Polycarbonates were successfully synthesized for the first time through the anionic copolymerization of epoxides with CO2, under metal-free conditions. Using an approach based on the activation of epoxides by Lewis acids and of CO2 by appropriate cations, well-defined alternating copolymers made of CO2 and propylene oxide (PO) or cyclohexene oxide (CHO) were indeed obtained. Triethyl borane was the Lewis acid chosen to activate the epoxides, and onium halides or onium alkoxides involving either ammonium, phosphonium, or phosphazenium cations were selected to initiate the copolymerization. In the case of PO, the carbonate content of the poly(propylene carbonate) formed was in the range of 92-99% and turnover numbers (TON) were close to 500; in the case of CHO perfectly alternating poly(cyclohexene carbonate) were obtained and TON values were close to 4000. The advantages of such a copolymerization system are manifold: (i) no need for multistep catalyst/ligand synthesis as in previous works; (ii) no transition metal involved in the copolymer synthesis and therefore no coloration of the samples isolated; and (iii) no necessity for postsynthesis purification.

Dendrimer-like poly(ethylene oxide)s (PEOs) were synthesized by an iterative divergent approach combining anionic polymerization of ethylene oxide from multi-hydroxylated precursors and branching reactions of PEO chain ends. Partial deprotonation of the hydroxyls (< 30%) and use of dimethyl sulfoxide as solvent proved crucial for a "controlled/living" polymerization of ethylene oxide at room temperature. These sequences of reactions allowed us to prepare a dendrimer-like PEO up to the eighth generation with a molar mass of 900 000 g mol(-1) and 384 external hydroxyl functions. All samples from generation 1 to 8 were characterized by 1H NMR spectroscopy, light scattering, and viscometry. The evolution of the intrinsic viscosity versus the generation number of these dendrimer-like PEO is similar to that of regular dendrimers.

The preparation and characterization of amphiphilic ABC miktoarm star copolymers based on polystyrene, and poly(ethylene oxide), poly(methyl acrylate) or poly(N-isopropylacrylamide) blocks are described in this paper. First, macrotransfer agent polySt-MAh-S-C(S)Ph with maleic anhydride and a dithio group at one end of polymer chain was synthesized by the reaction of a dithio group at the end of the polystyrene with maleic anhydride (MAh) in tetrahydrofuran solution. The second, reversible additionfragmentation chain transfer polymerization of methyl acrylate or N-isopropylacrylamide was carried out in the prescence of polySt-MAh-S-C(S)Ph and benzoyl peroxide. Finally, the anhydride group at the joint of two blocks was reacted with terminal hydroxyl group of poly(ethylene glycol methyl ether). The obtained ABC star copolymers were characterized by 1 H NMR spectroscopy and gel permeation chromatography.

Poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA), two polymers known to form pH-sensitive aggregates through noncovalent interactions, were assembled in purposely designed architecture -a dendrimer-like PEO scaffold carrying short inner PAA chains-to produce unimolecular systems that exhibit pH responsiveness. Because of the particular placement of the PAA chains within the dendrimer-like structure, intermolecular complexation between acrylic acid (AA) and ethylene oxide (EO) units-and thus macroscopic aggregation or even mesoscopic micellization-could be avoided in favor of the sole intramolecular complexation. The sensitivity of such interactions to pH was exploited to generate dendrimer-like PEOs that reversibly shrink and expand with the pH. Such PAA-carrying dendrimer-like PEOs were synthesized in two main steps. First, a fifth-generation dendrimer-like PEO was obtained by combining anionic ring-opening polymerization (AROP) of ethylene oxide from a tris-hydroxylated core and selective branching reactions of PEO chain ends. To this end, an AB(2)C-type branching agent was designed: the latter includes a chloromethyl (A) group for its covalent attachment to the arm ends, two geminal hydroxyls (B(2)) protected in the form of a ketal ring for the growth of subsequent PEO generations by AROP, and a vinylic (C) double bonds for further functionalization of the interior of dendrimer-like PEOs. Reiteration of AROP and derivatization of PEO branches allowed us to prepare a dendrimer-like PEO of fourth generation with a total molar mass of 52,000 g x mol(-1), containing 24 external hydroxyl functions and 21 inner vinylic groups in the interior. A fifth generation of PEO chains was generated from this parent dendrimer-like PEO of fourth generation using a "conventional" AB(2)-type branching agent, and 48 PEO branches could be grown by AROP. The 48 outer hydroxy-end groups of the fifth-generation dendrimer-like PEO obtained were subsequently quantitatively converted into inert benzylic groups using benzyl bromide. The 21 internal vinylic groups carried by the PEO scaffold were then chemically modified in a two-step sequence into bromoester groups. The latter which are atom transfer radical polymerization (ATRP) initiating sites thus served to grow poly(tert-butylacrylate) chains. After a final step of hydrolysis of the tert-butyl ester groups, double, hydrophilic, dendrimer-like PEOs comprising 21 internal junction-attached poly(acrylic acid) (PAA) blocks could be obtained. Dynamic light scattering was used to determine the size of these dendrimer-like species in water and to investigate their response to pH variation: in particular, how the pH-sensitive complexation of EO and AA units affects their overall behavior.

