POS1-0596
Anionic polymerization of functional styrenes in hydrocarbon solvent
When and Where
Nov 30, -0001
12:00am - 12:00am
Presenter(s)
yota sano (Institute of science tokyo)
Co-Author(s)
Abstract
Anionic polymerization of functional monomers in nonpolar hydrocarbon solvents has been limited because of the low solubility of the polymers and the inherent side reactions of the initiators and the propagating carbanion even at room temperature. We selected N,N-diethyl-4-vinylbenzamide (1) to expand the range of monomers applicable to anionic polymerization in hydrocarbons. We have succeeded in the living anionic polymerization of 1 with organolithium and organopotassium initiators in a polar THF at −78 °C. The steric hindrance and the electron-withdrawing property of the amide substituent played important roles in the suppression of undesirable side reactions and in the stabilization the propagating carbanion. The poly(1) was not soluble in hexane and cyclohexane but soluble in THF, methanol, toluene, and benzene. In fact, quantitative polymerization of 1 homogeneously proceeded in benzene with sec-BuLi at 0 °C without precipitation. The molecular weight distribution (MWD) of the resulting poly(1) was narrow (Mw/Mn < 1.1), but the observed molecular weight (8.4 kg/mol) was significantly higher than the theoretical value (4.0 kg/mol). The careful analysis of the reaction mixture revealed that half of sec-BuLi reacted with the carbonyl group of 1 to afford the corresponding ketone compound prior to the initiation. This side reaction caused the low concentration of the propagation species and the higher molecular weight of the resulting polymer. It is noted that this undesired side reaction is effectively suppressed by masking sec-BuLi with 1,1-diphenylethylene (DPE) in benzene. A 1:1 adduct of sec-BuLi and DPE quantitatively gave the well-defined poly(1) with predicted molecular weight and narrow MWD in benzene. The bulky and conjugated DPE anion prevent the carbonyl attack to attain the precise control of the molecular weight of poly(1). We also attempted the polymerization of 4-(N-tert-butylimino)styrene in hydrocarbons.
