Effect of surface swelling on diffusion on polymers. II. Delamination

Swelling in chloroform resulted in delamination of surface-hydroxylated styrene-butadiene-styrene block copolymers, with the formation of three fractions: crosslinked gel, reacted sol, and unreacted chloroform-soluble material. From the relative weights of these fractions, the depth of penetration of the reaction and the shape of the reaction front were determined. The weight of the gel fraction gave directly an estimate of the depth of penetration, λ_x which decreased with increasing film thickness. This was attributed to the increased amount of reacted polymer being noncrosslinked material (sol) in the interior compared to the 100% crosslinked nature of the surface region and to a reduction in the penetration of the reaction front resulting from the effect of stress transfer in lowering the permeation rate of peracetic acid. Comparison of the depth of penetration estimates λ_x and λ_s determined from the weight of the unreacted polymer demonstrated that, for the conditions used, the reaction front is quite broad. (For example, at 40°C, in 71% acetic acid for 80 min, the fully crosslinked portion is 15 μm thick and the partially reacted region extends for another 8.5 μm.) The combined influences of the increase in penetration of the reactants in the polymer and the relief of stress secondary to this increase in penetration were reflected in the time dependence of the depths of penetration λ_x and λ_s.     

Microchromatography of hemoglobins. V. Thin-layer chromatography of some hemoglobins on CM-cellulose.

By means of thin-layer ion-exchange chromatography, human hemoglobins A, S, and C in various combinations can be distinctly separated. Also, hemoglobin F can be separated from the A, S, and C components of cord blood samples from infants and in adult blood samples with a relatively high percentage of F (15% or more). The procedure uses CM-cellulose and solutions of Tris-HCl, NaCl, and KCN. A 0.3-mg sample in 5-10 mul of solvent is required. Development can be completed in 30-40 min.     

Studies on Quinones. XX. synthesis of 2-acetonylpyranonaphthoqoinones

A short and efficient synthesis of 2-acetonylpyranonaphthoquinones (13 and 14) starting from Michael adduct 5 is described.     

Further studies on palytoxin. II. structure of palytoxin

The full structure of palytoxin, a potent coelenterate toxin, is reported.