Preparation of Acrylic Pimaric-sucrose Ester by Solvent-free Process and Its Adsorption Properties at Air-water Interface

Acrylic pimaric-sucrose ester was synthesized from acrylamicarboxylic acid and sucrose by esterification at high temperature under solvent-free conditions, which structure was characterized by IR, NMR and gel permeation chromatography and critical micelle concentration (CMC) was measured. The reorientation theory was used to analyze the adsorption behaviors of acrylic pimaric-sucrose ester surfactant at the air-water interface, including morphological change and adsorption capacity. The results showed that the acrylic pimaric-sucrose ester was successfully synthesized by the method, and the CMC value the synthesized ester was 2.2 g/L. With the increase of surfactant concentration, the solvent molar fraction at the air-water interface decreased, while the molar fraction of acrylic pimaric-sucrose ester increased. The adsorption of acrylic pimaric-sucrose ester at the air-water interface was divided into state 1 and state 2, and the adsorption capacity on the interface was calculated respectively, which was up to 1.9 mmol/m² in state 2. As the surface pressure increased, the number of molecules in state 1 increased first and then decreased, while the number of molecules in state 2 dominated and continued to increase. The molar free energies (ΔG) of adsorption and micelles of acrylic pimaric-sucrose ester were -20.67 kJ/mol and -15.16 kJ/mol, respectively, indicating that acrylic pimaric-sucrose ester was preferentially adsorbed on the interface and formed micelles after reaching saturation.