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

• Published in: Macromolecules Vol. 50; no. 1; pp. 235 - 243
• Main Authors: Ji, Eunkyung, Pellerin, Virginie, Rubatat, Laurent, Grelet, Eric, Bousquet, Antoine, Billon, Laurent
• Format: Journal Article
• Language: English
• Published: American Chemical Society 10.01.2017
• Subjects: Chemical Sciences; Polymers; P3HT; morphology; block PMMA copolymer; Huisgen cycloaddition; ionic bonding
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b02101

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)-b-poly­(methyl 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 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.