Solvent-free oxidative coupling polymerization of 3-hexylthiophene using FeCl3 oxidant was conducted to synthesize poly­(3-hexylthiophene) grains. Optical and scanning electron microscopy studies confirmed production of submillimeter-sized atypical grains with rough surfaces. Solubility test, Fourier transform infrared spectroscopy, and 1H nuclear magnetic resonance studies indicated the branching and cross-linking of the poly­(3-hexylthiophene). Elemental microanalysis and X-ray photoelectron spectroscopy studies confirmed that the poly­(3-hexylthiophene) grains were doped with chloride ions. The poly­(3-hexylthiophene) grains showed hydrophobic character due to hexyl side chains, and the critical surface tension was determined to be 25.9 mN m–1. The poly­(3-hexylthiophene) showed a light-to-heat photothermal property, and near-infrared laser irradiation to the poly­(3-hexylthiophene) grains induced a rapid temperature increase up to 664 °C. The poly­(3-hexylthiophene) grains can work as an effective liquid marble stabilizer with a photothermal property, and the liquid marble exhibited locomotion on a water surface due to near-infrared laser-induced Marangoni flow.

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Free radical dispersion polymerization was conducted to synthesize near-monodispersed, micrometer-sized polystyrene (PS) particles carrying pH-responsive poly(4-vinylpyridine) (P4VP) colloidal stabilizer (P4VP-PS particles). The P4VP-PS particles were extensively characterized in terms of morphology, size, size distribution, chemical composition, surface chemistry, and pH-response using optical and scanning electron microscopies, elemental microanalysis, X-ray photoelectron spectroscopy, laser diffraction particle size analysis, and zeta potential measurement. The P4VP-PS particles can work as a pH-responsive stabilizer of aqueous bubbles by adsorption at the air-water interface. At and above pH 4.0, where the particles have partially protonated/non-protonated P4VP stabilizer with relatively hydrophobic character, particle-stabilized bubbles were formed. Optical and scanning electron microscopy studies confirmed that the P4VP-PS particles were adsorbed at the air-water interface of the bubbles in aqueous media. At and below pH 3.0, where the particles have cationic P4VP stabilizer with water-soluble character, no bubble was formed. Rapid disruption of the bubbles can be induced by decreasing the pH; the addition of acid caused the in situ protonation of pyridine groups in P4VP, which impart water-soluble character to the P4VP stabilizer, and the P4VP-PS particles were desorbed from the air-water interface. The bubble stabilization/destabilization cycles could be repeated at least five times.

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Near-monodispersed, colloidally stable, submicrometer-sized poly­(acid phosphoxy ethyl methacrylate) (PAPEMA) latex particles were synthesized by free-radical dispersion polymerization using poly­(N-vinylpyrrolidone) (PNVP) as both a steric colloidal stabilizer and a precipitating agent. Polymerization in the absence of PNVP led to a homogeneous transparent solution of PAPEMA, which indicates that the PNVP is essential for latex formation and the complex of PNVP and PAPEMA was formed during the dispersion polymerization. Dispersion copolymerizations with a divinyl cross-linking comonomer (∼20 wt % based on acid phosphoxy ethyl methacrylate) were also successful in synthesizing near-monodispersed, colloidally stable cross-linked PAPEMA latex particles, and the softness and pK a values of the resulting PAPEMA latex particles can be controlled by varying the divinyl comonomer concentration. These sterically stabilized latex particles were characterized by electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, elemental microanalysis, and Fourier transform infrared spectroscopy. Characterization results indicated that the PNVP colloidal stabilizer was likely to be located homogeneously on the particle surfaces and within the interior of particles. Finally, it was demonstrated that the PAPEMA latex particles worked as an effective surface modifier for metal surfaces.