Laser Scanning Confocal Microscopy Study of Dye Diffusion in Fibers

Abstract

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.

Variations in diffusion coefficient of disperse dyes in single PET fibres: monitored and interpreted by confocal laser scanning microscopy

“…As industrial processes are rarely equilibrium processes an appreciable effort has been spent on trying to understand the kinetics of the dyeing process with the main focus being on the dye diffusion process. Despite this effort, only few references were found that study the dye diffusion directly in single fibres [1,2]. So far the diffusion coefficient (D) of dyes for fibres is commonly determined via the so called 'film roll method' in which a concentrationdistance profile is measured based on the concentrations of dye in adjacent layers of film of known thickness [3][4][5][6][7][8][9][10][11][12].…”

The effect of dye structure on the dyeing and optical properties of dichroic dyes for PVA polarizing film

“…Since the orientation of the polymer chains in a drawn PVA film is not ideal, some part of the polymer chains that are less oriented would exist as defects. Dyes are believed to be adsorbed preferentially on these defects first because the diffusion of dyes in the defects is easier [20]. Therefore, as dyeing time increased, the portion of dyes with a larger q decreased and the dichroic ratios increased to their maxima.…”

Analysis of fibres using microscopy

“…Confocal fluorescence microscopy has also been used for imaging artificial fibres in order to understand dye penetration (Kelch et al 2000;song et al 2000;De Clerck et al 2004, 2005, to localise additives on the surface of fibres (Cortez et al 2004(Cortez et al , 2007Rous et al 2004), and to determine threedimensional structure (Kumar et al 2002).…”