Thermal Degradation of Poly(1,3‐cyclohexadiene) and its Dehydrogenated Derivatives: Influence of a Controlled Microstructure

Abstract

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).magnified imageThermogravimetric (TG) curves for completely dehydrogenated poly(1,3‐cyclohexadiene) (soluble polyphenylene homopolymer).

Hydrocarbon-based fuel cell membranes: Sulfonated crosslinked poly(1,3-cyclohexadiene) membranes for high temperature polymer electrolyte fuel cells

“…Assignment of thermal mass loss events based on related reported work [16,31] is as follows: For all samples, except unsulfonated XPCHD, there is mass loss of~5e20% at about 95 C. This initial loss is believed to be due to polymer chain depolymerization, which proceeds until more thermally stable units on the polymer backbone are reached [16]. The remaining backbone remains thermally stable until 200 C, after which more depolymerization takes place.…”

Thermal Stability of Fluorinated Polydienes Synthesized by Addition of Difluorocarbene

“…The decomposition profi les match previously reported data very well. [ 11 ] The weight loss at low temperature was initially believed to be caused by release of solvent that is "trapped in" the condensed polymer during polymer recovery process after polymerization because it was located in the vicinity of the glass transition of PCHD and the temperature seems to be too low for chain scission. However, All the characterization data lead us to conclude that the thermal pyrolysis of PCHD involves two kinds of decomposition mechanisms.…”

“…However, All the characterization data lead us to conclude that the thermal pyrolysis of PCHD involves two kinds of decomposition mechanisms. One mechanism is chain scission to lose volatile materials [ 11 ] (monomer, dimer, and oligomers) that were carried out by N 2 fl ow during heating; and the other mechanism is crosslinking caused by addition to double bonds or coupling of free radicals generated by homolytic bond cleavage. Chain crosslinking results in a three-dimensional structure as indicated by the higher T g of the residue and insolubility in common solvent, leading to enhanced thermal stability as well as retarded decomposition.…”

Ultrasound‐accelerated dehydrogenation of poly(1,3‐cyclohexadiene): efficient synthesis of poly(para‐phenylene)

“…Accordingly, a variety of different approaches have been attempted to improve the solubility of PPP. Ultimately, the most promising route to obtain soluble PPP is the dehydrogenation of poly(1,3‐cyclohexadiene) (PCHD) and its derivatives (Scheme ) 7–30. Therefore, various polymerization and dehydrogenation reactions for PCHD have been examined.…”

“…Therefore, various polymerization and dehydrogenation reactions for PCHD have been examined. As a result, the dehydrogenation of anionically polymerized PCHD with benzoquinones has been found to be one of the most effective methods to synthesize soluble PPP 10–30. However, although a high conversion of cyclohexadiene (CHD) units to phenylene (Ph) units can be achieved by the dehydrogenation of PCHD with benzoquinones, a long reaction time and/or a high reaction temperature are always required.…”