Abstract: Membranes have been developed for the pervaporative dehydration of lactic acid used for the production of biodegradable polymers: polylactides, polylactic acid, and medical plastics. Membranes were obtained by modifying poly-2,6-dimethyl-1,4-phenylene oxide with small amounts (5 wt %) of a new complex filler containing equal amounts of variegated star macromolecules having six polystyrene arms and six arms of the diblock copolymer poly-2-vinylpyridine-block-poly-tert-butylmethacrylate and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The structure and physical parameters of the membranes were analyzed using thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy, and the density of the membranes was measured by the flotation method. The transport properties of the membranes were investigated in sorption experiments, as well as by pervaporation of a water–lactic acid mixture. It has been shown that the introduction of small amounts of the new modifier into the membrane alters the internal structure of membranes and favorably affects the transport properties of membranes, improving the total permeate flux and increasing the separation efficiency by more than 7 times; the separation factor reaches 2560 in the case of dehydration of lactic acid containing 25 wt % water.