Effect of structure of HEMA–DEGMA hydrogel matrix on diffusion coefficients of PEG tracers. Variation of hydrogel crosslink density by change of polymer concentration
✍ Scribed by Jan Pilař; Jaroslav Kříž; Bohumil Meissner; Petr Kadlec; Martin Přádný
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 427 KB
- Volume
- 50
- Category
- Article
- ISSN
- 0032-3861
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✦ Synopsis
Dependence of diffusion coefficients of spin-labeled poly(ethylene glycol)s (PEGs, M w ¼ 1500, 3000, and 6000) determined by One-Dimensional Electron Spin Resonance Imaging (1D ESRI) on the properties of hydrogel matrices prepared by photopolymerization of 2-hydroxyethyl methacrylate (HEMA) and 2-(2 0hydroxyethoxy)ethyl methacrylate (DEGMA) was studied. The hydrogels were characterized by degree of crosslinking, n gel , by hydrodynamic correlation length, x gel , and by self-diffusion coefficient of water, D H2O . The tracer diffusion coefficients were analyzed in the frame of scaling reptation and hydrodynamic models. Molecular weight dependence of the tracer diffusion coefficients follow expression D w M w
x with exponent x ¼ À1.2 AE 0.1 which excludes contribution of reptation to the diffusion. Steep decrease of the tracer diffusion coefficients with increasing polymer concentration was observed. Decrease of the tracer diffusion coefficients with increasing ratio of the hydrodynamic radius of the tracer to the hydrodynamic correlation length of the hydrogel matrix, R H /x gel , was well fitted with predicted stretched exponential expression. Dependence of the tracer diffusion coefficients on the degree of crosslinking n gel suggested as a new scaling variable was found to closely follow empiric stretched exponential dependence in the whole n gel range studied.