Narrow Results

The viscosity behavior of polyvinylpyrrolidone (PVP) has been determined at 25°C in mixed solvents comprising of water/dimethylformamide (DMF) and water /methanol (MeOH). Analysis of the data has considered the PVP as being both host and guest polymer in solution. The intrinsic viscosity of PVP in DMF is higher than in water and in MeOH, but also increases in a mixed solvent with high water content because of the effect of polymer-solvent interactions. It was also found that the intrinsic viscosity of PVP at finite concentration, [η_PVP]_c decreases with an increase in the concentration of PVP in solution. The viscosity behavior of PVP in a mixed solvent is affected by the concentration-dependent intermolecular excluded volume effect, which can be quantitatively expressed by the parameter, b_Y, which reflects the shrinkage of PVP chain coils, resulting in a decrease of [η_PVP]_c. The effect of temperature on the viscosity behavior of PVP in MeOH shows that the interaction parameter increases up to a maximum value, and then decreases after a certain temperature.

The intrinsic viscosity [η], Huggins constant (K_H), [η]₀, α³ and flow activation energy values of nylon 6 have been measured in water/m-cresol (0/100–20/80) systems at different temperatures (20–60°C). It has been found that the intrinsic viscosity, [η]₀ and α³ increase with the increase in water contents in m-cresol up to 15% and then decrease. They increase with the increase in temperature irrespective of solvent composition. It has been noted that the percent increase of α³ is the highest at 60°C and the lowest at 20°C for a particular solvent system. The intrinsic viscosity data obey Arrhenius equation over the considered conditions. The activation energy and the K_H values decrease very sharply with the addition of water, giving a minimum value at 15% of water and then increase slowly. The variation of all the parameters has been explained in terms of variation in thermodynamic quality of solvent with the addition of water to m-cresol and change in temperature, resulting in the change of conformational and orientational properties of polymer molecules. This change of solvent quality also results in variation of selective sorption of solvent over the polymer, such as hydrogen bonding, etc.

The refractive index increment, dynamic and static laser light scattering, intrinsic viscosity [η] and Huggins constant (K_H) of nylon 12 have been measured in m-cresol and sulphuric acid/water system at 10–60°C. The intrinsic viscosity, R_H, R_g, A₂, and (< S >²)^1/2 (calculated from viscosity data) and "a" values of nylon 12 are found to be higher in m-cresol than in sulphuric acid. All these parameters decrease with the increase in water contents in sulphuric acid. The refractive index increment, K_H and activation energy show an opposite trend to that of [η]. The intrinsic viscosity, R_H, R_g, A₂, and (< S >²)^1/2 have maximum values around 30–40°C in sulphuric acid/water system, whereas in m-cresol they fall at about 20°C. It has been concluded that the variation in size, interaction parameter (second virial coefficient), [η] and K_H of the polymer solutions with the alteration in solvent composition and temperature are the out come of change in thermodynamic quality of solvents, selective adsorption, hydrogen bonding and conformational transitions. It has also been concluded that the increase in temperature first enhances the quality of the solvent, encourages hydrogen bonding and specific adsorption, and then deteriorates, bringing conformational transitions in the polymer molecules. However, the addition of water to sulphuric acid continuously deteriorates the solvent quality. This characteristic of the solvent system brings conformational changes in the polymer especially at low temperatures.

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay. The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (IV) values. The relative intensity of C=O/CH is increased while increasing the amount of clay. DSC showed the appearance of multiple endotherms of poly(glycolic acid). TGA showed the percentage weight residue remain above 750°C for polymer-nano composite system was 21% and hence proved the flame retardancy (char forming) nature. TEM confirmed the nano size of the clay used to catalyze the condensation reaction. The intrinsic viscosity value was increased with the increase of percentage weight of Hectorite type clay.

The adsorption amount of poly(styrene sulfonate) and poly(dimethyldiallyl ammonium chloride) (PSS/PDDA) self-assembled multilayer membranes in designed dipping solvents were measured by UV-Vis-spectroscopy and quartz crystal microbalance (QCM). Intrinsic viscosities of PSS and PDDA in corresponding dipping solvents were determined by an Ubbelohde viscometer. It is found that the adsorption amount of PSS/PDDA self-assembled multilayer membranes built up in different dipping solutions, added salt concentration, pH of solution and solvent quality, respectively changed oppositely with the corresponding intrinsic viscosity of PSS and PDDA in dipping solvents. A negative relation between the adsorption amount and intrinsic viscosity was revealed, and explained in term of the concept of excluded volume of polymer molecule in dilute solutions.