NOVELTY - Polymer comprising a reaction product of (a) one or more diacid or its diester and/or glycolide, and (b) one or more polyol, is new. The component (a) comprises (i) 2,6-naphthalene dicarboxylic acid (NDCA) or its 1-10C-alkyl diester and/or glycolide, and (ii) 2,5-furan dicarboxylic acid (FDCA), and/or its 1-10C-alkyl diester. The component (b) comprises isosorbide.    USE - The polymer is useful: in an article such as a film or sheet, preferably barrier film (all claimed), which is useful for packaging food (including meat, fish, cheese and other dairy products), pharmaceuticals and electronic and electronic component; as a carrier for magnetic tape or backing for pressure sensitive adhesive tapes, packaging trays and blister packs; as a substrate in thin film and solar cell applications; for forming injection molded articles, extruded sheets, profile extruded articles and extruded blow molded articles; and for medical packaging, shrink labels, rigid laminates for furniture, transaction cards (e.g. credit cards), bottles (including so-called clear handleware), housewares, appliances, equipment, and signage.    ADVANTAGE - The polymer simply and economically prepares the film with improved oxygen, carbon dioxide and moisture barrier properties, high-temperature heat sealability, enhanced toughness and chemical, heat and impact resistance and light weight thus improving shelf life of the packaged food.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a composition comprising one or more first polymer and one or more second polymer consisting of polymers of different from the first polymer and other polyesters, which are reaction product of (i) acids or esters and (ii) polyols, where the acids and esters do not include NDCA, 1-10C-alkyl diester of NDCA and/or glycolide, and FDCA and/or 1-10C-alkyl diester of FDCA, when the polyol comprises isosorbide, and the polyols do not include isosorbide, when the acids and esters comprise NDCA, 1-10C-alkyl diester of NDCA and/or glycolide, and FDCA and/or 1-10C-alkyl diester of FDCA;    (2) a method of forming a film comprising extruding the polymer to form an extrudate, shaping the extrudate by passing the extrudate through a flat or annular die, and cooling the extrudate to form a film or sheet having a machine direction and a cross direction; and    (3) a barrier film comprising a polyester-based polymer with (a) an oxygen gas permeability of 0.4 cc-mil/100 in2 24 hours atm (8 cc 20 mu /m2 24 hours atm) at 50% relative humidity (ASTM D-3985) or less, (b) a moisture permeability of 0.5 g mil/100 in2 24 hours atm (9.8 g 20 mu /m2 24 hrs atm) at 38 degrees C (ASTM F-1249) or less, and (c) a glass transition temperature (Tg) of 100 degrees C or higher.