Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:327

Article

Silva, Sergio M. C.^1,2  Pinto, Fatima V.¹  Antunes, Filipe E.³  Miguel, Maria G.¹  Sousa, Joao J. S.²  Pais, Alberto A. C. C.¹ 

[1] Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal

[2] Univ Coimbra, Fac Pharm, P-3000295 Coimbra, Portugal

[3] Univ Coimbra, Dept Chem Engn, P-3030290 Coimbra, Portugal

关键词: Hydroxypropylmethyl cellulose;    Gelation mechanism;    Rheology;    Micropolarity index;   

DOI  :  10.1016/j.jcis.2008.08.056

来源: Elsevier

【 摘 要 】

In this work we present an analysis of the thermal behavior of hydroxypropylmethyl cellulose aqueous solutions, from room temperature to higher temperatures, above gelation. We focus on significant aspects, essentially overlooked in previous work, Such as the correlation between polymer hydrophobicity and theological behavior, and the shear effect on thermal gelation. Micropolarity and aggregation of the polymer chains were monitored by both UV/vis and fluorescence spectroscopic techniques, along with polarized light microscopy. Gel formation upon heating was investigated using theological experiments, with both large strain (rotational) tests at different shear rates and small strain (oscillatory) tests. The present observations allow us to compose a picture of the evolution of the system upon heating: firstly, polymer reptation increases due to thermal motion, which leads to a weaker network. Secondly, above 55 degrees C, the polymer chains become more hydrophobic and polymer clusters start to form. Finally, the number of physical crosslinks between polymer clusters and the respective lifetimes increase and a three-dimensional network is formed. This network is drastically affected if higher shear rates, at non-Newtonian regimes, are applied to the system. (C) 2008 Elsevier Inc. All rights reserved.

【 授权许可】

Free