Thermoreversible Gelation of Poly(vinylidene fluoride-co-hexafluoro propylene) in Phthalates

Abstract

The thermoreversible gelation of poly(vinylidene fluoride-co-hexafluoro propylene) copolymer have been studied in a series of phthalates, Ph-(COO C(n)H(2n+1))(2) with n = 1-8. The gelation rate increases with increasing aliphatic chain length up to n = 6, and the gelation phenomena does not occur for higher n > 6. The fibrillar morphology is evident for dried gels whose dimension (both lateral and thickness) becomes shorter and thinner with increasing n. The structures of the gels formed in various phthalates have been investigated by small-angle neutron scattering and small-angle X-ray scattering techniques, suggesting sheet-like structure, where the interplanner distance increases with increasing aliphatic chain length. The scattering intensity I(q) decreases with q according to the Ornstein-Zernike model, where q = (4pi/lambda) sin theta (2theta and lambda are scattering angle and wavelength of neutron) and the correlation length, xi, assigned to the average distance between the neighboring crystallites, also increases with increasing aliphatic chain length of diesters. The detailed thermal analyses and phase diagrams of the copolymer gels have been studied in a wide range of phthalates. Further, polymer-solvent complexes leading to the formation of two distinct compounds have been reported. A systematic change of compound composition has also been observed in the whole range of phthalates studied here. On the basis of electronic structure calculation, a model has been proposed to elucidate the conformation of copolymer chain in presence of various phthalates and their complexes, which offer the cause of higher gelation rate for longer aliphatic chain length up to n = 6, no gelation phenomena occurs for n > 6, and formation of two copolymer-solvent compounds. The mechanical properties (storage modulus and viscosity) decrease with increasing aliphatic chain length of phthalates and realignment of fibrils occurs at particular frequency depending on the strength of fibrillar gels.

Thermoreversible Gelation of Poly(vinylidene fluoride-co-chlorotrifluoroethylene): Structure, Morphology, Thermodynamics, and Theoretical Prediction

“…20À24 Recently, we have reported thermoreversible gelation on PVDF copolymer, i.e., poly(vinylidene fluoride-co-hexafluoropropylene), in aromatic diesteres (phthalates) [Ph(COOC n H nþ1 ) 2 ]. 19 Gel has some definite capability to retain solvents in the network structure, and solvent retention power has been studied for pure PVDF in our earlier work 18 and other polymers 25 using thermogravimetric techniques. Small-angle neutron scattering and small-angle X-ray scatterings are powerful techniques to study the structure, mass, and surface fractals and morphology of gels.…”

“…Another important aspect of prediction of experimental results theoretically by means of energy minimization program, and there are only a few reports in the literature including our previous results on other systems. 17,19,33 Copolymer of vinylidene fluoride with chlorotrifluoroethylene P(VDF-co-CTFE) is an interesting polymer and are widely used ABSTRACT: Thermoreversible gelation of a copolymer, poly-(vinylidene fluoride-co-chlorotrifluoroethylene), has been studied in a series of aromatic diesters (phthalates) with varying aliphatic chain length, n. The gelation rate gradually increases with increasing n, but no gelation occurs in dioctyl phthalate (n = 8), giving rise to a solvent dependency. Structures of gels and dried gels have been studied through X-ray diffraction and FTIR studies.…”

Nanoclay Templated Poly(vinylidene fluoride) Gels

“…The composition of the compound formed shifts to lower weight fraction of PVDF in nanogel. The values are 0.57 and 0.46 for gel and nanogel, respectively, corresponding to the ratios of the monomeric units of PVDF and solvent (dibutyl phthalate) molecule 6:1 and 5:1, respectively . In other words, every single phthalate molecule needs 6 and 5 monomeric units to form a complex in gel and nanogel, respectively.…”

“…However, the lower q regions are best fitted, represented by solid line (inset figure), with Debye‐Bueche model (Eqn. ), where is the extrapolated structure factor at zero wavevector and is the correlation length . The correlation length, , essentially the blob dimension has drastically been reduced in nanogel (7.4 nm), thereby explain the term nanogel, as compared to pure gel (30.7 nm) in same solvent.…”

Effect of Isotacticity of Linear Poly(N-isopropylacrylamide) on its Gelation in Benzyl Alcohol

“…Similar type of observation was also noted for poly(vinylidene fluoride-co-hexafluoro propylene) copolymer systems in phthalates. 31 The corresponding comparative results of the complex viscosity vs. frequency in the temperature range of 40-53 • C are shown in the figure 5 (c). In general, viscosity decreases with increase in temperature throughout the measured frequency range.…”