Preparation of dendrimer-like copolymers based on polystyrene and poly(l-lactide) and formation of hollow microspheres

The three generations dendrimer-like copolymers C(PSt(PLLA(PSt-PNAS)2)2)3 and C(PSt(PLLA(PSt-PNAS)2)2)4 have been successfully synthesized by combination of ATRP and ROP. Diethanol amine and 2,2-bis(methylene-2-bromoisobutyrate) propionyl chloride (BMBIBPC) were used as divergent reagents, respectively, before preparations of the second and the third generations. The resultant polymers were characterized by GPC and 1H NMR. Then the outermost PSt-PNAS in the dendrimer-like copolymers was cross-linked via substitution reaction of NAS with ethylene diamine, and at the same time, the PLLA segments in the second generation were decomposed in dilute THF or CHCl3 solution, forming hollow particles. The resultant morphologies were characterized by SEM and DLS methods, and spherical particles with various sizes were observed. The hollow particles may have potential applications in catalysis and bioengineering.