Abstract
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The present work aimed to study the chemical crosslinking effect by using glutaraldehyde (GA) at various weight ratios (5, 8, and 10) % on the biological, mechanical, thermal, structural, and physical properties of polyvinyl alcohol/starch (PVA/St) blends, poly(vinyl alcohol)/ poly(ethylene glycol) (PVA/PEG) blends, and (PVA/St/PEG) blend films. PVA/St, and PVA/PEG blends at different ratios (25, 30, 35, 40, and 50) wt % of St and PEG as well as PVA/St/PEG ternary blend at (12.5/12.5) wt% of St/PEG were prepared by conventional solvent casting technique. The results of mechanical properties verified a decrease in the ultimate tensile strength with St and PEG ratios increase. The highest tensile strength was (28.2 MPa) for (PVA/ 25 wt% St), (20.95 MPa) for (PVA/25 wt% PEG), and (32.87 MPa) for (PVA/St/PEG), also with increasing GA from (5) to (10) %, the value of tensile strength of crosslinked (PVA/25% St) blends, (PVA/25% PEG) blends, and ternary blends increased from (33-41.19 MPa), (26.66-35.15 MPa), and (38-42.5MPa) respectively compared to PVA and its blend before crosslinking, while the elongation at break % decreased for all blends before and after crosslinking. FTIR results proved that the possibility of PVA and starch, as well as PVA and PEG, can interact physically with one another and formation of H-bond in the films which may increase the compatibility of the components. Also, it showed a chemical cross-linking reaction that happens between (PVA/St) blend and glutaraldehyde. DSC results demonstrated that PVA had glass transition temperature Tg (83oC), and a sharp maximum endothermic peak at (224oC) due to a melting transition (Tm), while starch had Tg (85 oC) and Tm (130 oC), also PEG had Tg (52 oC) and Tm (172 oC). One Tg value was found for PVA, St, PEG, (25, and 30) wt% of St blends, and (25, and 30) wt% of PEG blends owing to a good blend miscibility whereas, two Tg values were found for (35,40,50) wt% St, (35, 40, 50) wt% PEG and ternary blend owing to blend immiscibility. Also, it elucidated an increase in Tg, and reduction in Tm of (PVA/St) blends but a decrease in Tg, and a reduction in Tm of (PVA/PEG) blends as compared to the pure PVA.
Abstract
In thermogravimetric analysis "TGA", the weight loss happened in three stages of all blends, while in starch and 50 wt% PEG, it occurred in two stages and one stage in PEG.
The water absorption outcomes proved that there was an increase in swelling ratios with increasing starch and PEG ratio as a function of time. The lowest swelling ratio was for PVA, whereas the PVA/St (50/50 wt/wt %) and PVA/PEG (50/50 wt/wt %) had the highest values. The swelling behavior of the crosslinked polymer blends samples was investigated in several media, including neutral, acidic, and alkaline (pH7.3, pH2 and pH5.5, and PH8), as well as distilled water. The swelling ratio of the crosslinked polymer blends increased with the pH buffers increase as (pH8 > pH7.3 > distilled water> pH5.5> pH2), and the water absorption of all blends decreased with increasing GA concentration because of an increase in crosslinking in the polymers blends. The rate of the release of drug in pH7 was more than that of pH2.
FESEM results indicated that the (PVA/25 wt% St) blend and (PVA/25 wt% PEG) blend had a nearly homogeneous and smooth surface with some voids and with no signs of phase separation. The (PVA/25 wt% St) blend+10 %GA and (PVA/ 25 wt% PEG) blend+10% GA samples offered less homogeneity with one another, and an apparent phase separation took place. The PVA/St/PEG ternary blend image manifested that non-uniform surface and there some aggregates of St and PEG in the PVA matrix. While, many irregular aggregates were detected on the surface of the (PVA/St/PEG) blend +10% GA sample. It can be observed from the phase structures of (PVA/25wt % PEG) blend with 10% GA and 150 mg of Erythromycin drug that there is a much lesser agglomeration of PEG particles and also a very little formation of voids due to the drug. Cytoxicity test results evinced that there are good viability percentages; therefore there is no toxic effect of blends on the WRL 68 cells.
The current study proved that the prepared crosslinked samples (PVA/25%St, and PVA/25% PEG blends) could be used for drug delivery applications.