Formaldehyde-free curing of cotton cellulose fabrics in anhydrous media

The effect of formaldehyde-free curing on standard cotton cellulose fabrics in anhydrous media is studied. Different crosslinkers are applied via (1) a pad-cure-dry process (solid/liquid) and (2) in a vapor chamber (solid/gas). The performance of each crosslinker and set of conditions is assessed by measuring dry crease recovery angles, DCRAs. We find that in control samples (treatment without crosslinker) the DCRAs are altered depending on the solvent. Using DMF, carbonyldiimidazole shows the best DCRA (160.1°, 15° higher than the non-treated fabrics). In ethyl acetate, triglycidyl isocyanurate shows the highest DCRA (22° higher than the control). The most promising crosslinkers are applied with selected catalysts known from literature. Here, trigycidyl isocyanurate in combination with the superbase P4-t-Bu gives the best DCRA (35° higher than the control). Using the vapor-chemical finishing, divinylsulfone as crosslinker increases the DCRA to 162.7° (18° higher than non-treated fabrics). Hence, cotton cellulose fabrics can be successfully finished in anhydrous conditions. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48371. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc

Mechanical Characterization of Human Brain Tissue and SoftDynamic Gels Exhibiting Electromechanical Neuro-Mimicry

Synthetic hydrogels are an important class of materialsin tissue engineering, drug delivery, and other biomedicalfields. Their mechanical and electrical properties can betuned to match those of biological tissues. In this work,we report on hydrogels that exhibit both mechanical andelectrical biomimicry. The presented dual networks consistof supramolecular networks formed from 2:1 homoternarycomplexes of imidazolium-based guest molecules in cucu-bit[8]uril and covalent networks of oligoethylene glycol-(di)methacrylate. We also investigate the viscoelastic prop-erties of human brain tissues. The mechanical properties ofthe dual network gels are benchmarked against the humantissue, and we find that they both are neuro-mimetic and ex-hibit cytocompatiblity in a neural stem cell model.The Winston Churchill Foundation of the United States. The Newton International Fellowship

Homoserine Lactone as a Structural Key Element for the Synthesis of Multifunctional Polymers

The use of bio-based building blocks for polymer synthesis represents a milestone on the way to “green” materials. In this work, two synthetic strategies for the preparation of multifunctional polymers are presented in which the key element is the functionality of homoserine lactone. First, the synthesis of a bis cyclic coupler based on a thiolactone and homoserine lactone is displayed. This coupler was evaluated regarding its regioselectivity upon reaction with amines and used in the preparation of multifunctional polymeric building blocks by reaction with diamines. Furthermore, a linear polyglycidol was functionalized with homoserine lactone. The resulting polyethers with lactone groups in the side chain were converted to cationic polymers by reaction with 3-(dimethylamino)-1-propylamine followed by quaternization with methyl iodide

Plant diversity enhances production and downward transport of biodegradable dissolved organic matter

1. Plant diversity is an important driver of belowground ecosystem functions, such as root growth, soil organic matter (SOM) storage, and microbial metabolism, mainly by influencing the interactions between plant roots and soil. Dissolved organic matter (DOM), as the most mobile form of SOM, plays a crucial role for a multitude of soil processes that are central for ecosystem functioning. Thus, DOM is likely to be an important mediator of plant diversity effects on soil processes. However, the relationships between plant diversity and DOM have not been studied so far. 2. We investigated the mechanisms underlying plant diversity effects on concentrations of DOM using continuous soil water sampling across 6 years and 62 plant communities in a long‐term grassland biodiversity experiment in Jena, Germany. Furthermore, we investigated plant diversity effects on the molecular properties of DOM in a subset of the samples. 3. Although DOM concentrations were highly variable over the course of the year with highest concentrations in summer and autumn, we found that DOM concentrations consistently increased with plant diversity across seasons. The positive plant diversity effect on DOM concentrations was mainly mediated by increased microbial activity and newly sequestered carbon in topsoil. However, the effect of soil microbial activity on DOM concentrations differed between seasons, indicating DOM consumption in winter and spring, and DOM production in summer and autumn. Furthermore, we found increased contents of small and easily decomposable DOM molecules reaching deeper soil layers with high plant diversity. 4. Synthesis. Our findings suggest that plant diversity enhances the continuous downward transport of DOM in multiple ways. On the one hand, higher plant diversity results in higher DOM concentrations, on the other hand, this DOM is less degraded. The present study indicates, for the first time, that higher plant diversity enhances the downward transport of dissolved molecules that likely stimulate soil development in deeper layers and therefore increase soil fertility

