Benzoxazines 2.6- ditert-butylphenol reaction

With the exception of 2,6-ditert-butylphenol, which remained unreac-tive under the used experimental conditions, the reaction of benzoxazine with phenols and were shown to follow second order kinetics. 

Figure 2. Polymerization of benzoxazine lb in the presence of various amounts of 2,4-ditert-butylphenol. Fraction of unreacted benzoxazine versus reaction time at 140 C. 

Benzoxazine Ic Polymerization Kinetics. A kinetic study of the polymerization of benzoxazine Jx was carried out at 140 C in the presence of 1%, 5%, and 10% by weight of 2,4-ditert-butylphenol (Figure 3). Table 4 summarizes the variation of the average molecular weight with time during this reaction. 

Figure 4 shows the plot of this relationship in the case of benzoxazine lb and for three different concentrations of 2,4-ditert-butylphenol. The rate law is perfectly verified at 10% phenol. However, the observation that the straight lines do not pass through the origin at lower phenol concentration may imply a second reaction, i.e. a thermal degradation of benzoxazine which could lead to the pol3rmerization of benzoxazine in the absence of phenol, or at least loss of some of the initiator species. 

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