Self-Assembly of Ionizable "Clicked" P3HT-b-PMMA Copolymers: Ionic Bonding Group/Counterion Effects on Morphology.
Résumé
A novel methodol. to overcome the predominance of π-π interactions on the organization of rod-coil copolymer is reported. We demonstrated changes in the self-assembly morphol. of poly(3-hexylthiophene)-b-poly(Me methacrylate) (P3HT-b-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 cycloaddn. And then two 1,2,3-triazolium-based block copolymers with different counteranions were obtained by a quaternization of 1,2,3-triazole groups with Me iodide, and subsequent anion exchange 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 crystn. of the conjugated block is disrupted by the addnl. 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 crystn. was obsd. This methodol. could be a useful strategy to open the range of nanomorphologies reachable with a semiconducting polymer for electronic or photovoltaic applications.