Influence of Common Solvents on Micellization Behavior and Properties of the Amphiphilic Random Copolymer P(St-co-DM)

Styrene monomer (St) and dimethylaminoethyl methacrylate monomer (DMAEMA) were used to synthesize the amphiphilic random copolymer P(St-co-DM) via free radical copolymerization. The polymer structure was characterized by Fourier transform infrared (FTIR) spectroscopy, H-1 nuclear magnetic resonance (H-1 NMR) spectroscopy, gel permeation in chromatography (GPC), and differential scanning calorimetry (DSC). We investigated the influence on the microstructure of the P(St-co-DM) nanoscale micelles by self-assembly in three common solvents (co-solvent), and also investigated the effect of micelle structure on the emulsion properties. The morphologies and size distributions of the P(St-co-DM) colloid particles were studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The results show that the more critical water content, the higher hydrophilic and the bigger hydrodynamic radius of the micelles are observed when tetrahydrofuran (THF) is used as co-solvent. When dioxane or THF is used as co-solvent, the P(St-co-DM) self-assembles into spherical micelles with a relatively loose outer layer and a compact inner layer. In the case of N,N-dimethylformamide (DMF), particles are distributed uniformly inside the spherical micelles. The hydrophilic properties of the micelles were characterized by recording the contact angle for the toluene/water interface. The contact angles of all the micelles are less than 90 degrees. The O/W type (oil-in-water type) emulsions were obtained for three co-solvents. The type of emulsions was determined by drop test. The emulsifier experiment shows that the solid particulate emulsifiers have excellent emulsifying properties for dioxane and THF as co-solvents.