| High osmotic pressure chromatography (HOPC) is demonstrated to separate a large amount of water-soluble polymers into fractions of narrower polydispersity than preparative gel permeation chromatography. Separation of polyvinylpyrrolidone is presented. Typically, fractions with a polydispersity index (PDI) of 1.4 to 2 were generated from broad-distribution polymers (PDI∼5) in significant quantities from a single separation. By multi-stage separation, standard-grade fractions were obtained.; Phase fluctuation chromatography (PFC) is proposed to separate a large amount of random copolymers into fractions with different chemical compositions. PFC is based on the tendency of a concentrated solution of the copolymer to separate into different phases, each of which is enriched with components of a specific composition. When the multi-phase solution is injected into a column packed with porous materials that have specific moieties, domains rich in a component with greater affinity to (or less repulsion from) the surface will be retained longer than the domains rich in the other component. Styrene-acrylonitrile copolymers with different acrylonitrile contents were used as model copolymers. Silanol or diphenyl surface retained styrene-rich components longer, whereas cyano surface attracted acrylonitrile-rich components. The separation resolution was better when the pore had a large surface area and selective surface moieties and when selective solvents and higher concentrations were used. Results obtained agreed with a theoretical prediction presented here.; An interferometric imaging technique is applied to visualize the interior of a cylindrical polyacrylamide hydrogel immersed in water or an aqueous solution. The method can be used to evaluate uniformness of a hydrogel matrix, and to study various transient phenomena such as kinetics of the volume transition upon the solvent composition change and osmotic pressure change, infusion of a second substance into the gel and its release into the surrounding. It can also be used to measure dn/dw for any solute-solvent combinations and partition coefficient of a substance in the hydrogel. |
