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Magnetic and Thermal-sensitive Poly(N-isopropylacrylamide)-based Microgels for Magnetically Triggered Controlled Release
Published on: July 4, 2017
Hyperbranched polymers with thermoresponsive property highly sensitive to ions
Xun-Yong Liu1, Xu-Ran Mu, Yi Liu
1School of Chemistry and Materials Science, Ludong University, Yantai, Shandong, People's Republic of China.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 24, 2012
Summary
The study reveals that salts significantly impact the water solubility of thermoresponsive dendritic polymers, showing greater sensitivity than linear polymers. Anion and cation effects on cloud point temperature were observed, with unique behaviors at low salt concentrations.
Area of Science:
- Polymer Chemistry
- Solution Behavior of Polymers
- Thermoresponsive Materials
Background:
- Thermoresponsive polymers change solubility with temperature, crucial for applications like drug delivery and smart materials.
- Hyperbranched polymers offer unique properties due to their complex architecture compared to linear polymers.
- Understanding salt effects is vital for controlling polymer solubility and phase transitions in aqueous solutions.
Purpose of the Study:
- To systematically investigate the influence of various anions and cations on the water solubility of thermoresponsive hyperbranched polymers.
- To compare the salt sensitivity of dendritic polymers (HPEI-IBAm and HPAMAM-IBAm) with traditional thermoresponsive linear polymers.
- To elucidate the specific mechanisms and ordering of anion and cation effects on the cloud point temperature (T(cp)).
Main Methods:
- Systematic measurement of cloud point temperature (T(cp)) for HPEI-IBAm and HPAMAM-IBAm in aqueous solutions with varying salt concentrations.
- Inclusion of eight different anions (with sodium counterion) and ten different cations (with chloride counterion).
- Analysis of electrostatic interactions and Hofmeister series relevance at different salt concentrations.
Main Results:
- Dendritic polymers exhibited significantly higher sensitivity to salt addition compared to linear counterparts.
- Unusual anion effects observed at low concentrations, including nonlinear T(cp) decrease with kosmotropes, abnormal salting-out by chaotropes, and anti-Hofmeister ordering.
- At moderate to high concentrations, anion and cation effects largely followed the Hofmeister series, though cation ordering showed partial deviations.
Conclusions:
- The unique architecture of hyperbranched polymers leads to distinct salt-dependent solubility behavior compared to linear polymers.
- Electrostatic interactions play a dominant role at low salt concentrations, causing non-Hofmeister effects.
- Salt concentration is a critical factor in determining the salting-out efficacy and ordering of ions for thermoresponsive dendritic polymers.
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