Polymorphic Extended-Chain and Folded-Chain Crystals in Poly(vinylidene fluoride) Achieved by Combination of High Pressure and Ion鈥揇ipole Interaction

详细信息    查看全文

• 作者：Yue Li ; Saide Tang ; Ming-Wang Pan ; Lei Zhu ; Gan-Ji Zhong ; Zhong-Ming Li
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：December 8, 2015
• 年：2015
• 卷：48
• 期：23
• 页码：8565-8573
• 全文大小：640K
• ISSN：1520-5835

文摘

Manipulating polymorphism in extended chain-crystals (ECCs), which are commonly achieved by crystallization under high pressures, is important for enriching our understanding of basic polymer crystallization as well as for achieving high performance materials. In this study, the influence of high pressure and ion鈥揹ipole interaction on the polymorphism was investigated by comparing neat poly(vinylidene fluoride) (PVDF) and PVDF with 1 wt % cetyltrimethylammonium bromide (CTAB) nonisothermally crystallized from the melt at 210 掳C. Under low pressures (鈮?0 MPa), 纬 folded-chain crystals (FCCs), rather than 伪 FCCs, were obtained for PVDF/1 wt % CTAB because of the ion鈥揹ipole interaction. Under a moderate pressure (100 MPa), pure 尾 FCCs were formed in PVDF/1 wt % CTAB, owing to the synergistic effect of both high pressure and ion鈥揹ipole interaction. Under high pressures (鈮?00 MPa), mixtures of 尾/纬 FCCs and ECCs were obtained for PVDF/1 wt % CTAB. This was different from the neat PVDF, where mixtures of 伪 FCCs and 伪/纬/尾 ECCs coexisted when the pressure was between 200 and 400 MPa. The formation mechanisms of various crystalline forms and FCCs versus ECCs during the nonisothermal crystallization are discussed using the T鈥?i>P phase diagram for PVDF.