Synthesis of branched polymers by means of living anionic polymerization, 9 - Radical coupling reaction of 1,1-diphenylethylene-functionalized polymers with potassium naphthalenide and its application to syntheses of in-chain-functionalized polymers and star-branched polymers

Radical coupling reactions of both 1,1-diphenylethylene (DPE)-chain-end- and DPE-in-chain-functionalized polymers with potassium napbtlialenide have been studied under the conditions mainly in THF at -78degreesC. Chain-end-functionalized polymers having (M) over bar (n) values of less than 10 kg/mol were very efficiently coupled in more than 90% yield to afford the polymeric dianion that were dimeric coupled products with two 1,1-diphenylalkyl anions in the middle of the chains; However, the dimer yield decreased with increasing the molecular weight. The dimer was obtained in 59% yield with use of the chain-end-functionalized polymer having (M) over bar (n) of 33.9 kg/mol. Well-defined in-chain-functionalized polymers with two benzyl bromide and DPE moieties each have been successfully synthesized by the reaction of the polymeric dianion thus obtained with, 1-(4-bromobutyl)-4-(tert-butyldimethylsilyloxymethyl)benzene and, 1-[4-(4-bromobutyl)-phenyl]-1-phenylethylene, respectively. The radical coupling reaction of in-chaing-functionalized polymers with DPRE ((M) over bar (n) ca. 20 kg/mol) with potassium naphthalenide also proceeded efficiently to afford the coupled products that were A(2)A'(2) and A(2)B(2) four-arm star-branched polymers. with well-defined structures ((M) over bar (n) ca. 40 kg/mol).