Coumarin derivative polymers for thermo- and light-responsive monofunctional polymers: Effect of additives on thermo-responsivity

Methacrylic and acrylic homopolymers containing a coumarin unit in the side-chain, which undergoes reversible [2+2] cycloaddition by photoirradiation, are the very limited examples of the dual-stimuli responsive monofunctional polymers. The coumarin derivative polymers show lower critical solution temperature-type phase separation in some chlorinated organic solvents such as chloroform. In this study, the control of the cloud points of the coumarin derivative polymers by the addition of low-molecular-weight additives to the solution was investigated. It was revealed that the addition of low-molecular-weight compounds, which would interact with the coumarin derivative polymers, such as coumarin, 3,4-dihydrocoumarin, chromone, and 9-bromoanthracene resulted in significant increase in the cloud points. It was also found that the cloud points of the coumarin derivative polymer can be controlled by the addition amount of the additives up to near the boiling point of the solvent.