Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1, Omiya, Asahi-ku, Osaka 535-8585, Japan.
Department of Applied Chemistry, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan.
Soft Matter. 2016 May 25;12(21):4794-804. doi: 10.1039/c6sm00425c.
Submicrometer-sized polystyrene (PS) particles carrying stimuli-responsive poly[2-(diethylamino)ethyl methacrylate] (PDEA) hairs with degrees of polymerization of 30, 60 and 90 were synthesized by dispersion polymerization and used as a particulate foam stabilizer. The effects of the composition of these PDEA-PS particles and foam formation conditions on foamability, foam stability and foam microstructures were extensively investigated. The hairy particles were found to work as an effective stabilizer of aqueous foams in basic media, in which the PDEA hairs are not protonated and thus the particle surfaces exhibit suitable wettability at the air-water interface. In contrast, little to no foam or unstable foams were formed in acidic aqueous media, in which the hairs are protonated and are therefore water soluble. Particles carrying longer hairs resulted in greater foamability and more highly stabilized foams that were capable of persisting for more than one month. Foams were found to form in a narrower pH range when using PS particles with longer hairs, due to both entropic and image charge effects. Data obtained from the touch mixer mixing method showed that both foamability and foam stability increased with increases in the concentration of polymer particles up to 10 wt%, because higher concentrations allowed greater air-water interfacial areas to be stabilized. Conversely, only minimal foam was obtained at and above 15 wt% because of the high viscosity of the resulting aqueous particle dispersion. Trials using the homogenizer mixing method showed that foam with a cream-like texture could be formed even at 40 wt% particle concentration as a result of the improved mixing efficiency. Defoamation could be induced by exposing the foams to HCl vapor. Exposure to acidic vapor led to in situ protonation of the 2-(diethylamino)ethyl methacrylate residues, rendering the PDEA hairs hydrophilic and water soluble, and desorption of the PDEA-PS particles from the air-water interface.
载有刺激响应性聚[2-（二乙基氨基）乙基甲基丙烯酸酯]（PDEA）毛发的亚微米级聚苯乙烯（PS）颗粒，其聚合度分别为 30、60 和 90，通过分散聚合合成，并用作颗粒泡沫稳定剂。广泛研究了这些 PDEA-PS 颗粒的组成和泡沫形成条件对起泡性、泡沫稳定性和泡沫微观结构的影响。研究发现，毛发状颗粒在碱性介质中是有效的水性泡沫稳定剂，在碱性介质中 PDEA 毛发不会质子化，因此颗粒表面在气-水界面处表现出适当的润湿性。相比之下，在酸性水性介质中几乎没有泡沫或不稳定的泡沫形成，在酸性水性介质中，毛发质子化且因此水溶性。携带较长毛发的颗粒导致更大的起泡性和更高度稳定的泡沫，能够持续一个多月。由于熵和图像电荷效应，使用带有较长毛发的 PS 颗粒时，泡沫形成的 pH 范围变窄。通过触变混合器混合方法获得的数据表明，泡沫稳定性和泡沫稳定性都随着聚合物颗粒浓度增加到 10wt%而增加，因为更高的浓度允许更大的气-水界面面积得到稳定。相反，由于所得水相颗粒分散体的高粘度，仅在 15wt%及以上时获得最小的泡沫。使用匀浆器混合方法的试验表明，由于混合效率的提高，即使在 40wt%颗粒浓度下也可以形成具有奶油状质地的泡沫。通过暴露于 HCl 蒸汽可以引起消泡。暴露于酸性蒸汽会导致 2-（二乙基氨基）乙基甲基丙烯酸酯残基原位质子化，使 PDEA 毛发亲水且水溶性，并从气-水界面解吸 PDEA-PS 颗粒。
