Abstract: Novel difunctionalized cyclobutabenzene monomers of the general formula: ##STR1## wherein Z can be hydrogens or a cyclobutane ring; and X and Y are carboxyl, amino, alcohol, isocyanate, acid halide, or bis-acyl halide groups. Exemplary difunctional bitricyclodecatriene monomers are ?2,2'-bidicyclo?2.4.0!octa-1,3,5-triene!-5,5'-dicarboxylic acid (BXTA) and ?2,2'-bitricyclo?6.2.0.0!deca-1,3,(6),7-triene!-7,7'-dicarboxylic acid (QXTA). The difunctionalized bitricyclodecatriene monomers can form part of a polymer backbone chain in which the multiple butane ring functionalities can be easily opened to produce strong, three-dimensional covalent bond crosslinking between polymer chains. The crosslinking can be induced simply by heating the polymer to a temperature in excess of 250.degree. C.