Peculiar initiation behavior of azo‐initiators in allyl polymerization

Abstract

On the course of a series of studies concerned with the elucidation of the allyl polymerization mechanism, the bulk polymerization of allyl benzoate was carried out using a large amount of 2,2′‐azobis(isobutyronitrile) (AIBN) and dimethyl 2,2′‐azobis (isobutyrate) (DMAIB). Incidentally, the initial rate of polymerization initiated by DMAIB was more than two times higher than that by AIBN, although the decomposition rate constants of AIBN and DMAIB are almost same at 80 °C. This peculiar initiation behavior of azo‐initiators is discussed to clarify the initiation mechanism in allyl polymerization, especially focused on the competitive contribution to the initiation and termination reactions by primary radicals.

Tautomerism, crystal structure, and copper(ii) complexation of pyridonylazo dyes derived from methyl 4‐aminobenzoate

“…The adoption of the hydrazone tautomeric form can be evidenced by the related four bond lengths, as depicted in Figure 3, where dye 4 is given as an example. The N-N (a) and C-C (c) bond lengths are 1.305(6) and 1.446 (7) A, exhibiting a greater single-bond character compared with the conventional double bonds of azo and pyridine units. In contrast, the N-C (b) and C-O (d) bond lengths are 1.318(7) and 1.223 (7) A, exhibiting predominantly a more double-bond character.…”

“…The N-N (a) and C-C (c) bond lengths are 1.305(6) and 1.446 (7) A, exhibiting a greater single-bond character compared with the conventional double bonds of azo and pyridine units. In contrast, the N-C (b) and C-O (d) bond lengths are 1.318(7) and 1.223 (7) A, exhibiting predominantly a more double-bond character. The hydrazone tautomeric form in dye 4 can be further supported by the location of a proton H1 via difference Fourier synthesis.…”

“…During the past decades, azo dyes and their metal complexes have attracted considerable attention and found extensive applications in areas of non-linear optics, optical storage media, chemosensors, liquid crystals, photochemical molecular switches, indicators, and radical reaction initiators [1][2][3][4][5][6][7]. It is worth mentioning that heterocycle dyes comprise one of the most important categories of synthetic compounds because they are easily synthesised and have a broad colour spectrum and excellent fastness on versatile fabrics [8][9][10][11][12].…”

“…a = 1.305(6); b = 1.318(7) Complex 5: a = 1.300(4); b = 1.353(5) = 1.446(7); d = 1.223(7) c = 1.447(5); d = 1.276(5) Schematic illustration for the variations in related bond lengths ( A) in neutral dye 4 of hydrazone form and the corresponding Cu (II) complex 5 in the deprotonated azo form before and after Cu(II) ion complexation [Colour figure can be viewed at wileyonlinelibrary.com] Perspective view of p-p stacking interactions in the crystal structures of dyes 2 (a), 3 (b), and 4 (c) [Colour figure can be viewed at wileyonlinelibrary.com]…”

Preparation of a molecularly imprinted polymer containing Europium(III) ions for luminescent sensing

“…Without isolation of the complex, we carried out the copolymerization of its allylic groups with EGDMA using AIBN as an initiator. The radical polymerization of allyl monomers generally produces oligomers because of the chain transfer to the monomers,23–26 but they are copolymerized with acrylates 27,28. We used a considerably large amount of initiator to obtain a crosslinked, insoluble polymer as white fine powders.…”