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Subject: Amphiphilic block copolymers ×

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    Amphiphilic block copolymers featuring a reversible hetero Diels-Alder linkage
    (London [u.a.] : Royal Society of Chemistry, 2014) Langer, M.; Brandt, J.; Lederer, A.; Goldmann, A.S.; Schacher, F.H.; Barner-Kowollik, C.
    The present article reports the preparation of a novel class of switchable amphiphilic diblock copolymers with a temperature switchable linkage. Reversible addition fragmentation chain transfer (RAFT) polymerization was used to synthesize the individual blocks: for the preparation of the non-polar block, i.e. poly(isoprene-co-styrene) (P(I-co-S)) (9200 g mol-1 ≤ M n ≤ 50000 g mol-1, 1.22 ≤ ≤ 1.36), a chain transfer agent (CTA, 3-((2-bromo-2-methylpropanoyl)oxy)propyl 2-(((dodecylthio)carbonothioyl)thio)-2-methylpropanoate) carrying a bromine group was employed, ready for subsequent cyclopentadienyl (Cp) transformation. For the preparation of the polar block, triethylene glycol methyl ether acrylate (TEGA) was polymerized (6600 g mol-1 ≤ Mn ≤ 35000 g mol-1, 1.12 ≤ ≤ 1.30) using a RAFT agent carrying a phosphoryl Z-group, which is able to undergo hetero Diels-Alder (HDA) ligation with Cp moieties. Both building blocks were conjugated at ambient temperature in the presence of ZnCl2 as catalyst yielding the amphiphilic block copolymer P(I-co-S)-b-PTEGA (16000 g mol-1 ≤ Mn ≤ 68000 g mol-1, 1.15 ≤ ≤ 1.32). To investigate the bonding/debonding capability of the HDA linkage, high temperature nuclear magnetic resonance (HT-NMR) spectroscopy, high temperature dynamic light scattering (HT-DLS) and high temperature size exclusion chromatography (HT-SEC) were carried out, evidencing that efficiently switchable amphiphilic block copolymers were generated (>4 cycles).
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    Deepening the insight into poly(butylene oxide)-block-poly(glycidol) synthesis and self-assemblies: micelles, worms and vesicles
    (Cambridge : RSC, 2020) Wehr, Riccardo; Gaitzsch, Jens; Daubian, Davy; Fodor, Csaba; Meier, Wolfgang
    Aqueous self-assembly of amphiphilic block copolymers is studied extensively for biomedical applications like drug delivery and nanoreactors. The commonly used hydrophilic block poly(ethylene oxide) (PEO), however, suffers from several drawbacks. As a potent alternative, poly(glycidol) (PG) has gained increasing interest, benefiting from its easy synthesis, high biocompatibility and flexibility as well as enhanced functionality compared to PEO. In this study, we present a quick and well-controlled synthesis of poly(butylene oxide)-block-poly(glycidol) (PBO-b-PG) amphiphilic diblock copolymers together with a straight-forward self-assembly protocol. Depending on the hydrophilic mass fraction of the copolymer, nanoscopic micelles, worms and polymersomes were formed as well as microscopic giant unilamellar vesicles. The particles were analysed regarding their size and shape, using dynamic and static light scattering, TEM and Cryo-TEM imaging as well as confocal laser scanning microscopy. We have discovered a strong dependence of the formed morphology on the self-assembly method and show that only solvent exchange leads to the formation of homogenous phases. Thus, a variety of different structures can be obtained from a highly flexible copolymer, justifying a potential use in biomedical applications. This journal is © The Royal Society of Chemistry.
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    Polyacrylonitrile-containing amphiphilic block copolymers: self-assembly and porous membrane formation
    (Cambridge : RSC Publ., 2023) Gemmer, Lea; Niebuur, Bart-Jan; Dietz, Christian; Rauber, Daniel; Plank, Martina; Frieß, Florian V.; Presser, Volker; Stark, Robert W.; Kraus, Tobias; Gallei, Markus
    The development of hierarchically porous block copolymer (BCP) membranes via the application of the self-assembly and non-solvent induced phase separation (SNIPS) process is one important achievement in BCP science in the last decades. In this work, we present the synthesis of polyacrylonitrile-containing amphiphilic BCPs and their unique microphase separation capability, as well as their applicability for the SNIPS process leading to isoporous integral asymmetric membranes. Poly(styrene-co-acrylonitrile)-b-poly(2-hydroxyethyl methacrylate)s (PSAN-b-PHEMA) are synthesized via a two-step atom transfer radical polymerization (ATRP) procedure rendering PSAN copolymers and BCPs with overall molar masses of up to 82 kDa while maintaining low dispersity index values in the range of Đ = 1.13-1.25. The polymers are characterized using size-exclusion chromatography (SEC) and NMR spectroscopy. Self-assembly capabilities in the bulk state are examined using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) measurements. The fabrication of isoporous integral asymmetric membranes is investigated, and membranes are examined by scanning electron microscopy (SEM). The introduction of acrylonitrile moieties within the membrane matrix could improve the membranes’ mechanical properties, which was confirmed by nanomechanical analysis using atomic force microscopy (AFM).