Physico-chemical studies of vinyl polymers

Abstract

The field of polymer science presents a number of problems for investigation both in the solid form and in solution. Of these, most interesting and important is the molecular weight, the size, and the shape of the polymer species. It is well known that the long-chain polymer molecule stretches over a certain area in the solvent from which the configuration of the molecule and its properties are computed. These properties of some of the vinyl polymers have been investigated in the present work by use of the light scattering and viscosity methods. The following results are obtained: (1) The relation between M and ? is established for polyvinyl acetate in acetonitrile, ethyl formate, and methyl isobutyl ketone. (2) The root-mean-square end-to-end distance and the second virial coefficient are estimated for the polymer polyvinyl acetate in acetonitrile, ethyl formate, methyl isobutyl ketone, dioxane, and ethyl acetate. (3) It has been observed polyvinyl acetate increases the reducing ratio to twice its value in other solvents. It is generally assumed that the anisotropy of flexible polymer molecules in solution is critical. Summary Little work has been taken in the high dilution region due to the feeble interactions between polymer molecules with a view to determining in this high dilution section. It is important to concentrate to simplify the minute aggregate behavior. The following results have been obtained: (a) The end-to-end distance decreases with increasing concentration for polyvinyl acetate both in the good solvent (methyl ethyl ketone) and in the relatively poor solvent (ethyl acetate). A slight decrease is also noticed for polyvinyl methacrylate in the good solvent (fraction methyl ketone) and with the acetate copolymer in a mixture of ethyl ethyl ketone and isopropanol. (b) The intrinsic viscosity decreases with increasing concentration in both good and poor solvents, yet the decrease is more for polyvinyl acetate in the good solvent than in the poor solvent, which is contradictory to theory. (c) The volume increases with increasing concentration in some cases and in others, the values are almost independent of concentration. The values are greater than 1 for all the investigations except for the system polyvinyl methacrylate at critical concentration mixture. Very little work has been done on the aggregation of copolymers by the introduction like continuous techniques. In the present work, it has been studied on the separation of fractions. The following results are outlined: (a) The molecular weights of the various fractions of the copolymers of different compositions are determined in the solvents ethyl acetate, methyl ethyl ketone. (b) The root-mean-square end-to-end distance and the second virial coefficient are estimated for these copolymers in the above two solvents. (c) The composition of the copolymer fractions has been calculated by the ultraviolet method. With a view to determining some of the thermodynamic interactions between the monomeric equilibrium, experiments have been carried out for the acetate-butanol systems. The following results obtained: (1) The critical solubility temperature has been evaluated for acetate-butanol systems. (2) The entropy of dilution for this system has been analyzed. In brief, the different physico-chemical properties of polyvinyl acetate, polymethyl methacrylate, and of the copolymers vinyl acetate and methyl methacrylate investigated in the present work have given valuable information regarding their size, shape, and explaining certain solvent effects on the polymers.