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- ItemPros and Cons : Supramolecular or Macromolecular : What Is Best for Functional Hydrogels with Advanced Properties?(Weinheim : Wiley-VCH, 2020) Eelkema, Rienk; Pich, AndrijHydrogels are fascinating soft materials with unique properties. Many biological systems are based on hydrogel-like structures, underlining their versatility and relevance. The properties of hydrogels strongly depend on the structure of the building blocks they are composed of, as well as the nature of interactions between them in the network structure. Herein, gel networks made by supramolecular interactions are compared to covalent macromolecular networks, drawing conclusions about their performance and application as responsive materials. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemTuning the Volume Phase Transition Temperature of Microgels by Light(Weinheim : Wiley-VCH, 2021) Jelken, Joachim; Jung, Se-Hyeong; Lomadze, Nino; Gordievskaya, Yulia D.; Kramarenko, Elena Yu.; Pich, Andrij; Santer, SvetlanaTemperature-responsive microgels find widespread applications as soft materials for designing actuators in microfluidic systems, as carriers for drug delivery or catalysts, as functional coatings, and as adaptable sensors. The key property is their volume phase transition temperature, which allows for thermally induced reversible swelling/deswelling. It is determined by the gel's chemical structure as well as network topology and cannot be varied easily within one system. Here a paradigm change of this notion by facilitating a light-triggered reversible switching of the microgel volume in the range between 32 and 82 °C is suggested. Photo-sensitivity is introduced by photosensitive azobenzene containing surfactant, which forms a complex with microgels consisting of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AAc) chains when assuming a hydrophobic trans-state, and prefers to leave the gel matrix in its cis-state. Using a similar strategy, it is demonstrated that at a fixed temperature, for example, 37 °C, one can reversibly change the microgel radius by a factor of 3 (7–21 µm) by irradiating either with UV (collapsed state) or green light (swollen state). It is envisaged that the possibility to deploy a swift external means of adapting the swelling behavior of microgels may impact and redefine the latter's application across all fields. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH
- ItemTowards New Robust Zn(II) Complexes for the Ring-Opening Polymerization of Lactide Under Industrially Relevant Conditions(Weinheim : Wiley-VCH, 2019) Schäfer, Pascal M.; Dankhoff, Katja; Rothemund, Matthias; Ksiazkiewicz, Agnieszka N.; Pich, Andrij; Schobert, Rainer; Weber, Birgit; Herres-Pawlis, SonjaThe synthesis of bio-based and biodegradable plastics is a hot topic in research due to growing environmental problems caused by omnipresent plastics. As a result, polylactide, which has been known for years, has seen a tremendous increase in industrial production. Nevertheless, the manufacturing process using the toxic catalyst Sn(Oct)2 is very critical. As an alternative, five zinc acetate complexes have been synthesized with Schiff base-like ligands that exhibit high activity in the ring-opening polymerization of non-purified lactide. The systems bear different side arms in the ligand scaffold. The influence of these substituents has been analyzed. For a detailed description of the catalytic activities, the rate constants kapp and kp were determined using in-situ Raman spectroscopy at a temperature of 150 °C. The polymers produced have molar masses of up to 71 000 g mol−1 and are therefore suitable for a variety of applications. Toxicity measurements carried out for these complexes proved the nontoxicity of the systems. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemUndiscovered Potential: Ge Catalysts for Lactide Polymerization(Weinheim : Wiley-VCH, 2020) Rittinghaus, Ruth D.; Tremmel, Jakub; Růžička, Ales; Conrads, Christian; Albrecht, Pascal; Hoffmann, Alexander; Ksiazkiewicz, Agnieszka N.; Pich, Andrij; Jambor, Roman; Herres-Pawlis, SonjaPolylactide (PLA) is a high potential bioplastic that can replace oil-based plastics in a number of applications. To date, in spite of its known toxicity, a tin catalyst is used on industrial scale which should be replaced by a benign catalyst in the long run. Germanium is known to be unharmful while having similar properties as tin. Only few germylene catalysts are known so far and none has shown the potential for industrial application. We herein present Ge complexes in combination with zinc and copper, which show amazingly high polymerization activities for lactide in bulk at 150 °C. By systematical variation of the complex structure, proven by single-crystal XRD and DFT calculations, structure–property relationships are found regarding the polymerization activity. Even in the presence of zinc and copper, germanium acts as the active site for polymerizing probably through the coordination–insertion mechanism to high molar mass polymers. