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This article reports on the synthesis of a new pH-sensitive amphiphilic A2B mikto-arm star-shaped aliphatic copolyester [with A = poly(e-caprolactone) and B = tertiary amine-bearing poly(e-caprolactone)] with two hydrophobic arms and one hydrophilic arm when protonated at pH = 5.5. First, the ring-opening polymerization of e-caprolactone (eCL) was initiated by an aliphatic diol substituted by an alkyne. The copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) was use to convert the alkyne into a hydroxyl group prone to initiate the ring-opening copolymerization of γ-bromo-e-caprolactone (γBreCL) and eCL. After the substitution of the bromide atoms into azide functions, the N,N-dimethylprop-2-yn-1-amine was grafted onto the azide bearing PCL arm by CuAAC, with the purpose to make the B arm hydrophilic at low pH. The precursors of the A2B copolymers were characterized by 1H NMR, SEC, and MALDI-TOF. As expected, the A2B copolyester was soluble into water at pH = 5. The formation of polymersomes in water at pH 5 was assessed by DLS and TEM analyses. The effects of the architecture and the molecular weight of the A2B copolymers on the formation of polymersomes were investigated. Moreover, the versatility of our approach was demonstrated by the synthesis of an AB2 star-shaped copolyester. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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 s-caprolactone (eCL) and α-chloro-e-caprolactone (αCleCL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP), followed by ATRA of parts of the chlorinated units of poly(αCleCL-co-eCL) on the terminal double bond of α-MeO,ω-CH 2 =CH-CH 2 -CO 2 -poly(ethylene oxide) (PEO). The amphiphilic poly(eCL-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(eCL-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.