Poly(p-phenylene alkylene)s - A forgotten class of polymers

Within the wealth of hydrocarbon polymers, poly(p-phenylene alkylene)s ("al karotics") hold a special position since they have been a long forgotten cl ass of hydrophobic polymers. This is somewhat surprising, since the corners tones of this polymer family cover extremely broad materials properties and the few known representatives attract attention with very favorable charac teristics. In the course of this article, four new representatives this fam ily are presented. Whereas poly(p-phenylene octylene) (PPPO; 90 degrees C), poly(p-phenylene hexylene) (PPPH 120 degrees C) and poly(p-phenylene propy lene) (PPPPr; 110-130 degrees C) have surprisingly low melting temperatures , the highly crystalline poly(p-phenylene butylene) (PPPB), melting between 200 and 225 degrees C, meets many of the requirements that are essential f or a novel, hydrophobic, processable, engineering polymer. In connection wi th the efforts to tailor the melting temperature; polymers, a simple, semi- empirical methodology estimate melting temperatures of unknown representati ves of homologous series of polymers was developed verified. By means of th is approach, the melting temperatures of PPPH and PPPB could be predicted w ith accuracy. In addition, it was shown that the method is not restricted t o the present alkarotic polymers, but it seems to have a rather broad range of applications its shown by the successful description of the polymer ser ies, including various liquid-crystalline hydrocarbon polymers and differen t polyamides.