Unusual Transient Network and Rheology of a Photoresponsive Telechelic Associative Model Polymer in Aqueous Solution Induced by Dimerization of Coumarin End Groups

Abstract

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.

Reconstructable Gradient Structures and Reprogrammable 3D Deformations of Hydrogels with Coumarin Units as the Photolabile Crosslinks

“…[ 13,23 ] Both the photodimerization and photocleavage processes can be sped up by enhancing the power intensity of the light. [ 24 ]…”

“…[13,23] Both the photodimerization and photocleavage processes can be sped up by enhancing the power intensity of the light. [24] The mechanical properties of the hydrogels are examined by tensile tests. The as-prepared hydrogel with dimerized coumarins as additional chemical crosslinks shows moderate mechanical properties, with tensile breaking stress (σ b ) of 110 kPa, breaking strain (ε b ) of 155%, and Young's modulus (E) of 120 kPa (Figure S3, Supporting Information).…”

From Architectures to Cutting-Edge Properties, the Blooming World of Hydrophobically Modified Ethoxylated Urethanes (HEURs)

“…Combining the two stimuli led to even lower modulus and relaxation time ( Figure 13). Thereafter, in 2018, Du et al 68 reported novel sensitive HEURs end-functionalized by coumarin (Cou-HEUR), known for its photo-induced dimerization at 365 nm. 69 Before irradiation, the solution had a Newtonian behavior and was slightly viscous (1.75 Pa.s).…”

Linear Alternating Associative Polymer with Ultrahigh Molecular Weight: Facile Preparation by Self-Assembly Assisted Dimerization of Anthracene and Rheology in Aqueous Solution

“…Recently, we reported the dimerization and rheological behavior of a coumarin end-functionalized TAP in aqueous solution. 26 Due to a limited dimerization degree of coumarin, the average molecular weight of the resulting AAP is relatively small and few hydrophobic blocks in per polymer chain. So, the rheological behavior of the resulting network is more or less similar to typical TAP solutions.…”

“…Meanwhile, interesting rheological behavior and network structure will be obtained along with the reaction. Recently, we reported the dimerization and rheological behavior of a coumarin end-functionalized TAP in aqueous solution . Due to a limited dimerization degree of coumarin, the average molecular weight of the resulting AAP is relatively small and few hydrophobic blocks in per polymer chain.…”