Effects and measurements of polyoxyethylene block length in polyoxyethylene-polyoxybutylene copolymers

Block copolymer surfactants, made from 1,2-butylene oxide (BO), propylene oxide (PO) and ethylene oxide (EO), exhibit wide ranges of properties and performance. In particular, BO/EO block copolymers exhibit improved surfactant performance with respect to PO/EO analogs. One interesting difference between these two classes of surfactants is the EO capping efficiency of polyoxypropylene (POP) vs. polyoxybutylene (POB) hydrophobe secondary hydroxyl groups. In this regard, nuclear magnetic resonance measurements have shown that POP secondary diols react more readily with EO than POB diols. For the case of ethoxylated POB polymers, the amount of unethoxylated secondary hydroxyl is proportional to the average length of the polyoxyethylene (POE) blocks. Differential scanning calorimetry was used to observe crystallinity of POE blocks. For a given POB hydrophobe molecular weight and weight percentage EO, surfactant performance properties can be augmented by affecting POE block length in the ethoxylation process.