caa a22 4500 463231848 CHVBK 20180405153244.0 cr unu---uuuuu 170326e20071201xx s 000 0 eng 10.1007/s10853-007-1814-4 doi (NATIONALLICENCE)springer-10.1007/s10853-007-1814-4 The effect of salts and pH buffered solutions on the phase transition temperature and swelling of thermoresponsive pseudogels based on N- isopropylacrylamide [Elektronische Daten] [Luke Geever, Michael Nugent, Clement Higginbotham] The temperature sensitive nature of poly(N-isopropylacrylamide) makes it an attractive candidate for controlled drug delivery devices. A series of temperature responsive poly (N-isopropylacrylamide)-polyvinyl pyrrolidinone random copolymers were produced by free radical polymerisation using 1-hydroxycyclohexylphenyketone as a UV-light sensitive initiator. The chemical structure of the xerogels was characterised by means of Fourier transform infrared spectroscopy (FTIR). The copolymers possess a lower critical solution temperature (LCST) in pure water, but the transition temperature may be affected by the addition of various cosolutes. The LCST of the pseudogels (physically crosslinked gels) was investigated in distilled water and a variety of salt and pH buffer solutions, using modulated differential scanning calorimetry (MDSC) and rheological analysis. The pH buffer solutions prepared mimic the variety of conditions encountered by drug delivery systems administered orally. The pH effects on the LCSTs of the temperature sensitive gels appear not obvious; while the salts used to prepare the pH buffer solutions have a more notable effect (‘salting out effect') on the phase transition temperature. All swelling studies were carried out on the hydrogels at 37°C in distilled water, pH buffer 1.2 and pH buffer 6.8. The swelling/dissociation behaviour of the gels is found to be highly dependent on the pH buffer solution used, as the salts incorporated in preparing the pH buffer solutions lowers the phase transition of the copolymers to below the test temperature of 37°C, thus making them less soluble. Springer Science+Business Media, LLC, 2007 Geever Luke Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Rd, Athlone, Co, Westmeath, Ireland aut Nugent Michael Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Rd, Athlone, Co, Westmeath, Ireland aut Higginbotham Clement Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Rd, Athlone, Co, Westmeath, Ireland aut Journal of Materials Science Springer US; http://www.springer-ny.com 42/23(2007-12-01), 9845-9854 0022-2461 42:23<9845 2007 42 10853 https://doi.org/10.1007/s10853-007-1814-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-007-1814-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Geever Luke Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Rd, Athlone, Co, Westmeath, Ireland aut NATIONALLICENCE 700 1- Nugent Michael Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Rd, Athlone, Co, Westmeath, Ireland aut NATIONALLICENCE 700 1- Higginbotham Clement Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Rd, Athlone, Co, Westmeath, Ireland aut NATIONALLICENCE 773 0- Journal of Materials Science Springer US; http://www.springer-ny.com 42/23(2007-12-01), 9845-9854 0022-2461 42:23<9845 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer