Better, more polar solvent, such as DMF or DMSO that are able to better stabilize the ammonium cation intermediate and are capable of providing a higher temperature environment for the polymerization, yield very high molecular weight macromolecules that are insoluble in DMF and toluene, and are only soluble in DMSO. Thus, the COLBERT reaction can be used with aromatic dithiols and aromatic dibenzoxazines to afford high molecular weight linear polymers with potentially promising high temperature properties.