Design, synthesis, characterization, and surface activities of comb-like polymeric fluorinated surfactants with short fluoroalkyl chains

By Lingyun Song, Ruiguo Wang, Kaikai Niu, Yuxiu Liu, Junjie Kou, Hongjian Song, Jingjing Zhang, and Qingmin Wang
Colloids Surfaces A
October 13, 2020
DOI: 10.1016/j.colsurfa.2020.125666

Compared to hydrocarbon surfactants, fluorinated surfactants exhibit excellent surface activity. But long-chain linear perfluoroalkyl derivatives containing more than six CFn units have raised environmental concerns because they are persistent, bio accumulative, and highly toxic. Therefore, the development of new, environmentally friendly fluorinated surfactants is urgently required. Given that shortening the fluorocarbon chains of fluorinated surfactants can enhance their environmental safety, we designed and prepared a series of novel comb-like polymeric fluorinated surfactants by means of one-step free-radical copolymerization reactions of fluorinated methacrylates (FMAs) as hydrophobic monomers (containing two, four, or six CF2 groups; denoted FMA-4, FMA-8, and FMA-12, respectively) and poly(ethylene glycol) methyl ether methacrylates (PEGMEMAs) as hydrophilic monomers (Mn = 300, 500, or 950 Da; denoted PEGMEMA-300, PEGMEMA-500, and PEGMEMA-950, respectively) with initiation by 2,2-azobis(2-methylpropionitrile). The resulting surfactants, designated poly(PEGMEMAm-FMAn)^x, were characterized by ¹H and ¹⁹F nuclear magnetic resonance spectroscopy, gel permeation chromatography, static surface tension analysis, dynamic light scattering and transmission electron microscopy. The surface activities of the surfactants could be regulated by adjusting the ratio of the hydrophilic and hydrophobic monomers. A result that differs from that for previously reportedly fluorinated surfactants, we found for the first time that under certain conditions, the surface activities of these short-fluorocarbon-chain surfactants exceeded the activities of long-fluorocarbon-chain surfactants. The lowest static surface tension achieved with these poly(PEGMEMAm-FMAn)^x surfactants in water was 30.12 mN/m.