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Hyperbranched Multiarm Copolymers with a UCST Phase Transition: Topological Effect and the Mechanism
Meiwei Qi1, Ke Li1, Yongli Zheng1
1School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , China.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 13, 2018
Summary
Novel hyperbranched copolymers exhibit tunable temperature-responsive phase transitions. This study introduces a new class of polymers with controlled upper critical solution temperature (UCST) behavior for advanced material applications.
Area of Science:
- Polymer Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Thermoresponsive polymers are crucial for smart materials, with upper critical solution temperature (UCST) polymers exhibiting unique phase transition properties.
- Hyperbranched architectures offer distinct advantages over linear polymers, influencing solubility and phase behavior.
- Understanding the relationship between molecular structure and UCST behavior is key to designing advanced functional materials.
Purpose of the Study:
- To synthesize a novel thermoresponsive hyperbranched multiarm copolymer.
- To investigate the temperature-responsive phase transitions (UCST) of these copolymers in aqueous and electrolyte solutions.
- To explore the influence of molecular structure, including acrylonitrile content and arm length, on UCST behavior.
Main Methods:
- Reversible addition-fragmentation chain-transfer (RAFT) polymerization was employed for copolymer synthesis.
- Variable temperature nuclear magnetic resonance (VT-NMR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used for characterization.
- Systematic variation of acrylonitrile content and arm length to study structure-property relationships.
Main Results:
- Successful synthesis of hyperbranched multiarm copolymers with a hydrophobic core and poly(acrylamide-co-acrylonitrile) arms.
- Demonstrated reversible, sharp, and controlled UCST phase transitions in water and electrolyte solutions.
- UCST was tunable from 33.2 to 65.2 °C by adjusting AN content and arm length, with a significant amplification effect from the hyperbranched structure.
Conclusions:
- This work presents the first report of hyperbranched copolymers exhibiting UCST transitions.
- A mechanism involving hydrophilic/hydrophobic balance and multimicelle aggregates (MMA) was proposed for the UCST transition.
- The findings enrich the understanding of UCST polymer topology, structure-activity relationships, and transition mechanisms, paving the way for new smart materials.
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