Conversion of β-elemene into new β-elemene dicarbonates through epoxidation and halide salt-catalyzed CO2 cycloaddition reactions is reported. Step-growth polyaddition of this dicarbonate to five different, commercial diamines was investigated under neat conditions at 150 °C yielding non-isocyanate-based low molecular weight oligo(hydroxyurethane)s with 1.3≤Mn ≤6.3 kDa and 1.3≤Ð≤2.1, and with glass transition temperatures ranging from -59 to 84 °C. The preparation of one selected polyhydroxyurethane material, obtained in the presence of Jeffamine® D-2010 was scaled-up to 43 g. The latter, when combined in a formulation using Irgacure® 2100 and Laromer® LR 9000 allowed the preparation of coatings that were analyzed with several techniques showing the potential of these biobased oligourethanes towards the preparation of commercially relevant materials.

Nachrichten aus der ChemieVolume 68, Issue 7-8 p. 91-91 Service Nachruf auf Kilian Muniz (1970 - 2020) Jan Streuff, Search for more papers by this authorClaas Hövelmann, Search for more papers by this authorAlvaro Iglesias, Search for more papers by this author Jan Streuff, Search for more papers by this authorClaas Hövelmann, Search for more papers by this authorAlvaro Iglesias, Search for more papers by this author First published: 01 July 2020 https://doi.org/10.1002/nadc.20204099935Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume68, Issue7-8Juli ‐ August 2020Pages 91-91 RelatedInformation

The conversion of lignocellulosic biomass or wood into chemicals still poses a challenge due to the recalcitrance of this composite-like material consisting of lignin, hemicellulose and cellulose. A very high accessibility of cellulose is reported by a pretreatment with ionic liquids that enables high conversion rates by enzymatic hydrolysis. However, the underlying mechanisms have not yet been monitored in operando nor are they fully understood. We monitored the transformation of wood in ionic liquids using small-angle neutron scattering to observe changes in the material in operando and to elucidate the intrinsic effects. The data analysis shows three different stages that is (1) impregnation, (2) the formation of voids and (3) increasing structure size within cellulose fibrils. This consecutive mechanism coincides with macroscopic disintegration of the tissue. The analysis further reveals that the reduction of order in longitudinal direction along the fiber axis is a prerequisite for disintegration of cells along the radial direction. This understanding supports further research and development of pretreatment processes starting from lignocellulosic raw material. Graphic abstract

The structure and the dynamics of supramolecular comblike polymers in the melt state is studied by a combination of linear rheology, dielectric spectroscopy, and small angle neutron scattering. The system consists of blends of 1,2-polybutyleneoxide (PBO) entangled backbones, randomly functionalized with thymine (thy) and barely entangled PBO graft chains—modified with 2,4-diamino-1,3,5-triazine (DAT) end groups. These bioinspired groups associate into a transiently branched comb architecture through heterocomplementary interaction involving the two different hydrogen bonding groups thy and DAT. In the present manuscript, we focus on the comparison of the macroscopic dynamics of the associating blends and permanent comb analogs. The viscoelastic and dielectric response of covalent and reversible combs are found to be comparable. The viscoelastic response of mixtures of thy-functionalized entangled backbones and DAT-end-modified barely entangled chains show a relaxation mechanism, which is mostly attributed...

Poly(ethylene glycol) (PEG) is ideally suited for the synthesis of cyclic polymers. The cyclization reaction of PEG-via its tosylate intermediate is well established. We improved the cyclization reaction and obtained cyclic raw products in high yields. The quantities of linear precursor and higher molecular weight condensation byproducts were low. The latter byproducts can be removed efficiently by classical fractionation using chloroform/heptane as solvent/non-solvent pair. For the removal of linear precursor a process was developed which comprises the quantitative oxidation of alcoholic PEG chain ends to carboxyl groups and their subsequent removal with the help of a basic ion-exchange resin. The efficient cleaning processes allowed carrying out the ring closure reaction at relatively high concentrations and so increasing sample quantities. As a result, cyclic poly(ethylene glycol) was obtained in high purity up to a molecular weight of 20 000 g/mol in quantities of several grams. In order to monitor the oxidation reaction and to prove the absence of linear chains, a H-1 NMR characterization technique was developed, which is extremely sensitive up to high molecular weights.

A new dual network elastomer is developed that consists of polybutadiene crosslinked with both permanent and transient bonds. The transient network is formed by the association of urazole groups that are randomly attached to the polymer backbone. Subsequent orthogonal covalent crosslinking through hydrosilylation in the melt state leads to a dual network with variable permanent and transient crosslinking density. Small angle neutron scattering (SANS) investigations show a homogeneous distribution of the transient bonds in both the functionalized polymers and the dual network products. The enhanced mechanical properties of the dual networks compared to conventional polybutadiene elastomers are characterized by stress–strain measurements. The increased toughness can be explained by a protective mechanism where the weaker supramolecular bonds act as sacrificial bonds that dissipate energy.

In this work, an investigation of the hydrogen-bonding mechanism in a transiently branched comb-like polymer system in the melt is reported. The system under investigation consists of a polybutylene oxide (PBO)-based backbone, randomly functionalized with thymine (thy) groups, in combination with shorter PBO graft chains, end-functionalized with diaminotriazine (DAT) groups. The functional groups are able to associate through hydrogen bonding. The heterocomplementary association of these groups leads to the formation of a transiently branched comb-like polymer system. Since recently virtually exclusive heterocomplementary association could be observed in the supramolecular association of telechelically modified oligomeric PEG chains, here we aim to extend the supramolecular assembly mechanism toward branched structures. The present work combines small angle neutron scattering (SANS) experiments on a selectively labeled system with macroscopic dynamics measured in linear rheology response. The association ...

We describe the synthesis, analysis and rheological behavior of differently functionalized poly(1,2-butylene oxide) based supramolecular polymers.

An understanding of the factors that govern the rate of chemical reactions has proven elusive for many students who begin a survey course in the chemical sciences. Inquiry-based curricula built upon an understanding of common student misconceptions related to chemical kinetics have proven to be a more effective means by which to develop student understanding than traditional lecture formats. To facilitate teacher-guided discussion regarding the subject of catalysis, we have developed a simple and safe demonstration, whereby the hydrogen and oxygen components evolved upon electrolysis of water are recombined at room temperature with the aid of a platinum/ruthenium catalyst. This demonstration is designed to draw students' attention toward the dramatic change in reaction rate that can be affected by catalyst involvement and to provoke dialog regarding the mechanistic changes that accompany reaction catalysis.

We present a small angle neutron scattering (SANS) study of the association of heterocomplementary telechelic polypropylene glycol (PPG) polymers, bearing either diaminotriazine (DAT) or thymine (Thy) stickers as end-groups, both in the melt and in dilute solution. The SANS data are critically examined for the architecture and morphology as well as relative extent of linear assembly in the apolar solvent toluene. A random phase approximation (RPA) approach, adapted for a supramolecularly assembled multiblock copolymer is presented, which allows to extract the interaction parameters between the constituents and the medium. From the proposed approach, which describes very well heterocomplementary hydrogen-bonding telechelic polymers in both diluted toluene solution and in the melt, we conclude that linear association prevails.

In the present work we report on a Random Phase Approximation (RPA) which can be applied to multiblock copolymers consisting of supramolecular building blocks and hydrogen-bonded compounds including interactions in solution. These systems are model for the self-healing process due to the hydrogen-bonding interaction between the end-groups. This new analysis allowed to quantitatively access the assembly route with varying concentration.