Removal of dihydroxy-terminated components from monomethoxy-terminated poly(ethylene glycol)

A preparative method to remove dihydroxy-terminated components in a sample of presumably monomethoxy, monohydroxy-terminated poly(ethylene glycol) (PEG) is presented. Purification of the monomethoxy-terminated component allows one to prepare a diblock copolymer of PEG and poly(lactic acid) (PLLA) free of a PLLA-PEG-PLLA triblock copolymer in various biomedical applications of the copolymer. Efficiency of the purification is compared for high osmotic pressure chromatography (HOPC) and preparative size exclusion chromatography (SEC). In HOPC, various types of porous silica particles, surfaces, solvents, polymer concentrations have been screened for the optimal performance. It was found that HOPC is more efficient than SEC, especially HOPC of 30-40 wt% solutions in water by a column packed with acid-washed controlled pore glass is optimal in producing high-purity fractions.