Light‐Switchable Self‐Healing Dynamic Linear Polymers: Reversible Cycloaddition Reactions of Thymine‐Containing Units

Abstract

A dynamic linear polymer was formed by the [2π + 2π] reversible cycloaddition reaction of a thymine-based monomer under topochemical conditions and was used in self-healing applications. The reversible polymerisation of the thymine monomer was confirmed by UV and GPC analysis. Irradiation at 302 nm resulted in polymerisation of the monomer, and irradiation with wavelengths lower than 240 nm resulted in depolymerisation and the production of oligomeric units. This leads to a reduction in the glass transition temperature, and promoted healing of surface scratches due to the increased chain mobility. The self-healing ability of scratched samples was assessed based on the visual disappearance of the damage. In addition, the mechanical properties of the polymer before and after healing were found to be similar. [a] Dr. M. Abdallh, Mr. P. He, Prof. M. T.

Sunlight Stimulated Photochemical Self‐Healing Polymers Capable of Re‐Bonding Damages up to a Centimeter Below the Surface Even Out of the Reach of the Illumination

“…The opposite trends of tensile strength and failure strain obey the general law of polymers. Clearly, CPUDTC 4 possesses obviously higher tensile strength than the other photochemical self‐healing polymers reported in literature, [ 11–35 ] and decent elongation to break as well. The rigid structure of PMBAEIC only causes a slightly raise of glass transition temperatures ( T g ) from −49.3 °C to −44.5 °C (Figure S13 and Table S4, Supporting Information).…”

“…So far, reversible cycloaddition/isomerization reaction, [ 10–20 ] reversible exchange reaction, [ 21–32 ] and dynamic homolysis/recombination equilibrium [ 33–35 ] have been utilized to endow polymeric materials with photo‐reversible self‐healing capability. However, the reported excitations mainly came from artificial UV and visible lights.…”

Design and synthesis of waterborne light-responsive cellulose nanocrystal/fluorinated polyacrylate films toward oil/water repellent and self-healing properties

“…Compared to the sample exposed only to UV light, the scratches of the heated sample show only small changes on the surface (Fig. 13(c)), indicating the healing requires photo-stimulated depolymerisation, in other words, healing is impossible without UV light to induce cleavage and recombination of coumarin moieties in polymer chains (Abdallh et al 2019a). For the sample with a treatment of heat and UV light shows a noticeable healing effect (Fig.…”

Sustainable Light‐Stimulated Synthesis of Cross‐Linked Polymer Microparticles

“…During the last decade, our group has explored the lightinduced [2+2] cycloadditions for smart and eco-friendly polymer synthesis. [53][54][55][56][57][58][59] Harnessing the advantages of photopolymerization, the present work aims to prepare highly cross-linked and well-defined PMPs. The strategy involved the use of a 4-arm coumarin based monomer, expected to yield highly cross-linked microspheres via [2+2] cycloadditions.…”