Polymer composed of macromolecules containing exclusively alternating phenylene or substituted phenylene and ethynediyl (formerly ethynylene) constitutional repeating units in the backbone: where \(\ce{R^{1}}\), \(\ce{R^{2}}\), \(\ce{R^{3}}\) and \(\ce{R^{4}}\) are each hydrogen, alkyl, aryl, halogen, trialkylsilyl etc. (structure-based polymer class name).