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Published on: February 7, 2017
pH-responsive self-assembly of carboxyl-terminated hyperbranched polymers
Wenyong Dong1, Yongfeng Zhou, Deyue Yan
1College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, People's republic of China.
Physical Chemistry Chemical Physics : PCCP
|February 28, 2007
Summary
Terminal group modification significantly impacts hyperbranched polymer self-assembly. Carboxyl-terminated polymers form pH-responsive micelles, with size dictated by hydrogen bonding and solution acidity.
Area of Science:
- Polymer Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Hyperbranched polymers exhibit unique properties influenced by their structure and terminal groups.
- Controlling polymer self-assembly is crucial for developing advanced functional materials.
- The role of terminal functional groups in dictating self-assembly behavior requires further investigation.
Purpose of the Study:
- To investigate the influence of terminal groups on the self-assembly of hyperbranched polymers.
- To explore the pH-responsive self-assembly behavior of carboxyl-terminated hyperbranched polymers.
- To elucidate the mechanism of micelle formation and size control in aqueous solutions.
Main Methods:
- Synthesis of hyperbranched polymers with hydroxyl and carboxyl terminal groups.
- Characterization of polymer self-assembly using Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FT-IR), and Atomic Force Microscopy (AFM).
- Nuclear Magnetic Resonance (1H NMR) spectroscopy for structural confirmation.
Main Results:
- Hydroxyl-terminated hyperbranched polymers (HBPO-OH) are hydrophobic.
- Carboxyl-terminated hyperbranched polymers (HBPO-COOH) exhibit pH-responsive self-assembly.
- At high pH, HBPO-COOH forms unimolecular micelles; at lower pH, they aggregate into multimolecular micelles (10-500 nm) driven by hydrogen bonding.
- Micelle size increases with decreasing pH.
Conclusions:
- Terminal groups critically control hyperbranched polymer self-assembly.
- Carboxyl-terminated hyperbranched polymers can form tunable, pH-responsive micellar structures.
- Hydrogen bonding interactions are key to the pH-dependent secondary aggregation of unimolecular micelles into multimolecular micelles.
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