Structure and surface properties of polyacrylates with short fluorocarbon side chain: Role of the main chain and spacer group
2010
Wang, Qiongyan | Zhang, Qinghua | Zhan, Xiaoli | Chen, Fengqiu
The degradation of poly(fluoroalkyl acrylate)s with long perfluoroalkyl groups, especially with perfluorooctyl group, leads to the release of biopersistent perfluorooctanoic acid (PFOA) or perfluorooctanesulfonic acid (PFOS). To find the environmentally friendly substitutes, a series of nonbiopersistant fluorinated polymers containing perfluorohexyl groups in the side chains have been synthesized and characterized. This study was then focused on the role played by the main chain and spacer group located in the side chain between the backbone and the fluorinated segment and, in particular, on the properties of poly[2-[[[[2-(perfluorohexyl)]-sulfonyl]methyl]amino]ethyl] acrylate (PC6SA), methacrylate (PC6SMA) and poly[(perfluorohexyl)ethyl] methacrylate (PC6MA). Surface properties and bulk organization of fluorinated side chains of those polymers were investigated by contact angles, differential scanning calorimetry, optical polaring microscopy, and wide-angle X-ray scattering. Results were compared with those obtained with poly[(perfluorohexyl) ethyl] acrylate (PC6A). They all had very low surface free energies. Surprisingly, with the same perfluoalkyl chain, PC6SA and PC6SMA with a N-methylsulfonamide spacer group were found to be organized in a liquid crystalline lamellar structure, whereas PC6A and PC6MA were found to be amorphous. This was mainly attributed to the steric term and polarity of N-methylsulfonamide group that tended to facilitate the orientation of the perfluorinated segments in smectic phases. PC6SA, PC6SMA, and PC6MA had rich dynamic water repellency because of the low surface molecular mobility. This phenomenon relates to the crystallization of side chains or high glass transition temperature.
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