Ultraviolet absorption, 598 Poly

Table III. Ultraviolet Absorption Properties of High Molecular Weight Poly(organosilanes).

Vandercook and Rolle (11) investigated the ultraviolet absorption characteristics of alcoholic solutions of California-Arizona lemon juice. They reported that the ratio of the absorbance of 273-277 nm to the absorbance of 326-332 nm was essentially constant. From analyses of the spectra obtained of other fruit juices, they indicated if one were added to lemon juice its presence could be detected by a displacement of this ratio. Vandercook et aK (12) observed a significant increase in total poly-phenolic absorbance at 330 nm, of lemon juice, with extraction pressure. However, there was no significant change in the A/B absorbance ratio (273/326). 

Fig. 7. Ultraviolet absorption spectra of poly-L-lysine hydrochloride in aqueous solution random coil, pH 6.0, 25°C helix, pH 10.8, 25°C /3-form, pH 10.8, 52°C.

A comparison of the photosensitivity of poly(vinyl cinnamate) with the photodimerization of cinnamic acid in poly(vinyl alcohol) coatings was carried out by Nakamura and Kikuchi 44>. Cinnamic acid in polyvinyl alcohol) coatings was found to undergo photoisomerization as well as photodimerization. The ultraviolet absorption spectra used to follow the course of the reaction showed one isosbestic point together with other nonisosbestic curve intersections. Such complex curve changes indicated that photoisomerization and at least one other reaction, photodimerization, was occurring. 

Llumar, poly(ethylene terephthalate) (ICI, Melinex 0 that is aluminized and sold by Martin Processing Inc., PET /Al, 3 mil) and FEK-244, aluminized poly(methyl methacrylate) with adhesive backing, PMMA (3M)/Al/adhesive (3M 4 mil polymer). Some of the bulk polymers were compounded with 3 wt% carbon black (Cabot s Vulcan 3), designated with a subscript c, to reduce ultraviolet absorption. 

Stock solutions of the two polymers were prepared separately at about one-tenth the concentration to be used for the infrared spectra. The NaCl concentration was 0.01 i /, the sodium cacodylate concentration was 0.(X)5, and the pH was adjusted to 7.5. After the concentrations were determined by ultraviolet absorption, equivalent amounts of the polymers were mixed, and a 15 % decrease in intensity was observed in the solution, which was 0.0032i / in each polymer and 0.01 M in NaCl. The solution was allowed to stand 5 hr, then lyophilized, redissolved in 0.1 ml DjO, and the pH adjusted to 7.6. The NaCl concentration was then about 0.18 and the sodium cacodylate concentration was about 0.09. The 0.060 solution of poly A + poly U was made up with 0.1 ml of 0.1 NaCl and 0.1 M sodium cacodylate instead of pure DjO. A molar absorptivity of 15,400 was calculated from the values 9800 for poly A (Warner, 1957) and 9430 for poly U (Felsenfeld and Rich, 1957) as reduced by a 20% hypochromic effect in the more concentrated salt solution. The concentration of an aliquot of the polymer solution was then determined using this value. 

Figure 8.2. Ultraviolet absorption spectra of 0.05-mm polymer films and spectral irra-diance of July noon sunlight (direct beam) at 41°N latitude AP = aromatic polyester PAR = polyarylate PC = polycarbonate PE = polyethylene PET = poly(ethylene tere-phthalate) PS = polystyrene PSF = polysulfone PVC = poly(vinyl chloride). (Reprinted with permission of Technomic Publishing Co. [4].)...

Fig. 3.23. Ultraviolet absorption spectra of poly(vinyl acetate) film (123 fxM thick) UV irradiated (253.7 nm) at room temperature under vacuum Irradiation time (1) = 0 (2) = 6 min (3) = 12 min (4) = 25 min (5) 52 min and (6) (103) min. (Reprinted with permission from [749], Pergamon Press Ltd, Oxford, England.)...

Fig. 3.27. Ultraviolet absorption spectra of a poly(phenyl acrylate) film after different times of UV irradiation at room temperature [874]. (Reprinted with permission from [874]. Copyright (1984) American Chemical Society.)...

Fig. 339. Ultraviolet absorption spectra of poly(styrene-butadiene) films at different UV irradiation times. (Reprinted with permission from [293], Pergamon Press Ltd, Oxford, England.)... 

Fig. 4. Ultraviolet absorption spectra of poly(2,6-dimethyl-l,4-phenylene oxide) UV irradiated (at 253.7 nm) in air at different times 0, 1, 2, 5,10, 20, 30,45, 60,120, 240 min (provided by Dr H. Kaczmarek).

Fig. 4.9. Change in the ultraviolet absorption spectrum of poly(hexamethylene-a-truxillamide) during UV irradiation at 224 nm [2088]. (Reproduced with permission from [2088] published by John Wiley Sons, Inc., 1971.)...

Chen, R., Johnson, J.M., Bradforth, S.E., and Hogen-Esch, TJi. (2003) Ultraviolet absorption and fluorescence emission spectroscopic studies of macrocyclic and linear poly(9,9-dimethyl-2-vinylfluorene). Evidence far ground-state chromophore interactions. Macromolecules, 36,9966-9970. 

Imahori, K., Tanaka, J. Ultraviolet absorption spectra of poly-L-glutamic acid. J. molec. Biol. 1, 359—364 (1959). 

Figure 3. Ultraviolet Absorption Spectra for 3.5 micrometer thick film of PMDA/ODA based poly(amic ethyl ester).

The absorption and emission of radiation in the near ultraviolet (UV) and visible regions of the electromagnetic spectrum are associated with electronic (and associated vibronic) transitions involving n- and/or n-electron systems of molecules. Synthetic and natural polymers absorb in the UV region and particularly strong absorption spectra are recorded for polymers containing aromatic and heteroaromatic groups (e.g., poly(styrenes), poly(vinyl naphthalenes), poly(vinyl carbazoles)). 

Fig. 23. Spectra photoconductivity of poly(p,p -diethynylazobenzene ]), the same after 10 min under ultraviolet irradiation (2) photoelectromotive force (3) absorption in diffuse reflection (4) [95]...

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