Simple Systems Conforming to Four-reactions Scheme

First we describe the copolymerization of oxetanes, as an example for microstructure and structure/reactivity studies. Then we discuss the copolymerization of thietanes, azetidines and oxazolines. Finally, we show the relationship between structure of heterocyclics (basicity, ring strain) and their nucleophilic reactivity. 

The cationic copolymerization of oxetanes provides a good example that shows agreement between two treatments, namely determination of the reactivity ratios from kinetic treatment and microstructure studies 11 12). 

In the copolymerization of 3,3-dimethyloxetane (A) with oxetane (B) four possible triads may arise. Thus, taking the A unit in the central position we have  

The proportions of the triads vary with the monomer feed. As shown in Fig. 15.2, the proportions of the experimentally found triads agree well with the values calculated from Eq. (15-16a) using r obtained from the content of comonomers in the copolymer (method from Ref. 6)). This agreement means that in this system the penultimate effect, reversibility of propagation, interconversion of active species without propagation [Eq. (15-4)] and redistribution of the initially formed copolymer can be neglected and the process can be described by two reactivity ratios. 

3-Methyl-2-chloromethyloxetane was copolymerized with a number of cyclic ethers, in order to establish the structure-reactivity correlation. Results are summarized in Table 15.1. 

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