Reversible chain breaking Solution is the appropriate choice of reaction

Reversible chain breaking solution is the appropriate

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Reversible chain breaking ° Solution is the appropriate choice of: reaction temperature nucleophile solvent Lewis-acid and added common ion salt Dynamic fast equilibrium between propagating and non-propagating species
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Synthesis of well-defined polyisobutylene (PIB) with low polydispersity [1] ° Reaction condition Reaction temperature : ~(-30)-(-80) °C /If the reaction temperature increases the chain transfer increases relative to the propagation/ Nucleophile : pyridine /It acts by driving of the dynamic equilibrium toward the covalent species and/or decreasing the reactivity of ion pair/ Solvent : CH 3 Cl/ hexane (40: 60 V/V) /Nucleophiles work best in nonpolar solvents/ Initiator-coinitiator : TCC (tricumyl chloride) -TiCl 4 [1] R. F. Storey, Y. Lee, J.M.S.-Pure Appl. Chem., A29(11), pp. 1017-1030 (1992)
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Equilibrium between the propagating and non-propagating species Initiator from cumyl clhoride Poly(isobutylene) Nucleophile pyridine Lewis-acid coinitiator Growing chain Non-growing chain TiCl 4 N TiCl 5 - propagation CH 3 CH 3 + TiCl 4 PIB + N TiCl 4 CH 3 CH 3 Cl CH 2 CH 3 CH 3 PIB CH 3 CH 3 CH 2 + n IB +
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The characterization of PIB [1] Mw/Mn ~ 1.04-1.13
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