A linear polymer has repeating units represented by the formula ##STR00001## wherein (a) n is an integer greater than or equal to 0, (b) x is an integer greater than or equal to 1, and ##STR00002## represents an unconjugated acetylenic group when x is equal to 1 or conjugated acetylenic groups when x is greater than 1; (c) Ar is an aromatic group, and (c) R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are independently selected from the group consisting of alkyl, aryl, alkylaryl, haloalkyl, haloaryl and mixtures thereof. The linear polymer may be thermally cured to form a crosslinked polymer.