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemMechanoresponsive diselenide-crosslinked microgels with programmed ultrasound-triggered degradation and radical scavenging ability for protein protection(Cambridge : RSC Publishing, 2022) Kharandiuk, Tetiana; Tan, Kok Hui; Xu, Wenjing; Weitenhagen, Fabian; Braun, Susanne; Göstl, Robert; Pich, AndrijIn the context of controlled delivery and release, proteins constitute a delicate class of cargo requiring advanced delivery platforms and protection. We here show that mechanoresponsive diselenide-crosslinked microgels undergo controlled ultrasound-triggered degradation in aqueous solution for the release of proteins. Simultaneously, the proteins are protected from chemical and conformational damage by the microgels, which disintegrate to water-soluble polymer chains upon sonication. The degradation process is controlled by the amount of diselenide crosslinks, the temperature, and the sonication amplitude. We demonstrate that the ultrasound-mediated cleavage of diselenide bonds in these microgels facilitates the release and activates latent functionality preventing the oxidation and denaturation of the encapsulated proteins (cytochrome C and myoglobin) opening new application possibilities in the targeted delivery of biomacromolecules.
- ItemZwitterionic Nanogels and Microgels: An Overview on Their Synthesis and Applications(Weinheim : Wiley-VCH, 2021) Saha, Pabitra; Ganguly, Ritabrata; Li, Xin; Das, Rohan; Singha, Nikhil K.; Pich, AndrijZwitterionic polymers by virtue of their unique chemical and physical attributes have attracted researchers in recent years. The simultaneous presence of positive and negative charges in the same repeat unit renders them of various interesting properties such as superhydrophilicity, which has significantly broadened their scope for being used in different applications. Among polyzwitterions of different architectures, micro- and/or nano-gels have started receiving attention only until recently. These 3D cross-linked colloidal structures show peculiar characteristics in context to their solution properties, which are attributable either to the comonomers present or the presence of different electrolytes and biological specimens. In this review, a concise yet detailed account is provided of the different synthetic techniques and application domains of zwitterion-based micro- and/or nanogels that have been explored in recent years. Here, the focus is kept solely on the “polybetaines,” which have garnered maximum research interest and remain the extensively studied polyzwitterions in literature. While their vast application potential in the biomedical sector is being detailed here, some other areas of scope such as using them as microreactors for the synthesis of metal nanoparticles or making smart membranes for water-treatment are discussed in this minireview as well.
- ItemDual Stimuli-Responsive Self-Assembly Behavior of a Tailor-Made ABC-Type Amphiphilic Tri-Block Copolymer(Hoboken, NJ [u.a.] : Wiley, 2020) Pal, Sanjay; Kather, Michael; Banerjee, Sovan Lal; Saha, Pabitra; Pich, Andrij; Singha, Nikhil K.This investigation describes the synthesis of a dual stimuli-responsive, amphiphilic ABC tri-block copolymer (BCP) based on the functional monomers via RAFT polymerization. In this case, ABC-type BCP was prepared based on N-isopropylacrylamide, n-butyl acrylate, and 4-vinylpyridine in DMF solvent using cyanomethyl dodecyl trithiocarbonate as the RAFT agent and azobisisobutyronitrile as a thermal initiator in a subsequent macro-RAFT approach, respectively. The BCPs were characterized by SEC, 1H-NMR, FTIR spectroscopy, and DSC analyses. Temperature and pH-dependent properties of the smart BCP micelles in aqueous medium were investigated using dynamic light scattering. Transmission electron microscopic images were taken at cryogenic and dry conditions to study the morphology of molecular assemblies of block copolymers in an aqueous medium. The phase and topographical images were captured by atomic force microscopy to understand the assembly of block copolymers in solvents of different polarities. The morphology of BCP micelles was transformed from flower-like to spherical in the presence of solvents with different polarities (H2O or CHCl3). © 2020 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc.
