Poly(<i>p</i>-phenylene)s. Synthesis, Optical Properties, and Quantitative Analysis with HPLC and MALDI−TOF Mass Spectrometry

Abstract

A series of soluble low molecular weight poly(p-phenylene)s (PPP) has been synthesized by an excess polycondensation with the Suzuki coupling method. The reaction mixture therefore only contains oligomers of an odd number of phenylene units which are terminated by bromine atoms. The mixture has been preparatively separated into monodisperse fractions of the respective oligomers of up to 17 phenylene units. The absorption and emission spectra as well as the extinction coefficient of each fraction have been measured. On the basis of these data, the effective conjugation length can be estimated to be around 11 phenylene units. The fraction xi of each oligomer in the reaction mixture has been calculated and quantified by analytical HPLC and MALDI−TOF mass spectrometry. The theoretically expected exponential decay of the fraction sizes with increasing length is found in the HPLC analysis; however, significant deviations are found if analyzed by MALDI−TOF mass spectrometry. Possible reasons for this deviation will be discussed.