Application of a new thermodynamic model to the swelling behaviour of poly(N-isopropylacrylamide) gels in aqueous solutions of alcohols

• Applicant: Professor Dr. Jörg Kreßler, since 4/2016
• Subject Area: Technical Thermodynamics
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 272101716

Three dimensional cross linked poly (N-isopropylacrylamide) (PNIPAM) forms non-ionic and thermo-sensitive hydrogels that have been experimentally studied very thoroughly. Cooling the gel there is a transition from a shrunken to a strongly swollen state at approximately 32°C. Because of the convenient transition temperature these hydrogels have found a wide range of medical applications, including controlled drug delivery systems, artificial blood vessels and muscles as well as contact lenses. In the classical swelling theory a gel is an infinitely large cross-linked polymer molecule that encages the solvent molecules. A new model is based on swelling equilibria and permits many cross-linked polymer molecules that encage different amounts of solvent. Until now, this model was applied only to the swelling behaviour of PNIPAM in pure water using a simple expression for the Helmholtz energy. Here, this expression is to be improved by incorporation of chemical association models. Furthermore, the model is to be extended to the case of two solvents (in detail: swelling of PNIPAM in mixtures of water and an alcohol). In this, the main goal is the calculation of the swelling degree as function of the temperature and of the composition of the solvent mixture.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Privatdozent Dr. Dieter Browarzik, until 4/2016 (†)