Trans-crystalline morphologies

A special kind of morphology found in polymers crystallizing in contact with a nucleating surface is the trans-crystalline structure. The nucleating object may be a flat surface or a fibril. The densely appearing nucleations at the surface of the nucleating object result in a one-dimensional (columnar) growth in a direction parallel to the normal of the surface. The thickness of the trans-crystalline layer depends on the outcome of the competition between surface nucleation and bulk nucleation. 

Based on both these morphological and thermal evaluations, it was possible to get a better representation of the overall structure of the nanocomposite. The latter is a multiphase system in which filler particles are covered by a trans-crystalline interphase in which polymer chains display a reduced segmental mobility [confinement]. These coated filler fibers proved to be dispersed in an "unaffected bulk-like continuous iPP phase in which the polymer crystal perfection is lower than the one of the lamellae grown perpendicularly to the filler surface. 

Figure 5.2 TEM bright-field images of ultrathin film samples of [a] pure iPP-g-MA showing cross-hatched morphology and trans-crystalline organization of iPP-g-MAaround [b] MWCNTs and (c) SWCNTs. (Reproduced with permission from ref. 14. Copyright 2008 American Chemical Society)...

EPM > CO > TP > CB. The highly crystalline TB had an etch rate about six times that of CB, ascribable to a morphology difference, while the partially crystalline TO had an etch rate somewhat higher than that of amorphous CO. Cis/trans content had little or no effect on the etch rate of the polyalkenamers. A mechanism involving crosslinking through vinyl units is proposed to explain the unexpected protection imparted to vinylene-rich polybutadienes by the presence of 1,2 double bonds. 

The data of Table II indicate that the etch rates for CB and its "homologues"—TP, CO (or TO), and EPM—tend to increase monotonically with a decrease in vinylene (-CH=CH-) unsaturation. The elastomeric EPM was chosen instead of crystalline polyethylene as a model for the fully saturated CB to avoid a morphology factor in etch rates, as was observed with crystalline TB. The difference in etch rates for the partially crystalline TO and the elastomeric CO (ratio of about 1.2 1.0) is attributable more to a morphology difference between these polyoctenamers than to the difference in their cis/trans content. Cis/trans content had likewise no perceptible effect on etch rates in the vinyl-containing polybutadienes (see Table I) if there was a small effect, it was certainly masked by the dominant effect of the vinyl groups. 

G. (1999) Structural chemistry of uranium associated with Si, Al, Fe gels in a granitic uranium mine. Chem. Geol. 158 81-103 Allen, G.C. Kirby, C. Sellers, R.M. (1988) The effect of the low-oxidation-state metal ion reagent tris-picolinatovanadium(II) formate on the surface morphology and composition of crystalline iron oxides. J. Chem. Soc. Faraday Trans. I. 84 355-364... 

K. Sangwal and R. Rodriguez-Clemente, Surface Morphology of Crystalline Solids, Zurich, Trans. Tech., 1991... 

It was first reported that the topochemical photopolymerization of diolefin crystals gave rise to cracks and deformation [7]. An atomic force microscopic (AFM) study made possible the observation that the photodimerizations of trans-cinnamic acids and anthracenes in the crystalline state induced surface morphological changes at the tens and hundreds of nanometers level by the transportation and rebuilding of the surface molecules [8]. The appearance of a surface relief grating on the single crystal of 4-(dimethylamino)azobenzene was demonstrated by repeated irradiation with two coherent laser beams [9]. 

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