Synthesis and characterization of poly(multidimethylsiloxane-1,4-ethynylenephenyleneethynylene)s

Abstract

A series of poly(multidimethylsiloxane-1,4-ethynylenephenyleneethynylene)s were synthesized by condensation reactions of 1,4-diethynylbenzene magnesium reagents with various α,ω-dichlorodimethylsiloxanes. The polymers obtained were solids or viscous liquids and are soluble in common organic solvents at room temperature. The structures and properties of the polymers were characterized by Fourier transform infrared, 1H nuclear magnetic resonance (NMR), 13C NMR, differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) techniques. DSC analyses showed that these polymers can be thermally cured to form highly crosslinked structures. DMA studies revealed that the glass transition temperatures of the cured polymers decreased with increasing siloxane chain length. TGA measurements showed that the cured polymers were thermally stable up to almost 450 °C in both N2 and air. With increasing length of the siloxane units, the thermal stability of the cured polymers decreased. Silicon oxycarbide ceramics with high thermal stability were produced when the cured polymers were pyrolyzed at 1200 °C under argon. A series of poly(multidimethylsiloxane-1,4-ethynylenephenyleneethynylene)s were synthesized by condensation reactions of 1,4-diethynylbenzene magnesium reagents with various α,ω-dichlorodimethylsiloxanes. These polymers can be thermally cured to produce highly crosslinked structures. The glass transition temperatures of the cured polymers decrease with an increase in the siloxane chain length. The cured polymers are thermally stable up to almost 450 °C in both N2 and air. The silicon oxycarbide ceramics were obtained when the cured polymers were pyrolyzed at 1200 °C under argon.