It was found that, with increase in AA and EGDMA content, the cross-link http://www.selleckchem.com/products/MG132.html density (q) increases, causing a decrease in the average mass between the two cross-links (Mc). This results in decreased free volume available; thus an insufficient space is available for the water molecules to diffuse into the hydrogel; consequently, a decreased swelling was achieved. However, increasing PVSA content resulted in a decreased cross-link density (q), causing an increase in the mass between the two neighbouring cross-links (Mc) which provides sufficient space for the water molecules to diffuse into the hydrogel and a higher swelling was achieved.Table 2Structural parameters of hydrogels.The polymer volume fraction (Vs), calculated using (5), ranged from 0.16 to 0.22 for S1, S2, andS3; from 0.14 to 0.

24 for S4, S5, andS6; and from 0.14 to 0.16 for S7, S8, andS9, respectively. The volume fraction (Vs) of the polymer in the swollen state describes the amount of water that can be imbibed into a hydrogel and is described as the ratio of the polymer volume to the swollen gel [12]. The volume fraction of polymer was increased with an increase in AA and EGDMA content, which, in turn, indicates a decrease in swollen polymer content. Furthermore, this indicates that the distance between two cross-linking points decreases with increasing the content of AA and EGDMA; thus, free volume available decreases. Reverse was true for the formulations in which PVSA content was increased. The solvent-polymer interaction (��) was in the range of 0.

5 for all formulations indicating that there is a weak interaction between polymer and water and a strong interaction between the polymer chains [32].In order to confirm interaction between AA and PVSA, samples were analysed using FTIR (Figure 3(a)). The FTIR of AA showed a strong absorption band at 1707cm?1 which is typical of carbonyl (?C=O) stretching of COOH groups of AA. Absorption bands at 1580cm?1, 1458cm?1, and 1401cm?1 Anacetrapib are also arisen from AA and assigned to asymmetric ?COO stretching vibration, bending vibration of �CCH, and symmetric ?COO stretching vibration [33]. Peaks at 2954.45cm?1, 2930.18cm?1, and 2854.45cm?1 indicate ?OH stretching vibration of carboxylic acid [34]. The FTIR spectra of AA/PVSA hydrogel showed the absorption bands at 1170cm?1 and 1040cm?1 which are due to ?SO3? and S=O vibration [35]. FTIR spectra indicated the main changes in the region of 2300�C3000cm?1which is evidence of interaction between monomers. It could also be due to the bonds overlapping. From the FTIR it is clear that there is no significant shift in major peaks, which indicates that there is no chemical interaction between the polymer and the drug used.Figure 3Characterization of hydrogels using (a) FTIR, (b) DSC, and (c) TGA.