What is the most significant result of this study?Developing green solvents to replace petrochemically-derived conventional solvents is currently one of the major challenges in sustainable chemistry.T he most significant result of our work is that Hansen Solubility Parameter Space can be used to predict mixtures of two green solvents that have similar properties to conventional solvents such as chloroalkanes for which no effective single-component replacements exist. We illustrate the applicability of the methodology by applying it to solid-phase peptide synthesis and polymer dissolution, but many other applications can be envisaged.

The influence of various physical and chemical factors on the swelling of polystyrene and PEG based resins in greener organic solvents has been systematically investigated. In general, chemical factors: the nature of the functionality/linker and the degree of loading were found to have a far larger influence on the swelling of the resins than physical parameters such as bead size. The results are interpreted in terms of Hansen solubility parameters for the solvents and there is evidence that some solvents interact with the polymeric core of a resin whilst others interact with the functionality. The results are extended to a study of the changes in resin swelling observed during both deprotection and chain elongation reactions during solid phase peptide synthesis.

Invited for the cover of this issue is the group of Michael North and co‐workers at the University of York. The image depicts the use of a mixture of two green solvents to swell a solid‐phase synthesis resin bead that does not swell in either pure solvent. Read the full text of the article at 10.1002/chem.201900228.

3D Hansen solubility space is used to explain why the ability of binary mixtures of two solvents to swell crosslinked resins does not vary linearly with the solvent mole fractions. The cover artwork, which is loosely based on the famous 1979 poster for the film Alien, shows a series of small eggs at the bottom representing unswollen resin beads each surrounded by a single solvent. The centre of the image shows a much larger egg representing a swollen resin bead, now surrounded by a mixture of two solvents. Coming off the egg is a tripeptide representing the solid‐phase peptide synthesis reported in the paper. More information can be found in the Full Paper by M. North et al. on page 4951.