2,2′,6,6′-Tetrachloro-4,4′-propane-2,2-diyldiphenol, 2,2′,6-tribromo-4,4′-propane-2,2-diyldiphenol and 2,2′,6,6′-tetrabromo-4,4′-propane-2,2-diyldiphenol

Three flame retardants with very similar molecular structures showing three different packing patterns have been studied. The crystal structure of 2,2′,6,6′-tetrachloro-4,4′-propane-2,2-diyldiphenol, C₁₅H₁₂Cl₄O₂, can be described as a packing of sheets. The packing shows a very short intermolecular Cl⋯Cl contact distance of 3.094 (2) Å between pairs of mol­ecules inside each sheet. The crystal structure of 2,2′,6-tribromo-4,4′-propane-2,2-diyldiphenol, C₁₅H₁₃Br₃O₂, can be described as a packing of doubly stranded helical square tubes. These square helices are interconnected through Br⋯Br contacts between different helices. Finally, a previously known structure, 2,2′,6,6′-tetrabromo-4,4′-propane-2,2-diyldiphenol [Simonov, Cheban, Rotaru & Bels'skii (1986). Kristallografiya, 31 , 397–399], C₁₅H₁₂Br₄O₂, which is the most commonly used flame retardant and which has twofold rotational symmetry, has been refined in the correct absolute configuration. The structure shows large differences from the chloro analogue with regard to packing, van der Waals distances and hydrogen-bond distances.     

An interpenetrating primitive cubic net formed by hydrogen bonds and coordination bonds in catena‐poly[[bis(methanol‐κO)bis(thiocyanato‐κN)iron(II)]‐μ‐1,2‐bis(4‐pyridylmethylene)hydrazine‐κ2N:N′]

In the title compound, [Fe(NCS)₂(C₁₂H₁₀N₄)(CH₄O)₂]_n, at 153 (2) K, the Fe atom is located on an inversion centre, as is the centre of the N—N bond in the ligand molecule. The structure contains a one‐dimensional coordination polymer with an Fe...Fe distance of 15.866 (7) Å and can be described as two interpenetrating six‐connected primitive cubic (pcu) three‐dimensional networks when additional intermolecular O—H...S hydrogen bonds are taken into account. The compound is not isostructural with the corresponding Mn^II compound as they differ in the rotation around the M—O bond by 90°, giving rise to completely different hydrogen‐bond patterns. This study demonstrates the impact of conformational differences on the final supramolecular arrangement.     

Molecular modeling of interfaces between cellulose crystals and surrounding molecules: Effects of caprolactone surface grafting

A technical problem in cellulosic nanocomposite materials is the weak interaction between hydrophilic cellulose and hydrophobic polymer matrices. One approach to solve this difficulty is to chemically graft monomers of the matrix polymer onto the cellulose surface. An important question is to understand the effect such surface modification has on the interfacial properties. Semi-empirical approaches to estimate work of adhesion based on surface energies do not provide information on specific molecular interactions. Details about these interactions were obtained using molecular dynamics (MD) simulation. Cellulose interfaces with water and caprolactone medium were modeled with different amounts of grafted caprolactone. The modification lead to an increased work of adhesion between the surface and its surrounding medium. Furthermore, the MD simulations showed that the interaction between cellulose, both modified and non-modified, and surrounding medium is dominated by Coulomb interactions, predominantly as hydrogen bonds.     

High Loading Efficiency and Controlled Release of Bioactive Immunotherapeutic Proteins Using Vaterite Nanoparticles

Nanoparticles may limit off-tumor/on-target ubiquitous activation of signaling by protein-based drugs. However, many challenges still exist in the design of a nanoparticle for protein delivery. In this study, conditions to establish vaterite nanoparticles as a pH-sensitive drug delivery system (DDS) for encapsulated protein drugs are comprehensively evaluated. Low coprecipitation pH of vaterite and protein prevents protein denaturation and yields high loading efficiency. Unprotected vaterite recrystallizes in aqueous solutions within 3 h to calcite and releases the loaded protein completely, but surface-modified particles with carboxyl groups containing polymers prove stable for more than 5 months. Notably, modification of vaterite with sulfonated polymers increases the loading of cationic proteins by a multiple. A system is developed for vaterite exposure to (pH) conditions under body-like-flow rates, with the dissolution of vaterite and simultaneous release of active proteins at tumor microenvironmental pH reaching up to 80% and only 20% at physiological pH within 2 h. Importantly, the immunomodulatory protein tumor necrosis factor preserves its native structure and fully retains functional activity in vitro after release from the particles. In conclusion, the studies described here provide a framework for the development of vaterite-based DDS as a carrier for bioactive protein-based therapeutics.     

Effect of SIMS ionization probability on depth resolution for organic/inorganic interfaces

Secondary ion mass spectrometry (SIMS) relies on the fact that surface particles ejected from a solid surface are ionized under ion bombardment. By comparing the signal of molecular secondary ions desorbed from an organic film with that of the corresponding sputtered neutral precursor molecules, we investigate the variation of the molecular ionization probability when depth profiling through the film to the substrate interface. As a result, we find notable variations of the ionization probability both at the original surface and in the interface region, leading to a strong distortion of the measured SIMS depth profile. The experiments show that the effect can act in two ways, leading either to an apparent broadening or to an artificial sharpening of the observed film‐substrate transition. As a consequence, we conclude that care must be taken when assessing interface location, width, or depth resolution from a molecular SIMS depth profile.