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

Characterization Study of CO₂, CH₄, and CO₂/CH₄ Hydroquinone Clathrates Formed by Gas–Solid Reaction

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO₂ and CH₄. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO₂, pure CH₄, and an equimolar CO₂/CH₄ mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and ¹³C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications