Polycarbonate compositions having improved barrier properties

A halogen-free high molecular weight aromatic polycarbonate compound having an IV of about 0.40-1.0 dl/g in methylene chloride at 25.degree. C. and exhibiting improved water vapor transmission and gas barrier properties, said polycarbonate compound consisting essentially of the following general repeating unit:

• ##STR7## wherein the X and Y moieties can each independently be selected from the group consisting of hydrogen, an unsubstituted alkyl of C.sub.1 -C.sub.10, and mixtures thereof with the proviso that at least either X or Y is a C.sub.1 -C.sub.10 alkyl and that neither a cyclic nor an aryl group is bonded directly to a phenyl group;
• n is an integer of about 2-2,000;
• and, W is a member selected from the following group:
• (a) --CH.sub.2).sub.r wherein r is 0 or an integer from 2-10;
• (b) ##STR8## wherein R is a member selected from the group consisting of C.sub.1 -C.sub.10 alkyl, C.sub.5 -C.sub.10 cycloalkyl and C.sub.6 -C.sub.14 aryl;
• (c) ##STR9## wherein R and R' can each independently be the same as R in (b) above with the proviso that when both R and R' are each CH.sub.3, X and Y are not both symmetrically substituting CH.sub.3 ;
• (d) ##STR10## wherein m is an integer of 4-20;
• (e) ##STR11## wherein p and q can each be an integer of 0-1;
• and, (f) --O--.