- ItemOne‐Pot Two‐Step Chemoenzymatic Cascade for the Synthesis of a Bis‐benzofuran Derivative(Weinheim : Wiley-VCH Verl., 2019) Mertens, M.A. Stephanie; Thomas, Fabian; Nöth, Maximilian; Moegling, Julian; El‐Awaad, Islam; Sauer, Daniel F.; Dhoke, Gaurao V.; Xu, Wenjing; Pich, Andrij; Herres‐Pawlis, Sonja; Schwaneberg, UlrichChemoenzymatic cascades enable reactions with the high productivity of chemocatalysts and high selectivity of enzymes. Nevertheless, the combination of these different fields of catalysis is prone to mutual deactivation of metal- and biocatalysts. In this study, a one-pot sequential two-step catalytic cascade reaction was successfully implemented for the synthesis of a methylene-bridged bis(2-substituted benzofuran). In the first step, a palladium-free Sonogashira reaction is used for the synthesis of a benzofuran derivative. In the subsequent step, the formed 2-substituted benzofuran is hydroxylated by the monooxygenase P450 BM3 variant (A74S-F87V-L188Q) and undergoes further elimination reactions. The study proofs that combination of Cu scorpionate catalyzed Sonogashira cross-coupling and P450 mediated oxidation is possible and results in up to 84 % yield of the final product. The oxidation reaction is boosted by capturing inhibiting reaction components.
- ItemSynthesis of Polyampholyte Janus-like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization(Weinheim : Wiley-VCH, 2020) Xu, Wenjing; Rudov, Andrey; Oppermann, Alex; Wypysek, Sarah; Kather, Michael; Schroeder, Ricarda; Richtering, Walter; Potemkin, Igor I.; Wöll, Dominik; Pich, AndrijControlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli-responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus-like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self-assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus-like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemHeterolepic β‐Ketoiminate Zinc Phenoxide Complexes as Efficient Catalysts for the Ring Opening Polymerization of Lactide(Weinheim : Wiley-VCH, 2019) Ghosh, Swarup; Schäfer, Pascal M.; Dittrich, Dennis; Scheiper, Christoph; Steiniger, Phillip; Fink, Gerhard; Ksiazkiewicz, Agnieszka N.; Tjaberings, Alexander; Wölper, Christoph; Gröschel, André H.; Pich, Andrij; Herres‐Pawlis, Sonja; Schulz, StephanZinc phenoxide complexes L1ZnOAr 1–4 (L1=Me2NC2H4NC(Me)CHC(Me)O) and L2ZnOAr 5–8 (L2=Me2NC3H6NC(Me)CHC(Me)O) with donor-functionalized β-ketoiminate ligands (L1/2) and OAr substituents (Ar=Ph 1, 5; 2,6-Me2-C6H3 2, 6; 3,5-Me2-C6H3 3, 7; 4-Bu-C6H4 4, 8) with tuneable electronic and steric properties were synthesized and characterized. 1–8 adopt binuclear structures in the solid state except for 5, while they are monomeric in CDCl3 solution. 1–8 are active catalysts for the ring opening polymerization (ROP) of lactide (LA) in CH2Cl2 at ambient temperature and the catalytic activity is controlled by the electronic and steric properties of the OAr substituent, yielding polymers with high average molecular weight (Mn) and moderately controlled molecular weight distribution (MWDs). 1 and 5 showed a living polymerization character and kinetic studies on the ROP of L–LA with 1 and 5 proved first order dependencies on the monomer concentration. Homonuclear decoupled 1H-NMR analyses of polylactic acid (PLA) formed with rac-LA proved isotactic enrichment of the PLA microstructure. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.