Thermal transformations of oligoarylenes

Abstract

Thermal transformations of oligoarylenes, relating to polymers with conjugate systems, have been investigated in air and in vacuo, depending on the molecular weight and degree of branching of the original material. The extreme character of the thermostability in air versus the M-n value of oligoarylene, and the possibility of increasing the thermal oxidative stability by enhancing the degree of branching have been explained by different intensities of intermolecular processes of dehydropolycondensation in the period before the starting of substantial weight losses. The influence of the solidification (or carbonization) conditions of the oligoarylenes on the structures and thermooxidative stabilities of the resulting samples was studied.Oligoarylenes deserve attention with a view to creating polymer systems which display high thermal stability [1 ]. In the present work thermal transformations of oligoarylenes (based on condensed aromatic compounds) were investigated in air and in vacuo, at 20-800 ~ depending on Mn and the degree of branching in the starting material. The effects of the solidification (or carbonization) conditions (heating rate and final temperature) on the thermooxidative stability and structure of the resulting products were also__investigated. These investigations were carried out for oligoarylenes of various M, values and degrees of branching.

Reaction Capacity and Chemical Conversion of Carbo-Oligoarylenes

“…This latter is an extra indication in favour of a higher reaction capacity of high-polymeric OA fractions in polycondensation structurisation processes in the initial period of heat treatment in air, in comparison with the low-polymeric fractions (ref. 15 for the initial product on the thermo-oxidative stability is, it seems, common to all polymers with a conjugation system. In work (ref.…”

“…It is also shown that, when evaluating the thermo-oxidative stability of OAs using the TGA method, one must take into account the rate of temperature rise, since it influences the degree of completion of the structure of the products formed at the intermediate stages of heat treatment (ref. 15), and also the resistance to further thermo-oxidation. All these features must be considered in a comparative evaluation of the thermal stability of various oligomers with a conjugation system.…”