Summary: The thermal degradation and carbonization of poly(1,3-cyclohexadiene) (PCHD) with a controlled polymer chain, and its soluble dehydrogenated derivatives are reported for the first time. For PCHD, thermogravimetric (TG) analysis revealed a three-stage thermal degradation. PCHD was completely decomposed and consumed at 600 °C. 1,2-Cyclohexadiene (1,2-CHD) units showed higher thermal stability than 1,4-cyclohexadiene (1,4-CHD) units in the polymer chain. The weight residue of approximately 75% dehydrogenated PCHD was between 55 and 65 wt.-% at 800 °C. These extremely stable residues seem to originate from dehydrogenated CHD units (phenylene units), and are regarded as carbonized compounds. For soluble polyphenylene (PPH) homopolymer (i.e. completely dehydrogenated PCHD), a gradual thermal degradation was observed during the carbonization process. The weight residue for each polymer was between 60 and 70 wt.-% at 800 °C. 1,4-Phenylene (1,4-Ph) units showed higher thermal stability than 1,2-phenylene (1,2-Ph) units. The existence of CHD units in the polymer chain accelerated the carbonization of Ph units (sequence). The results suggest that the soluble PPH homopolymer is one soluble precursor that can be utilized to obtain a new class of graphitic compounds.
Thermogravimetric (TG) curves for completely dehydrogenated poly(1,3-cyclohexadiene) (soluble polyphenylene homopolymer).