Click synthesis by Diels-Alder reaction and characterisation of hydroxypropyl methylcellulose-based hydrogels

The Diels-Alder reaction was used to fabricate hydroxypropyl methylcellulose-based hydrogels. First, hydroxypropylmethylcellulose (HPMC) was modified by a carboxyl-containing diene molecule (SFA) which was synthesised from furfurylamine and succinic anhydride. Second, dienophile groups were introduced into HPMC by the coupling reaction with N-maleoyl alanine (AMI) using N,N′-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). Subsequently, the asprepared furan- and maleimide-modified HPMC were dissolved in water and gelation was observed at a pre-determined temperature after a period of time. The samples thus obtained were characterised by FTIR, NMR, SEM, etc. The gelation time changing with temperature, concentration of the solution, and solvent was measured. It was found that gelation time decreased with increasing temperature and concentration of the solution, and that water had a rate-accelerating effect on Diels-Alder reaction. The swelling behaviour indicates that the hydrogels have a high swelling ratio in water and the swelling ratio increases with the increasing temperature. Taking into consideration that the HPMC-based hydrogels are prepared under mild reaction conditions with an adjustable gelation time and thermal stability, the method described here has a potential application in biomaterials, especially in the areas of tissue-engineering and drug-controlled release carriers.