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Dynamical and structural behavior of hydroxyethylcellulose hydrogels obtained by chemical gelation
Author(s) -
Maleki Atoosa,
Kjøniksen AnnaLena,
Knudsen Kenneth D,
Nyström Bo
Publication year - 2006
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1978
Subject(s) - rheology , swelling , materials science , self healing hydrogels , aqueous solution , dynamic light scattering , chemical engineering , relaxation (psychology) , chemical physics , turbidity , neutron scattering , percolation (cognitive psychology) , syneresis , polymer chemistry , scattering , chemistry , composite material , nanotechnology , nanoparticle , optics , organic chemistry , psychology , social psychology , oceanography , physics , neuroscience , geology , engineering , biology
Rheological, dynamical, de‐swelling, turbidity, and structural features during gelation with a chemical cross‐linking agent of semi‐dilute aqueous solutions of hydroxyethylcellulose (HEC) were investigated at different cross‐linker concentrations. A higher level of cross‐linker leads to faster gelation and stronger incipient hydrogel. The rheological results favor the percolation model. The cross‐linking reaction proceeds over a long time in the post‐gel region, and this produces gels with a solid‐like response. Dynamic light‐scattering experiments reveal a fast and a slow relaxation mode. The slow relaxation time increases and the sample becomes more heterogeneous in the course of gelation. In the post‐gel region, the gels shrink during a long period of time and this phenomenon is accompanied by strong turbidity enhancement. Small‐angle neutron scattering results from samples quenched at a certain stage in the post‐gel regime disclose growth of heterogeneity in the gel with increasing level of cross‐linker addition. At smaller length scales, no effect of cross‐linker addition could be detected on the structural organization, and scattered intensity in this domain suggests that the HEC chains are locally stretched. Copyright © 2006 Society of Chemical Industry