Novel quaternary ammonium-functionalized diacetylenes: Their synthesis and photopolymerization

• We synthesized four novel trimethylammonium substitued diacetylenes.
• The photopolymerization of the diacetylenes was spectroscopically investigated.
• The polydiacetylenes properties were studied in the solid state and in solution.
• UV–vis, fluorescence, FT-IR and FT-Raman spectroscopies were employed.
• The role of the head and tail groups in the polymerization process was highlighted.

In this paper, we report the synthesis of novel diacetylenes bearing trimethylammonium end groups, their photochemical polymerization and the spectroscopic characterization of the polymers by different techniques (UV–vis, fluorescence, FT-IR, Raman). The obtained results shed light on the role of the trimethylammonium head group (and its counterions) in the polymerization process. It is also demonstrated that the presence of an internal, H-bondable amide function in the diacetylene tail favors the photopolymerization process as well as the formation of the polydiacetylene in its blue, highly-conjugated form. Moreover, the corresponding polymer in the less-conjugated red phase, typical of polydiacetylenes in solution, shows significantly enhanced emission properties with respect to its counterparts carrying all-saturated lateral chains.

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