On predicting free radical polymerizability of allyl monomers. MINDO/3 and ¹³C NMR results

Abstract

Two new methods of predicting free radical polymerizability of allyl monomers have been developed. MINDO/3 calculations of eigenvalues for the C—H bond a to the atlyl substituent allow comparison of relative bond strengths. Monomers known to undergo degradative chain transfer display more positive eigenvalues correlating with weaker α‐C—H bonds. Polymerizable monomers have more negative eigenvalues and stronger α‐C—H bonds. The latter possess strongly polarized or protonated substituents not capable of resonance stabilization of a chain‐terminating allyl radical. The inductive effect of such substituents on the 13C NMR peaks of the vinyl carbons is the basis for the empirical spectroscopic method. Allyl compounds display β‐carbon peaks farther downfield than the γ‐carbon peaks. Polymerizable monomers generally have β peaks shifted upfield and γ peaks shifted downfield from those of poor monomers. This effect brings the two peaks closer together in the spectrum. Thus, the smaller the Δδ value (δβ − δγ), the more likely the monomer is to polymerize well. Monomers with intermediate eigenvalues or Δδ values may polymerize with difficulty or only under special conditions. Combined use of the theoretical and empirical techniques can allow prediction of inherent polymerizability and can facilitate evaluation of reaction media most favorable to polymer formation.

Influence of Structure on Polymerization Rates and Ca‐Binding of Phosphorus‐Containing 1,6‐Dienes

“…The 13 C NMR chemical shift differences (Δ δ ) of the CC double bonds of allyl monomers (C β H 2 C α ) were correlated with the radical polymerizability in the literature 21, 23. One proposed explanation is that electron withdrawing substituents cause downfield shifts of the β ‐carbon peak while the α ‐carbon is shifted upfield.…”

Cyclopolymerization XXIII. Design of Unconjugated Dienes with High Polymerizability Using Functional Groups with No Homopolymerization Tendency and Synthesis of Completely Cyclized Polymers Therefrom: Radical Polymerizations of N-Substituted N-Allyl-2-(methoxycarbonyl)allylamines

“…monomers were correlated to LI b to show that those with a value of more than 6 ppm for Lib are reluctant to polymerize. 24 This clearly indicates that the polymerization tendency of the allylic monofunctional counterparts of SAMC may be extremely low because of the large Lib values (Table IV) observed for the ally! groups of SAMC.…”

Cyclopolymerization of amine-linked diacrylate monomers

“…This reduces chain transfer of hydrogens on the ences of vinyl carbons of typical monomers. 16,17 The stronger the electron-donating power of the connecting CH 2 groups. Similar results were observed for ester vs. ether derivatives of a-hydroxysubstituents, the larger the difference and the lower the radical polymerizability.…”