Novel Poly(arylene ether)s with Pendent Trifluoromethyl Groups

Abstract

Six novel perfluoroalkyl-activated bishalo monomers 4a,b−6a,b have been synthesized successfully using Pd(0)-catalyzed cross-coupling reaction of 4-chloro- or 4-fluoro-3-trifluoromethylphenylboronic acid with 1,4-dibromobenzene, 2,6-dibromopyridine, and 2,5-dibromothiophene. These monomers were converted to poly(arylene ether)s by nucleophilic displacement of the halogen atoms on the benzene ring with several bisphenols. The products obtained by displacement of the fluorine atoms exhibit weight-average molar masses up to 3.52 × 105 g mol-1 in GPC. Displacement of the chlorine atoms from the analogous monomer structures by bisphenols was not successful in obtaining high molar mass products. These poly(arylene ether)s showed very high thermal stability even up to 536 °C for 5% weight loss in TGA in synthetic air. Comparatively low thermal stability for the thiophene ring containing polymers was attributed to the oxidation of the sulfur atom of the thiophene ring at high temperature in air, which destroyed the aromatic character of the thiophene ring. This was confirmed by investigating the thermal stability of these polymers in an inert environment. The polymers exhibit glass transition temperatures (Tg) up to 234 °C in DSC. The glass transition temperatures taken as peak in tan δ in DMTA measurements are in good agreement with the DSC Tg values. All the polymers are soluble in a wide range of organic solvents, e.g., CHCl3, THF, NMP, and DMF. Transparent thin films of these polymers cast from THF exhibited tensile strengths up to 70 MPa, a modulus of elasticity up to 2.69 GPa, and elongation at break up to 30% depending on their exact repeating unit structures.