Deterministic modelling of indoor radio propagation at 40–60 Ghz

Factors that influence the accuracy of high frequency models for indoor radio propagation at 40–60 GHz are identified and discussed. Simulation results obtained on the basis of Geometrical Optics are presented. The reliability of these results is examined by comparing them with those obtained from empirical measurements.     

Guanidinium binding modulates guest exchange within an [M4L6] capsule

Take it slow! A metal-organic container molecule has been shown to bind guanidinium cations (blue) between the sulfonate groups on its periphery, as well as accommodating guests such as cyclopentane and cyclohexane in its internal cavity (red). Kinetic studies on the system demonstrated a linear relationship between the amount of bound guanidinium ions and the rate of guest exchange.     

How to Distinguish Isodesmic from Cooperative Supramolecular Polymerisation

To study the supramolecular polymerisation mechanisms of a self‐assembling system, concentration‐ and temperature‐dependent measurements can both be used to probe the transition from the molecular dissolved state to the aggregated state. In this report, both methods are evaluated to determine their effectiveness in identifying and quantifying the self‐assembly mechanism for isodesmic and cooperative self‐assembling systems. It was found that for a rapid and unambiguous determination of the self‐assembly mechanism and its thermodynamic parameters, temperature‐dependent measurements are more appropriate. These studies allow the acquisition of a large data set leading to an accurate determination of the self‐assembly mechanism and quantification of the different thermodynamic parameters that describe the supramolecular polymerisation. For a comprehensive characterisation, additional concentration‐dependent measurements can be performed.     

Molecular control over vitrimer-like mechanics – tuneable dynamic motifs based on the Hammett equation in polyimine materials

In this work, we demonstrate that fine-grained, quantitative control over macroscopic dynamic material properties can be achieved using the Hammett equation in tuneable dynamic covalent polyimine materials. Via this established physical-organic principle, operating on the molecular level, one can fine-tune and control the dynamic material properties on the macroscopic level, by systematic variation of dynamic covalent bond dynamics through selection of the appropriate substituent of the aromatic imine building blocks. Five tuneable, crosslinked polyimine network materials, derived from dianiline monomers with varying Hammett parameter (σ) were studied by rheology, revealing a distinct correlation between the σ value and a range of corresponding dynamic material properties. Firstly, the linear correlation of the kinetic activation energy (E_a) for the imine exchange to the σ value, enabled us to tune the E_a from 16 to 85 kJ mol⁻¹. Furthermore, the creep behaviour (γ), glass transition (T_g) and the topology freezing transition temperature (T_v), all showed a strong, often linear, dependence on the σ value of the dianiline monomer. These combined results demonstrate for the first time how dynamic material properties can be directly tuned and designed in a quantitative – and therefore predictable – manner through correlations based on the Hammett equation. Moreover, the polyimine materials were found to be strong elastic rubbers (G′ > 1 MPa at room temperature) that were stable up to 300 °C, as confirmed by TGA. Lastly, the dynamic nature of the imine bond enabled not only recycling, but also intrinsic self-healing of the materials over multiple cycles without the need for solvent, catalysts or addition of external chemicals.

Controlling macroscopic material properties of dynamic covalent polyimines via the electronic effect of dianiline monomers based on the Hammett equation.     

Self‐Assembly of Functional Discrete Three‐Dimensional Architectures in Water

Construction of discrete, self‐assembled architectures in water has gained significant interest in recent years as a wide range of applications arises from their defined 3D structure. In this review we jointly discuss the efforts of supramolecular chemists and biotechnologists who previously worked independently, to tackle discipline‐specific challenges associated with construction of assemblies from synthetic and bio‐derived components, respectively. Going forward, a more interdisciplinary research approach will expedite development of complexes with real‐world applications that exploit the benefits of compartmentalisation. In support of this, we summarise advances made in the development of discrete, water‐soluble assemblies, with particular focus on their current and prospective applications. Areas where understanding and methodologies can be transferred from one sector to the adjacent field are highlighted in anticipation this will yield advances not possible from either field alone.     

Mössbauer and channeling measurements on buried layers of CoSi2 in Si

Single crystalline multilayered structures of Si/CoSi₂/Si were made by high dose implantation of Co into a Si wafer which was subsequently annealed. These structures were then investigated with both Mössbauer spectroscopy and channeling measurements. The experiments show that a change occurs in the structure of the CoSi₂ at a temperature between 150 K and 220 K.