Scalable PEO-PPO-PEO triblock copolymer purification from Pluronics through competitive adsorption

Abstract

A new scalable method for large scale purification of Pluronic block copolymers has been developed using a slurry of cyano(CN)-modified silica particles and Pluronic block copolymers in a solution. We have taken advantage of the competitive adsorption of polymers onto nanoporous CN-modified silica particles in solution to purify polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers from as-received (AR) Pluronic samples, such as F108, F127 and F68. Interaction chromatography and size exclusion chromatography revealed that significant levels of low molecular weight (MW) impurities exist in AR Pluronics. We found that more than 20 wt.% impurities exists in AR F108 and AR F127, while the purified PEO-PPO-PEO triblock copolymers contained less than 2 wt.% of the low MW impurities after using the silica slurry method. In the case of AR F68, which contains about 9 wt.% impurities, it is possible to completely remove the low MW impurities. A multiple injection interaction chromatography technique has been employed to reveal the surface displacement of pre-adsorbed low MW impurities by the triblock copolymers in solution. By tuning the solvent quality, this report finally highlights that the impurities can be effectively removed in laboratory for a large scale purification using the silica slurry. For example, using about 10 g of the bulk silica packing material, it was possible to obtain 1 g of purified triblock copolymers.