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- ItemThermo-Responsive Ultrafiltration Block Copolymer Membranes Based on Polystyrene-block-poly(diethyl acrylamide)(Weinheim : Wiley-VCH GmbH, 2023) Frieß, Florian V.; Hartmann, Frank; Gemmer, Lea; Pieschel, Jens; Niebuur, Bart‐Jan; Faust, Matthias; Kraus, Tobias; Presser, Volker; Gallei, MarkusWithin the present work, a thermo-responsive ultrafiltration membrane is manufactured based on a polystyrene-block-poly(diethyl acrylamide) block copolymer (BCP). The poly(diethyl acrylamide) block segment features a lower critical solution temperature (LCST) in water, similar to the well-known poly(N-isopropylacrylamide), but having increased biocompatibility and without exhibiting a hysteresis of the thermally induced switching behavior. The BCP is synthesized via sequential “living” anionic polymerization protocols and analyzed by 1H-NMR spectroscopy, size exclusion chromatography, and differential scanning calorimetry. The resulting morphology in the bulk state is investigated by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) revealing the intended hexagonal cylindrical morphology. The BCPs form micelles in a binary mixture of tetrahydrofuran and dimethylformamide, where BCP composition and solvent affinities are discussed in light of the expected structure of these micelles and the resulting BCP membrane formation. The membranes are manufactured using the non-solvent induced phase separation (NIPS) process and are characterized via scanning electron microscopy (SEM) and water permeation measurements. The latter are carried out at room temperature and at 50 °C revealing up to a 23-fold increase of the permeance, when crossing the LCST of the poly(diethyl acrylamide) block segment in water.
- ItemNanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV-Mediated Cross-Linking Strategies(Weinheim : Wiley-VCH, 2021) Frieß, Florian V.; Hu, Qiwei; Mayer, Jannik; Gemmer, Lea; Presser, Volker; Balzer, Bizan N.; Gallei, MarkusIn this work, a block copolymer (BCP) consisting of poly((butyl methacrylate-co-benzophenone methacrylate-co-methyl methacrylate)-block-(2-hydroxyethyl methacrylate)) (P(BMA-co-BPMA-co-MMA)-b-P(HEMA)) is prepared by a two-step atom-transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self-assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4-dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30 nm is confirmed via scanning electron microscopy (SEM). UV-mediated cross-linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross-linked and cross-linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross-linking on the porous structures. Finally, the influence of the herein described cross-linking protocols on water-flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV-mediated cross-linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies.
- ItemUltrasoft and High-Mobility Block Copolymers for Skin-Compatible Electronics(Weinheim : Wiley-VCH, 2020) Ditte, Kristina; Perez, Jonathan; Chae, Soosang; Hambsch, Mike; Al-Hussein, Mahmoud; Komber, Hartmut; Formanek, Peter; Mannsfeld, Stefan C.B.; Fery, Andreas; Kiriy, Anton; Lissel, FranziskaPolymer semiconductors (PSCs) are an essential component of organic field-effect transistors (OFETs), but their potential for stretchable electronics is limited by their brittleness and failure susceptibility upon strain. Herein, a covalent connection of two state-of-the-art polymers—semiconducting poly-diketo-pyrrolopyrrole-thienothiophene (PDPP-TT) and elastomeric poly(dimethylsiloxane) (PDMS)—in a single triblock copolymer (TBC) chain is reported, which enables high charge carrier mobility and low modulus in one system. Three TBCs containing up to 65 wt% PDMS were obtained, and the TBC with 65 wt% PDMS content exhibits mobilities up to 0.1 cm2 V−1 s−1, in the range of the fully conjugated reference polymer PDPP-TT (0.7 cm2 V−1 s−1). The TBC is ultrasoft with a low elastic modulus (5 MPa) in the range of mammalian tissue. The TBC exhibits an excellent stretchability and extraordinary durability, fully maintaining the initial electric conductivity in a doped state after 1500 cycles to 50% strain. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH
- ItemCharge Carrier Mobility Improvement in Diketopyrrolopyrrole Block-Copolymers by Shear Coating(Basel : MDPI, 2021) Ditte, Kristina; Kiriy, Nataliya; Perez, Jonathan; Hambsch, Mike; Mannsfeld, Stefan C.B.; Krupskaya, Yulia; Maragani, Ramesh; Voit, Brigitte; Lissel, FranziskaShear coating is a promising deposition method for upscaling device fabrication and enabling high throughput, and is furthermore suitable for translating to roll-to-roll processing. Although common polymer semiconductors (PSCs) are solution processible, they are still prone to mechanical failure upon stretching, limiting applications in e.g., electronic skin and health monitoring. Progress made towards mechanically compliant PSCs, e.g., the incorporation of soft segments into the polymer backbone, could not only allow such applications, but also benefit advanced fabrication methods, like roll-to-roll printing on flexible substrates, to produce the targeted devices. Tri-block copolymers (TBCs), consisting of an inner rigid semiconducting poly-diketo-pyrrolopyrrole-thienothiophene (PDPP-TT) block flanked by two soft elastomeric poly(dimethylsiloxane) (PDMS) chains, maintain good charge transport properties, while being mechanically soft and flexible. Potentially aiming at the fabrication of TBC-based wearable electronics by means of cost-efficient and scalable deposition methods (e.g., blade-coating), a tolerance of the electrical performance of the TBCs to the shear speed was investigated. Herein, we demonstrate that such TBCs can be deposited at high shear speeds (film formation up to a speed of 10 mm s−1). While such high speeds result in increased film thickness, no degradation of the electrical performance was observed, as was frequently reported for polymer−based OFETs. Instead, high shear speeds even led to a small improvement in the electrical performance: mobility increased from 0.06 cm2 V−1 s−1 at 0.5 mm s−1 to 0.16 cm2 V−1 s−1 at 7 mm s−1 for the TBC with 24 wt% PDMS, and for the TBC containing 37 wt% PDMS from 0.05 cm2 V−1 s−1 at 0.5 mm s−1 to 0.13 cm2 V−1 s−1 at 7 mm s−1. Interestingly, the improvement of mobility is not accompanied by any significant changes in morphology.