1:1 Complexes of a range of Lewis acids with crotonaldehyde (1) have been systematically investigated by 1H and 13C nmr spectroscopy. Lewis acids employed were: BF3, BCl3, BBr3, SnCl4, TiCl4, SbCl5, AlCl3, EtAlCl2, Et2AlCl, Et3Al2Cl3, and Et3Al. Chemical shift changes in 1H nuclei remote from the Lewis acid group were found to be remarkably regular and consistent. The study has been extended to tiglaldehyde (2), pent-3-en-2-one (3), cyclohexenone (4), methyl crotonate (5), and crotonitrile (6) and the relationships between the chemical shift differences associated with complexation of these have been explored.

The distribution of poly(acrylic acid) in a microporous polypropylene support membrane has been measured quantitatively by scanning transmission X-ray microscopy (STXM). Singular value decomposition analysis of X-ray microscopy images recorded at carefully selected photon energies was used to obtain quantitative maps of the polypropylene membrane and the poly(acrylic acid) gel, the two components of this system. The sample was studied fully hydrated in order to perform the quantitative mapping when the membrane is the same as in its state of application. Optimum strategies of data acquisition for quantitative X-ray microscopy analysis of radiation sensitive materials are discussed, along with a brief comparison of this technique to alternative methods of mapping the chemical components of structured multicomponent polymeric systems.

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A general model for the formation of thin-film composite membranes, that considers both diffusion- and reaction-controlled interfacial polymerization, under non-steady-state conditions, has been developed. Special models for either diffusion-controlled or reaction-controlled interfacial polymerization with steady- and non-steady-state conditions have been obtained by simplification; these agree with similar models, where available, in the literature. The porosity of the thin film is dependent on the amount of water that diffuses with the aqueous monomer into the formed film. The analytical solution for the model is consistent with the effect of diamine concentration and successfully predicts it for a polysulfonamide composite membrane fabricated from 1,2-ethanediamine and a disulfonyl chloride. The model allows simulation of various factors that affect thin-film formation, particularly for those factors that are difficult to measure experimentally. This work significantly extends existing theories and provides an important guide for effective control of the thickness of the surface barrier layer of thin-film composite membranes prepared by interfacial polymerization.

Abstract:The spectroscopic and structural properties of the perchlorate and triflate salts of N-n-butyl-retinylidene imine, 2 and 3, have been examined in solution and solid phases. In solution these salts were found to exhibit very similar UV and NMR spectroscopic properties. However, in the solid state marked differences in their absorption spectra (2, A, , = 504 nm; 3, A, , , = 445 nm) and I3c NMR spectra were found. The structures of the two salts were determined by X-ray crystallography. The cations in each of the salts were shown to have very similar conformations, detailed structures, and packing in their crystal lattices. The differences in the spectroscopic properties of the salts in the solid state could not be accounted for on the basis of any structural differences in the cations themselves. In terms of cation-anion interactions, a strong hydrogen bonding interaction was found in each case between the N-H proton and an oxygen atom of the counterion. However, there were significant differences between the two salts in terms of the N-H..O internuclear distances (2, N-H...O = 2.939(7) A and in 3,2.85(1) A). The results are strongly suggestive that the wavelength and positive charge delocalization in retinylidene iminium salts are controlled by variation of the distance between the anion and the proton bonded to the Schiff base nitrogen atom. The work reported here represents the first examples of secondary retinylidene iminium salts containing an N-alkyl substituent to be successfully analyzed by X-ray crystallography. The relationship of these observations in the solid state to the spectroscopic properties of the natural visual pigments is explored.Key words: retinylidene iminium salts, iminium salts, cation-anion interactions. Resum6: On a Ctudie les propriCtCs spectroscopiques et structurales des perchlorate et triflate de la N-n-butyl-ritinylidene imine, 2 et 3, tant en solution qu'en phase solide. En solution, on a trouvC que ces sels prCsentent des propriCtCs spectroscopiques UV et RMN qui sont tres semblables. Toutefois, ii I'ttat solide, on a observe des difftrences marqutes dans leurs spectres d'absorption (2, A, , , = 504 nm; 3, A, , , = 445 nm) et dans leurs spectres RMN du I3c. On a determint les structures des deux sels par diffraction des rayons X. Dans chacun de ces sels, les cations ont des conformations, des structures dCtaillCes et des empilements trks semblables. On ne peut pas expliquer les differences observCes dans les propri6tCs spectroscopiques des sels ii l'etat solide sur la base de differences de structures dans les cations eux-mtmes. En termes d'interactions cation-anion, on a observe une forte interaction de liaison hydrogene entre le proton N-H et l'atome d'oxygkne du contre-ion. Toutefois, il existe des differences importantes entre les deux sels en termes de distances internuclCaires (2, N-H...O = 2,939(7) A et dans 3,2,85(1) A. Les rksultats suggerent fortement que la longueur d'onde et la dClocalisation de la charge positive dans les sels rktinylidkne iminium est contr6...