Key Laboratory of Surface and Interface Sciences of Henan Province, Zhengzhou University of Light Industry, Zhengzhou 450002, China.
J Colloid Interface Sci. 2013 Jul 1;401:50-7. doi: 10.1016/j.jcis.2013.03.021. Epub 2013 Mar 28.
In this study, the effects of solvent and magnesium chloride hexahydrate (MgCl2·6H2O) on the polymorphism of polyvinylidene fluoride (PVDF) thin films were systematically investigated. Wherein, N,N-dimethylformamide (DMF) and water with different volume ratio were used as mixed solvents to obtain the solution casting films, P series. In addition, MgCl2·6H2O was comparatively added to prepare PVDF/MgCl2·6H2O hybrid films, P-M series. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimeter (DSC) were utilized to study the influence of the water content in the mixed solvents and the hydrated salt on crystallization behavior of PVDF. Further, the morphologic images from scanning electronic microscopy (SEM) and polarized optical microscopy (POM), as well as the pizoelectirc d33 test also supplies the corresponding evidences. As indicated, the water in the mixed solvent shows different effect on main crystal forms of PVDF. At low water content, the solvents may favor the polar phase (β- and γ-phase) mainly by hydrogen bonds interactions between PVDF and water, together with dipolar interactions between PVDF and DMF. At high water content, the nonsolvent water will impose confinement effect on polymer chain diffusion and crystal growth which facilitate the formation of α-phase PVDF. Moreover, magnesium chloride hexahydrate mainly functioned as the nucleation sites for PVDF crystallization. The result of small-angle X-ray scattering (SAXS) implies the content of water or MgCl2·6H2O has little impact on the structure of the long period.
在这项研究中，系统研究了溶剂和六水合氯化镁（MgCl2·6H2O）对聚偏氟乙烯（PVDF）薄膜多晶型的影响。其中，使用 N,N-二甲基甲酰胺（DMF）和不同体积比的水作为混合溶剂来获得溶液浇铸膜，记为 P 系列。此外，还比较性地添加了 MgCl2·6H2O 来制备 PVDF/MgCl2·6H2O 杂化膜，记为 P-M 系列。利用傅里叶变换红外光谱（FT-IR）、X 射线衍射（XRD）和差示扫描量热仪（DSC）研究了混合溶剂中含水量和水合盐对 PVDF 结晶行为的影响。此外，扫描电子显微镜（SEM）和偏光显微镜（POM）的形貌图像以及压电 d33 测试也提供了相应的证据。结果表明，混合溶剂中的水对 PVDF 的主要晶型有不同的影响。在低含水量时，溶剂可能通过 PVDF 与水之间的氢键相互作用以及 PVDF 与 DMF 之间的偶极相互作用有利于形成极性相（β-相和γ-相）。在高含水量时，非溶剂水会对聚合物链扩散和晶体生长施加限制作用，有利于形成α-PVDF。此外，六水合氯化镁主要作为 PVDF 结晶的成核位点。小角 X 射线散射（SAXS）的结果表明，水或 MgCl2·6H2O 的含量对长周期结构的影响很小。
