Soluble, Allyl-Functionalized Deoxybenzoin Polymers

We describe the synthesis of allyl-substituted deoxybenzoin-based aromatic polyesters that combine the advantageous thermal properties of deoxybenzoin with the processability and reactivity of pendent unsaturated groups. A thermally induced Claisen rearrangement of bis-allyl ether-substituted deoxybenzoin 2 produced 3,3'-bis-allyl-4,4'-bishydroxydeoxybenzoin (BA-BHDB, compound 1) as a novel A(2) monomer. BA-BHDB 1 polymerized readily with isophthaloyl chloride to produce a novel set of functional aromatic polyesters. These allyl-substituted polymers exhibited marked solubility advantages over deoxybenzoin-based polymers lacking such pendent groups, affording homogeneous solutions in numerous organic solvents. The processability contributed by the allyl groups afforded access to relatively high molecular weight aromatic polyesters, with estimated number-average molecular weight (M-n) values exceeding 20 kDa. Interestingly, evaluation of the thermal properties of these polymers revealed that the pendent allyl groups led to small increases in heat release relative to the unsubstituted deoxybenzoin polymers. Thus, this work represents an advantageous design of nonflammable polymer materials, offering benefits with respect to both processability and heat release properties. Moreover, the utility of these functional deoxybenzoins in post-polymerization cross-linking was demonstrated using multifunctional thiols and thiol-ene reactions.