Reaction of dicyanates with monophenols — modeling of network buildup

Abstract

Chemical as well as structural modifications of highly branched polycyanurates can be achieved by using the reaction of dicyanates with monofunctional phenols.The key products of this reaction are iminocarbonic esters formed by addition of cyanato and phenolic groups. Two mechanisms are discussed for the second reaction step: an addition of two cyanato groups and an iminocarbonic ester (Route A) and a stepwise addition of iminocarbonic esters (Route B).The crucial difference between the two reactions is the number of abstracted phenolic groups per formation of one triazine ring: one for Route A and three for Route B. The effects of these reaction mechanisms on the gelation behavior and network buildup are studied theoretically with the help of cascade theory as well as experimentally by the reaction of dicyanate of bisphenol A with five different monophenols. The results clearly show that only with a model which is based on Route B can both the critical conversions at the gelation threshold and the gel fractions be modeled quantitatively. Furthermore, phenols with low pK, values were found to have an increased tendency of incorporation into the network.

Curing of Cyanates with Primary Amines

“…[12] The first step is the addition of a cyanate ester and an amine to form an isourea 1 (Scheme 3). The isourea can be isolated under mild conditions only (low temperature, low concentration, see literature [1,2] ) and reacts immediately under the reaction conditions applied with another isourea or cyanate ester to form the adducts 2 a and 2 b, which differ in the aryloxy or arylamino substituents.…”

Developing predictive models for polycyanurates through a comparative study of molecular simulation and empirical thermo-mechanical data

“…There have also been some previous studies by our group involving molecular modelling of polycyanurates 15,19 as well as some studies of network build up in the same polymers conducted by other researchers 20,21 . However, this paper represents a new and exciting step in this process.…”

Formation of new thermosets by the reaction of cyanates with thiophenols

“…6. TP should have a similar effect on the cyanate network buildup Figure 5 Fractions of (l) 4tbP and (n) DPDS after 4 h at 1508C versus the initial molar fraction of TP determined by HPLC.…”

“…The complete conversion of all cyanate groups was checked by FTIR, for which the disappearance of the characteristic OCN valance vibration between 2200 and 2350 cm 21 was used as an indicator. 6,7 The measured FTIR spectra of a mixture with 50 mol % TP after mixing and after the reaction are shown in Figure 3 as examples.…”

“…6 The first step is the addition of a cyanate ester (RÀ ÀOCN) and a thiol (R 0 À ÀSH) to form the thioimino carbonic ester 1 (see Scheme 4).…”