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Published on: December 23, 2013
Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions.
Sérgio M C Silva1, Fátima V Pinto, Filipe E Antunes
1Chemistry Department, University of Coimbra, Rua Larga, 3004-535 Coimbra, Portugal.
Journal of Colloid and Interface Science
|September 23, 2008
Summary
Hydroxypropylmethyl cellulose (HPMC) aqueous solutions show thermal gelation due to increased polymer hydrophobicity and cluster formation above 55°C. Shear rates significantly impact the resulting 3D network structure.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Hydroxypropylmethyl cellulose (HPMC) is a widely used polymer in various applications.
- Understanding the thermal gelation of HPMC solutions is crucial for optimizing its use.
- Previous studies have not fully explored the link between polymer hydrophobicity, rheology, and shear effects during HPMC gelation.
Purpose of the Study:
- To analyze the thermal behavior of HPMC aqueous solutions up to and beyond gelation.
- To investigate the correlation between polymer hydrophobicity and rheological properties.
- To determine the influence of shear on the thermal gelation process.
Main Methods:
- UV/vis and fluorescence spectroscopy to monitor micropolarity and aggregation.
- Polarized light microscopy for visual observation of polymer behavior.
- Rheological experiments (rotational and oscillatory tests) at various shear rates.
Main Results:
- Increased polymer reptation and network weakening with rising temperature.
- Hydrophobicity enhancement and polymer cluster formation above 55°C.
- Formation of a 3D network with increased crosslinks and lifetimes, sensitive to high shear rates.
Conclusions:
- Thermal gelation of HPMC involves a transition from reptation to hydrophobic aggregation and crosslinking.
- The rheological behavior and final network structure are significantly influenced by shear conditions.
- This study provides a comprehensive understanding of HPMC thermal gelation dynamics.
