国内精品国产三级国产在线专_欧美日韩在线播放一区二区_成人xxxx视频_欧美激情视频一区_色女人综合av_久久久亚洲影院_久久久久久九九_成人免费网站在线_日韩美女毛茸茸_狠狠干一区二区

The single-chain mechanics of two similar thermosensitive polymers, poly(N,N-diethyl-acrylamide) (PDEAM) and poly(N-isopropyl-acrylamide) (PNIPAM), have been studied by atomic force microscopy-based single-molecule force spectroscopy (SMFS). In a typical nonpolar organic solvent, octane, both the two polymers show the same inherent elasticity, although they have different substitutional groups. However, the mechanics of the two polymers present large differences in water. The energies needed for the changes of the bound water during elongation at room temperature are estimated by the SMFS method at the single-chain level, which is ~1.13 ± 0.10 and ~5.19 ± 0.10 kJ/mol for PDEAM and PNIPAM, respectively. In addition, PNIPAM shows a temperature-dependent single-chain mechanics when the temperature is increased across the lower critical solution temperature (LCST), while PDEAM does not. These differences observed in aqueous solution originate from the different structures of the two polymers. With a hydrogen bond donor in the amide group, PNIPAM will be more hydrated when T < LCST. When T > LCST, PNIPAM will have a larger change in both conformation and hydration. These findings also suggest that PNIPAM is a good candidate for thermo-driven single-molecule motor, while PDEAM is not.