Solution and adsorption properties of polymeric amphiphiles.

摘要

Fine particle dispersions have found numerous applications in ink, coating, cosmetics or pharmaceutical formulations. In most cases water is the main solvent to carry the complex ingredients. Because of the nature of particle surface, they may not be easily dispersed in water and flocculation or coagulation occurs. In order to stabilize the particles in waterborne formulations, amphiphiles are often added to act as dispersants or surface modification agents by adsorbing onto these particles. Cosolvents are used to serve as cosurfactant or other specific functions.; In our system, we use polymeric amphiphiles to stabilize carbon black (CB) nanoparticles. These amphiphile molecules will self-associate to form micelles in aqueous solution owing to their structural characteristics as well as the solvophobic interactions. We first used spectrophotoscopy methods to realize the association behavior and structure of micelles. Through the local variations of refractive index or nonuniform distribution of nuclei in the solution, novel techniques such as dynamic light scattering (DLS) and small angle neutron scattering (SANS) can be used to obtain the micelle size and shape information. Considerable structural transition of micelles was observed either by adding polar cosolvents or at elevated temperature.; We next studied the adsorption behavior of amphiphiles onto CB and how the micelle formation significantly influenced the adsorption properties. First of all, we characterized the CB structure by TEM, DLS and SANS and the data suggested that particles were fractal-like. We examined the physicochemical properties of particle surface by electron microscopes and ESCA (electron spectroscopy of chemical analysis). A dialysis method was developed to construct the adsorption isotherm. The adsorbed layer thickness was estimated complementarily by viscometry, DLS and SANS. Based on the results from these techniques, we found micelle formation made a distinct borderline on the structure of adsorbed layer and thus the stability of the particles.; Further studies on SANS matching technique and adsorption of amphiphiles on other solid surfaces are also included in this report to provide comprehensive ideas regarding applications of amphiphiles.