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Hydrophobic-electrostatic balance driving the LCST offset aggregation-redissolution behavior of
Paula M López-Pérez1, Ricardo M P da Silva, Iva Pashkuleva
13B's Research Group-Biomaterials, Biodegradables and Biomimetics, University of Minho Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, 4806-909 Taipas, Guimarães, Portugal.
Langmuir : the ACS Journal of Surfaces and Colloids
|December 10, 2009
Summary
Synthesized terpolymers show temperature-induced phase separation influenced by hydrophobicity. Increasing N-tert-butylacrylamide (NTBAAm) content lowers cloud point and LCST, affecting aggregation rates and redissolution behavior.
Area of Science:
- Polymer Chemistry
- Materials Science
- Physical Chemistry
Background:
- Temperature-induced phase separation in polymers is crucial for applications like drug delivery and smart materials.
- Understanding the interplay of monomer composition and solution conditions is key to controlling polymer behavior.
Purpose of the Study:
- To synthesize and characterize terpolymers of N-isopropylacrylamide (NIPAAm), AMPS, and N-tert-butylacrylamide (NTBAAm).
- To investigate the influence of NTBAAm content on the temperature-induced phase separation, including cloud point and LCST.
- To elucidate the molecular mechanisms governing phase separation using DLS and turbidity measurements.
Main Methods:
- Free radical polymerization for terpolymer synthesis.
- Turbidimetry to determine cloud point and redissolution temperatures.
- Dynamic light scattering (DLS) to study molecular aggregation and determine LCST.
Main Results:
- Terpolymers exhibited temperature-induced phase separation only in the presence of NaCl.
- Cloud point temperature (CPT) was consistently higher than the low critical solution temperature (LCST).
- Increased NTBAAm content (hydrophobicity) decreased both CPT and LCST.
- A critical NTBAAm molar fraction (0.25-0.30) altered aggregation rates and redissolution behavior.
Conclusions:
- The balance between electrostatic repulsion (AMPS) and hydrophobic attraction (NTBAAm) dictates phase separation behavior.
- Metastable nanosized aggregates form due to this balance.
- Terpolymer properties, including aggregation and redissolution, can be tuned by adjusting NTBAAm content.
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