Kitabata Masahiro, Taddese Tseden, Okazaki Susumu
Research Association of High-Throughput Design and Development for Advanced Functional Materials (ADMAT), 2266-98 Anagahora, Shimo-Shidami, Moriyama-Ku, Nagoya, Aichi 463-8560, Japan.
Department of Materials Chemistry, Graduate School of Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya, Aichi 464-8603, Japan.
Langmuir. 2020 Apr 7;36(13):3633-3644. doi: 10.1021/acs.langmuir.9b03307. Epub 2020 Mar 26.
This study investigated the wettability of poly(vinylidene fluoride) (PVDF) surfaces by a good pure solvent and a good solvent/nonsolvent mixture based on all-atom molecular dynamics (MD) simulations. In particular, droplets of pure -methyl-2-pyrrolidone (NMP) and of mixed NMP/water molecules were brought into contact with both crystalline and amorphous PVDF surfaces. The contact angles of the macroscopic droplets on the crystalline surface were higher and those on the amorphous surface were lower than the experimental values. As the PVDF sheet surface is a mixture of crystalline and amorphous phases, the experimental contact angles being between those on crystalline and amorphous surfaces is reasonable. On the crystalline surface, the decrease in the contact angle with increasing NMP concentration in the droplets can be explained by the increase in the NMP density near the solid-liquid interface. On the amorphous surface, however, the contact angle is strongly affected by the swelling of PVDF by the mixed droplets at high NMP concentrations. The solvation free energy of PVDF in NMP is greater than that in water, suggesting that this may be a driving force of the swelling of the amorphous PVDF. Furthermore, when the Cassie equation for mixed crystalline and amorphous surfaces was assumed, the calculated contact angle corresponded well with the experimental value.
本研究基于全原子分子动力学（MD）模拟，研究了聚偏氟乙烯（PVDF）表面在良纯溶剂以及良溶剂/非溶剂混合物中的润湿性。具体而言，将纯N-甲基-2-吡咯烷酮（NMP）液滴以及NMP/水分子混合液滴与结晶态和非晶态PVDF表面接触。结晶表面上宏观液滴的接触角高于实验值，而非晶表面上的接触角低于实验值。由于PVDF片材表面是结晶相和非晶相的混合物，实验接触角介于结晶表面和非晶表面的接触角之间是合理的。在结晶表面上，随着液滴中NMP浓度的增加，接触角的减小可归因于固液界面附近NMP密度的增加。然而，在非晶表面上，高NMP浓度下混合液滴使PVDF溶胀，这对接触角有很大影响。PVDF在NMP中的溶剂化自由能大于在水中的溶剂化自由能，这表明这可能是非晶态PVDF溶胀的驱动力。此外，当假设混合结晶和非晶表面的Cassie方程时，计算得到的接触角与实验值吻合良好。
