Thermal properties and kinetic investigation of chitosan-PMAA based dual-responsive hydrogels

• Chitosan-MAA–MBA-based stimuli-responsive hydrogels was synthesized via free-radical copolymerization in an aqueous medium at 70 °C.
• MBA and MAA composition on thermal stability, degradation kinetic and life time were investigated.
• To be composition-dependent and critical point at MAA = 300 mg/ml and MBA = 15 mg/ml.
• Higher Ea and t1/2 has been attributed to the greater cross-linking in N2 atmosphere.
• The synthesised materials results in the increased of drug-release rate.

The influence of cross-linker (N,N-methylenebisacrylamide, MBA) and methacrylic acid (MAA) composition on the thermal stability, degradation kinetic, and lifetime, of Chitosan-based [Chitosan-poly(methacrylic acid, (Cs-PMAA)] dual responsive hydrogels was investigated in detail using the Flynn–Wall–Ozawa (F–W–O) method. The Cs-MAA–MBA derivatives showed only a glass transition temperature (Tg) that increased as the content of MAA increased. The stability of Cs-MAA–MBA has been achieved at a critical point where the MAA content was 300 mg/ml and MBA was 15 mg/ml. The lifetime of Cs-PMAA hydrogels (time at 5% mass loss) was estimated by increased temperature delivery in nitrogen atmosphere. On average, a higher Ea has been attributed to the greater cross-linking density of Cs hydrogel. Likewise, the lower swelling ability of Cs hydrogel can be due to the slower relaxation rate of the polymer chain, which then results in an increased lifetime of the potential drug-release rate.

Figure optionsDownload as PowerPoint slideDescription:We dealt with the influence of N,N-methylenebisacrylamide (MBA) and methacrylic acid (MAA) composition in chitosan-based (Cs-poly(methacrylic acid)) stimuli-responsive hydrogels on thermal stability, degradation kinetic and life time. Cs-PMAA hydrogels series were synthesized using the free-radical copolymerization method in an aqueous medium at 70 °C. The apparent activation energy (Ea) and lifetime prediction of each step were determined, using the Flynn–Wall–Ozawa method. The stability of Cs-MAA–MBA has been achieved at a critical point where the MAA content was 300 mg/ml and MBA was 15 mg/ml. The equilibrium swelling/shrinking ratios and the volume phase changes of the microgels (induced by pH and temperature variations), were found to be composition-dependent [doi: 10.1007/s10965-013-0273-7]. On average, a higher Ea has been attributed to the greater cross-linking density of Cs hydrogel. Likewise, the lower swelling ability of Cs hydrogel can be due to the slower relaxation rate of the polymer chain, which then results in an increased lifetime of the drug-release rate.