Synthesis and Light Scattering Study of Hydroxypropyl Cellulose Microgels

Abstract

The thermally responsive hydroxypropyl cellulose (HPC) microgels have been synthesized and characterized. The microgel particles were obtained by chemically cross-linking collapsed HPC polymer chains in water−surfactant (dodecyltrimethylammonium bromide) dispersion above the lower critical solution temperature of the HPC. The size distributions of microgel particles, measured by dynamic light scattering, have been correlated with synthesis conditions including surfactant concentration, polymer concentration, and reaction temperature. The final microgel size is determined by the balance between the hydrophobic interaction among HPC polymer chains and intermicelle electrostatic repulsion. The swelling and phase transition properties of resultant HPC microgels have been analyzed using both static and dynamic light scattering techniques as a function of temperature and cross-linker concentration. It is found that the increase in the cross-linker concentration reduces the shrinkage extent. The dilute HPC microgel particles (C < 1.0 × 10-5 g/mL) form a stable colloidal dispersion at room temperature and at 44 °C (above the volume phase transition temperature), probably due to steric effects. Adding salt to water leads to a decrease of the volume phase transition temperature of HPC microgels.