Azobisisobutyronitrile → Methyl Methacrylate 3-Allyl-4,4'-Dimethoxy-2-Hydroxy-Benzophenone

Participants

Reaction Conditions

Reaction Steps

A 250 ml., three-necked flask equipped with nitrogen inlet, condender, thermometer, and a magnetic stirrer was charged with a solution of 0.5 grams of 3-allyl-4,4'-dimethoxy-2-hydroxy-benzophenone, 5 grams of freshly distilled methyl methacrylate and 0.1 grams of α,α'-azobisisobutyronitrile in 100 ml of dimethyl sulfoxide/dioxane (1:9). All starting materials and solvents were dried prior to use. The reaction vessel was flushed with dry nitrogen for 10-15 minutes and then placed in a constant temperature water bath at 55 degrees C. for 12 hours, then was raised to 80 degrees C., and maintained at that temperature for an additional 24 hours. The contents of the flask were then slowly poured into a waring blender, containing 500 ml of methanol. The product was collected by filtration, washed with two-50 ml portions of methanol, and dried in vacuo at 40 degrees C. The crude polymer was dissolved in methylene chloride, the solution was filtered and the filtrate added to a large excess of methanol as described above. The polymer was further purified by exhaustive extraction with methanol in a soxhlet extraction apparatus for 100 hours. Small samples of the polymer were taken out, dissolved in methylene chloride and their UV-spectrum taken. The polymer extraction continued until a constant UV-absorbance was obtained at 320 mm. The product contains 0.43% of the 2-hydroxy-benzophenone UV-absorber as copolymer, and no other change in this concentration was observed after the 40th hour of extraction. The final product was dried in vacuo at 40 degrees C. to yield 4.95 grams of copolymer. The gel-permeation chromatography curve indicates that homogenous copolymer with Mw =83,000 has been produced. A Waters associates, Model 6000 gel permeation chromatograph, packed with a bank of four styragel columns and standardized with commercial monodisperse polystyrene fractions was used to obtain the GPC curves. The ultraviolet spectrum of the materials exhibits λ max at 304 nm (a=0.264) in methylene chloride.

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