Multimodal stimuli-responsive behaviors of photochromic spiropyran-bearing telechelic poly(2-isopropyl-2-oxazoline)

Spiropyran-bearing telechelic poly (2-isopropyl-2-oxazoline) (SP-PiPrOx-SP) was designed as a multi modal stimuli-responsive polymer. Formed via living cationic ring-opening polymerization and ester coupling of spiropyran units, the resultant SP-PiPrOx-SP had an average molecular weight of 8.0 kDa with a narrow molecular weight distribution. SP-PiPrOx-SP exhibited a sharp hydrophilic-hydrophobic thermal transition at a specific temperature. Moreover, SP-PiPrOx-SP showed reversible photochromic changes between the colorless SP-PiPrOx-SP and purple MC-PiPrOx-MC states upon UV or visible light irradiation. The addition of DBU to MC-PiPrOx-MC resulted in the formation of a stable yellow complex that did not exhibit photochromic behavior. When CO2 was added to the yellow DBU adduct of MCPiPrOx-MC, the solution immediately changed to purple due to the dissociation of DBU from MCPiPrOx-MC. The addition of DBU to MC-PiPrOx-MC induced dramatic changes to the thermal transition temperature. Because SP-PiPrOx-SP simultaneously shows thermal transition, photochromic, and chemoresponsive properties, the introduction of spiropyran units has great potential for the design of functional materials. (C)& nbsp;2022 Elsevier Ltd. All rights reserved.