Click chemistry as a powerful tool for the construction of functional poly(p-phenyleneethynylene)s:: Comparison of pre- and postfunctionalization schemes

1,3-Dipolar cycloadditions have been used to prepare a series of functionalized poly(p-phenyleneethynylene)s (PPEs). This was accomplished by employing a PPE with pendent triisopropyl-silylacetylene groups. The triisopropylsilyl groups can be removed in situ, exposing free alkynes in the side chains of the polymer to react with azides in a postpolymerization functionalization strategy in a 1,3-dipolar cycloaddition. The properties of these polymers were explored and compared to polymers of the same molecular structure but synthesized by a prepolymerization functionalization approach. Polymers of the same structure exhibit identical H-1 NMR, C-13 NMR, and IR spectra regardless of whether they were obtained by a conventional route or by postfunctionalization of a suitable PPE. UV-vis and fluorescence spectra are similar in solution. Postmodification through click chemistry, when compared to premodification, is an excellent method to produce functionalized, defect-free PPEs. Reaction of the azides with the main chain alkyne units is not observed.