Lichtstreubefunde zur Kettenspaltung von Polystyrol in sauerstoffreien CCl₄‐ und CHCl₃‐Lösungen bei Lichteinwirkung der Wellenlängen λ ≥ 270 nm

Abstract

The photodegradation of polystyrene (PS) in deoxygenated solutions of CCb and CHCl, by irradiation with ultraviolet light of wavelengths 1 2 270 nm is investigated by quasielastic and integral light scatte_ring techniques. Molar mass distributions w (M), number-and weight-average molar masses % and M , as well as the average number of chain scissions per macromolecule x ( t ) as a function of the time of irradiation t were determined. The results obtained prove that efficient photodegradation occurs in CCb-and CHC1,-solutions of PS, although measurable changes in molar mass of irradiated PS starts to occur only after several hours of irradiation.

Effect of Medium Acidity and Photostability of 3‐(4‐Dimethylamino‐phenyl)‐1‐(2,5‐dimethyl‐thiophen‐3‐yl)‐propenone (DDTP): A New Green Emitting Laser Dye

“…The photodecomposition of several compounds has been reported earlier. [23][24][25][26][27][28][29] Also a similar behavior has been reported earlier for some heteroaryl chalcone derivatives. [12][13][14] Laser activity of DDTP in DMF solvent DDTP is characterized by high fluorescence quantum yield (ϕ f ＝0.78), high molar absorptivity at 337 nm (ε＝18300 L•mol -1 •cm -1 ) and high photostability (ϕ c ＝ 0.0018) in DMF ( Figure 5).…”

Photophysical Parameters, Excitation Energy Transfer, and Photoreactivity of 1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOP) Laser Dye

“…The net photochemical quantum yields of the underlying reaction were calculated as 0.61, 0.103, and 0.067 for CCl 4 , CHCl 3 , and CH 2 Cl 2 , respectively ( Figure 9). The formation of photoproduct is a one photon process as represented by the well-known mechanism [64][65][66][67]:…”

Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye

“…The net photochemical quantum yield (f c ) of the underlying reaction was calculated as 0.054. The formation of photoproduct is a one-photon process and is represented by the following scheme as reported earlier [40][41][42][43][44][45][46] for some aliphatic and aromatic amines and for aromatic hydrocarbons such as anthracene and perylene derivatives. It was proposed that the electron transfer from excited singlet DEAC n to CCl 4 within transient excited charge-transfer complex is the main primary photochemical process (step 3).…”