Self-Assembly of Ionizable “Clicked” P3HT‑<i>b</i>‑PMMA Copolymers: Ionic Bonding Group/Counterion Effects on Morphology

A novel methodology used to overcome the predominance of π–π interactions on the organization of rod–coil copolymer is reported in this paper. We demonstrated changes in the self-assembly morphology of poly­(3-hexylthiophene)-<i>b</i>-poly­(methyl methacrylate) (P3HT-<i>b</i>-PMMA) block copolymer BCP, by introducing an ionic group to the linking unit between the two blocks. A neutral polymer precursor was synthesized from ethynyl-terminated P3HT and azido-terminated PMMA via Huisgen’s 1,3-dipolar cycloaddition. Then two 1,2,3-triazolium-based block copolymers with different counteranions were obtained by a quaternization of 1,2,3-triazole groups with methyl iodide, and subsequent anion exchange was observed with a fluorinated salt, bis­(trifluoromethane) sulfonimide salt. Atomic force microscopy, modulated differential scanning calorimetry, and X-ray scattering were used to prove that the crystallization of the conjugated block is disrupted by the additional ionic interactions imposed to the system. The 1,2,3-triazolium-based BCP with iodide as the counterion exhibited highly organized well-defined fibrils, as the diblock phase segregation χ becomes predominant over the rod–rod interaction μ. When the more stable and larger NTf₂^– was used as counterion, P3HT phase was disrupted and no crystallization was observed. This methodology could be a useful strategy to open the range of nanomorphologies reachable with a semiconducting polymer for electronic or photovoltaic applications

Photophysics and Light-Activated Biocidal Activity of Visible-Light-Absorbing Conjugated Oligomers

The photophysical properties of three cationic π-conjugated oligomers were correlated with their visible light activated biocidal activity vs <i>S. aureus</i>. The oligomers contain three arylene units (terthiophene, <b>4a</b>; thiophene-benzotriazole-thiophene, <b>4b</b>; thiophene-benzothiadiazole-thiophene, <b>4c</b>) capped on each end by cationic −(CH₂)₃NMe₃⁺ groups. The oligomers absorb in the visible region due to their donor–acceptor–donor electronic structure. Oligomers <b>4a</b> and <b>4b</b> have high intersystem crossing and singlet oxygen sensitization efficiency, but <b>4c</b> has a very low intersystem crossing efficiency and it does not sensitize singlet oxygen. The biocidal activity of the oligomers under visible light varies in the order <b>4a</b> > <b>4b</b> ≈ <b>4c</b>