Heterograft copolymers of poly(epsilon-caprolactone) prepared by combination of ATRA "grafting onto" and ATRP "grafting from" processes

This paper aims at reporting on the synthesis of a heterograft copolymer by combining the "grafting onto" process based on atom transfer radical addition (ATRA) and the "grafting from" process by atom transfer radical polymerization (ATRP). The statistical copolymerization of epsilon-caprolactone (epsilon-CL) and alpha-chloro-epsilon-caprolactone (alpha-Cl-epsilon-CL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP), followed by ATRA of parts of the chlorinated units of poly(alpha-Cl-epsilon-CL-co-epsilon CL) on the terminal double bond of alpha-MeO,omega-CH2=CH-CH2-CO2-poly(ethylene oxide) (PEO). The amphiphilic poly(epsilon CL-g-EO) graft copolymer collected at this stage forms micelles as supported by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The unreacted pendant chloro groups of poly(epsilon-CL-g-EO) were used to initiate the ATRP of styrene with formation of copolymer with two populations of randomly distributed grafts, that is PEO and polystyrene