1-tert-Butylaziridine

The absence of a termination reaction in the polymerization of 1-tert.butylaziridine is explained by the high steric hindrance caused by the tert.butyl groups around the nitrogen atoms of the polymer chain. As a consequence a nucleophilic attack by these nitrogen atoms on the active species is no more possible. Poly-(tert.butylaziridine) is a highly crystalline polymer with a m.p. of 142 C. 

Grafting on technique was used to produce a graft copolymer silica- -poly(](-tert-butylaziridine) (187). The technique used was the coupling of a silica-containing amine group with a temporarily living poly(tert-butylaziridine). 

These effects have been experimentally observed in the polymerization of some cyclic acetals7-8) and THF 2 3). In the polymerization of n-tert-butylaziridine, the presence of the secondary amino groups also favours end-to-end cyclization 28). 

The absence of transfer reactions is confirmed by the possibility to produce block-copolymers of tert.butylaziridine by using "living" cationic poljrmers as initiator. This has been achieved with living poly(tetrahydrofurane) at 0 C (O and with living polystyrene perchlorate, at -60 C (7 ). In both cases the formation of block-copolymers was demonstrated by the solubility properties of the obtained polymers which were different from those of homo poly-(tert.butylaziridine), and by gel permeation chromatography. 

The cationic polymerization of cychc amines is well known [98-100]. Low-molecular-weight initiators such as ethyltosylate induce the polymerization of cyclic amines, such as 1-fert-butylaziridine. The concept of using a macroinitiator bearing a tosylate end group to polymerize cyclic amines prompted Kazama etal. [101] to attempt the polymerization of 1-tert-butyl aziridine, using PDMS with a terminal tosylate group. The fact that no polymerization occurred when the macroinitiator was used provided a clear demonstration of the initiative behind studying the transformation reaction between anionic and cationic polymerizations. 

---