Title of Thesis

Characterization of Polymers by Light Scattering Techniques

Author(s)

Javaid Khan

Abstract
The present investigation has been carried out on cellulose acetate obtained from Ravi Rayon Ltd. Kala Shah Kaku, Lahore. The characterizations of cellulose acetate Has been done by determining the different parameters, such as molecular weight, size and shape by light scattering and viscosity techniques. The fractionation of cellulose acetate has been carried out Pad molecular weight distribution was studied. Nine fractions of cellulose acetate were obtained by fractional precipitation method. Instrumental constant was determined by computational method at 25°C. Specific refractive index increments of different fractions were determined at 25^oC using 456 nm and 546 nm wavelengths. Molecular weights of different fractions were determined at 25^oC at 456 nm and 546 am wavelength by light scattering methods. It was observed that molecular weight of different fractions decreases from highest fraction to lowest fraction. The size or cellulose acetate particles was obtained by dissymmetry method. The values of the diameters of the particles were calculated and compared with the standard data of coil like and rod like shape as in the literature. It was concluded that at higher concentration, the shape of particles changes from coil like to rod like. The values of molecular weight of different cellulose acetate fractions were also obtained by viscosity method at 25^oC and were compared with the molecular weights by light scattering methods. It has been concluded that the values obtained by all the methods ere in good agreement with one another. The effect of temperature wee also studied using different temperatures 10^o, 15^o,20^o, 25^o and 30^oC. The value of intrinsic viscosity decreases from highest to lowest fraction and also with the increase in temperature. The molecular weight of unfractionated cellulose acetate was also determined under similar conditions. The molecular weight of cellulose acetate was found to be equal to the average of molecular weights of different fractions.

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