Cellulose absorption wavelength

Air drawn through a cellulose ester membrane (to remove any arsenic particulate) in front of a charcoal tube (100 mg/50 mg) arsine desorbed into 1 mL 0.01 M HN03 (in an ultrasonic bath for more than 30 min contact time) arsenic analyzed by graphite furnace-atomic absorption spectrophotometer at the wavelength 193.7 nm (NIOSH Method 6001, 1985) recommended air flow rate 0.1 L/min sample volume 5 L. 

In a polar polymer, i.e., cellulose acetate (CA) or nitrocellulose (NC) 35E, 35Z, and 36 had a relatively longer absorption maximum wavelength than in less polar matrices. In NC the of 36 shifts to 528 nm, which is also longer than in organic solvents. The role of polymer films in the quantum yields of photoreactions is not clear. In a comparison of the photochemical properties of 35 in polymer films and in solvents, it was found that the E c in polymer matrices was substantially smaller than that in the corresponding solvent with similar polarity. However, the decoloration quantum yield Oc e in a polymer film was larger than that in solvents. In conclusion, the polymer matrix properties, such as polarity, viscosity, and glass transition temperature (Tg) are quite important for photochromic reactions and applications. The coloration, E — Z and Z —> E isomerizations were suppressed in polymer matrices. 

The surface absorptivity or cmissivity of cellulose chars cannot be safely assumed to be near unity. Near unity values are found for wavelengths in the mid-infrared, but at the shorter wavelengths characteristic of thermal radiation in combustion environments, the cmissivity may be closer to 0,8. Significant energy balance errors may be made in assuming higher values. 

Figure 3 is the result of pulse radiolysis experiment about the reaction of hydrated electron with polymer chains(0 or 30 mM carboxymethyl chitosan solution with 0.3 M terf-butanol under Ar saturation), and shows the decay of the absorbance as a function of time. This absorbance was measured at wavelength 720 nm, which is the absorption peak of hydrated electron. As seen in Figure 3, the absorbance increases immediately after the irradiation, and attenuates afterwards. This means that hydrated electron is generated immediately after irradiation and diminishes gradually by some reactions of hydrated electron. Compared the absorbance decay of polymer solution with the decay of solution without polymer, the decay of polymer solution is faster than without polymer, so it is obvious that hydrated electron reacts with polymer chains. The decay curve can be fitted by pseudo first-order decay. The pseudo first-order decay is shown by equation (8). From estimating the slope of the pseudo first-order decay rate of the absorbance at 720 nm against polymer concentration, the rate constant of the reaction of hydrated electron with polymer chains can be calculated Figure 4). The rate constants of the reaction of hydrated electron with CM-chitin and CM-chitosan was determined as l.lxlO7 and MxlO M V1]. These values are almost the same with the value of carboxymethyl cellulose(2< ).

Summarizing, therefore there seems little doubt that direct, photolytic breakdown of cellulose can take place under the influence of wavelengths in the region of 2537 A., although the mechanism of absorption of energy cannot as yet be clearly envisaged. 

The optica] absorption spectra of lignins extend into the visible wavelength region and exhibit peaks at about 205 and 280 nm, and shoulders at 230 and 340 nm [17a]. Polysaccharides such as cellulose and amylose essentially do not absorb light at k > 200 nm. 

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