On the gelation rates of thermoreversible poly(vinylidene fluoride) gels

Mal, Sukumar ; Maiti, Pralay ; Nandi, Arun K. (1995) On the gelation rates of thermoreversible poly(vinylidene fluoride) gels Macromolecules, 28 (7). pp. 2371-2376. ISSN 0024-9297

Full text not available from this repository.

Official URL: http://pubs.acs.org/doi/abs/10.1021/ma00111a034

Related URL: http://dx.doi.org/10.1021/ma00111a034


The gelation rates of poly(vinylidene fluoride) (PVF2) gels have been measured for three commercial samples each in two different solvents at different polymer concentrations and also at different temperatures. The rate has been expressed as a combination of temperature-dependent function f(T) and concentration-dependent function (φ)n ; φ is the reduced overlapping concentration of the polymer chains. φ has a resemblance with the P - Pc term of percolation theory, P being the conversion factor and Pc its critical value. Exponent n has been measured from double logarithmic plots of tgel-1 and φ, and it lies between 0.45 and 0.6 which is closer to percolation exponent β (0.45) of a three-dimensional lattice. This indicates that three-dimensional percolation is a suitable model for this thermoreversible gelation process. The temperature-dependent function of the gelation rate has been found to be analogous to the temperature-dependent function of the nucleation rate of crystalline polymers in dilute solutions. There is some dependency of the gelation rate on the amount of H-H defect (-CF2CF2-) structures present in the polymers and also on the molecular weight of the samples. Solvents also have a significant influence on the gelation rate of the polymer : the poorer the solvent, the faster is the gelation rate. The critical gelation concentration (Ct=α ) measured from gelation kinetics by an extrapolation procedure increases with temperature in each case. Thermodynamic analysis of the variation of Ct=α with temperature reveals that about three to six crystallites (depending on the solvent and sample) are involved to produce a single crosslink in the gel.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:24100
Deposited On:29 Nov 2010 10:26
Last Modified:08 Jun 2011 07:04

Repository Staff Only: item control page