Unusual Transient Network and Rheology of a Photoresponsive Telechelic Associative Model Polymer in Aqueous Solution Induced by Dimerization of Coumarin End Groups
Telechelic associative polymers (TAPs) can form a dynamic transient network in water and have been widely used as rheological modifiers for improving solution rheological properties in many industrial fields. In this work, we designed and prepared a novel photoresponsive coumarin-functionalized telechelic associative model polymer (CouTAP), which was used to investigate the influence of light-induced dimerization of coumarin end groups on the polymer structure and solution rheological properties. The effects of light intensity, irradiation time, polymer concentration, and temperature on the transient network and rheological behavior of the CouTAP aqueous solution were studied in detail. The rheological properties of the dimerized CouTAP aqueous solution show weak temperature dependence, and the dynamics hardly depends on concentration due to the transformation of triblock to multiblock polymers. A novel transient network model composed of train loops and bridges covalently linked to train loops was proposed to describe the unique solution properties. This work will not only provide new insights into the influence of the light-induced dimerization of coumarin end groups on the network structure and rheological properties of CouTAP solution but also opens a new perspective for the controlled self-assembly of amphiphilic polymers and some special applications of TAPs in the manufacturing and transmission of soft materials, waterborne coating, inks, medicines, cosmetics, and so on.
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