Polymerization isomerization

These are manifested by the formation of a polymer with a structure which can only be explained by monomer isomerization in the course of addition. An active centre rich in energy is sometimes transformed to a more stable form by a transfer of atoms or atom groups, and further monomer is added only to this more stable form 

Instability (reactivity) of an active centre may cause rearrangements of atoms or of whole substituents in the centre prior to or during the addition of further monomer. The structure of the generated chain in such a case is different from that corresponding to simple propagation. The practical im- 

Orr derived high — AH and AS values for an imaginary polymerization of cyclooctatetraene, not stabilized by resonance, into resonance-stabilized polyene chains [9, 85]. The heat of polymerization would be even higher for the transformation of cyclooctatetraene to polystyrene ( 460 kJ mol ). The nature of isomerization reaction will be better illustrated by several examples  

Cho and Ahn studied the radical polymerization of 1,1-disubstituted 2-vinylcyclopropanes (X = COOEt, or CN) 

The authors explain the easy 1,5-polymerization of these monomers by the substituent stabilization of the growing radical [351]. 

Saegusa et al. observed a proton transfer during anionic polymerization of hydroxyalkylacrylates [352] 

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Kennedy, J. P. and Johnston, J. E. The Cationic Isomerization Polymerization of 3-Methyl-1-butene and 4-Methyl-l-pentene. Vol. 19, pp. 57—95. 

Repeating unit isomerization is similar in several respects to isomerization polymerization (26,27). Isomerization polymerization may be defined as a process whereby a monomer of structure A is converted to a polymer of repeating unit structure B, wherein the conversion of A to B represents a structural change which is not a simple ring opening or double bond addition ... 

The product of an isomerization polymerization is thus determined by the relative rates of the propagation and isomerization steps i.e., it is kinetically determined. If isomerization is much faster than propagation, the homopolymer of B is obtained competitive rates will lead to A-B copolymers. 

The compounds in this section—fulvenes, isotoluenes, xylylenes—are characterized by trivial names. Our various reference citations document their nontrivial chemistry isomerization, polymerization and oxidation befall the unwary experimentalist who would study them. 

Atmospheric oxygen may initiate in situ polymerization [55] as well as hght as exemplified by the photo-induced isomerization/polymerization of (Z,Z)-muconate anions in the gallery space of LizAl LDH [61] and the photoisomerization of indolinespirobenzopyran [62]. 

The key role of the hydrogen atoms of the methyl group in monomer 3a in allowing the occurrence of the reorganization of the chain carrier is proved by the fact that similar structures bearing CF3, Ph or tBu instead of CH3, i.e. monomers 3b, 3c and 3d, do not polymerize anionically because they cm not have a mobile hydrogen atom at the 4-position to insure the 4-to-2 proton shift. On the other hand, the non-intervention of the C5 position in this isomerization polymerization is confirmed by the fact that monomer 3f behaves exactly like 3a. 

Isomerization polymerizations are polyaddition reactions where the propagating species rearranges to energetically preferred structures prior to subsequent chain growth. 

In 1962, Kennedy reported the first isomerization polymerization using 3-methyl-1-butene to give a 1,1-dimethyl PP as below ... 

Isomerization polymerizations can be associated with coordination catalyst systems, ionic catalyst systems, and free radical systems. The cationic isomerization polymerization of 4-methyl-1-pentene is of interest because the product can be viewed as an alternating copolymer of ethylene and isobutylene. This structure cannot be obtained by conventional... 

Isomerization polymerizations yield high-molecular-weight products when reaction proceeds through relatively simple rearrangement routes involving stable carbocations. Thus... 

The driving force in some isomerization polymerizations is relief of steric strain. Polymerization of P-pinene proceeds by the first-formed carbocation XVI rearranging to XVII... 

Other monomers that undergo isomerization polymerization include 5-methyl-l-hexene,... 

Hydrogen fluoride also is used as a catalyst in alkylation of aromatic compounds and for dimerization of isobutene. Other catalytic applications are in isomerization, polymerization, and dehydration reactions. Other uses are in... 

McPherson, L. J., and M. F. Olive. 1992. Alkylation, isomerization, polymerization, hydrotreatment and sulfur production. In Modern Petroleum Technology, ed. G. D. Hobson, pp. 517-575, London Institute of Petroleum. 

Isomerism in the Metal-ammines.—Werner claimed for the coordination theory that in certain cases isomerism should occur, that isomerism being brought about by different causes. lie divided isomerism in the ammines into five groups, namely, structure isomerism, ionisation isomerism, hydrate isomerism, polymerism, and stereoisomerism. 

Isomerism in Metal-Ammines—Structure Isomerism—Ionisation Isomerism— Hydrate Isomerism—Polymerism—Stereo-isomerism. 

Base-catalyzed carbanionic alkylation, isomerization, polymerization reactions are of major significance. Base-catalyzed alkylation of alkylarenes, in contrast to acid-catalyzed ring alkylation, leads to alkylation of the side chain in the benzylic position [Eq. (1.28) see also Chapter 5] of particular interest is the alkylation of toluene to ethylbenzene (for styrene production). 

The Cationic Isomerization Polymerization of 3-Methy 1-1 -butene and 4-Methyl-l-pentene... 

This paper concerns the cationic isomerization polymerization of 3-methyl-1-butene and 4-methyl-1-pentene. Specifically, the microarchitecture (composition) of poly(3-methyl-l-butene) and poly(4-methyl-1-pentene) has been investigated, and the effect of synthesis conditions on polymer composition, polymer molecular weight and polymerization rate of 4-methyl-1-pentene has been studied. 

Previous work, (T-5) has shown that cationic isomerization polymerization of 3-methyl-1-butene produces a copolymer of two repeat units, the 1,2- i-CH2CH(iPrH-, and the 1,3- fCH2CH2C(CH3)2. Similarly, 4-methyl-l-pentene produces a terpolymer of 1,2-, 1,3-, and 1,4- -fCH2CH(iBu)-)-, -fCH2CH2CH(iPr)-f, and CH2CH2CH2C(CH3)2f, respectively. 

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