NOVELTY - Polymer composition comprises: a thermally conductive filler having thermal conductivity greater than or equal to 5 W/mK; a covalently crosslinked polymer network including connecting ester bonds; and at least a transesterification catalyst. The amount of thermally conductive filler is sufficient for the composition to have thermal conductivity greater than or equal to 0.5 W/mK. The crosslinking is sufficient for the polymer network to be beyond the gel point. The number of connecting ester bonds is sufficient for the network to relax stresses and/or flow when conditioned at an appropriate temperature.    USE - The polymer composition is useful for forming article and device comprising: heat sinks for electronic components, especially in computers, consumer electrical appliances, solar cells and batteries, such as processors, lamps, LED-lamps, electric motors, thermic motors and electric circuits; packing of electric or electronics elements, such as coils, chassis structures, housings or casings e.g. solar cell back sheets and battery casings; heat exchangers such as like heat exchangers for energy transfer applications e.g. in transformers, or electrically insulating sheath for electric cables, geothermal heat exchangers and thermal pads; coatings such as a varnish, a paint, an anticorrosion protective coat or a protective coat on an electronic circuit or an electronic component; and a seal or a layer of glue or adhesive.    ADVANTAGE - The polymer composition: provides article that has a transverse thermal conductivity superior or equal to 0.5 W/mK (claimed); contains the polymer network that is able to reorganize by exchange reactions that allow it to relax stresses and/or flow while maintaining network connectivity; and exhibits improved adhesion, self-repairing, greater processing flexibility, better mechanical properties, improved electrical conductivity and improved chemical resistance.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an article resulting from the forming and hardening of the polymer network composition; and    (2) a device comprising at least two adjoining or contacting parts, where at least one part (A1) is the article, and at least one part is of a material (B1) different from the material of (A1), preferably (B1) is of a metal.