The diffusion of fluorescein into nylon-66 fibers has been studied for the first time by laser scanning confocal microscopy (LSCM). LSCM makes it possible to noninvasively obtain high-resolution three-dimensional images of the spatial distribution of dyes (fluorescein) in fibers dyed for various length of times. Integration over the dye distribution yields the total amount of dye in the fiber, which is found to be in close agreement with that determined by UV−vis spectrophotometry after dissolving the fibers. Thus, the diffusion coefficients determined noninvasively by LSCM ((6.9 ± 1.0) × 10-11 cm2/s) and the destructive traditional means ((7.8 ± 1.9) × 10-11 cm2/s) also agree. The LSCM method has several significant advantages. Among these are its speed, nondestructive nature, and the ability not only to determine the total dye content of the fiber but also to image the dye distribution profile across the fiber diameter. This latter ability is demonstrated to be important to understanding the visual appearance of dyed fibers and fabrics. Two fibers, one ring-dyed and one uniformly dyed, each with the same over all dye content, show remarkably different shades of color. The ring-dyed fiber is lighter, an observation confirmed by the reflectivities measured for each fiber, which were in the ratio ring-dyed/uniformly dyed = 2/1. LSCM observation of dyed fibers provides us not only with a means to measure the dye diffusion coefficient in the fiber, but also the time-dependent, three-dimensional distribution of dye molecules.

S~O P S i SAn analysis is given of the principal thermodynamic factors that influence the distribution of an ion between a macroscopically homogeneous polymer phase and a second homogeneous phase and a general method is proposed for the computation of the equilibrium ion sorptions in well-defined model systems. Particular attention is paid to the sorption of ions by polymers containing ionizable groups and the method is used to clarify some of the current problems in the theoretical explanation of the mechanism of sorption of acid dye anions by polyamide fiben. The method is applicable in principle to any dyeing system in which the fiber phase may be regarded a t equilibrium as a macroscopically homogeneous, equipotential volume.

The mobility of nonionic spin probes in nylon films was investigated by electron spin resonance (ESR). Dried samples were used to avoid the effects of water in the polymer matrices. Effects of drawing were observed only for spin probes having an amino or amide group, suggesting that the orientation of the nylon chain molecules affects the interaction of these spin probes with the macromolecules. Tm, the temperature at which the extrema separation of the ESR spectra becomes 5 mT (50 G), decreased with increasing methylene chain length of the nylon. In other words, the longer the methylene chain, the larger the mobility of the spin probes. In the Arrhenius plots of rotational correlation times one or two crossover points were defined. The number of crossover points was found to vary from probe to probe. For probe molecules carrying substituent groups linked by single bonds two crossover points could be defined. The crossover point at the lower temperature, T, , ', is presumed to be the temperature at which rotation around the single bond occurs, and that at the higher temperature, T,, is considered to be the temperature at which Fotational motion of the whole probe molecule takes place. The dependence of the activation energy for rotation, in the temperature region above T,, on the methylene chain length of the nylon is influenced by the interaction of the probe molecules with the nylons and by the jumping distance of the spin probes.

The equilibrium sorption of ten cationic dyes by porous and regular acrylic fibers has been investigated. The data have been interpreted by a simple Donnan approach, based on the assumption that there are two different types of acidic groups in these fibers. The ionic distribution coefficients KD for the dyes and the fibers were calculated. These coefficients provide an indirect measure of the “affinity” of the dyes for the fibers. The values of KD have been discussed in relation to the structures of the dyes and fibers, and in relation to the effects of salts, pH, and temperature.

The development of a simple but general approach to equilibrium dyeing has stimulated a re-examination of existing data on the sorption of anionic dyes by, cellulosic fibeis. New data are also analyzed.The volume term V of the conventional theories has been replaced by the concept of an average practical ionic distribution coethcient ( K 1 ) P for the inorganic ions in the system. ( K 1 ) P can be measured independently of the dye sorption data.The conventional theories ignore the acidic groups in cellulosic fibers and appear to use incorrect values for V. For these reasons the conventional theories appear to be seriously in error. A direct experimental test of these conclusions is proposed.

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A simple theoretical model of the ion sorption equilibria in cationic dyeing systems has been developed. This model accounts for several aspects of the behavior which cannot be handled by, the existing theories. The parameter values required to fit the model to the data are in agreement with direct independent measurements of these parameters.The selectivity coefficient K Na D shows a complex behavior which cannot be explained by conventional formulations of "ion-binding" processes in the fiber.

The diffusion of Chlorazol Sky Blue FF into cellulose sheet has been studied under a wide range of conditions. Measurements have been made during sorption, desorption and in the steady state. The results explain clearly the variation of apparent diffusion coefficient with salt concentration in this system as first determined by Neale and Stringfellow,l and the disadvantages of the apparent or integral diffusion coefficients as guides to diffusion behaviour are discussed.