BIOPHYSICAL STUDIES OF γ-IRRADIATED GLYCOGEN/POLYVINYL ALCOHOL BLENDS DOPED WITH DYE

Abstract

The present thesis deals with the preparation, characterization and investigation of some biophysical properties of polyvinyl alcohol (PV A), glycogen homopolymers and their blends. In addition, it shows the influence of y-iiTadiation with doses in the range from 5 up to I 00 kGy on the initial properties for blend sample of composition 70/30 (wtlwt %) PYA/glycogen undoped and doped with eosin. Studies were can•ied out using X-ray diffraction, IR spectroscopy, UV/visible spectroscopy, differential scanmng calorimetry (DSC), thermogravimetric analysis (TGA) and electrical measurements, viz., temporal variation of conduction current, 1-V characteristics, de electrical conductivity, dielectric constant, dielectric loss and ac conductivity. A con•elation between the investigated properties was discussed. Blends of PV A/glycogen of compositions I 00/0, 85115, 70/30, 50/50 and

30/70 (wt/wt %) were prepared in the form of thin films by casting technique. The dried films were optically clear, irrespective of blend composition. The glycogen homopolymer was used as a powder in the form of a pellet. Preliminary X-ray structure analysis of homopolymers and their blend samples indicated that blending an amorphous material such as glycogen by about :::: 50 wt % with a semi-crystalline polymer as PVA gives rise to an amorphous structure with two halo peaks at positions identical to those found in pure glycogen. X-ray diffraction pattems of all blend samples under investigation proved the miscibility of PVA and glycogen polymers in the full composition range. lm1diation of the semi-crystalline blend 70/30 (wtlwt %) PYA/glycogen with various y-doses produced extensive chain scission of taut tie molecules plus crosslinking in amorphous regions leading to increased crystallinity and crystal perfection. A significant decrease in degree of crystallinity values is observed for pristine and irradiated blend sample doped with eosin compared to their counterparts for undopcd sample.