A series of porphyrin-containing polymers with triazole rings as linkers have been successfully synthesized by click polymerization. The polycycloadditions of porphyrin-containing dialkyne 1 and 1,4-diazidobenzene 2 were initiated either by simple heating or by Cu(I)-catalyst, affording polymers P1-P8 with relatively high molecular weight. The polymerization process was monitored by gel permeation chromatography analysis. The polymer prepared by thermally initiated click polymerization has unimodal molecular weight distribution and moderate polydispersity index after prolonging reaction time to 170 h. Compared with the metal-free click polymerization, the rate of molecular weight growth in Cu(I)-catalyzed click polymerization declined, leading to relatively low molecular weight of the resulting polymer. The as-synthesized polymers are soluble in common organic solvents and stable at a temperature up to 350 °C. The photophysical properties of the porphyrin monomer and the polymer were investigated by UV–vis and fluorescence spectroscopy. This approach offers practical advantages over other synthetic methods used to prepare main-chain porphyrin-containing polymers with regard to the absence of byproducts generated during the polymerization reaction.
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INTRODUCTIONThe design and synthesis of arrays of oligomeric porphyrins or metalloporphyrins having well-defined shapes and dimensions is currently a topic of great interest to improve the photophysical properties, absorption cross-section and directed energy-transfer reactions [
The parent porphyrin is porphine, ..
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Significant advances in understanding the fundamental photophysical behavior of single-walled carbon nanotubes (SWNTs) have been made possible by the development of ionic, conjugated aryleneethynylene polymers that helically wrap SWNTs with well-defined morphology. My contribution to this work was the design and synthesis of porphyrin-containing polymers and the photophysical investigation of the corresponding polymer-wrapped SWNTs. For these new constructs, the polymer acts as more than just a solubilization scaffold; such assemblies can provide benchmark data for evaluating spectroscopic signatures of energy and charge transfer events and lay the groundwork for further, rational development of polymers with precisely tuned redox properties and electronic coupling with the underlying SWNT. The first design to incorporate a zinc porphyrin into the polymer backbone, PNES-PZn, suffered from severe aggregation in solution and was redesigned to produce the porphyrin-containing polymer S-PBN-PZn. This polymer was utilized to helically wrap chirality-enriched (6,5) SWNTs, which resulted in significant quenching of the porphyrin-based fluorescence. Time-resolved spectroscopy revealed a simultaneous rise and decay of the porphyrin radical cation and SWNT electron polaron spectroscopic signatures indicative of photoinduced electron transfer. A new polymer, S-PBN(b)-Ph2PZn3, was then synthesized which incorporated a meso-ethyne linked zinc porphyrin trimer. By changing the absorption profile and electrochemical redox potentials of the polymer, the photophysical behavior of the corresponding polymer-wrapped (6,5)-SWNTs was dramatically changed, and the polymer-wrapped SWNTs no longer showed evidence for photoinduced electron transfer.