Fig 1: Structures of the studied model compounds DMDPE (left) and DIMEOH (right).
In this contribution we will report experimental studies of the compounds 2,6-dimethyl-diphenylether (DMDPE) and 4-(2',6'-dimethyl-phenoxy)-2,6-dimethyl-phenol (DIMEOH). There structures are given in the figure above. Both compounds were selected because of the structural parallels to the polymer and there good solubility in different solvents.
The aromatic ethers were synthesized with the commonly used Ullmann condensation and purified by either sublimation or repeated recrystallization. The solvent methylcyclohexane was spectroscopic grade (Aldrich).
For each compound absorption spectra in methylcyclohexane were recorded after irradiation of the samples using a Hg-Xe lamp (Oriel 200 W). The spectra were measured using a commercial absorption spectrometer (Perkin-Elmer Lambda 2) which was equipped with a liquid flow cryostat (Leybold VSK 4-300). With this setup we were able to control the temperature of the samples during irradiation and recording of the spectra.
For each sample, measurements at four different temperatures (293, 223, 173 and 147 K) were carried out. Absorption spectra were recorded after irradiating the samples for a defined time interval from 1 to 30 minutes.