formation of a model crosslinked polymer a n d lower adhesion of t h e polymer binder t o glass cloth due t o t h e low content of polar groups i n t h e model polyarylene.
3. Experiinental
4-Acetylbiphenyl of "pure" grade was purified by repeated recrystallization from alcohol and subsequent sublimation, m.p.: 121.3...121.5°C. In order to study the kinetics of ABPh condensation, ketone portions were introduced into ampoules repeatedly washed with argon, evacuated t o a residual pressure of m 15 Pa and sealed. The ampoules were maintained a t a constant temperature of 250, 325 and 3 5 0 T for a certain time, sealed off and opened and the water eliminated was transferred into tubes packed with anhydrone.
Low-conversion polycondensation of DAA was carried out in ampoules flushed with argon. DAA was melted, degassed, evacuated and maintained a t 300 (330)"C for a certain time. Conversion was followed by changes in viscosity and the measurement of water evolved4). The study of the kinetics of polycondensation and some experiments on the low-conversion polycondensation of DAA were carried o a t in a vessel in which dry nitrogen was bubbled through tlre DAA melt and water was removed into traps packed with anhydrone and periodically weighed.
p-Toluenesulphonic acid was used in the form of a mono- hydrate of the ''pure'' grade.
I R spectra of monomers, oligomers and polymers were taken in KBr disks with a Specord-75 IR spectrophotometer.
The lH-NMR spectra of samples as 10...15y0 solutions in CCI, were taken with a JEOI, C-60 HI, spectrometer.
*)
In order to avoid gelation the process was discontinued when 3 0 to 35% of water was eliminated.