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The morphological evolution of graft copolymer-based nano-objects was monitored by light scattering and electron microscopy during their formulation in water by polymerization induced self-assembly using a photo-mediated reversible addition–fragmentation chain transfer mechanism. The copolymer models used were composed of a dextran backbone bearing poly(2-hydroxypropyl methacrylate) grafts of two degrees of polymerization (X). At a full monomer conversion, unilamellar vesicles (ULVs) and large compound nano-objects (LCNs) were formed when targeting X= 100 and 500, respectively. For X= 100, some spherical, worm-like, then jellyfish-like structures were progressively observed before the ULVs formation. For X= 500, electron cryotomography revealed an unprecedented intermediate morphology formed from the onset of self-assembly called a multicompartment vesicle (MCV) that fused to form LCN. The formation of MCV was attributed to a local phase separation between dextran and the residual 2-hydroxypropyl methacrylate inducing the appearance of multiple hydrophilic cores.

Polymersomes are multicompartmental vesicular nano-objects obtained by self-assembly of amphiphilic copolymers. When prepared in the aqueous phase, they are composed of a hydrophobic bilayer enclosing water. Although such fascinating polymeric nano-objects have been widely reported with synthetic block copolymers, their formation from polysaccharide-based copolymers remains a significant challenge. In the present study, the powerful platform technology known as polymerization-induced self-assembly was used to prepare in situ pure vesicles from a polysaccharide-grafted copolymer: dextran-g-poly(2-hydroxypropyl methacrylate) (Dex-g-PHPMA). The growth of the PHPMA grafts was performed with a dextran-based macromolecular chain transfer agent in water at 20 °C using photomediated reversible addition fragmentation chain transfer polymerization at 405 nm. Transmission electron microscopy, cryogenic electron microscopy, small-angle X-ray scattering, atomic force microscopy, and dynamic light scattering revealed that amphiphilic Dex-g-PHPMAX= 100–300(X is the targeted average degree of polymerization, Xn̅, of each graft at full conversion) exhibit remarkable self-assembly behavior. On the one hand, vesicles were obtained over a wide range of solid concentrations (from 2.5% to 13.5% w/w), which can facilitate posterior targeting of such rare morphology. On the other hand, the extension of Xn̅ induces an increase in the vesicle membrane thickness, rather than a morphological evolution (spherical micelles to cylinders to vesicles).

The whole controlled synthesis of novel amphiphilic polylactide (PLA)-grafted dextran copolymers was achieved. The control of the architecture of such biodegradable and potentially biocompatible copolymers has required a three-step synthesis based on the “grafting from” concept. The first step consisted of the partial silylation of the dextran hydroxyl groups. This protection step was followed by the ring-opening polymerization of D,L-lactide initiated from the remaining OH functions of the partially silylated polysaccharide. The third step involved the silylether group deprotection under very mild conditions. Based on previous studies, in which the control of the first step was achieved, this study is focused on the last two steps. Experimental conditions were investigated to ensure a controlled polymerization of D,L-lactide, in terms of grafting efficiency, graft length, and transesterification limitation. After polymerization, the final step was studied in order to avoid degradation of both polysaccharide backbone and polyester grafts. The chemical stability of dextran backbone was checked throughout each step of the synthesis. PLA-grafted dextrans and PLA-grafted (silylated dextrans) were proved to adopt a core-shell conformation in various solvents. Furthermore, preliminary experiments on the potential use of these amphiphilic grafted copolymers as liquid/liquid interface stabilizers were performed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2577–2588, 2004

This paper reviews the possibilities of engineering novel macromolecular topologies via “living” ring‐opening metathesis polymerization (ROMP) of miscellaneous macromonomers. It is shown that multibranched polystyrene poly(ethylene oxide) and polybutadiene polymacromonomers of varying compactness and branch number can be prepared by ROMP of corresponding macromonomers, provided the macromonomers carry an end‐standing norbornene unsaturation. Janus‐type architectures are also accessible by this technique: such entirely novel topologies can be obtained by sequential ROMP of two different macromonomers whereas their statistical copolymerization affords heteroarmed macromolecules. Advantage has also been taken of the versatility of this technique to prepare compact polymeric architectures that behave like unimicellar systems: structures whose inner part and outer layer are chemically different can be derived through homopolymerization of macromonomers that are themselves block copolymers. © 1998 John Wiley & Sons, Ltd.

This paper reviews the possibilities of engineering novel macromolecular topologies via “living” ring-opening metathesis polymerization (ROMP) of miscellaneous macromonomers. It is shown that multibranched polystyrene poly(ethylene oxide) and polybutadiene polymacromonomers of varying compactness and branch number can be prepared by ROMP of corresponding macromonomers, provided the macromonomers carry an end-standing norbornene unsaturation. Janus-type architectures are also accessible by this technique: such entirely novel topologies can be obtained by sequential ROMP of two different macromonomers whereas their statistical copolymerization affords heteroarmed macromolecules. Advantage has also been taken of the versatility of this technique to prepare compact polymeric architectures that behave like unimicellar systems: structures whose inner part and outer layer are chemically different can be derived through homopolymerization of macromonomers that are themselves block copolymers. © 1998 John Wiley & Sons, Ltd.

Supercritical fluids have been used for the fractionation of poly(ethylene oxide). Indeed, supercritical fluids are well known for their efficiency in the fractionation of polymers. Polymer fractions of similar or lower molar mass distribution can be isolated with higher purity and lower energy costs than with other fractionation methods. The fractionation of poly(ethylene oxide) (POE) is reported at 423 K in the pressure range 8–35 MPa. Used as supercritical fluid HCFC 142b (1-chloro-1,1-difluoroethane, CH3CClF2) was found to be quite efficient, yielding polymers with a very narrow molar distribution. These results enable tochose the optimum pressure conditions for molecular architecture fractionation. The fractionation of a binary mixture of star and linear chains of poly(ethylene oxide) has been studied. The separation of linear chains and star structure appears to be very efficient for a short elution time.

This paper concerns the synthesis of two different structures of styrene‐butadiene block copolymers that were respectively obtained viasequential and statistical ring‐opening metathesis copolymerization of norbornene‐terminated polystyrene (PS) and polybutadiene (PB) macromonomers. The stimulus for preparing such styrene‐butadiene copolymers originates from the observation that phase‐separated morphologies in block copolymers not only depend on the respective size of the blocks and the interaction parameter (χ), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetry study that was carried, it can be inferred that the two types of copolymers ‐prepared by sequential and statistical copolymerization of PS and PB macromonomers respectively‐ exhibit quite different phase separation behaviors, indicating that they develop distinct equilibrium domain morphologies.

Norbornene-ended polybutadiene (PBu) macromonomers have been prepared via two different routes: α-norbornenyl-polybutadiene was derived from a norbornene-containing carbanionic initiator, whereas ω-norbornenyl samples were obtained through deactivation of living polybutadienyl anions by a norbornene-based deactivator. Out of four alkylidene complexes tried, the molybdenum alkylidene complex that contains two alkoxide ligands was found to be the most suitable initiator for the ring-opening metathesis polymerization of these macromonomers.

Norbornene-ended polybutadiene (PBu) macromonomers have been prepared via two different routes: α-norbornenyl-polybutadiene was derived from a norbornene-containing carbanionic initiator, whereas ω-norbornenyl samples were obtained through deactivation of living polybutadienyl anions by a norbornene-based deactivator. Out of four alkylidene complexes tried, the molybdenum alkylidene complex that contains two alkoxide ligands was found to be the most suitable initiator for the ring-opening metathesis polymerization of these macromonomers.