Alternating Copolymerization of Butadiene and Acrylic Compounds

Abstract

ABSTRACT:A kinetic investigation on the alternating copolymerization of butadiene (BD) and methyl methacrylate (MMA) was undertaken by using EtAlClz (Al) and VOCh (V) as catalysts. The rate orders with respect to both components were the same as those for the butadiene (BD)-acrylonitrile (AN) system as reported previously; the rate of polymerization, Rp,o These relations are interpreted in terms of the mechanism involving a rapid initiation followed by stepwise propagation through a BD-MMA-Al complexed monomer. The formation of a benzene-MMA-Al complex as well as a MMA-Al complex is supposed. The rate order with respect to BD and acrylic monomer (A) was found to be complicated, i.e., in the BD-AN system Rp,o is proportional to [BD][ANJ-2, whereas in the BD-MMA system Rp,o depends on neither [BD] nor [MMA]. This fact may be accounted for in terms of the equilibrium of the BD-A-Al complex and the (A)n-Al complex. It is assumed that in a BD-AN-Al system the equilibrium constant for the (AN)n-Al complex is very large, whereas in a MMA-BD-Al system the equilibrium constant for the (MMA)n-Al complex is smaller than that of the BD-MMA-Al complex.KEY WORDS Alternating Copolymerization / Butadiene-Acrylonitrile / Butadiene-Methyl Methacrylate / Vanadyl Chloride-Ethylaluminum Dichloride/ Rate/ Molecular Weight/ Mechanism/ NMR of Copolymer/ A kinetic study on the alternating copolymerization of butadiene (BD) and acrylonitrile (AN) with an EtAlCl2-VOC13 catalyst system was described in a previous report. 1 The polymerization proceeds through a step-growth mechanism by the reaction of a growing radical with the BD-AN-EtA1Cl2 complex. Vanadium compounds act not only as a regenerator of aluminum compounds but also as a cocatalyst forming a redox system with aluminum compounds. amount of AN monomer.This report deals with an alternating copolymerization of BD and methyl methacrylate (MMA) in relation to the BD-AN system, because the former polymer is quite soluble in the system in a wide range of monomer composition. A complex formation between MMA and EtAlCl2 and a ternary complex among MMA, benzene and EtAlCl2 were supposed.However, the detailed mechanism of polymerization, especially the participation of monomer in the alternating copolymerization, is not yet discussed, since the polymer is sparingly soluble except in the reaction system containing a large EXPERIMENTALThe procedure of the catalyst purification and the polymerization are almost the same as those in the preceding report 1 unless otherwise described. MonomersThe purification of BD and AN is the same as in the previous report1 and MMA is purified by conventional method.

Carbon‐13 NMR spectroscopy of acrylic monomer and Lewis acid complexes

“…n n -CH7CH-N + EtAlCl, -+CH,-CH=C=N-AlEtCl, (1) d a I Methacrylonitrile indicated a similar polarization, but the positive charge at the @-carbon is considerably smaller than that of acrylonitrile. This fact is expected from the electrondonating effect of methyl hyperconjugation:…”

220‐MHz NMR spectra of acrylic monomer–2‐substituted 1,3‐diolefin alternating copolymers

“…A method proposed by Houkg appears to be useful for the determination of regioselectivity because of its good agreement between observed and predicted one. The preferred Diels-Alder regioisomer can be predicted by using the following assumptions: (1) the principal stabilization of the transition state will arise from interaction of the HO-LU (highest occupied orbital-lowest unoccupied orbital) pair of addend frontier orbitals which are closest in energy; (2) the larger terminal coefficient on each addend will become bonded preferentially in the transition state. For the Diels-Alder reactions of unsymmetrical addends involving "conjugated" or "electron-rich" dienes and "conjugated" or "electron-deficient" dienuphiles, the diene HO-dienophile LU interaction is largest, and the para regioisomer is favored with 2-substituted butadienes.…”

Kinetic study of the alternating copolymerization of butadiene and methyl methacrylate

“…The preparation of the catalyst and the procedure of copolymerization of butadiene (BD) and methyl methacrylate (MMA) are similar to those described in the previous paper. 3 The degree of alternation of the copolymers was found to be very high by NMR measurement. The intrinsic viscosity [v] was measured at 3OoC in toluene, and the number-average molecular weight M n was measured by the osmotic pressure method with a Mechrolab 502 instrument at 27OC in toluene.…”