Biodegradable polymers from renewable sources: Rheological characterization of hemicellulose-based hydrogels

Hemicellulose-based hydrogels were prepared by radical polymerization of 2-hydroxyethyl methacrylate or poly(ethylene glycol) dimethacrylate with oligomeric hydrosoluble hemicellulose modified with well-defined amounts of methacrylic functions. The polymerization reaction was carried out in water at 40 degrees C using a redox initiator system. The hydrogels were in general elastic, soft, and easily swellable in water. Their viscoelastic properties were determined by oscillatory shear measurements on 2 mm thick hydrogels under a slight compression to avoid slip, over the frequency range 10(-1) to 10(2). The rheological characterization indicated that the elastic response of the hydrogels was stronger than the viscous response, leading to the conclusion that the hydrogel systems displayed a predominantly solidlike behavior. The curves showed an increase in shear storage modulus with increasing cross-linking density. The nature of the synthetic comonomer in the hemicellulose-based hydrogels also influenced the shear storage modulus. Comparison of hemicellulose-based hydrogels with pure poly(2-hydroxyethyl methacrylate) hydrogels showed that their behaviors were rather similar, demonstrating that the synthetic procedure made it possible to prepare hemicellulose-based hydrogels with properties similar to those of pure poly(2-hydroxyethyl methacrylate) hydrogels.