Vapor phase deposition was carried out on multifunctional aliphatic and aromatic benzoxazoles to yield powdered samples of poly(dimethylenebenzoxazoles). Representative aliphatic and aromatic poly( dimethylenebenzoxazoles) were also synthesized through solution methods using 4-amino-3-hydroxyhydrocinnamic acid and 2-(4-(bromomethyl)phenyl)-6-(bromomethyl)benzoxazole, respectively, as monomers. Both aromatic and aliphatic polybenzoxazoles containing -CH2CH2- units in the polymer backbone displayed catastrophic weight loss over a very narrow temperature range. This is in contrast with other polybenzoxazoles which show a gradual weight loss over 500-1000 degrees C. Vapor phase deposition carried out under vacuum on the polymers gave similar polymers in the collection zone suggesting the catastrophic weight loss is attributed to thermal depolymerization of the polymer through a diradical intermediate similar to the thermolysis and polymerization of [2.2] paracyclophane.