Dyes In Polymer Films Research Articles

PH indicator based ammonia gas sensor: studies of spectral performance under variable conditions of temperature and humidity

Polymer-dye films, incorporating immobilized Bromocresol Purple pH indicator, can be used for ammonia gas sensing under the temperature and humidity variations that can occur during field operating conditions. To reveal the spectral features of the polymer-dye films, comparative spectral studies of the indicator dissolved in water and immobilized on the polymer matrix were performed. The modified absorption band of the immobilized indicator base form indicates the formation of an indicator-polymer ionic complex. Variations in the temperature (20–40 °C) and relative humidity (50–85%) of the monitored ammonia gas produced noticeable distortions of the short-wavelength wing of the band profile and also of its peak. The long-wavelength wing of the band profile was relatively stable under these conditions and demonstrated a good correspondence to the Gaussian-shaped curve.

Spectral hole-burning study of squaraine dyes in polymer films

A study of the hole-burning mechanisms of bis[4-(diethylamino)-2-hydroxyphenyl]squaraine (DEAH) and bis[4-(disethylamino)-phenyl]squaraine (DEA) in hydrogen-bonding and non-hydrogen-bonding polymers is presented. Intramolecular H-bonding is only possible for DEAH. In all systems, the spectral holes are not persistent and decay with a distribution of rates ranging from 10 -5s -1 to about 1 s -1, the time resolution of the experiment. In H-donating matrices, this distribution varies with the burning wavelength. From the hole-burning efficiencies and the kineticsof the hole refilling, four different types of nonphotochemical hole-burning mechanisms are postulated. The efficiency of these mechanisms depends mainly on the occurrence of processes slowing down the relaxation to the initial product state.

Absorption studies of polymer-dye films oriented by corona poling

In this letter we describe the corona poling of thin films of a guest-host material and the use of ordinary linear-optical absorption to monitor the orientational order and its temporal decay. Disperse orange 3 (DO3) was used as the guest for the polymer host poly(methyl methacrylate) (pmma)

Absorption Studies of Optically Nonlinear Side-Chain Polymer and Polymer-Dye Films Oriented by Corona Poling

Absorption Studies of Optically Nonlinear Side-Chain Polymer and Polymer-Dye Films Oriented by Corona Poling

Photo-induced reaction of dye in polymer media—I. Unannealed polymer matrices

The amber Aberchrome 540 dye [( E)-α-(2,5-dimethyl-3-furylethylidene) (isopropylidene) succinic anhydride] in its ring-opened form ( A) when irradiated with u.v. light ( λ > 300 nm) undergoes conrotatory ring-closure to give a red dye ( B) [7,7a-dihydro-2,4,7,7,7a-pentamethylbenzo [b] furan-5,6-dicarboxylic anhydride]. The red form B may be reversed to form A in the photodecolouration reaction using visible light. The kinetics of the photodecolouration of form B in a number of unannealed solid polymer films have been investigated over the range 303–343 K by following the changes in λ max at 493 nm with a spectrophotometer. Analyses of the results have shown that the photodecolouration in various polymer matrices follows a simple first-order reaction. This allows for the extraction of the apparent first-order rate constants and activation energies. The polymer matrices employed are polystyrene, poly( p-t-butylstyrene), poly(methyl methacrylate), poly(n-butyl methacrylate) and poly(vinyl acetate). The rate of the photo-induced reaction of the dye has been found to be very sensitive to changes in the micro-environment of the dye in the polymer matrix such as the polarity, free volume and the molecular motions. This finding is consistent with the results of the dielectric relaxation studies of some of the polymers. A comparison is made between this reaction and the thermally induced isomerization of other dyes in polymer films, e.g. spiropyran derivatives.

Micrometer-domain fluorescence dynamics of xanthene dyes in polymer films

We present fluorescence decays of xanthene dyes in polymer films from spatial domains as small as 0.5 μm, observed from submicron gold/quartz heterostructures, spin coated by dye/polymer solutions. The fluorescence decays observed from gold and quartz domains were nonexponential and had components with lifetimes between 0.2–3.9 ns for 3×10 −3 M rhodamine 3B/PMMA. In case of 1 μm thick polymer films, the gold domains typically decayed faster than the inter-electrode quartz domains. Comparative studies of spincoated films and bulk systems showed that the fluorescence dynamics depend strongly on the method of sample preparation. Dye/polymer systems, produced by polymerization of dye/precursor solutions, revealed a strong annealing effect of the host matrix by in situ monitoring the temperature-dependent fluorescence dynamics of the guest.

Tryptophan sensitised fading of acid dyes in polymer films

It has been shown that tryptophan, the strongly absorbing and most photo-active component of wool, sensitises the fading of acid dyes in poly(vinyl alcohol) and methyl cellulose films. The effect is more pronounced in the PVA which is impervious to oxygen. The triplet state of tryptophan is involved, most probably by the formation of an excited state complex with the dye. Derivatives of tryptophan containing no ionised carboxyl groups gave no sensitisation, thus indicating that protein bound tryptophan would not sensitise dye fading by this mechanism.

Ablative optical recording using organic dye-in-polymer films

Ablative optical recording using dissolved dyes in polymer films has been investigated. Polyester yellow dissolved in poly(vinyl acetate) was used as a model to study the potential for high-sensitivity, high-density optical storage applications. With 20% dye loading, a 59-nm film was more sensitive at 457 nm than a 15-nm Te monolayer, and marks down to 0.5 μm were recorded. The signal contrast (Rf−Ri)/(Rf+Ri) was approximately 0.68 for marks ablated with high-energy laser pulses. The morphology of the marks shows a clean removal of recording material. Suitable polymeric overcoatings, used to simulate second-surface recording situations, had little effect on the results.

The Diffusion of Disperse Dyes in Polymer Films

The diffusion of disperse dyes in various polymer films has been studied by a microdensitometric technique. The films were dyed in aqueous dye dispersions, in presence and in absence of dyeing accelerants, and in solutions of dye in organic solvents. Dyeing of appropriately pretreated films conformed to the model of Fickian sorption, whereas dyeing of polymer films in the presence of dyeing accelerants showed in some instances marked deviations from this model. These results are discussed in terms of modern theories of diffusion.

Diffusion of dyes in polymer films. Part 4.—Benzopurine 4B and its meta isomer in cellulose

Diffusion of dyes in polymer films. Part 4.—Benzopurine 4B and its meta isomer in cellulose

A Study of the Diffusion of Dyes in Polymer Films by a Micro densitometric Technique

The concentration distributions of dye which are established inside polymer films during dyeing have been determined for the following systems: a disperse dye in cellulose acetate and in nylon, a direct dye in cellulose, and an acid dye in nylon. The results have been analysed to give the variation of diffusion coefficient with dye concentration: this information has been correlated with the practical behaviour of these systems and with their thermodynamic properties.