A series of differentially alkyl- and alkoxy-substituted poly(para-pheneyleneethynylene)s of different molecular weight were prepared and their rheological properties investigated. It was found that the side chain structure of the PPEs of roughly equal molecular weight and degree of polymerization has a significant influence on the rheology and printing behavior of the PPEs. Introduction of branched alkoxy or alkyl substituents improve the printing behavior of the PPEs dramatically.