| High osmotic pressure chromatography (HOPC) is an efficient way to preparatively separate a polymer into fractions with a narrow molecular weight distribution (MWD). Poly (ϵ-caprolactone) (PCL) was separated by HOPC in a good solvent (dioxane) and in a near-theta solvent (toluene). The separations in toluene produced fractions with a narrower MWD in a larger amount compared to the separations in dioxane. Slight adsorption of PCL onto the pore surface in toluene increased the injection amount and helped narrow MWD.; Monomethoxy-terminated poly(ethylene glycol) (MePEG) has dimeric, trimeric, and tetrameric components at twice, three times, and four times as high a molecular weight (MW) as that of the main component. We used two-dimensional column chromatography to evaluate MW and identify the terminal groups in each component. The first step is HOPC to prepare a sufficient amount of fractions that contain different percentages of the multimeric components. In the second step, each of the fractions was characterized by using regular size exclusion chromatography (SEC) and high-resolution NMR. Decomposition of the chromatogram combined with isolation of the terminal methoxy peak in the NMR spectrum led to unique identification of the terminal groups. We thus found that the monomeric component is monomethoxy-terminated, whereas the dimeric and other multimeric components are mostly dihydroxy-terminated.; HOPC was used to remove the high-MW, dihydroxy-terminated components in McPEG. Various types of porous silica particles, surfaces, solvents, polymer concentrations were screened for the optimal purification. Efficiency was compared for HOPC and preparative SEC.; Because of dihydroxy-terminated components, a block copolymer PEG-PLLA prepared by growing poly(L-lactide) (PLLA) from hydroxy ends of McPEG contains multiple components, such as a PLLA-PEG-PLLA triblock copolymer. Phase fluctuation chromatography (PFC) was used to separate the block copolymer. Porous silica attached with PLLA brushes was prepared to enrich lactate content in late fractions. Fractions were analyzed by SEC and NMR to evaluate the effects of size exclusion and surface interaction in the separations. |
