The interactions and partitioning of low molecular weight polyethylene glycols and diethyl phthalate in ethylcellulose/hydroxypropyl methylcellulose blends

The interactions and partitioning of diethyl phthalate and low molecular weight polyethylene-glycols in blends of ethylcellulose/hydroxypropyl methylcellulose have been studied. Both plasticizers were shown to diffuse in both phases according to the overall volume composition. The plasticizers interacted preferentially with one polymer component of the blend as predicted from studies of the individual polymers. Diethyl phthalate, a preferential plasticizer for ethylcellulose, demonstrated increased partitioning in the ethylcellulose-rich phase only at 80/20 w/w ethylcellulose/hydroxypropyl methylcellulose compositions. Polyethylene glycols, PEG200 and PEG400, preferential plasticizers for hydroxypropyl methylcellulose, showed increased partitioning in the hydroxypropyl-methycellulose-rich phase also in blends containing 80% w/w ethylcellulose. The general effect of the mechanism and kinetics of the phase separation of the blend on the plasticizer partitioning has also been discussed.