We report the first cocrystal as an intermediate in a solidstate organic reaction wherein molecules of barbituric acid and vanillin assume a favorable orientation for the subsequent Knoevenagel condensation.The Knoevenagel condensation is an important carbon-carbon bond forming reaction. More than a hundred years after the original report by Knoevenagel, 1 Suzuki 2 and Kaupp 3 demonstrated an efficient and quantitative Knoevenagel condensation in the solid state achieved by milling. Other studies of solvent-free Knoevenagel condensation reactions soon followed. 4-10 The reaction of barbituric acid (barb) and vanillin (van) was even used as a model mechanochemical organic reaction for assessing energetics of milling, 11,12 to test twin-screw extrusion for solid-state organic synthesis, 13 and latest, to reveal a peculiar deviation of solid-state reaction kinetics from the one observed in solution, stemming from changes in the rheology of the milled sample. 14 However, studies of barb-van Knoevenagel condensation were thus far limited to ex situ reaction monitoring by, e.g., solution UV-Vis 11 or NMR spectroscopies. 14 In this work, we employ real-time in situ Raman spectroscopy monitoring 15,16 to reveal that the solid-state Knoevenagel condensation (Scheme 1) of barb and van proceeds through a cocrystal intermediate. In the cocrystal, packing of barb and van is such that molecules of barb are suitably positioned for the nucleophilic

This article describes the use of commercial silica (SiO 2 ) and calcium carbonate (CaCO 3 ) nanofillers as compatibilizers in immiscible polylactide/low-density polyethylene (PLA/LDPE) blends. The general aim of the study was to investigate the possibilities of replacing standard commodity plastics such as LDPE based on non-renewable mineral oil resources with the biodegradable renewable polymer PLA in compatibilized PLA/LDPE blends for use in the packaging industry. The calculations of the minimal interfacial energy and optimal wetting abilities indicated that SiO 2 filler was a better potential compatibilizer than CaCO 3 for a given PLA/ LDPE blend. This was due to its preferential localization at the interface. The significantly improved morphology of the ternary PLA/ LDPE/SiO 2 blend was found to present an increased strength, toughness, and crystallinity.

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Properties of samples containing polyurethane (PU), poly(vinyl acetate) (PVAc) and nanosize particles of calcium carbonate (CaCO3) are correlated with concentrations of these components. Interphase phenomena in PU/PVAc/CaCO3 nanohybrids have been studied before, we focus here on wear and scratch resistance. In addition to polymer blends containing CaCO3, the effects of adding CaCO3 with grafted PVAc, and CaCO3 with grafted silane and PVAc in varying ratios are also evaluated. For blends that do not contain the filler, a hypothesis explaining the concentration dependence of friction called the Bump Model is advanced and supported by the experimental results. In particular, we explain how creating a blend containing only 10% of a second polymer results in a dramatic drop of friction of the majority polymer. In single scratch testing, above 3% the filler displays 'its own' resistance to scratching. Chemical modification of the filler results in shallower residual depths--a consequence of improved interaction of the filler with the polymeric matrix. In sliding wear determination, strain hardening is seen for blends as well as for filler-containing composites. In tensile testing, addition of an unmodified filler increases the elongation at break and thus lowers the brittleness; the effect is even larger for chemically modified fillers.

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