Abstract
Temperature and pH responsive macromolecular colloidal materials have widespread applications. pH/thermo-responsive benzyl modified cellulose based microgels (BMC-PNIPAAm-PAAc) were synthesized by copolymerization of benzyl modified cellulose with poly(N-isopropylacrylamide) [PNIPAAm], and acrylic acid (AAc) by emulsion polymerization. In order to enhance the copolymerization ability of cellulose, its hydroxyl groups were modified by treating with benzyl chloride. Microgels were characterized using Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrsocopy, rheology, dynamic light scattering (DLS), flow viscometry, and density measurements. FTIR was used to investigate the various functional groups in the microgels. The influence of experimental conditions such as chemical composition and temperature/pH of microgel solutions on the sol-gel behavior of microgels was studied through rheology, light scattering, viscometry and densimetry. The shear stress and gel viscosity was measured under various shear rates and temperatures. By increasing the shear rate, a decrease in viscosity was observed. The microgels behaved as viscoelastic solids over a wide frequency range as the loss modulus was found to be smaller than the storage modulus. Temperature-dependent spectral changes of the microgels were also investigated by UV-Vis spectroscopy at various temperatures. The relative viscosity of the synthesized microgels was also studied at various pH/temperature using concentration based times of flow Ostwald's viscometry. Similarly, the specific volume of the gel particles was traced from the solution density The results revealed that various colloidal and physicochemical parameters of the polymer gels could be easily adjusted by changing various experimental variables, suggesting their potential use as drug delivery carriers.