Elastomers

An elastomer consisting essentially of

• A. from about 5 to 25 wt. % of --X-- units where --X-- is part of a repeat unit having the structural formula
• --Y--X--Z--
• where --Y-- and --Z-- are independently selected from --O--, ##STR31## --X-- is a divalent organic radical consisting of a chain of ring structures except for trans-amide, carbonyl, trans-vinylene, azo, and azomethine linkages which may be present and whose shortest length between centers of its terminal junctions measured from a Dreiding model laid flat is at least 11 Angstroms;
• and when --X-- is in the compound:
• ##STR32## the compound exhibits a melting point that is at least about 225.degree. C.;
• and
• B. from about 75 to 95 wt. % of units selected from the following:
• ##STR33## in which both free bonds are connected to oxygen and/or nitrogen, and/or ##STR34## where R, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each aliphatic divalent organic radicals, having from 2 to 15 carbon atoms within the chain, with each having a molecular weight of under 450 and R.sup.5 is a hydrocarbon radical.