Synthesis of high refractive-index melt-stable aromatic polyphosphonates

The synthesis of aromatic polyphosphonates based on the step polymerization of various bisphenols and dichlorophenyl phosphine oxide was investigated. The effect of catalyst, type, concentration, and polymerization time were systematically varied to obtain high molecular weight polymers. Very high m olecular weight tough, ductile materials with a high degree of optical clar ity were synthesized. In contrast with the aromatic polycarbonates, the ref ractive index was increased from 1.58 to 1.60 (for the bisphenol A-based sy stem) and 1.64 for a biphenol-based system. The latter was still an amorpho us soluble polymer as a result of the non-coplanar nature of the phenyl pho sphine oxide bond, unlike the analogous polycarbonate. Hydrolytically stabl e melt-processable cumyl phenol end-capped polyphosphonates were successful ly achieved for the first time. Rheological studies show that these end-cap ped systems are melt-stable at 200 degreesC, whereas the systems of initial ly higher molecular weight but without any well-defined end capping clearly degraded quickly probably as a result of an acid-catalyzed hydrolysis proc ess. Extensive high char yields were produced upon pyrolysis in either nitr ogen or air, suggesting good fire resistance. (C) 2001 John Wiley & Sons, I nc.