Thermoreversible Gelation of Poly(Vinylidene Fluoride) in Phthalates:  The Influence of Aliphatic Chain Length of Solvents

Abstract

Thermoreversible gelation of poly(vinylidene fluoride) (PVDF) has been studied in a new series of solvents (phthalates), for example, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and dihexyl phthalate (DHP) as a function of temperature and polymer concentration, both by test tube tilting and dynamic light scattering (DLS) method. The effect of aliphatic chain length (n) of diesters on the gelation kinetics, structure/microstructure and morphology of PVDF gels has been examined. Gelation rate was found to increase with increasing aliphatic chain length of diester. DLS results indicate that the sol-gel transformation proceeds via two-steps: first, microgel domains were formed, and then the infinite three-dimensional (3D) network is established by connecting microgels through polymer chains. The crystallites are responsible for 3D network for gelation in phthalates, and alpha-polymorph is formed during gelation producing higher amount of crystallinity with increasing aliphatic chain length of diester. Morphology of the networks of dried gels in different phthalates showed that fibril thickness and lateral dimensions decrease with higher homologues of phthalates. The scattering intensity is fitted with Debye-Bueche model in small-angle neutron scattering and suggested that both the correlation length and interlamellar spacing increases with n. A model has been proposed, based on electronic structure calculations, to explain the conformation of PVDF chain in presence of various phthalates and their complexes, which offer the cause of higher gelation rate for longer aliphatic chain length.

Crystalline polymorphism in poly(vinylidenefluoride) membranes

“…Its gelation processes forming α phase in camphor, organic diesters, and phthalates, forming β phase in ethylene carbonate (EC), have been investigated using molecular modeling [91]. Molecular modeling of the PVDF-EC system indicated that electrostatic and Hbonding forces are responsible for fixing the conformation of the β phase ( Fig.…”

“…Molecular modeling of the PVDF-EC system indicated that electrostatic and Hbonding forces are responsible for fixing the conformation of the β phase ( Fig. 9) [91]. It was believed that the interacting sites of PVDF and the diester were the >CF 2 and >C=O moieties, respectively, between which dipole-dipole-type interactions exist due to electronic polarization.…”

Nanoclay Templated Poly(vinylidene fluoride) Gels

“…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.…”

Thermoreversible Gelation of a Vinylidene Fluoride‐Based Copolymer in Methyl Ethyl Ketone: Dynamics and Structure

“…PVDF gels were prepared in the concentration range 1–30 wt% and gelation kinetics in MEK was studied as a function of polymer concentration by using the tube‐tilting method. In another set of measurements, the effect of temperature on the gelation kinetics was probed in the temperature range −40 to −20 °C for concentrations in the range 17–30 wt% …”