92��C and 200.38��C with heat of fusion of 27.23J/g and 30.73J/g, respectively. Thus, a decrease in the endothermic transition temperature, disappearance of exotherm, and appearance of one more endotherm in TPSY were obtained on thiolation of PSY. Further the results of thermogravimetric selleck screening library analysis of PSY revealed two major stages of decomposition. The first stage was characterized by the initial decomposition temperature (IDT) of 229��C and final decomposition temperature (FDT) of 310��C. The first stage corresponds to major breakdown of polymer chain which resulted in 54.81% weight loss accompanied by a large exothermic enthalpy change which may be attributed to degradation of PSY with evolution of carbon dioxide and water vapors and so forth.
The second stage of decomposition was characterized by degradation temperature of 553��C with 70.7% weight loss. The TGA curve of TPSY also reveals two major stages of decomposition. The first stage is characterized by IDT of 121.78��C and FDT of 268.48��C accompanied by small exothermic enthalpy change. Further 41.92% of weight loss was observed during first decomposition stage. The second decomposition stage of TPSY was characterized by IDT of 368��C and FDT of 540.58��C with weight loss of 68.46%. Figure 1(c) displays the X-ray diffraction spectra of PSY and TPSY. X-ray diffractogram of PSY is typical of amorphous materials with no sharp peaks while the diffractgram of TPSY shows two characteristic sharp peaks at 32�� and 45�� (2��) which indicates slight increase in crystallinity of PSY on thiolation.
Figure 2 shows the shape and surface morphology of PSY and TPSY, examined under a scanning electron microscope. The shape of PSY and TPSY particles was found to be polyhedral. A close examination of surface morphology reveals that surface of PSY is fibrous while the surface of TPSY is granular. Figure 2Scanning electron micrographs showing shape and surface of PSY and shape and surface of TPSY.PSY possesses good swelling property. Swelling power studies conducted on PSY and TPSY revealed that 1g of PSY and TPSY on hydration in water swells to 86.6 and 100mL, respectively. Thus, thiolation of PSY results in 1.16- fold increase in swelling power. The mucoadhesive applications of synthesized TPSY were comparatively evaluated by formulating gels of PSY and TPSY employing metronidazole as the model drug.
The gels were prepared by adding PSY or TPSY at concentration of 2% (w/v) in aqueous solution of metronidazole 1% (w/v) under constant stirring and allowing them to hydrate overnight. The metronidazole loaded PSY gel (GPSY) and TPSY gel (GTPSY) were characterized mechanically (Figure 3) for their hardness, adhesiveness, Drug_discovery and cohesiveness. The height of the positive peak on the force time curve gives the hardness of the formulation. It indicates the resistance to compression indicating the ease by which product can be removed from the container.