The high-pressure crystallization behaviours and piezoelectricity of extended chain lamellar crystals of vinylidene fluoride trifluoroethylene copolymers with high molar content of vinylidene fluoride

Stress-induced structural changes in electrospun polyvinylidene difluoride nanofibers collected using a modified rotating disk

“…The increased crystallinity for PVDF and PVDF/MWCNT may come from both the a and b-phases as from the WAXD patterns and FTIR spectra of the sample d and e(ii) we can observe very slight enhancement of the a-phase as compared with the sample c and e(i). The melting temperatures of the fibrous thin films collected using the modified rotating disk are only marginally higher than that from the unmodified rotating disk but much lower than that of the b-form extendedchain crystals obtained under high-pressure conditions [3], which is probably due to the much smaller crystal size in the nanofibers. …”

“…Depending on processing conditions, PVDF can exhibit at least four distinct polymorphs, which involve three different chain conformations, namely (1) slightly twisted all-trans zigzag (TTTT, T denotes trans) for b-phase, (2) TGTG 0 (G denotes gauche) for a and d (a p ) phases and (3) TTTGTTTG 0 for g phase [1,2]. Folded-chain crystals are formed in PVDF under common conditions, while under high pressure and temperature PVDF can also form b-form extendedchain crystals [3]. When PVDF chains are packed into crystal lattices, their dipoles are either additive, which leads to a net dipole as in b, g and a p phases, or subtractive, resulting in no net dipole as in a-phase.…”

Localized Pressure‐Induced Ferroelectric Pattern Arrays of Semicrystalline Poly(vinylidene fluoride) by Microimprinting

“…Approximately 50 MPa was required to increase T m by more than 10°C. [19] The pressure (200-800 kPa)…”

Structure and electric properties of Poly(vinylidene cyanide-tetracyanoethylene) copolymer predicted with density functional theory

“…The main motivation is that the ferroelectric polymer materials could offer the unique features of large strain without structure fatigue, light weight, low cost, great mechanical strength, easy processability into thin and flexible films of various shapes and sizes, chemical inertness coupled with substantial piezoelectric and pyroelectric properties, and most importantly, flexible architecture design via molecular tailoring [1][2][3][4][5]. Therefore, since Kawai's [6] pioneering work in the area of piezoelectric polymers, it has led to the development of strong piezoelectric activity in polyvinylidene fluoride (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)) [7][8][9][10][11] and tetrafluoroethylene (P(VDF-TeFE)) [9,12,13], and to the search for other classes of novel ferroelectric polymeric materials. Actually, researchers have extended their work to explore the chemistry, physics and technology in the ferroelectric polymers such as odd numbered polyimides [14,15], cyanopolymers [16], polyurethane [17,18], and polythioureas [19,20].…”