Rose Bengal polymeric

The resultant polymeric rose bengals are soluble in solvents like methylene chloride and chloroform, but are not soluble in MeOH with the exception of P -RB- 1520 vrtiich is soluble in a mixture of MeOH/CH2Cl2 (1 1). In addition all of the polymers show the typical carbonyl absorption of an ester between 1725 and 1741 am-1. 

This indicated that the polymer degradation process was likely sensitized by monomeric rather than polymeric rose bengal. 

Quantum Yields of Singlet Oxygen Formation of Soluble Polymeric Rose Bengals in Solution... 

The quantum yields of singlet oxygen fontation from Polymeric Rose Bengals (P-RB) in solution were obtained using the actinone trie method described by Schaap, Thayer, Blossey and Neckers2. 

Neckers, D.C. (1988) Properties of Polymeric Rose Bengals - Polymers as Photochemical Reagents, in Synthesis and Separations Using Functional Polymers (eds D.C. Sherrington and P. Hodge), John Wiley Sons, Inc., New York, pp. 209-26. 

The covalent bonding of photosensitizer moieties such as benzophenone, rose bengal, and eosin to polystyrene yields polymeric photosensitizers that can be used to bring about excitation and subsequent chemical reaction in low-molecular-weight substrates [Neckers, 1986 Nishikubo et al., 1989]. 

Fig. 9 Top Rose-bengal-stained fluorescence images of photograft-polymerized regions of Models Ay B and C as a function of photopolymerization time or copolymer composition of CMS (see Fig. 8 legend). These indicate that stem-chain length (Model A), daughter-chain length (Model B) and daughter-chain density (Model C) are well-controlled. Bottom Change in fluorescence intensity as a fimction of photopolymerization time or copolymer composition of CMS CMS Chloromethyl styrene...

Fig. 11 Visualization of the sequential progress of branching stage by staining with rose bengal. DC-derivatized PST surface (GO) was graft-copolymerized with CMS and dimethylaminoethyl acrylamide (DMAEMA), and subsequent quarternization, while narrowing the irradiation area in each polymerization stage (item, GI item, GI+GII item, GI+GII- -GIII) by the combination of three kinds of masks with linear openings (line widths 2 mm for GI, 1 mm for GII, 0.5 mm for GUI). Bar=0.5 mm...

Photoreduction of Eosin, Erythrosin, and Rose Bengal with amines has been employed for a number of years to initiate polymerization of monomers in the absence of solvent. Examples of recent applications include the production of volume holograms [181], color images on plain paper [182], printing plates [183-185], and, in the presence of suitable peroxides, manufacture of coatings for glass fibers [186]. 

Electron transfer to the xanthenes, particularly reduction with amines, has been used for a number of years to initiate acrylate polymerization. A typical system is that reported to form volume holograms—lithium or zinc acrylate, triethanolamine and Eosin, Erythrosin, or Rose Bengal [290], Similar mixtures are used to form printing plates photoreducible dye, phenylac-ridine, and acrylate monomer [292], A recent patent application discloses aryl iodonium salts, Rose Bengal, and oxidizable triazines such as 2-methyl-4,6-bis(trichloromethyl)-s-triazine to polymerize acrylates [292],... 

Among the more interesting applications of polymer Rose Bengal is that of a sensitizer in studying the oxidation of other polymeric substrates [301]. Rose Bengal immobilized on Sepharose has been reported as a sensitizer for protein photooxidation [302], The oxygen uptake by the amino acids cysteine, hisitidine, methionine, tryptophan, and tyrosine was reported to be about 20% as much from the immobilized dye as from the free dye in aqueous solution. 

The patent and open literature were searched for examples of dye sensitized photopolymerization in which a common monomer (acrylamide), and one of several common dyes (thionine, T methylene blue, MB or rose bengal, RB) were used in combination with a stated concentration of an activator. The polymerization conditions (monomer concentration, light intensity absorbed, and extent conversion) were stated in each case chosen for inclusion. The relative photospeed of the system was calculated based on several corrections to the raw data. We here define the relative photospeed of a composition as the inverse of the exposure time t needed to effect some fixed percentage of monomer conversion. 

Until the beginning of this work, little was known about the effect of the polymer on the behavior of the sensitizer, rose bengal. In this paper we shall establish that the polymer is indeed an extremely important component of the chemistry of polymeric derivatives of rose bengal. 

It was our intention when this new work began to outline, more fully, the effect of the polymeric structure on the effectiveness of rose bengal as a photosensitizer and to compare the behavior of the polymer-bound dye to the behavior of the dye - free - in solution. In the present paper, therefore, we report on the photochemical and spectral properties of new singlet oxygen sensitizers based on soluble polystyrenes. These new derivatives are referred to as P -RB. 

It is clear that as the amount of rose bengal attached to the polymeric support increased in the regime where the polymer can be called "lightly functionalized", the quantum yield of singlet oxygen formation increases also, reaching a maximum value for the... 

Both curves have similar shapes and it is clear that the photooxidation process is controlled by the diffusion of oxygen into the rose bengal sites in the polymer solution. These results suggest that when a snail amount of rose bengal is attached to the polymeric backbone (P-RB-51, 102 152 305) the quantum yield of of singlet oxygen formation is essentially the same (about 0.38). 

Another similar example, also used in polymerization initiation, is the case of the iodonium salts of Rose Bengal (RB2-) [224, 225]. Methylene chloride solutions of these salts bleach in a few seconds in room light through an electron transfer photoinduced from the excited RB2- to the iodonium cation the resulting phenyl radicals were reported to initiate polymerization of acrylate. 

Figure 6. Rate of heat evolution during argon-ion laser-photoinitiated polymerization of 1-methyl-2-pyrrolidinone (MP), 9 ML of 2-ethyl-2-(hydroxymethyl)-l,3-propanediol triacrylate (TMPTA), and the dyes at a concentration of 10 m. Initiators 1) 19, 2) 18, 3) 10, 4) 16, 5) RBAX (rose bengal derivative prepared from rose bengal, which is first decarboxylated and then acetylated [36]),...

The use of dye-sensitized initiation in polymerization dates to 1949 when Bamford and Dewar observed that some vat dyes could sensitize the photopolymerization of styrene. This was quickly followed up hy Gerald Oster s discovery " in 1954 that the polymerization of acrylonitrile and of acrylamide could be photoinitiated by fluorescein, rose bengal, and similar dyes, in the presence of reducing agents (such as phenylhydrazine, ascorbic acid) and oxygen. Remarkably, the amount of dye required for the photoinitiation event was extremely small ( 0.1% of the weight of monomer), and the quantum yield of monomer consumption was in excess of 4000 monomer units per photon. " ... 

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