A straightforward and original methodology allowing the synthesis of Janus-type dendrimer-like poly(ethylene oxide)s (PEOs) carrying orthogonal functional groups on their surface is described. The use of 3-allyloxy-1,2-propanediol (1) as a latent AB 2 -type heterofunctional initiator of anionic ring-opening polymerization (AROP) of ethylene oxide (EO) and of selective branching agents of PEO chain ends served to construct the two dendrons of these dendrimer-like PEOs, following a divergent pathway. Thus, the first PEO generation of the first dendron was grown by AROP from 1 followed by the reaction of the corresponding α-allyl,ω,ω′-bishydroxy-heterofunctional PEO derivative with 2-(3′-chloromethybenzyloxymethyl)-2-methyl-5,5-dimethyl-1,3-dioxane (2) used as a branching agent. This afforded the dendron A with four latent peripheral hydroxyls protected in the form of two ketal rings. The remaining α-allylic double bond of the PEO thus prepared was transformed into two hydroxyl groups using OsO 4 in order to create the first PEO generation of the dendron B by AROP of EO. Allyl chloride (3) was then used as another (latent) branching agent to react with the terminal hydroxyl of the corresponding PEO chains. Deprotection under acidic conditions of the ketal groups of dendron A, followed by AROP of EO, afforded the second PEO generation on this face. This alternate and divergent procedure, combining AROP of EO and selective branching of PEO branches, could be readily iterated, one dendron after the other up to the generation six, leading to a Janus-type dendrimer-like PEO exhibiting a total mass of around 300 kg/mol and possessing 64 peripheral groups on each face. The possibility of orthogonal functionalization of the surfaces of such Janus-type dendritic PEOs was exploited. Indeed, a dendron of generation 4 was functionalized with hydroxyl functions at its periphery, whereas the other was end-capped with either tertiary amino or disulfide groups. In a variant of this strategy, azido groups and acetylene could also be orthogonally introduced at the periphery of the fourth generation Janus-type dendrimer-like PEO and subjected to polycondensation by a 1,3-dipolar cycloaddition reaction. This afforded a necklacelike covalent assembly of dendrimer-like PEOs through the formation of stable [1,2,3]-triazole linkages.

Tetrabutylammonium carbonate (TBAC) which is obtained by treating CO 2 with tetrabutylammonium hydroxide is shown to perform as an ideal difunctional initiator for the copolymerization of carbon dioxide (CO 2) and propylene oxide (PO) in the presence of triethylborane (TEB). In this system, CO 2 thus serves as the initiating moiety of its own copolymerization with epoxides when used in the form of a carbonate salt. Based on this remarkable result, mono-, tri-, and tetrafunctional ammonium carboxylate initiators and also other difunctional carboxylate initiators were synthesized and used for the synthesis of well-defined ωhydroxyl-polycarbonates with linear and star structures. Well-defined telechelics, three-and four-armed star samples of molar mass varying from 1 kg/mol to 10 kg/mol, with around 95% carbonate content, were successfully synthesized. The structure of the obtained polycarbonate ω-polyols were characterized by 1 H NMR, MALDI-TOF, and GPC. The terminal hydroxyl functionality of polycarbonate diol was further used for polycondensation with diisocyanates to afford polyurethanes. Finally, taking TBAC as an example, the recyclability of this ammonium-based initiator is demonstrated for the preparation of polycarbonate diols. 65 polycarbonate diols and polyols eventually obtained under 66 these conditions are contaminated with monofunctional 67 chains, which is detrimental to the subsequent polycondensa-68 tion applications. As clearly demonstrated by Sugimoto et al., 69 polycarbonate tetrol and hexeol samples using

A new class of highly branched polymers referred to as dendrimer-like polymers has been developed in the last decade, the first synthetic example dating back to 1995. Dendrimer-like polymers exhibit molecular features similar to those of regular dendrimers, such as the presence of a central core, a precise number of branching points and terminal functions, but comprise of generations of macromolecular size between their branching junctions. In this highlight article synthetic strategies to dendrimer-like polymers are reviewed as well as some of their characteristic properties. A special emphasis is placed on synthetic methodologies designed in our group to generate dendrimer-like homopolymers and block copolymers by iterative divergent approaches based on anionic ring-opening polymerization of ethylene oxide and atom transfer radical polymerization. Are also thoroughly described the methods used for selectively branching polymeric chain-ends and introducing o-geminal functionalities from which further macromolecular generations could be grown.

Polytetrahydrofuran (PTHF)/poly(1,3-dioxepane) (PDOP)/polystyrene (PSt) ABC miktoarm star copolymers were synthesized by combination of cationic ring-opening polymerization (CROP) and atom transfer radical polymerization. Two different functional groups, carboxylic acid and CHBr, were capped at one end of PTHF through the reaction of PTHF-OH with 2-bromosuccinic anhydride (BSA). After PTHF-OOCCHBrCH 2COOH reacted with thionyl chloride, block copolymer PTHF-b-PDOP was synthesized by CROP of DOP at -30 to -35 °C with PTHF-OOCCHBrCH2COCl and AgClO4 as catalyst. Finally, (PTHF) (PDOP)-Br was used to initiate the polymerization of St in the presence of CuBr and bipyridine at 110 °C, and ABC miktoarm star polymer, s-[(PTHF) (PDOP) (PSt)] was successfully prepared. The copolymers obtained were characterized by 1 H NMR and gel permeation chromatography measurements.