The monomer concentration affecting the morphology of the in situ synthesized block copolymer nano-objects during the macro-RAFT agent mediated dispersion polymerization is investigated. It is found that the monomer concentration exerts great influence on both the polymerization kinetics of the poly(ethylene glycol) trithiocarbonate macro-RAFT agent mediated dispersion polymerization and the morphology of the in situ synthesized nano-objects of the poly(ethylene glycol)-block-polystyrene (PEG-b-PS) diblock copolymer. The poly(ethylene glycol) trithiocarbonate macro-RAFT agent mediated dispersion polymerization of styrene in the alcoholic solvent at 50% high monomer concentration follows similar kinetic behaviour to homogeneous RAFT polymerization as indicated by the linear ln([M]0/[M])-time plot, and the good control both on the molecular weight of the PEG-b-PS diblock copolymer and the molecular weight distribution is achieved. With the extension of the PS block, the morphology of the in situ synthesized PEG-b-PS nanoobjects changes from the porous nanospheres to the bicontinuous nanospheres and finally to the entrapped vesicles, which is much different from the dispersion RAFT polymerization under low monomer concentration. Our results demonstrate that the monomer concentration is an important parameter affecting the morphology of the in situ synthesized block copolymer nano-objects.

Hollow polymeric nanotubes have the potential to be employed as advanced nanomaterials in a variety of applications; however, their synthesis from the assembly of coil−coil diblock copolymers (DBCPs) has typically been limited. Herein, we report a novel method for synthesis of coil−coil DBCP nanotubes by implementing RAFT dispersion polymerization in low molecular weight poly(ethylene glycol) (PEG). This method for the in situ synthesis of coil−coil DBCP nanotubes is particularly versatile and can be achieved with a range of block copolymers including poly(N-isopropylacrylamide)-blockpolystyrene (PNIPAM-b-PS), poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS), and poly(methyl methacrylate)-blockpolystyrene (PMMA-b-PS). Using this approach, several interesting coil−coil DBCP tubular morphologies are observed, including single-wall nanotubes, multiwall nanotubes, and porous nanotubes. Furthermore, RAFT dispersion polymerization conducted in the presence of Ag nanoparticles can be used to yield complex tubular nanocomposites. The structure of these nanotubes such as the wall thickness and surface roughness can be tuned by varying the degree of polymerization (DP) of the solvophobic polystyrene block and/or the Ag fraction in the Ag/DBCP nanocomposites.

A new method for the synthesis of metal/block-copolymer nanocomposites of poly(4-vinylpyridine)-b-polystyrene (P4VP-b-PS) and Ag nanoparticles by dispersion RAFT polymerization is proposed.

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