离子-偶极相互作用下压力诱导聚偏氟乙烯多晶型生成研究

Manipulating polymorphism can be achieved by different pressures during crystallization of poly(vinylidene fluoride), and understanding of its crystallization under pressure is important for achieving high performance materials. In this study, the influence of high pressure and ion-dipole interaction on the polymorphism was investigated by comparing neat PVDF and PVDF with 1 wt.% cetyltrimethylammonium bromide (CTAB) non-isothermally crystallized from the melt at 210℃. Under low pressures (≤10 MPa), γ folded-chain crystals (FCCs), rather than α FCCs, were obtained for PVDF/1 wt.% CTAB because of the ion-dipole interaction. Under a moderate pressure (100 MPa), pure β FCCs were formed in PVDF/1 wt.% CTAB, owing to the synergistic effect of both high pressure and ion-dipole interaction. Under high pressures (≥200 MPa), mixtures of β/γ FCCs and ECCs were obtained for PVDF/1 wt.% CTAB. This was different from the neat PVDF, where mixtures of α FCCs and α/γ/β ECCs coexisted when the pressure was between 200 and 400 MPa. The formation mechanisms of various crystalline forms and FCCs versus ECCs during the non-isothermal crystallization are discussed by T-P phase digram.