e-Polymers 2003, no. 042. ISSN 1618-7229 http://www.e-polymers.org Glutaraldehyde-crosslinked poly(glycidol-block-ethylene oxide-block-glycidol) networks with temperature- responsive swelling behaviour Darinka Christova 1 , Sijka Ivanova 1 , Barbara Trzebicka 2 , Wojciech Walach 2 , Rumiana Velichkova 1 , Andrzej Dworak 2,3 * 1 Bulgarian Academy of Sciences, Institute of Polymers, Acad. G. Bonchev St. 103A, 1113 Sofia, Bulgaria; Fax +359 2 8707523; rumivel@polymer.bas.bg 2 Polish Academy of Sciences, Institute of Coal Chemistry, ul. Sowinskiego 5, 44-121 Gliwice, Poland; Fax +48 32 2312831; adworak@karboch.gliwice.pl 3 University of Opole, Institute of Chemistry, ul. Oleska 48, 45-052 Opole, Poland; Fax +48 77 4410740 (Received: June 6, 2003; published: August 21, 2003) Abstract: In order to obtain temperature-responsive hydrogel networks, poly- (glycidol-block-ethylene oxide-block-glycidol) copolymers were chemically cross- linked by using glutaraldehyde and tetraethoxysilane in a sol-gel reaction. The crystallinity of copolymer networks prepared has been estimated by differential scanning calorimetry. Thermo-responsive properties were evaluated by measuring the equilibrium swelling degree for a series of copolymer hydrogels as a function of temperature. Introduction Networks and gels sensitive to the action of external stimuli such as temperature, pH, radiation, etc. are subject of numerous studies. For their synthesis, polymers that exhibit lower critical solution temperature (LCST) in water are most frequently used. Stimuli-responsive networks display abrupt contraction in volume in response to a change in the environment. The temperature sensitivity of the network, like the LCST of the linear (non-crosslinked) chains, can be engineered by changing the hydro- philic/hydrophobic balance of its constituents. The swelling/deswelling processes of stimuli-responsive networks can be used in drug delivery [1-4], enzyme activity control [5-8], membrane separation [9,10], biosensors, artificial tissues [11-13] and others. Poly(ethylene oxide) (PEO) is a water-soluble polyether with envisaged biomedical applications due to its lack of toxicity and immunogenicity, rapid clearance from the body and large exclusion volume in water. It is used to obtain stimuli-responsive networks [14-17]. Linear PEO however has an LCST of over 100°C [18,19]. To modulate the temperature behaviour of PEO macromolecules, hydrophobic groups or segments have to be introduced [20-24]. PEO-containing thermosensitive materials are obtained via crosslinking of EO copolymers with another thermosensitive [25-27] 1