Thiolactone based coupling agents for the synthesis of poly(amide/urethane)s

In the present thesis, three different coupling agents are synthesized, which consist each of two cycles: (i) ethylene carbonate - thiolactone, (ii) bis(thiolactone) and (iii) epoxy - thiolactone. The syntheses of each are optimized to give high yields and pure products. Each coupling agent is thoroughly investigated concerning the orthogonal reactivity of its cycles. For the ethylene carbonate thiolactone coupling agent, a one-pot procedure is established where four different building blocks are incorporated into one molecule. Every intermediate in this reaction sequence is isolated and fully characterized. The bis(thiolactone) coupler is again investigated regarding its chemoselectivity towards amines at different temperatures. Then, the bis(thiolactone) is reacted as an AA-type monomer with diamines as BB-type comonomers in a step-growth polymerization. Using two comonomers in different ratios for the polyaddition, thermal properties of the resulting polymers are adjusted. The obtained polymers, which carry thiol groups in the side chain, are functionalized via a simple Michael addition to different substrates. The Michael addition with acrylate functional PEG building blocks gives access to water-soluble polymeric amphiphiles. Regarding the last coupling agent, the reactivity of the cycles is explored towards mono- and dialkylamines. In a one-pot procedure, a four component reaction is carried out using the coupler and three other building blocks. Upon amidation of the thiolactone at low temperatures, an epoxy thiol intermediate is prepared, which undergoes a base-catalyzed thiol-epoxy polyaddition in situ. This polyaddition is put to sound investigations regarding the used catalyst, the catalyst loading, concentration of the monomer, the solvent polarity and the formation of cyclic oligomers. The reaction conditions are optimized to obtain high number average molecular weights and low dispersities. Finally, the use of this coupler for the synthesis of bulk hydrogels is demonstrated. In a second part, this epoxy thiolactone is used for the synthesis of polyelectrolytes. The provided substrates are amino acids and derivatives of such. Upon polyaddition, pH-responsive polyelectrolytes and -ampholytes are obtained. Using two oppositely charged polyelectrolytes, polyelectrolyte complex nanoparticles are synthesized via macromolecular salt formation in solution. The particles are analyzed regarding their size and morphology

Tough Hydrogels for Load-Bearing Applications

Tough hydrogels have emerged as a promising class of materials to target load-bearing applications, where the material has to resist multiple cycles of extreme mechanical impact. A variety of chemical interactions and network architectures have been used to enhance the mechanical properties and fracture mechanics of hydrogels. In recent years, the mechanical properties of high-performance hydrogels are benchmarked, however this is often incomplete as important variables like water content are largely ignored. In this review, we aim to clarify the reported mechanical properties of state-of-the-art tough hydrogels by providing a comprehensive library of fracture and mechanical property data. First, we briefly discuss modes of energy dissipation at work in tough hydrogels, which we use to categorize the individual data sets. Next, we introduce common methods for mechanical characterization of high-performance hydrogels, followed by a detailed analysis of the current materials and their (fracture) mechanical properties. Finally, we consider several current applications, compare high-performance hydrogels with natural materials, and discuss promising future opportunities of tough hydrogels

γ-Functional Iminiumthiolactones for Single or Double Modification of Peptides

Thiolactones have been extensively studied as efficient ligation strategy, yet, their reactivity towards bio-based building blocks remains limited. In this manuscript, we present their more reactive successors, iminiumthiolactones (ITL), which show superior reactivity towards amine-containing substrates. Based on the Traut’s reagent we synthesized several ITLs from glycidol precursors and investigated several orthogonal modification reactions. After performing basic calculations on our substrates to substantiate their predicted reactivity, we picked one of our derivatives (γ-allyl functional ITL 3b) to study model reactions and explore the orthogonality of its different reaction pathways. As a more challenging substrate, we further choose Lysozyme C to be modified with our γ-allyl ITL (3b) using low reactant concentrations (1 mM or 50 μM), near-neutral pH (7.4 or 8.0) and stoichiometric reactant ratios. Under the studied conditions, we successfully demonstrate that our ITL derivative exhibits orthogonal and enhanced reactivity in a single or double modification towards biological substrates. As such, we believe that γ-functional ITLs may open up promising opportunities to incorporate biological building blocks into existing functional molecules, polymeric frameworks and materials

One-Pot Synthesis of Amino Acid-Based Polyelectrolytes and Nanoparticle Synthesis

In this manuscript, a biscyclic monomer with an epoxide and a thiolactone ring connected by a urethane bond is used for the synthesis of amino acid-functional polyelectrolytes. In a first step, lithium salts of amino acids react selectively with the thiolactone ring by ring-opening, formation of an amide bond, and a thiol group. In a second step and in the presence of a base a polymeric building block is formed by polyaddition of the thiolate to the epoxide ring. The reaction occurs at room temperature in water as solvent. The resulting polymeric building block has a poly­(thioether urethane) backbone, with hydroxyl- and amino acid side groups; the connection of the amino acid to the backbone occurs by an amide bond. As proof of concept, a selected series of amino acids and derivatives of such is used: glycine, alanine, tyrosine, glutamic acid, ε-amino caproic acid (as a lysine surrogate), BOC-lysine-O-methyl ester, BOC-lysine, and the dipeptide carnosine. The resulting polymer building blocks with molecular weights of <i>M</i>_n = 1830–9590 g/mol are entirely based on both bio-based and biodegradable components. Exemplarily, using the lithium salts of glycine and lysine methyl ester, anionic and cationic polyelectrolyte building blocks are obtained. A mixture of the two polyelectrolyte solutions results in the formation of polyelectrolyte complexes (PECs). With decreasing concentration of the polyelectrolyte solutions, the radii of PECs decrease

Mechanical Characterization of Human Brain Tissue and SoftDynamic Gels Exhibiting Electromechanical Neuro-Mimicry

Synthetic hydrogels are an important class of materialsin tissue engineering, drug delivery, and other biomedicalfields. Their mechanical and electrical properties can betuned to match those of biological tissues. In this work,we report on hydrogels that exhibit both mechanical andelectrical biomimicry. The presented dual networks consistof supramolecular networks formed from 2:1 homoternarycomplexes of imidazolium-based guest molecules in cucu-bit[8]uril and covalent networks of oligoethylene glycol-(di)methacrylate. We also investigate the viscoelastic prop-erties of human brain tissues. The mechanical properties ofthe dual network gels are benchmarked against the humantissue, and we find that they both are neuro-mimetic and ex-hibit cytocompatiblity in a neural stem cell model.The Winston Churchill Foundation of the United States. The Newton International Fellowship