Poly(p-phenylene)

{{DISPLAYTITLE:Poly(p-phenylene)}}

Image:Poly(p-phenylene)-repeat-2D-skeletal.svg

File:Poly(para-phenylene)-based-on-xtal-3D-view-2-sf.png of a short section of PPP]]

Poly(p-phenylene) (PPP) is made of repeating p-phenylene units, which act as the precursor to a conducting polymer of the rigid-rod polymer family. The synthesis of PPP has proven challenging, but has been accomplished through excess polycondensation with the Suzuki coupling method.{{cite journal

|first1=Marcus

|last1=Remmers

|first2=Beate

|last2=Müller

|first3=Kai

|last3=Martin

|first4=Hans-Joachim

|last4=Räder

|title=Poly(p-phenylene)s. Synthesis, Optical Properties, and Quantitative Analysis with HPLC and MALDI−TOF Mass Spectrometry

|journal=Macromolecules

|volume=32

|issue=4

|pages=1073–1079

|doi=10.1021/ma981260s

|date=1999}}{{ cite journal | title = A New Solution to an Old Problem: Synthesis of Unsubstituted Poly(para-phenylene) | first1 = Ali | last1 = Abdulkarim | first2 = Felix | last2 = Hinkel | first3 = Daniel | last3 = Jänsch | first4 = Jan | last4 = Freudenberg | first5 = Florian E. | last5 = Golling | first6 = Klaus | last6 = Müllen | authorlink6 = Klaus Müllen | journal = J. Am. Chem. Soc. | year = 2016 | volume = 138 | issue = 50 | pages = 16208–16211 | doi = 10.1021/jacs.6b10254 }}

Early efforts typically produced black, insoluble powders that were difficult to characterize. For example, a 1962 paper reports "The solid glowed red-hot in a Bunsen flame, with no evidence of flame formation, and disappeared only slowly."{{cite journal|last1=Kovacic|first1=Peter|last2=Kyriakis|first2=Alexander|title=Polymerization of benzene to p-polyphenyl|journal=Tetrahedron Letters|date=1962|volume=3|issue=11|pages=467–469|doi=10.1016/S0040-4039(00)70494-1}} (J. Polym. Sci. (1960), 47, 45) Initially, the chemical and thermal stability of the material drove interest in its synthesis. It was used in rocket nozzles and some fabrics requiring high thermal stability.

Oxidation or the use of dopants is used to convert the non-conductive form to a semiconductor.