The anionic ROP of CL is an attractive protocol to melting cast
polyamide 6 (MC PA6) in industry owing to the shorter reaction
time (10–30 min), lower reaction temperature (150–180 8C) and
pressure (atm) [14–16]. The anionic polymerization was usually
conducted by a two-component system of a catalyst and an Nacyllactam
type activator. The growing chain ends are always
corresponding to N-acyllactam and the number of the polymer
chains should be equal to that of the N-acyllactam if there are no
side reactions. Thus, non-linear PA6 could be theoretically
fabricated by adding multifunctional N-acyllactam type activators
[17,18]. Ashida et al. explored a tertiary amine centered trifunctional
activator from Desmodur L-2291A and CL [6]. Santos et al.
synthesized a star-like PA6-block-polyurethane copolymer using a
tri-arm polyurethane activator with glycol as a core moiety [19].
They found that the star-like copolymer showed better mechanical
properties compared with the linear ones. However, these
multifunctional activators suffered from the tedious synthesis and toxic isocyanate reagent. There is a great need to systematically
investigate simple and novel multifunctional activators and
SPA6.