Format

Send to

Choose Destination
See comment in PubMed Commons below
J Phys Chem B. 2013 Dec 5;117(48):15111-21. doi: 10.1021/jp408782e. Epub 2013 Nov 25.

Multiregion shear thinning for subsequent static self-thickening in chitosan-graft-polyacrylamide aqueous solution.

Author information

1
MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University , Hangzhou 310027, China.

Abstract

A special shear thinning phenomenon followed by static self-thickening in chitosan-graft-polyacrylamide (GPAM) aqueous solutions was investigated. This multiregion shear thinning can be defined as the first stage of the recently reported shear induced self-thickening (SIT) in our previous work. The three thinning regions (labeled as N1, N2, and N3) are considered very important, and they can reflex the complex variations of intermolecular interactions among and inside the aggregates in solution with increasing shear rate. To verify this multiregion shear thinning, a critical concentration of GPAM for this three-region shear thinning was first investigated. Shear recovery tests with the maximal shear rates located in the N1-N3 were carried out to ascertain the crucial role of shear thinning in SIT. The mechanisms of these three shear thinning regions were proposed based on the dependence of shear rheological behavior on various conditions in each region, including GPAM concentration, grafting ratio, temperature, added hydrogen bonding breaker, and salt. The above results confirm that N1 is due to the breakage of the interactions among hydrogen bonding aggregates, while N2 and N3 are attributed to the progressive destruction of the aggregates. As the first stage of SIT, shear thinning can markedly break the original aggregate and expose additional hydrogen bonding stickers to reform more aggregates with bigger size, resulting in the final higher viscosity.

PMID:
24236534
DOI:
10.1021/jp408782e
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for American Chemical Society
    Loading ...
    Support Center