Evaluation of the Composition, Thermal and Mechanical Behavior, and Color Changes of Artificially and Naturally Aged Polymers for the Conservation of Stained Glass Windows.

Investigations of historical conservation materials on historical stained glass windows of the Naumburg Cathedral in Germany offered an opportunity for the study of polymers, naturally aged in a non-controlled environment. This allowed the conservation history of the cathedral to be traced and expanded by valuable insights. The historical materials were characterized through the use of spectroscopy (FTIR, Raman), thermal analysis, PY-GC/MS, and SEC on taken samples.

Deep Learning for Reconstructing Low-Quality FTIR and Raman Spectra─A Case Study in Microplastic Analyses.

Herein we report on a deep-learning method for the removal of instrumental noise and unwanted spectral artifacts in Fourier transform infrared (FTIR) or Raman spectra, especially in automated applications in which a large number of spectra have to be acquired within limited time. Automated batch workflows allowing only a few seconds per measurement, without the possibility of manually optimizing measurement parameters, often result in challenging and heterogeneous datasets. A prominent example of this problem is the automated spectroscopic measurement of particles in environmental samples regarding their content of microplastic (MP) particles.

Agricultural application of microplastic-rich sewage sludge leads to further uncontrolled contamination.

Municipal sewage sludge has been shown to be high in microplastics (MP) and is applied to agricultural land as fertiliser in many countries. The authors recently proposed in a viewpoint article that MP applied to land in this way may well contaminate other areas in an uncontrolled way. This study examined experimental plots with known history of application of sewage sludge.

High-Throughput Analyses of Microplastic Samples Using Fourier Transform Infrared and Raman Spectrometry.

Determining microplastics in environmental samples quickly and reliably is a challenging task. With a largely automated combination of optical particle analysis, Fourier transform infrared (FT-IR), and Raman microscopy along with spectral database search, particle sizes, particle size distributions, and the type of polymer including particle color can be determined. We present a self-developed, open-source software package for realizing a particle analysis approach with both Raman and FT-IR microspectroscopy.

Quantitative Analysis of Step-Growth Polymers by Size Exclusion Chromatography.

We report an advanced analysis protocol that allows to quantitatively study the course of step-growth reactions by size exclusion chromatography on the example of the depolymerization of a Diels-Alder polymer based on a furane/maleimide couple at elevated temperatures. Frequently occurring issues of molar mass calibrations and overlap of monomer with solvent signals are addressed for determining reliable molar masses. Thereby, even kinetic parameters (e.

Entropy-Driven Selectivity for Chain Scission: Where Macromolecules Cleave.

We show that, all other conditions being equal, bond cleavage in the middle of molecules is entropically much more favored than bond cleavage at the end. Multiple experimental and theoretical approaches have been used to study the selectivity for bond cleavage or dissociation in the middle versus the end of both covalent and supramolecular adducts and the extensive implications for other fields of chemistry including, e.g.

Entropy driven chain effects on ligation chemistry.

We report the investigation of fundamental entropic chain effects that enable the tuning of modular ligation chemistry - for example dynamic Diels-Alder (DA) reactions in materials applications - not only classically the chemistry of the applied reaction sites, but also the physical and steric properties of the molecules that are being joined. Having a substantial impact on the reaction equilibrium of the reversible ligation chemistry, these effects are important when transferring reactions from small molecule studies to larger or other entropically very dissimilar systems. The effects on the DA equilibrium and thus the temperature dependent degree of debonding (%) of different cyclopentadienyl (di-)functional poly(meth-)acrylate backbones (poly(methyl methacrylate), poly(iso-butyl methacrylate), poly(-butyl methacrylate), poly(iso-butyl acrylate), poly(-butyl acrylate), poly(-butyl acrylate), poly(methyl acrylate) and poly(isobornyl acrylate)), linked a difunctional cyanodithioester (CDTE) were examined high temperature (HT) NMR spectroscopy as well as temperature dependent (TD) SEC measurements.

State-of-the-art analytical methods for assessing dynamic bonding soft matter materials.

Dynamic bonding materials are of high interest in a variety of fields in material science. The reversible nature of certain reaction classes is frequently employed for introducing key material properties such as the capability to self-heal. In addition to the synthetic effort required for designing such materials, their analysis is a highly complex--yet important--endeavor.

Adaptable hetero Diels-Alder networks for fast self-healing under mild conditions.

A novel adaptable network based on the reversible hetero Diels-Alder reaction of a cyanodithioester and cyclopentadiene is presented. Reversible between 50-120 °C, the adjustable and self-healing features of the network are evidenced via temperature dependent rheology experiments and repetitive tensile tests whereas the network's chemical structure is explored by temperature dependent (1) H MAS-NMR spectroscopy.

Temperature-dependent size exclusion chromatography for the in situ investigation of dynamic bonding/debonding reactions.

Polymers capable of dynamic bonding/debonding reactions are of great interest in modern day research. Potential applications can be found in the fields of self-healing materials or printable networks. Since temperature is often used as a stimulus for triggering reversible bonding reactions, an analysis operating at elevated temperatures is very useful for the in situ investigation of the reaction mechanism, as unwanted side effects can be minimized when performing the analyses at the same temperature at which the reactions occur.