Click Chemistry as a Powerful Tool for the Construction of Functional Poly(<i>p</i><i>-</i>phenyleneethynylene)s:  Comparison of Pre- and Postfunctionalization Schemes

Abstract

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 triisopropylsilylacetylene 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 1 H NMR, 13 C 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.