Structure, phase transition and electric properties of poly(vinylidene fluoride-trifluoroethylene) copolymer studied with density functional theory

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

“…A possible explanation is that the chain curvature increases slightly with increasing VDCN content (as above discussed) that leads to the decreasing dipole moment contribution. This behavior is similar to P(VDF-TrFE) [52], P(VDCN-TrFE) [53], P(VDF-TeFE) [51], and P(VDCN-TeFE) [54] copolymers containing different TrFE and TeFE contents. A fit to the parabolic equation provides an estimate of the contributed magnitude of dipole moment per monomer unit (in 10 -30 C/m) in the b-chain P(VDCN-TeCN) with 12 Figure 5 shows that the mean polarizability per monomer unit in the b-chain P(VDCN-TeCN) or PVDCN is very similar to or slightly higher than that in the corresponding a-chain.…”

“…Similar to P(VDCN-TeFE) copolymer system (the energy difference is -4.7 kJ/mol in the alternate copolymer with 0.50 mole fraction of TeFE [54]), the energy difference are also negative values (-3.8 and -0.8 kJ/mol in P(VDCNTeCN) with 0.50 and 0.33 mole fractions of TeCN). This is the second system found among the alternate copolymer systems of P(VDF-TrFE) [52], P(VDF-TeFE) [51], P(VDCN-TrFE) [53], P(VDCN-TeFE) [54], and P(VDCNTeCN) that the b-conformation is more stable than the corresponding a-conformation thermodynamically. This result shows that introducing TeCN into VDCN is also in favor of forming the lower energetic trans-conformation (or b-chains), especially in the copolymer with 0.50 mole fraction of TeCN.…”

“…The theoretical level is the same as that in the study of the homopolyers of VDF [26] and VDCN [38], and their copolymers with TrFE [52,53], TeFE [51,54] , were also obtained. The tensor, e.g., a xy mol , is defined as the linear response to an externally applied electric field [58].…”

“…The chain conformation as well as the chain structure is J Mater Sci (2012) 47:5774-5783 5775 especially important in understanding the origin of piezoelectricity not only in crystalline but also in amorphous polymers. Based on the previous work concerning the structure-property relationships of PVDF [26], PVDCN [38] and their copolymers [38,[51][52][53][54] studied with density functional theory (DFT), this work carried out theoretical calculations on the internal rotation potentials, geometries, and electrical properties of the a-and b-chains P(VDCNTeCN) using the first principle DFT method in a number of structural models. Energy, permanent dipole moment and molecular polarizability of the models were obtained.…”

Crystalline polymorphism in poly(vinylidenefluoride) membranes

“…DFT simulation results show that the β conformation is more thermodynamically stable than the α conformation, and the β→α transition in P(VDF-co-TFE) [106] and P(VDF-TrFE) [107] is more difficult than that in PVDF. This is one of the reasons why the β phase is easier to obtain in these copolymers than in PVDF homopolymers.…”