Ruma Ray

Influence of gamma irradiation on the molecular weight distribution and related properties of a polymer: study through simulation and experiment

The morphology of a polymer system gets modified by gamma irradiation through scission and cross-linking of chains, which may occur simultaneously. The effect of gamma irradiation on the associated properties of poly(ethylene oxide), e.g. molecular weight distribution, viscosity and microstructure, is reported in the present paper. A computer simulation study is performed to model and understand the experimentally observed changes that are induced by gamma irradiation on the associated properties of the polymer. The primary assumption of the model considers terminal monomers of the chain to be inactive. The probability of a monomer to be a reactive site participating in scission or cross-linking is assumed to be proportional to its distance from the ends, and hence is maximum at the center of the chain. Correlation is established between the irradiation dose and simulation time steps using molecular weight distribution pattern and intrinsic viscosity. The dependence of polymer viscosity on the preparation techniques, e.g. ultrasonic and magnetic stirring, is studied and fitted with Huggins equation in lower concentration range. Solution parameters, like intrinsic viscosity and the Huggins constant, are determined from plot extrapolation and they are studied for their variation with irradiation dose and concentration. The change in polymer microstructures with irradiation dose is also reported.

Investigation of ionic conduction in PEO–PVDF based blend polymer electrolytes

We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)–Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion – polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10–3 S/cm) is obtained for PEO – rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The reduction of conductivity at higher salt concentrations is the consequence of decrease in the carrier concentration due to the formation of an ion pair and ion aggregates. PVDF–rich compositions (20 wt. % PEO and 80 wt. % PVDF), on the other hand, show a very complex porous microstructure. We also observe a much lower ionic conductivity (maximum ∼ 10–6 S/cm at 15 wt. % salt) in these composite systems relative to PEO-rich composites.We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)–Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion – polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10–3 S/cm) is obtained for PEO – rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The ...

Fractal model of polymer electrolyte to investigate influence of high energy irradiation in molecular distribution and molar mass average

The present work is completely based on the theoretical investigation i.e. computer simulated study of the effect of gamma irradiation on the molecular weight distribution and the molar mass averages of solid polymer electrolytes which is relevant with the present trends of experimental works in this field. We propose a fractal model corresponding to polymer molecules by deterministic loop-less fractal (Vicsek). An initial un irradiated symmetrical molecular weight distribution has been considered. Application of high energy perturbation, for example gamma irradiation, affects the molecules mainly by two processes-scission and cross-linking of molecules which results morphological changes inside the system. A new parameter named as weight fraction, has been introduced to compare the structural modification of the sample with the experimental results. The four basic parameters representing the molar mass averages have been introduced in this context to analyze various structural properties such as intrinsic viscosity, number, weight and Z-average molecular weight etc. The results of our simulation work enables us an easy understanding about the nature of the response of solid polymer electrolyte to the external perturbation.