AbstractThe incorporation ofN,N‐dimethylacrylamide (DMA) as a comonomer in polyethylene yields a material possessing dramatically improved mechanical compatibility with poly(vinyl chloride) (PVC). At increased levels of DMA (25–30 wt.‐%) miscibility with PVC is achieved. This behavior is believed to be due to the specific interaction of the tertiary hydrogen of poly(vinyl chloride) (weak “acid” or proton donor) with the disubstituted amide in the ethylene copolymer (weak “base” or proton acceptor). Dynamic mechanical characterization of the ethylene/DMA copolymer (EDMA)/PVC blends reveals separate glass transitions temperatures at DMA levels below 20 wt.‐%; they merge into a singleTgwhen the DMA content reaches a value above 25 wt.‐% in the ethylene copolymer. The secondary loss transition for PVC (−40°C) is lowered in temperature and greatly suppressed in magnitude. This is further evidence of molecular miscibility. Mechanical property data obtained on the EDMA/PVC blends are consistent with the fore