Supramolecular elastomers: Switchable mechanical properties and tuning photohealing with changes in supramolecular interactions

Abstract

To study light-triggered self-healing in supramolecular materials, we synthesized supramolecular thermoplastic elastomers with mechanical properties that were reversibly modulated with temperature. By changing the supramolecular architecture, we created polymers with different temperature responses. Detailed characterization of the hydrogen-bonding material revealed dramatically different temperature and mechanical stress response due to two different stable states with changes in the hydrogen bonding interactions. A semicrystalline state showed no response to oscillatory shear deformations while the melt state behaved as a typical energy dissipative material with a clear crossover between storage and loss moduli. Comparison studies on heat generation after light excitation revealed no differences in photo-thermal conversion when an Fe(II)-phenanthroline chromophore was either physically blended into the H-bonding polymer or covalently attached to the supramolecular network. These materials showed healing of scratches with light-irradiation, as long as the overlap of material absorbance and laser excitation was sufficient. Differences in the efficiency and rate of photohealing were observed, depending on the type of supramolecular interaction, and these were attributed to the differences in the thermal response of the materials' moduli. Such results provide insight into how materials can be designed with chromophores and supramolecular bonding interactions to tune the lighthealing efficiency of the materials.

Restricted Photoinduced Conformational Change in the Cu(I) Complex for Sensing Mechanical Properties

“…The reported emission spectra were collected in a time-gated regime utilizing an iStar ICCD camera; therefore, the absolute value for the emission maximum could be different from the one obtained on a steady-state fluorimeter with a PMT detector. We start labels from "P2" instead of "P1" to be consistent with our upcoming publication 33 where the same P2 polymer was used and "P1" label was already assigned for the different polymer.…”

Tuning Mechanical Properties of Biobased Polymers by Supramolecular Chain Entanglement

“…M e is very high for polymers with bulky side groups from biomass such as soybean oil (>200 kDa), rosin acids (>90 kDa), and terpenes (>30 kDa). − A few strategies have been developed to overcome high M e : (1) the use of ultrahigh molecular weight polymers, (2) utilization of chain architectures such as block copolymers to allow for stress dissipation, ,− and (3) incorporation of physical or dynamic chemical cross-linking to induce chain entanglement. − Dynamic cross-linking is a viable approach with the aid of a wide variety of chemistries such as supramolecular interactions and exchangeable bonding. Supramolecular interactions such as hydrogen bonding (H-bonding) have been widely used as dynamic bonds to improve properties of polymers. − …”

Generating Photonastic Work from Irradiated Dyes in Electrospun Nanofibrous Polymer Mats

“…We previously published results illustrating light-induced macroscopic bending in a co-polymer of norbornene that was ascribed to isomerization of a pendant photochromic ruthenium sulfoxide unit. − We noticed a nontrivial role for photothermal bending in that study. Since then, we have noted literature reports on photosoftening, etc., which appear to imply a significant role for a photothermal or photoinduced heating effect in macroscopic bending of polymer or crystalline materials. ,, Here, we preform the critical bilayer or bimorph structure for bending by creating nanofibrous mats from electrospinning techniques. The fibers comprise simple dyes that generate heat following visible light excitation from the excited state processes described above.…”

“…Since then, we have noted literature reports on photosoftening, etc., which appear to imply a significant role for a photothermal or photoinduced heating effect in macroscopic bending of polymer or crystalline materials. 30,34,35 Here, we preform the critical bilayer or bimorph structure for bending by creating nanofibrous mats from electrospinning techniques. The fibers comprise simple dyes that generate heat following visible light excitation from the excited state processes described above.…”