In Jun Park

Synthesis of fluorine-containing graft copolymers of poly(perfluoroalkylethyl methacrylate)-g-poly(methyl methacrylate) by the macromonomer technique and emulsion copolymerization method

A new method of synthesizing graft copolymers having a poly(perfluoroalkylethyl methacrylate) (PFMA) backbone has been suggested and illustrated by preparing poly(perfluoroalkylethyl methacrylate)-g-poly(methyl methacrylate)s (PFMA-g-PMMA). These copolymers were prepared using the macromonomer technique and emulsion copolymerization method. PMMA macromonomers were synthesized by acylation of hydroxyl-group terminated PMMAs which were prepared by radical oligomerization of methyl methacrylate with a chain-transfer agent. The PMMA macromonomer was copolymerized with a comonomer of perfluoroalkylethyl methacrylate (FMA) by emulsion polymerization to obtain graft copolymers of PFMA-g-PMMA. Toluene was chosen as a suitable solvent to obtain stable emulsions containing PMMA macromonomer and FMA for copolymerization. Graft copolymers having various PMMA compositions and branch lengths could be prepared. It is confirmed that the desired graft copolymers were successfully prepared and that the method suggested for synthesizing PFMA-g-PMMAs is useful in the manufacture of various surface modification agents.

Surface properties of core-shell particles containing perfluoroalkyl acrylate in shell

The preparation and surface properties of core-shell latex particles containing fluorinated shell were considered in this study. The core-shell particles were prepared by a two-stage emulsion polymerization under kinetically controlled conditions. Alkyl methacrylate monomers having different side chain length were used as a comonomer to form the shell with perfluoroalkyl acrylate. The surface properties of the latex films produced from the core-shell particles were investigated by sliding angle measurement as well as contact angle method. Although the latex films produced from the core-shell particles exhibited similar surface free energy of 10 mN/m, there existed significant difference in the sliding angles of water and oil droplets depending on the side chain length of alkyl methacrylate comonomers.

Synthesis of pillar and microsphere-like magnesium oxide particles and their fluoride adsorption performance in aqueous solutions

We synthesized pillar and microsphere-like MgO particles and their fluoride removal performance. Samples of MgO were synthesized by calcination of precursors derived from MgCO3·3H2O and characterized using field emission scanning electron microscopy, X-ray diffraction, and N2 adsorption-desorption isotherms. The fluoride removal performance of the MgO samples was investigated in terms of adsorption kinetics and adsorption equilibrium. The effects of pH and the presence of other anions on the fluoride adsorption were also considered. The adsorption capacities of pillar and microsphere-like MgO particles were 151.51 and 166.66 mg/g, respectively. The pH of the aqueous solutions did not significantly affect the fluoride adsorption at pH 9 or lower. Except for phosphate, the effect of co-existing anions on fluoride adsorption was not considerable. Fluoride removal occurred through the substitution of hydroxyl groups on the surface of MgO with fluorides.

Enhanced biocompatibility in poly(3-hexylthiophene)-based organic thin-film transistors upon blending with poly(2-(2-acetoxyacetyl)ethyl methacrylate)

Polymer blends with both biocompatibility and organic thin film transistor (OTFT) characteristics are developed by mixing a biocompatible polymer, poly(2-(2-acetoxyacetyl)ethyl methacrylate) (PHEMAAA) and a conducting polymer, poly(3-hexyl thiophene) (P3HT) at different weight ratios (i.e. P3HT/PHEMAAA = 75/25, 50/50, 25/75). Their OTFT performances were maintained at a similar level to those of pristine P3HT in spite of adding an insulator in the form of PHEMAAA. On the other hand, the biocompatibility of the P3HT/PHEMAAA blend films was found to be as good as that of PHEMAAA, indicating the successful contribution of the biocompatible polymer. In particular, these combined properties were optimized at a 25/75 weight ratio as described above. These results could be correlated with surface properties such as molecular orientation, morphology, and composition that change upon blending. Such P3HT/PHEMAAA blends are promising materials for applications in biomedical fields where materials come into contact with the human body.

Tuning Surface Properties of Poly(methyl methacrylate) Film Using Poly(perfluoromethyl methacrylate)s with Short Perfluorinated Side Chains.

To control the surface properties of a commonly used polymer, poly(methyl methacrylate) (PMMA), poly(perfluoromethyl methacrylate)s (PFMMAs) with short perfluorinated side groups (i.e., -CF3, -CF2CF3, -(CF3)2, -CF2CF2CF3) were used as blend components because of their good solubility in organic solvents, low surface energies, and high optical transmittance. The surface energies of the blend films of PFMMA with the -CF3 group and PMMA increased continuously with increasing PMMA contents from 17.6 to 26.0 mN/m, whereas those of the other polymer blend films remained at very low levels (10.2-12.6 mN/m), similar to those of pure PFMMAs, even when the blends contained 90 wt %PMMA. Surface morphology and composition measurements revealed that this result originated from the different blend structures, such as lateral and vertical phase separations. We expect that these PFMMAs will be useful in widening the applicable window of PMMA.

Surfactant-free preparation of poly(vinylidene fluoride) nanoparticle dispersions and their use as surface coating agents

Surfactant-free emulsion polymerisation of vinylidene fluoride was performed using poly(ethylene glycol) and a dispersion of poly(vinylidene fluoride) (PVDF) nanoparticles instead of typical fluorinated surfactants. This approach allows facile preparation of PVDF-nanoparticle-coated surfaces, thus expanding the application scope of PVDF nanoparticles and their copolymer dispersion products.

Synthesis and characterization of poly(trifluoroethylene- co -hexafluoropropylene) and the optical properties of its thin films

Copolymers of trifluoroethylene (TrFE) and hexafluoropropylene (HFP) were synthesized and characterized by various instrumental techniques. The maximum incorporation of HFP was 19.6 mol%. It was found that the reactivity ratios of TrFE and HFP were rTrFE=4.12 and rHFP≈0, respectively, by applying Mayo-Lewis method. It was also found that the incorporation of HFP in copolymer chain influenced thermal properties. As increasing HFP content in copolymers, the melting temperature and crystallinity of copolymers were decreased and the glass transition temperature of copolymers gradually shifted to low temperature. Reduced crystallinity of copolymers was helpful to prepare coating layers having much even surface. Compared with coating layer prepared from TrFE homopolymer, the surface roughness was decreased and light transmittance through the coating layer increased when the copolymers of TrFE and HFP were used. This tendency was more appreciable as increasing HFP content in the copolymers.

Silica-core perfluorinated polymer-shell composite nanoparticles for highly stable and efficient superhydrophobic surfaces

Silica-core/perfluorinated polymer-shell composite nanoparticles (NPs) were spray-coated onto an adhesive-coated surface to fabricate robust superhydrophobic surfaces. The spontaneous assembly of the NPs led to complex micro/nano dual-scale roughness and the epoxy adhesive layer in between the NPs and the substrate imparted high mechanical robustness to the surface against external damage.