bifunctional initiators by living cationic polymerization having narrow molecular weight distributions (Mw/Mn=1.23᧩1.29) and contained very little, if any, presence of the linear homopolymer precursor, as evidenced by GPC. The LCST of this polymer depended on the end group fluorine composition and significant changes in cloud points were observed in water, as confirmed by static light scattering (SLS) measurements. As an example, aqueous solutions the star-shaped polymers without fluorine terminal groups showed no cloud point below up to 60 ºC in aqueous solution. After the fluoro-functionality was incorporated into the terminal groups, the cloud point of the aqueous solutions decreased to almost 20 ºC. INTRODUCTION Fluorine is a remarkable element that can impart outstanding properties to a macromolecule, including low surface energy, low refractive index, high thermal stability, enhanced chemical resistance and so on when compared to their non-fluorinated analogues [1,2]. Miktoarm star-shaped copolymers show interesting properties in the solid state, as well as in solution, due to their unique architectures. Star-shaped polymers, which are usually defined as branched macromolecules that consist of linear polymer arms joined together by a central core, have been of great interest in the past decade.[3] We have demonstrated that cloud points of aqueous solutions of end-functionalized poly(vinyl ethers) with oxyethylene side groups synthesized by living cationic polymerization were governed by the properties of a terminal group[4]. Stimuli responsive polymers with various shapes were prepared. In the case of star-shaped polymers, the effect of end groups on the thermo sensitivity was controlled by the structure of the arms. The properties of star-shaped
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polymers and polymer micelles consisting of amphiphilic diblock copolymers w
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