Type of publicationArticle (peer-reviewed) Link to publisher's versionhttp://dx.doi.org/10.1039/c3sm27130gAccess to the full text of the published version may require a subscription. The stability of polystyrene thin films of low molecular weight on a solid substrate is shown to be controlled by the presence of uniformly distributed gold sputtered at the air-polymer interface. Continuous gold coverage causes the formation of wrinkles. High coverage and Au nanoparticle (NP) density leads to the development of a spinodal instability while low coverage and NP density retards the nucleation dewetting mechanism that beads up the thin polymer film into drops when no coverage is 10 present. Heating at temperature larger than the polymer glass transition temperature for extended periods allows the gold NPs to coalesce and rearrange. The area of polymer surface covered by NPs decreases as a result and this drives the films from unstable to metastable states.When the gold NPs are interconnected by polymer chains a theoretically predicted spinodal instability that patterns the film surface is experimentally observed. Suppression of the instability and a return to a flat film occurs when the 15 polymer interconnections between particles are broken. While the polymer films maintain their physical continuity changes in their chemical surface composition and thickness are observed. The observed film metastability is nevertheless in agreement with theoretical prediction that includes these surface changes. Rights

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Evidence is presented for the secondary nucleation of beta-L-glutamic acid on the surface of the alpha-polymorph, using a combination of Scanning Electron Microscopy and Raman spectroscopy.

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The influence of a range of amino acid additives on the crystallization of l-glutamic acid has been investigated. The presence of a bulky side chain (phenyl) in l-phenylalanine and l-tyrosine was identified as an essential feature in achieving stabilization of the α-polymorph at low additive concentrations. Minute quantities of these additives were incorporated into the α-l-glutamic acid product crystals when the additive/l-glutamic molar ratio was 1:30 in solution; in this condition no β-form inclusions were observed inside the α-form crystals. At higher additive/l-glutamic acid molar ratios in solution (1:6), a significant amount of additive uptake was observed and changes in α-form morphology were noted under these conditions. A key feature was the disappearance of the {011} and {001} facets of α-l-glutamic acid and the emergence of the {111}and {110} facets. The overall hypothesis is that additives disrupt the developing β/α interface and this stabilizes the α-form.