Ultrasonic synthesis of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene]

Poly [2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene](MEH-PPV) is a typical example of solution processable conjugated polymers for polymeric light emitting diodes application, which shows good solubility in common organic solvents. However, gelation or micro-gelation always occurs during the polymerization process. Herein, we report the synthesis of fully soluble MEH-PPV by ultrasonic irradiation method. The raw material was 4-methoxyphenol, and ultrasonic irradiation method was used in the etherification, bromomethylation and polymerization. The polymer is prepared from the bis-bromomethyl monomer through the Gilch route. Compared with the conventional mechanical stirring, ultrasonic irradiation method has shown great advantages with respect to the shorter reaction time, lower reaction temperature, higher yields and higher molecular weight ( M) of MEH-PPV. The optimized reaction conditions including reaction solvent, temperature, and time, were determined for the related etherification I bromomethylation and polymerization with ultrasonic method. Especially, using ultrasonic method, the gelatification in the polymerization had been overcome. MEH-PPV obtained was fully soluble in THF and chloroform and no gel or micro-gel existed. The structures of the intermediate products and MEH-PPV were determined by IR and H-1-NMR. It was found the MEH-PPV synthesized by ultrasonic irradiation processes had higher luminescence quantum efficiency than that by mechanical stirring.