(SPB) or y.y.kim@leeds.ac.uk (YYK). 2Structural biominerals are inorganic/organic composites that exhibit remarkable mechanical properties. However, the structure-property relationships of even the simplest building unitmineral single crystals containing embedded macromolecules -remain poorly understood. Here, by means of a model biomineral made from calcite single crystals containing glycine (0-7 mol%) or aspartic acid (0-4 mol%), we elucidate the origin of the superior hardness of biogenic calcite.We analyzed lattice distortions in these model crystals by using x-ray diffraction and molecular dynamics simulations, and by means of solid-state nuclear magnetic resonance show that the amino acids are incorporated as individual molecules. We also demonstrate that nanoindentation hardness increased with amino acid content, reaching values equivalent to their biogenic counterparts. A dislocation pinning model reveals that the enhanced hardness is determined by the force required to cut covalent bonds in the molecules.3 Biominerals such as bones, teeth and seashells are characterized by properties optimized for their functions. Despite being formed from brittle minerals and flexible polymers, nature demonstrates that it is possible to generate materials with strengths and toughnesses appropriate for structural applications 1 . At one level, the mechanical properties of these hierarchically structured materials are modelled as classical composites consisting of a mineral phase embedded in an organic matrix 2 . However, the single crystal mineral building blocks of biominerals are also composites 3 , containing both aggregates of biomacromolecules as large as 20 nm 4,5 and inorganic impurities 6,7 . While it should be entirely possible to employ this simple biogenic strategy in materials synthesis 8,9 , the strengthening and toughening mechanisms that result from these inclusions are still poorly understood 10,11 . This work addresses this challenge by analyzing hardening mechanisms in a simple model biomineral system: calcite single crystals containing known amounts of amino acids. We report synthetic calcite crystals with hardnesses equivalent to those of their biogenic counterparts, and offer a detailed explanation for the observed hardening.Since plastic deformation in single crystals occurs by the motion of dislocations, hardness is enhanced by features that inhibit dislocation motion. The mechanisms by which guest species may harden ionic single crystals generally fall into two categories. Second phase particles directly block dislocation motion, requiring a dislocation to either cut through (shear) a particle or bypass it by a diffusive process to keep going 12 . Solutes (point defects) do not directly block dislocation motion, but the stress fields of the dislocations interact with those associated with misfitting solutes, retarding dislocation motion 12 . Biominerals, notably calcite, often deform plastically by twinning 11 , but since twins grow by motion of "twinning dislocations" 13 , these concep...

Macromolecular binding to minerals is of great importance in the formation of biofilms, and carboxylate functional groups have been found to play a pivotal role in the functioning of these macromolecules. Here we present both fluorescence time-resolved anisotropy measurements and simulation data on the conformational behaviour and binding of a poly acrylic acid polymer. In solution the polymer exhibits a pH dependent behaviour, with a coiled conformation at a low pH and extended conformation at higher pH values. The polymer is readily adsorbed on the surface of calcite, preferring to bind in an extended conformation, with the strength of the adsorption dependent on the pH and presence of counter ions. We discuss the reasons why the calculated adsorption free energy differs from that obtained from a Langmuir isotherm analysis, showing that they refer to different quantities. The enhanced binding of the extended conformations shows the importance of flexibility in the binding of macromolecules.

Reaction of 1-azidoadamantane with aromatic substrates in the presence of aluminium chloride gave the corresponding 3-aryl-4-azahomoadamantane, presumably m a an imine intermediate ALKYL azides are reported to undergo reactions involving elimination of nitrogen gas, azide ion, or both, in the presence of aluminium chloride and benzene The resulting products were N-alkylanihnes, imines from rearrangement, or alkylbenzeiies The imines apparently did not participate in Friedel-Crafts alkylation We report the first reaction of an alkyl azide with aromatic compounds catalysed by aluminium chloride, resulting in rearrangement followed by aminoalkylation of the aromatic reagent When 1-azidoadamantane (1) was exposed a t 80 "C for 1.25 h to aluminium chloride in the presence of an aromatic resulted With sulphuric acid, 3-hydroxy-4-a~ahomo-Acknowledgement is made to the donors of the Petroleum adamantane is formed l2 Analogously, l-NN-dichloro-Research Fund, administered b y the American Chemical aminoadamantane, on rearrangement with aluminium Societv, for support of this research chloride, followed by treatment with nucleophiles, such as water, alcohol, thiols, or aromatic compounds, gave the corresponding 3-substituted-4-azahomoadamantantanes l3(Recezved, 4th December 1979, C o m 1270 )

Despite their inability to model bond breaking molecular dynamics simulations are shown to predict thermal degradation temperatures of polycyanurate (cyanate ester) homopolymers and nanocomposites in very close agreement with experimental data. Simulated polymer density, used to predict Tg also shows a reduction within the same temperature range as experimental values for the thermal degradation.

Cover: Molecular modeling and molecular dynamics simulations are shown to be capable of predicting the thermal degradation temperature of crosslinked thermosetting polymers and nanocomposites produced therefrom. Further details can be found in the article by A. Baggott, J. R. Bass, S. A. Hall, I. Hamerton, B. J. Howlin,* L. Mooring, and D. Sparks http://doi.wiley.com/10.1002/mats.201300141.