Polar phase formation in poly(vinylidene fluoride) induced by melt annealing

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 50; no. 20; pp. 1433 - 1437
• Main Authors: Pan, Huayan, Na, Bing, Lv, Ruihua, Li, Chun, Zhu, Jie, Yu, Zhiwei
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.10.2012; Wiley
• Subjects: Annealing; Applied sciences; Coils; Cooling; Crystallization; Exact sciences and technology; Fluorides; infrared spectroscopy; melt annealing; Melting; Melts; Organic polymers; Physicochemistry of polymers; polar phase; poly(vinylidene fluoride); Polymer physics; Properties and characterization; Annealing; poly(vinylidene fluoride); polar phase; Experimental study; Polymorphic transformation; Alpha form; Gamma form; melt annealing; Beta form; Vinylidene fluoride polymer; crystallization; Memory effect; infrared spectroscopy
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23146

It is still a challenge to obtain polar phase of poly(vinylidene fluoride) from melt crystallization at normal conditions. This study demonstrates that polar β‐ and γ phases can be produced through melting re‐crystallization of α phase, provided that moderate memory effects in the melt is achieved by annealing. Otherwise, it is inevitable to re‐crystallize into α phase without any trace of polar phase. Small fragments, generated from the disintegration of long TGTG′ sequences, most likely adopt trans conformation in the melt before approaching random coils, thus responsible for the formation of polar phase upon cooling. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 Melt crystallization of PVDF usually results in the formation of nonpolar α phase. In this case polar β‐ and γ phases, without any trace of α phase, have been successfully achieved via controlled annealing of the melt generated by initial α phase. Moreover, formation of β phase competes with γ phase, depending on the cooling rate. The decrease in the cooling rate favors the formation of γ phase rather than β phase.