Chen, Yinshan published the artcileEffect of molecular size and hydrogen bonding on three surface-facilitated processes in molecular glasses: Surface diffusion, surface crystal growth, and formation of stable glasses by vapor deposition, HPLC of Formula: 72509-76-3, the main research area is mol size hydrogen bonding surface diffusion; crystal growth stable glass vapor deposition.
Recent work has shown that diffusion and crystal growth can be much faster on the surface of mol. glasses than in the interior and that the enhancement effect varies with mol. size and intermol. hydrogen bonds (HBs). In a related phenomenon, some mols. form highly stable glasses when vapor-deposited, while others (notably those forming extensive HBs) do not. Here we examine all available data on these phenomena for quant. structure-property relations. For the systems that form no HBs, the surface diffusion coefficient Ds decreases with increasing mol. size d (d = Ω1/3, where Ω is the mol. volume); when evaluated at the glass transition temperature Tg, Ds decreases ∼5 orders of magnitude for 1 nm of increase in d. Assuming that center-of-mass diffusion is limited by the deepest part of the mol. in the surface-mobility gradient, these data indicate a mobility gradient in reasonable agreement with the Elastically Collective Nonlinear Langevin Equation theory prediction for polystyrene as disjointed Kuhn monomers. For systems of similar d, the Ds value decreases with the extent of intermol. HB, x (HB), defined as the fraction of vaporization enthalpy due to HB. For both groups together (hydrogen-bonded and otherwise), the Ds data collapse when plotted against d/[1 – x(HB)]; this argues that the HB effect on Ds can be described as a narrowing of the surface mobility layer by a factor [1 – x(HB)] relative to the van der Waals systems. Essentially the same picture holds for the surface crystal growth rate us. The kinetic stability of a vapor-deposited glass decreases with x(HB) but is not better organized by the combined variable d/[1 – x(HB)]. These results indicate that surface crystal growth depends strongly on surface diffusion, whereas the formation of stable glasses by vapor deposition may depend on other factors. (c) 2019 American Institute of Physics.
Journal of Chemical Physics published new progress about Crystal growth. 72509-76-3 belongs to class pyridine-derivatives, name is 3-Ethyl 5-methyl 4-(2,3-dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, and the molecular formula is C18H19Cl2NO4, HPLC of Formula: 72509-76-3.