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OEGylated Cyclodextrin-Based Polyrotaxanes Showing Remarkable Thermoresponsive Behavior and Photocontrolled Degradation

Qian, Apan, Liu, Kun, Chen, Peiyun, Yao, Yi, Yan, Jiatao, Li, Wen, Zhang, Xiacong, Zhang, Afang
Macromolecules 2019 v.52 no.9 pp. 3454-3461
aqueous solutions, cooling, cyclodextrins, hydrophilicity, hysteresis, methylation, phase transition, polymers, rotaxanes, temperature, ultraviolet radiation
OEGylated cyclodextrin-threaded polyrotaxanes (PRXs) capped with UV-cleavable stoppers were synthesized, and their thermoresponsive and degradable behavior were investigated. These PRXs in aqueous solutions exhibit fast thermally induced phase transitions and small hysteresis as well as tunable phase transition temperatures, which are quite distinct from previous methylated PRXs. Based on the mechanically interlocked architecture, PRXs are stable in solutions but can be completely degraded into hydrophilic components upon UV cleavage of stoppers. As a consequence, the thermoresponsive behavior of PRXs was switched off. Furthermore, micrometer-scale globular aggregates were formed from thermoresponsive PRXs above their phase transition temperatures but disaggregated quickly upon cooling or UV irradiation. This phenomenon was utilized to take these PRXs as unique carriers for guests with dually controlled release by both temperature and light. The present work provides efficient synthesis of a new class of thermoresponsive interlocked polymers with on-demand degradation, and the findings illustrate the prominent effect of PRX architecture on the remarkable thermoresponsive and degradable behavior.