Polymer compositions having improved barrier properties

A dual-metallocene catalyzed bimodal polyethylene polymer having a higher molecular weight (HMW) component and a lower molecular weight (LMW) component wherein the LMW component is present in an amount of from about 60% to about 90% based on the total weight of the polymer and the HMW component is present in an amount of from about 10% to about 40% based on the total weight of the polymer;

• a melt index of from about 0.5 g/10 min to about 4.0 g/10 min;
• a density of equal to or greater than 0.96 g/cc;
• having a ratio of z-average molecular weight to weight average molecular weight of from about 3 to about 7;
• which when formed into a 1-mil blown film displays a moisture vapor transmission rate as determined in accordance with ASTM F 1249 at 1 mil, 100% humidity, and 100° F. ranging from equal to or greater than about 0 to equal to or about 20% greater than X where X=k1 {−61.95377+39.52785(Mz/Mw)−8.16974(Mz/Mw)2+0.55114(Mz/Mw)3}+k2{−114.01555(τ)+37.68575(Mz/Mw)(τ)−2.89177(Mz/Mw)2(τ)}+k3{120.37572(τ)2−25.91177(Mz/Mw)2}+k4{18.03254(τ)3};
• Mw is from about 100 kg/mol to about 180 kg/moL;
• Mz is from about 300 kg/mol to about 1000 kg/mol;
• τ is from about 0.01 s to about 0.35 s;
• k1 is 1 g/100 in2·day:
• k2 is 1 g/100 in2·day·s;
• k3 is 1 g/100 in2·day·s2;
• k4 is 1 g/100 in2·day·s3;
• and τ is determined by small-strain oscillatory shear measurements at 190° C.