Poly(ethylene oxide) (PEO) of molecular weight from 200,000 to 2,000,000 was crosslinked by exposure to ultraviolet radiation with a high-pressure 150 W mercury lamp. Photochemical crosslinking of PEO proceeds in the presence of photoinitiators such as benzophenone and acetophenone which act as a hydrogen-abstracting agent. Gel fraction yield exceeds 90%, and the number-average molecular weight between crosslinks determined by equilibrium swelling in chloroform varies from 3,000 to 100,000. The degree of crosslinking can be controlled by changing the irradiation temperature.

Novel soluble polyimides containing perylene units have been synthesized. The polymers were prepared in a one-step polycondensation reaction from 1,6,7,12-tetrakis(4-tert-butylphenoxy)-3,4 : 9,lO-perylenedianhydride and aliphatic and aromatic diamines. The amorphous polyimides have a very good solubility in a wide range of organic solvents and exhibit thermal stability up to 350 "C. The polymers consist of 10 to 30 monomer units and show a narrow molecular weight distribution. The dark red materials can be used as polymeric dyes (absorption wavelength A , , = 590-610 nm) and exhibit fluorescence near 620 nm.

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