SEQUENCE-REGULATED OLIGOMERS AND POLYMERS BY LIVING CATIONIC POLYMERIZATION .2. PRINCIPLE OF SEQUENCE REGULATION AND SYNTHESIS OF SEQUENCE-REGULATED OLIGOMERS OF FUNCTIONAL VINYL ETHERS AND STYRENE DERIVATIVES

Vinyl ether oligomers with controlled repeat unit sequences were prepared by living cationic polymerization initiated with the hydrogen iodide/zinc iodide (HI/ZnI2) system. The synthesis involved sequential and successive reactions of two, three, or four vinyl ethers (each equimolar to hydrogen iodide) in toluene at -40 to -78 °C, starting from quantitative formation of an adduct [HCH2CH(OR)I] of HI and a vinyl ether, followed by activation with Znl2; thus, the repeat unit sequence was controlled by the order of monomer addition. The employed vinyl ethers (CH2=CHOR) included not only alkyl (R = alkyl) but functionalized derivatives with such pendant groups as ethyl malonate [R = CH2CH2CH(COOEt)2], benzoyloxy (R = CH2CH2OCOPh), methacryloyl [R = CH2CH2OCOC(CH3)=CH2], and chlorine (R = CH2CH2Cl). A sequence-regulated trimer having a p-methoxystyrene unit was also prepared: CH3CH(OC4H9)CH2CH-(OCH2CH2OCOPh)CH2CH(C6H4OCH3)OCH3. The yields of the sequence-regulated oligomers were greatly dependent on the order of monomer addition, and the highest yields were obtained by adding monomers in the order of their decreasing reactivity. Thermospray mass spectroscopy permitted us to determine the absolute molecular weights and the repeat unit sequence of the oligomers. © 1990, American Chemical Society. All rights reserved.