Naturally occuring and synthetic cyclic macromolecules

International audienc

Synthesis of macrocyclic copolymer brushes and their self-assembly into supramolecular tubes

We report on an efficient route to design large macrocyclic polymers of controlled molar mass and narrow dispersity. The strategy is based on the synthesis of a triblock copolymer ABC, in which the long central block B is extended by two short A and C sequences bearing reactive antagonist functions. When reacted under highly dilute conditions, this precursor produces the corresponding macrocycle by intramolecular coupling of the A and C blocks. Chloroethyl vinyl ether was selected as the monomer for the central block B, because it can be readily derivatized into brushlike polymers by a grafting process. The corresponding macrocyclic brushes were decorated with polystyrene or randomly distributed polystyrene and polyisoprene branches. In a selective solvent for the polyisoprene branches, the macrocyclic brushes self- assemble into cylindrical tubes of up to 700 nanometers

From combs to comb-g-comb centipedes

International audienc

Atomic Force Microscopy Imaging and Dilute Solution Properties of Cyclic and Linear Polystyrene Combs

Large macrocyclic poly(chloroethyl vinyl ether)s (PCEVE)s of controlled ring size and narrow distribution were synthesized by a ring-closure process involving the intramolecular formation of acetal linkages between the two external blocks of linear ABC triblock precursors prepared by living cationic polymerization. The corresponding shape-persistent ring P(CEVE-g-PS) combs having macrocyclic poly(chloroethyl vinyl ether) backbones and polystyrene side chains were then synthesized by a “grafting onto” technique and characterized by size exclusion chromatography (SEC) analysis and atomic force microscopy (AFM) imaging of isolated molecules. Quantitative hydrolysis of the acetal linkages of the macrocyclic PCEVE backbone in acidic conditions yields the linear poly(chloroethyl vinyl ether)-g-polystyrene) homologue and allows a direct comparison of the characteristics and dimensions of cyclic and linear comb architecture. The influence of the chain architecture and PS graft dimensions on the dilute tetrahydrofuran (THF) solution properties, radius of gyration, and hydrodynamic radius of the comb copolymers is also studied and compared to data reported for linear and cyclic polystyrene chains

AFM image analysis applied to the investigation of elementary reactions in the synthesis of comb star copolymers

International audienc

Janus combs with polystyrene and poly(methyl vinyl ether) branches: Design, characterization and properties

The synthesis of Janus like comb copolymers constituted of polystyrene and poly(methyl vinyl ether) branches attached to a diblock backbone has been achieved using living/controlled cationic and anionic building steps associated to grafting from and grafting onto coupling processes. These comb-b-comb structures behave as isolated objects in good solvents as well as when deposited on an appropriate substrate from a good solvent. In contrast, thanks to their amphiphilic Janus-like structure, they behave like linear diblock copolymers when placed in a selective solvent of one of the comb moieties, forming stable large spherical super-micelles that could be observed on mica support

Synthesis of (poly(chloroethyl vinyl ether)-g-polystyrene)comb-b-(poly(chloropyran ethoxy vinyl ether)-g-polyisoprene)comb copolymers and study of hyper-branched micelle formation in dilute solutions

Poly(styrene)comb-b-poly(isoprene)comb copolymers having a heterofunctional polyvinyl ether diblock backbone were synthesized by the grafting onto method. Their synthesis involves in a first step the selective coupling reaction of polystyryllithium chains onto the reactive chloroether functions of a poly(chloroethyl vinyl ether) first block while the second block poly(pyranethoxy vinyl ether) remains unchanged, yielding Poly(styrene)comb with a poly(pyranethoxy vinyl ether) tail. In a second step, living polyisoprenyllithium chains are grafted onto the second block previously modified to introduce reactive chlorobutyl functions. The obtained high molar masses PScomb-b-PIcomb copolymers exhibit a low polydispersity and a controlled number of branches. Their characteristics and behavior were further studied as isolated objects using imaging technique such as atomic force microscopy and using light scattering in a good solvent for PS and PI moieties, and in a selective solvent of PIcomb blocks. The PScomb-b-PIcomb copolymers adopt a cylindrical conformation in good solvent and self-assemble in micelles by association of the combPS blocks in heptane