Functional azo-initiators - Synthesis and molecular characteristics

The series of azo-esters have been synthesized in Pinner's reaction of 2,2'-azobis(2-methylpropionitrile) (AIBN) with some diols (Scheme A, Table 1): 1,4-butanediol (1,4-BD), tri(oxyethylene)diol [Tri(OE)D], tetra(oxyethylene)diol [Tetra(OE)D] or with polydisperse oligo(oxyethylene)diols [OOED(200)] or [OOED(400)]. Ten-time molar excess of particular diols or of polydisperse OOED(200) one let prepare the monomeric initiators characterized with average molecular weight (M-n), determined by vapor osmometry VPO, corresponding with theoretical molecular weight of monomeric azoester (according to Formula 1, n = 1, Table 2). The application of polydisperse OOE(400) diol showing the broad molecular weight distribution leads, dependently on the substrates ratio, to either the mixture of mono- and dimeric azoesters (in which fractional part of monomeric molecules is about 0.80) or monomeric azoesters with fragments of introduced molecules of diol characterized with molecular weight smaller (230 g.mol(-1)) than average one (400 g.mol(-1)) (Table 2). All azoesters obtained are ditelechelic i.e. they contain two OH end groups (Table 4). All the above settlements were done on the basis of molecular weights measurements by VPO, H-1 NMR analysis of azoester and AIBN mixtures' spectra (Figs. 2, 3) (AIBN was an additional internal standard), as well as C-13 NMR investigations (Fig. 1), IR (Fig. 4) and UV-VIS (Fig. 5) ones.