Semi-fluorinated polyarylenes: Microwave-assisted synthesis andstructure-propertyrelationships

A series of three fluorine containing and three non-fluorinated Diels-Alder step-growth polyarylene polymers and copolymers was synthesized via conventional oil bath heating (days/weeks). A drastic time reduction was realized with a microwave-assisted polymerization (hours). The polymers were characterized by multinuclear (H-1,C-13, and(19)F) NMR and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, thermal analysis (thermogravimetric analysis [TGA], differential scanning calorimetry [DSC], and dynamic mechanical analysis [DMA]), gel permeation chromatography, X-ray diffraction (XRD), water contact analysis, and refractive index (RI) measurements. The NMR spectra indicated a mixture ofparaandmetaconformations through the polymer backbone increasing to moreparawith greater fluorine content. TGA revealed the fluorine-containing polyarylenes possessed the highest char yields at almost 80% at 1000 degrees C under nitrogen, and all the polyarylenes possessed onset of degradation temperatures above 550 degrees C under nitrogen and air atmospheres. XRD analysis indicated more ordering for the fluorine-containing polyarylenes which afforded the high char yields. DMA gave storage moduli values in the range of 1-10 GPa for the polyarylenes. Molecular weights for all samples were above 100 kg/mol. Water contact angles did not change with fluorine content due to the shielding effect of the pendant phenyl groups. However, the RI decreased to 1.6497 at 632.8 nm for the polyarylene with the highest fluorine content.