Anionic synthesis of [1,4-poly(diene)-b-syndiotactic poly(methyl methacrylate)] diblock copolymers:7Li NMR study of the intermediate reaction of lithium poly(diene) anion with 1,1-diphenylethylene

Abstract

SUMMARY:The end-capping with 1,1-diphenylethylene (DPE) of living 1,4-poly(diene) lithiated anions prepared in cyclohexane (Chx) and toluene is a major but poorly controlled step in the synthesis of syndiotactic poly(methyl methacrylate) (sPMMA) containing block copolymers. The kinetics of the reaction have been studied by means of 7 Li NMR not only in Chx and toluene but also in their mixtures with polar solvents, since the solvent polarity must be increased for MMA to be predominantly converted into sPMMA. Although the addition of a polar solvent (tetrahydrofuran (THF), diethyl ether) to Chx and toluene is known to increase the reactivity of living polymeric anions, contaminating lithium salts, such as lithium hydroxide, slow down the end-capping reaction even when 10 vol.-% polar solvent is added. Moreover, the polymeric diphenylalkyllithium anions are unstable in 1/9 (v/v) THF/Chx mixture, as a result of the nucleophilic attack of THF. On the basis of all these observations, new experimental conditions are proposed for improving the control of the anionic block copolymerization of 1,3-dienes and MMA to yield 1,4-poly(diene) and sPMMA containing block copolymers.

Determination of Polyisoprene‐block‐poly(methyl methacrylate) Domain Sizes Using 1H Spin Diffusion

“…[18][19][20] The spin diffusion curve is corrected for T 1 relaxation. [7,[12][13][14][15][16][17][18][19][20][21][22][23][24] This correction is achieved by multiplying all intensities by exp. (t m /T 1 ), where T 1 is the relaxation time for the detected domain.…”

“…Experimental details are described in ref. [16] For the block copolymer IM-1 we found M n (PI) ¼ 31 000; M n (PMMA) ¼ 45 000; MWD ¼ 1.14. Block copolymer IM-2 was prepared accordingly with M n (PI) ¼ 40 500; M n (PMMA) ¼ 21 000; MWD ¼ 1.06.…”

Synthesis and Characterization of ABC-type Star and Linear Block Copolymers of Styrene, Isoprene, and 1,3-Cyclohexadiene

“…The dramatic effect of Lewis base on the rate of addition was explained in terms of its effect on aggregation of the organolithium chain ends . In the presence of THF, these chain ends tended to disaggregate, thus improving the reactivity of anions …”

“…34 In the presence of THF, these chain ends tended to disaggregate, thus improving the reactivity of anions. 40 The coupling reaction was completed within 4-5 h. GPC monitoring in Figure 5 shows that the peaks for PS macromonomer (line a, cyan) and polyisoprenyllithium (line b, black) disappeared, while a new peak (line c, red) appeared with negligible residual precursors. This demonstrated that the coupling reaction was nearly quantitative.…”

Influences of co‐monomers and electrolyte acidity on morphological structure of copper‐in‐copolymer gradient film

“…Obviously, chemical and physical interactions among polymer groups and metal ions in SCF affect the ion transport. From this point of view, the ion transport in SCF is similar to lithium ion motion in polymer electrolyte in rechargeable lithium batteries 11–13. On the other hand, electrochemical conditions like a voltage drop in the SCF are important influencing factors on ion transport.…”