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This work deals with the use of a supersorbent, i.e., sodium hydroxyethylcellulose succinate (HEC-Suc-Na), for the removal of Cd(II) ions from aqueous solution. HEC-Suc was fabricated via esterification of HEC with succinic anhydride in the presence of dimethylaminopyridine (DMAP) as a catalyst. The treatment of HEC-Suc conjugate with saturated NaHCO3 solution provided HEC-Suc-Na (sodic form). These acidic and sodic forms of the sorbent were characterized by Fourier transform infrared and energy-dispersive spectroscopy. The surface morphology and charge on the surface of sorbent were monitoredby SEM and pH corresponding to point of zero charge. Sorption data conceded well to the pseudo-second-order kinetic and Langmuir isotherm model. Maximum sorption capacity of HEC-Suc-Na for Cd(II) removal as calculated by Langmuir model was 714.2 mg g-1. Moreover, no significant decrease in the sorption capacity of the sorbent was found after five regeneration cycles suggesting its repeated use. Thermodynamic parameters (∆G°, ∆H° and ∆S°) showed negative values that indicate spontaneity and exothermic nature of the sorption process. Removal of Cd(II) in presence of Ni(II) was also studied. [ABSTRACT FROM AUTHOR]

Succinylation of starch was carried out with succinic anhydride homogeneously using N,N-dimethylacetamide (DMAc) at 70°C for 24 h. Starch succinates (SS) were then cross-linked using 1,1'-carbonyldiimidazole (CDI). This green method for cross-linking of SS using CDI is being reported for the first time. The SS and cross-linked starch succinate (CLSS) were characterized by FTIR spectroscopy and thermal analysis. The CLSS was found thermally more stable than SS as degradation maxima (Tdm) of CLSS (311°C) was 70°C higher than Tdm of SS (241°C) noted for first and major step of degradation. Additionally, initial (Tdi) and final (Tdf) degradation temperatures of CLSS were higher than SS which is indicative of extra thermal stability imparted after cross-linking of starch via succinylation. Thermal degradation kinetics were calculated using Friedman, Broido and Chang methods. Energy of activation (Ea) was calculated for each step of degradation for SS and CLSS. Order of reaction (n) was calculated from Chang model and it was found that degradation in first step follows first order kinetics in SS and CLSS. [ABSTRACT FROM AUTHOR]

Naturally occurring hydrophilic polysaccharides are nowadays attracting the vigil eye of researchers working in areas of drug design and development. Amongst them, hydrophilic biopolymer hydroxypropylcellulose (HPC) is of particular interest. Its unique geometry allows the attachment of drug molecules with higher covalent loading as the hydroxyls are projected outside the polymer chains. The HPC-Ibuprofen conjugates as macromolecular prodrugs were therefore synthesized employing homogenous and one pot reaction methodology using p-toluenesulfonyl chloride. Present strategy appeared effective to synthesize conjugates with high yield (77-81%). Acid-base titration after saponification and 1H-NMR spectroscopic analyses have revealed high degree of drug substitution (DS 0.88-1.40) on to HPC. Uni-modal absorptions were observed in gel permeation chromatograms which indicated no significant degradation of polymer. Macromolecular prodrugs with different DS of ibuprofen were synthesized, purified, characterized and found soluble in organic solvents. From thermogravimetric analysis, initial, maximum and final degradation temperatures of the conjugates were calculated and compared for relative thermal stability. Thermal degradation kinetics was also studied and results have indicated that degradation of conjugates follows about first order kinetics as calculated by Kissinger model. The energy of activation was also found moderate 92.38, 99.34 and 87.34 kJ/mol as calculated using Friedman, Broido and Chang models. It was found that these novel prodrugs of ibuprofen were thermally stable therefore these may have potential pharmaceutical applications. [ABSTRACT FROM AUTHOR]