Interfacial Nanostructuring of Poly(vinylidene fluoride) Homopolymer with Predominant Ferroelectric Phases
Interfacial Nanostructuring of Poly(vinylidene fluoride) Homopolymer with Predominant Ferroelectric Phases
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DOI：
10.1021/acs.langmuir.0c02667
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发表时间：
2020-11-24
期刊：
影响因子：
3.9
通讯作者：
Mitsuishi, Masaya
中科院分区：
文献类型：
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作者：
Fu, Chang;Zhu, Huie;Mitsuishi, Masaya
采用两种界面组装方法，在非溶剂（水/甲醇）-溶剂（二甲基甲酰胺（DMF））-聚合物（PVDF）三元体系中制备了粒径分布均匀、铁电相占优势的聚偏氟乙烯（PVDF）均聚物纳米粒子（NPs）。首先，通过在PVDF溶液下引入非溶剂（水）来产生由两种可混溶溶剂组成的流体液-液界面。界面形成后，界面向DMF相方向移动，通过非溶剂诱导相分离制备PVDF纳米粒子。随着非溶剂中的水含量通过与甲醇混合而降低，PVDF结构从平均直径为252 nm的纳米颗粒（PVDF NP-1）通过膜包裹的NPs变成多孔膜。发现这种现象与溶剂、非溶剂和PVDF之间的相互亲合力有关。当通过磁力搅拌（再沉淀法）向水-DMF-PVDF体系引入额外的外力时，获得直径为61.4nm的较小PVDF NP（PVDF NP-2）。所制备的两种PVDF NP都被证明具有在结晶相中高达97-98%的主要铁电（电活性（EA））相，这显然是PVDF均聚物NP所报道的最高值。值得注意的是，PVDF NP-2显示出比PVDF NP-1更高的β相比率，如使用傅里叶变换红外（FT-IR）光谱所证明的。此外，差示扫描量热法（DSC）和X射线衍射（XRD）测量显示，PVDF NP-1具有较高的结晶度和PVDF NP-2经历了良好的分离两步加热下的相变。结果表明，控制界面形成与DMF和水起着至关重要的作用，在操纵铁电PVDF纳米结构的结晶度和铁电β相-γ相的比例。
Facile preparation of poly(vinylidene fluoride) (PVDF homopolymer nanoparticles (NPs) with monodispersed size distribution and predominant ferroelectric phases was done in an interfacial nonsolvent (water/methanol)-solvent (dimethylformamide (DMF))-polymer (PVDF) ternary system using two interfacial nanoassembly methods. First, a fluidic liquid-liquid interface consisting of two miscible solvents was created by introducing nonsolvent (water) under the PVDF solution. After the interface was created, the interface moved up to the DMF phase direction; PVDF NPs were produced through nonsolvent-induced phase separation. As the water content decreased in the nonsolvent by mixing with methanol, PVDF structures changed from nanoparticles with 252 nm average diameter (PVDF NP-1) to a porous membrane through membrane-wrapped NPs. The phenomena were found to be related to the mutual affinity of solvent, nonsolvent, and PVDF. When an additional external force was introduced to the water-DMF-PVDF system through magnetic stirring (reprecipitation method), smaller PVDF NPs with 61.4 nm diameter were obtained (PVDF NP-2). Both the as-prepared PVDF NPs were demonstrated with the predominant ferroelectric (electroactive (EA)) phase up to 97-98% among crystalline phases, which is apparently the highest value ever reported for PVDF homopolymer NPs. It is noteworthy that PVDF NP-2 showed a higher beta phase ratio than that of PVDF NP-1, as proved using Fourier transform infrared (FT-IR) spectroscopy. Also, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements revealed that PVDF NP-1 exhibited higher crystallinity and that PVDF NP-2 underwent a well-separated two-step phase transition under heating. Results suggest that controlling interface formation with DMF and water plays a crucial role in manipulating ferroelectric PVDF nanostructures in terms of crystallinity and the ferroelectric beta phase-to-gamma phase ratio.