Multitunable Thermoresponsive and Aggregation Behaviors of Linear and Cyclic Polyacrylamide Copolymers Comprising Heterofunctional Y Junctions
Jian Zhang, Siyu Li, Zhigang Wang, Peng Liu, Youliang Zhao*（赵优良）
State and Local Joint EngineeringLaboratory for Novel Functional Polymeric Materials, JiangsuKey Laboratory of Advanced Functional Polymer Design andApplication, College of Chemistry, Chemical Engineering andMaterials Science, Soochow University, Suzhou 215123,China;
Macromolecules 2021, 54, 17, 8229--8242
The incorporation of asymmetric Y junctions into thermoresponsive polymers allows access to hierarchical self-assembly, and self-assembly of cyclic polymers can further amplify the topology effect. At present, systematic insights into the influence of Y junctions on physicochemical properties remain at the early stage. A diversity of linear and cyclic polyacrylamide copolymers with substituent-variable Y junctions are designed to reveal the effects of topology, chain length, composition, concentration, and temperature. With the increasing size of substituents, copolymer aqueous solutions gradually shift from dual upper and lower critical solution temperatures (UCST/LCST) to a single LCST until the lack of phase transition. The LCST can be elevated by introduction of a cyclic architecture, longer polymer chain, and smaller substituent. Owing to the changes in degree of hydration of subunits, heat can induce sphere–vesicle–nanosheet–nanoribbon–sphere (linear copolymer) and sphere–nanosheet–nanoribbon (cyclic copolymer) transitions. In addition, the cyclization effect is also reflected in cooperative hydration of distinct subunits upon heating, higher ceiling temperatures to form stable lamellae, and more pronounced hysteresis of the turbidity curve upon cooling. This research using Y junction bearing thermoresponsive copolymers may provide a promising platform to achieve on-demand phase transitions and nanostructures.
链接：//pubs.acs.org/doi/abs/10.1021/acs.macromol.1c00794
