Mass transfer coupled with the relaxation of a polymeric matrix: A controlled release process

A solution to Fick's equation is presented which accurately predicts the transfer of mass out of a polymeric rod or sheet undergoing relaxation by a solvent permeating it by Case II transport. There is a critical length. Before the solvent permeates to this length the diffusible material can diffuse away from the moving boundary faster than it is becoming available at the boundary. Afterward the reverse is true. Five sets of experimental data from three different sources have been used to test the model. The agreement is excellent.     

Synthesis and antimicrobial activity of 4-aza-5α-sitostane and the 4-methyl derivative

Synthesis of 4-aza-5α-sitostane (IX), and 4-methyl-4-aza-5α-sitostane (XII) were accomplished through a set of reactions involving oxidative opening of ring A of α,β-unsaturated ketone, ring closure, followed by catalytic hydrogenation and lithium aluminum hydride reduction, respectively. The antimicrobial activity for X and XII is reported.     

Quantized RRK theory of unimolecular reaction rates

The main difference between the simple RRK theory and the better based but more complex RRKM theory is explained. Starting from the premise that the classical versus quantum mechanical estimation of the density of states is the major source of the difference, earlier attempts to incorporate the quantum effects in an effective value for the number of oscillators s are noted. By examining the expression for the RRKM rate coefficient it is found that a single effective s value will generally not suffice, but a much better representation of the quantum effects can be obtained if it is recognized that the problem inherently contains two different effective s values. A theory based on this analysis is constructed. It reproduces RRKM results to much improved accuracy, removing difficulties found earlier with single-s-value theories.     

Friedel crafts reactions of three-member heterocycles I. Reaction of propylene oxide with benzene

The Friedel Crafts reaction of propylene oxide with benzene has been reinvestigated, and under anhydrous conditions the product is 2-phenylpropanol.     

Thermal and photo-decomposition of 1,4-disubstituted alkylaminoanthraquinone dyes in polymers and solution: A chromatographic and spectroscopic study

The photo-decomposition products of five 1,4-disubstituted anthraquinones produced in polyester and nylon 6,6 fabrics and related solvents have been compared with those produced in the thermal oxidation of the dyes on silica gel plates at 150°C. Using TLC, ultraviolet-visible absorption spectroscopy and mass spectrometry, the decomposition products were found to be generally very similar. The number and complexity of the products formed were found to be very dependent on the duration of exposure. These results indicated that the thermal and light stability of the dye is considerably less than that predicted by normal visual colour assessments. From an analysis of the products of decomposition early theories on N-dealkylation are confirmed and their arguments on N-formylation are partially resolved.     

Light absorbing species in polyolefins: A fluorescence/derivative UV spectroscopy study

Further novel observations are reported on the nature of the hexane extractable fluorescent species in four polyolefins, namely low and high density polyethylene, polypropylene and poly (4-methylpent-1-ene). The concentration of fluorescent species extracted follows the order poly(4-methylpent-1-ene) > polypropylene > low density polyethylene ≡ high density polyethylene which follows closely the known photo-oxidation rates of the polymers. The total fluorescence spectrum is shown to be a complex mixture of several components and this is supported by second order derivative ultraviolet spectroscopy. Comparison of corrected fluorescence excitation spectra of the polymers with that of naphthalene shows several anomalies which suggest that the latter is not the major fluorescent species.     

An equation for creep in terms of craze parameters

The creep curves of poly(chlorotrifluoroethylene) (PCTFE) and poly(methyl methacrylate) (PMMA) were measured at temperatures near 78°K in nitrogen environments so that practically all the creep strain was produced by crazing. Data were obtained over a range of temperatures, stresses, and partial pressures of the nitrogen. It was found that all creep curves had the form, ε^1/3 = ε + st, where ε₀ is the initial strain (～10^?4) and s is a constant which depends on the conditions of the test. The microparameters such as number, dimensions, and velocity of the crazes were measured in each speciman. A theoretical creep equation was derived in terms of these microparameters. There was good quantitative agreement between theory and the experiments.     

A structure theory for two-dimensional translation planes of order q 2 that admit collineation groups of order q 2

This paper is devoted to the study of translation planes of order q ² and kernel GF(q) that admit a collineation group of order q ² in the linear translation complement. We give a representation of this group by a suitable set of matrices depending on some functions over GF(q). Using this representation we obtain several results concerning the existence and the collineation group of the plane.