Chromic polymers

Kago, K., Fiirst, M., Matsuoka, H., Yamaoka, H., and Seki, T. Nanostructure of photo-chromic polymer/liquid crystal hybrid monolayer on water surface observed by in-situ x-ray rellectometry. Langmuir, 15, 2237 (1999). 

The utilization of such field-induced chromic effects 1 be the subject of this chapter and we will review some examples in which the external stimuli can be varied from heat, light, ions or biological moieties while the side-chain moieties are tuned accordingly. A brief presentation of conjugated polymers will be also provided as well as a presentation of different chromic polymers and finally some possible applications will be discussed. 

Etcole F, Davis TP, Evans RA (2010) Photo-responsive systems and biomaterials photo-chromic polymers, light-triggered self-assembly, surface modification, fluorescence modulation and beyond. Polym Chem l(l) 37-54. doi 10.1039/b9py00300b... 

D. M. Welsh, A. Kumar, M. C. Morvant, and J. R. Reynolds. 1999. Fast electro-chromic polymers based on new poly(3,4-alkylenedioxythiophene) derivatives. 

J. L. Reddinger, G. A. Sotzing, and J. R. Reynolds. 1996. Multicoloured electro-chromic polymers derived from easily oxidized bis[2-(3,4-ethylenedioxy)thie-nyl]carbazoles. Chem Commun 1996 1977-1978. 

Sihcone products dominate the pressure-sensitive adhesive release paper market, but other materials such as Quilon (E.I. du Pont de Nemours Co., Inc.), a Werner-type chromium complex, stearato chromic chloride [12768-56-8] are also used. Various base papers are used, including polyethylene-coated kraft as well as polymer substrates such as polyethylene or polyester film. Sihcone coatings that cross-link to form a film and also bond to the cellulose are used in various forms, such as solvent and solventless dispersions and emulsions. Technical requirements for the coated papers include good release, no contamination of the adhesive being protected, no blocking in roUs, good solvent holdout with respect to adhesives appHed from solvent, and good thermal and dimensional stabiUty (see Silicon COMPOUNDS, silicones). 

ABS plastic, a polymer consisting of polybutadiene spheroids is dispersed in a continuous phase of poly(styrene—acrylonitrile). The chromic acid attacks the polybutadiene at a much higher rate than the continuous phase. This gives an excellent microroughened surface with superior metal-to-plastic bond strength. A typical recommended formulation consists of 20 vol % sulfuric acid, 420 g/L chromic acid, and 0.1—1.0% of a fluorocarbon wetting agent. The plastic is treated with this formulation for 6—10 min at 60—65°C. 

While polymeric surfaces with relatively high surface energies (e.g. polyimides, ABS, polycarbonate, polyamides) can be adhered to readily without surface treatment, low surface energy polymers such as olefins, silicones, and fluoropolymers require surface treatments to increase the surface energy. Various oxidation techniques (such as flame, corona, plasma treatment, or chromic acid etching) allow strong bonds to be obtained to such polymers. 

When a polymer is soaked in a heavily oxidative chemical liquid, such as chromic anhydride-tetrachloroeth-ane, chromic acid-acetic acid, and chromic acid-sulfuric acid, and treated under suitable conditions, polar groups are introduced on the polymer surface and the surface characteristics are improved [49,50]. The sur-... 

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

Chromium(III) is a commonly-used crosslinker for preparing profile control gels with polymers having carboxylate and amide functionalities (la,b). Cr(III) is applied in many forms. For example, it can be used in the form of simple chromic salts of chloride and sulfate, or as complexed Cr(III) used in leather tanning (2), or as in situ generated Cr(III) from the redox reaction of dichromate and bisulfite or thiourea. The gelation rate and gel quality depend on which form of Cr(III) is used. 

Through a combination of X-ray crystallography and solid-state NMR studies, they were able to correlate chromic transitions with motion, and an increase in disorder within the backbone of the polymer [1]. As the temperature increased, so did disorder within the polymer, resulting in a blue-shift of the UV-vis spectra (Fig. 4). 

Optical transitions of CPs can also be induced by switching the net charge of the polymer side chain. By using a zwitter-ionic polythiophene derivative, POWT, Nilsson and co-workers were able to induce different chromic transitions by... 

Although conjugated polymers can be both n-doped and p-doped - and thus, in principle, be capable of behaving either as negative or as positive electrodes - the majority of applications have been confined to the p-doping, positive side. Conductive polymers have been proposed and tested in a variety of advanced electrochemical devices. Due to lack of space, we will confine our attention to the description of the most illustrative examples which are rechargeable lithium batteries and multi-chromic optical displays. 

Marsella MJ, Swager TM. Designing conducting polymer-based sensors—selective iono-chromic response in crown-ether containing polythiophenes. J Am Chem Soc 1993 115 12214-12215. 

Polyolefins are resistant to aqueous solutions of inorganic acids such as hydrochloric, phosphoric, and sulfuric acids. These polymers are also resistant to chromic and nitric acids but react with them as well as with dinitrogen tetroxide at elevated temperatures. Polymers with tertiary hydrogen atoms, such as PP, are more readily oxidized than those with only secondary hydrogen atoms, such as hope. 

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