Plasma-enhanced chemical vapor deposition (PECVD) of SiOx thin coatings on polymer surfaces yields tough hybrid materials with the gas barrier properties and transparency of glass. Combination of these properties makes these materials ideally suited for food packaging and biomedical device applications. In this study, we employ a Non-Parametric Response Surface Methods optimization to identify the Magnetron-PECVD conditions responsible for superlative SiOx barrier coatings on poly(ethylene terephthalate) (PET). Oxygen and water vapor permeances of optimized PET/SiOx composites produced by hexamethyldisiloxane and trimethylsilane have been measured as functions of temperature and are found to exhibit Arrhenius behavior. The thermal activation energy for water vapor permeation, unlike that for oxygen permeation, depends on barrier performance and increases by as much as 20 kJ/mol with an increase in barrier efficacy. Examination of these materials by phase-imaging atomic force microscopy and energy-filtered transmission electron microscopy reveals a correlation between SiOx morphology (including defects) and barrier performance. Morphological and permeation results are compared to identify some of the physical factors governing water vapor permeation through SiOx-modified polymers.

IN a previous paper (Senier and Shepheard, Trans., 1909, 95, 1944) it was suggested that phototropic and thermotropic phenomena should be explained by some less drastic hypothesis than that of intramolecular decomposition and rearrangement, and theref ore use was not made of Hantzsch and Werner's hypothesis or of any of its more recent modifications, and, if intramolecular rearrangement is excluded as an explanation, polymorphism is still more so, the same crystal changes backwards and forwards yielding the darker or lighter phototrope or thermotrope a t will, without the least indication whatever of change in crystalline form. Moreover, we call attention in this paper to two instances of distinctly dimorphous arylideneamines, in which each of the dimorphic varieties is both phototropic and thermotropic. I n one case the two dimorphic varieties exhibit a marked difference in their phototropy. Some new hypothesis is wanted t o explain this phenomena, and it seems to us that this may be found in the direction indicated in the paper referred to, that is, by assuming the existence of complex solid molecular aggregates related to gaseous molecules as gaseous molecules are related to atoms. The Relation of Phototropy to Temperature: A Study of Schiff's Bases or Anils.Our own experience and that of other workers in phototropy have shown t h a t this phenomenon is influenced to an important degree by temperature ; thus Marckwald (Zeitsch. physikal. Chem., 1899, 30, 140), who first observed phototropy, noticed that in one case, a t the ordinary temperature, the effect of exposure t o light was rapid, but that the reverse action in the dark was very slow, requiring some twenty-four hours. When, however, the reverse action was tried a t a temperature of 90°, the change was instantaneous. Other instances of the influence of temperature on phototropy are mentioned by Biltz (Zeitsch. physikal. Chern., 1899, ( A n d e n , 1908, 369, 1). 30, 527), and particularly by StobbeIt seemed to us desirable, first, to study the effect of light, a t temperatures up to their melting points, on Schiff's bases, which are known to be phototropic at the ordinary temperature, and secondly, to seek for phototropy among the numerous Schiff's bases,

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The o-nitrobenzylidenearylamines examined were all easily prapared by bringing together the aldehydes and amines in alcoholic solution. All of them axe thermotropic, and several exhibit phckotropic properties. It is noteworthy, however, that in most case6 the prolonged effect of sunlight was to change the bases into non-reversible dimorphic varieties which could be restored generally t o the original form by heating to a temperature just below their melting points or by actual melting. The analogy between the structure of these bases and the o-nitrocompounds studied by Ciamician and Silber (Ber., 1901, 34, 2040) and by Sachs and Kempf (Ber., 1902; 35, 2704) led us to try if VOL. cv.

Dielectric Increments of Amino Acid Polypeptides 1379 fractions tested for formaldehyde and furfural as described above. Neither was detected. DiscussionThe experiments described show that when either of the isomeric aloins is decomposed by treatment with borax followed by hydrochloric acid, formaldehyde is formed. The same result is obtained when sodium perborate is used, but in this case the acid treatment is unnecessary, indicating that the oxidizing action of the perborate can bring about the same change as the acid. Hydrochloric acid, without the preliminary borax treatment, cannot bring about the formation of formaldehyde.These results show, also, that hydrolysis with borax produces little if any pentose, whereas with sodium perborate, presumably due, again, to the oxidizing action, pentose is formed in appreciable amounts as indicated by the formation of furfural after acidification and distillation. This is in agreement with the results of Goldner.6 Summary Some of the conditions for the formation of formaldehyde and of a pentose (detected by furfural formation) from the aloins have been determined.