Ayako Ichimura

Synthesis of microspheres with microphase‐separated shells

Novel structural microspheres of the Janus type, with microphase-separated polystyrene (PS) and poly(tert-butyl methacrylate) (PBMA) shells and crosslinked poly(2-vinyl pyridine) (PVP) cores, were synthesized with the crosslinking of PVP spherical domains in poly(styrene-block-2-vinyl pyridine-block-tert-butyl methacrylate) ABC triblock terpolymer film with PS/PBMA lamellae–PVP spherical structures. For the formation of lamellae-sphere structures, toluene, which was a selective solvent for the ABC triblock terpolymer, was used. With the crosslinking of PVP spheres in the microphase-separated film with 1,4-diiodobutane gas, the microphase structure of the terpolymer was fixed, and microspheres composed of microphase-separated PS and PBMA shells and P2VP cores were obtained. The size distribution of the purified microspheres was narrow. The characteristics of the microspheres and their aggregation behaviors in selective solvents were investigated by transmission electron microscopy and light scattering methods.

Synthesis of cyclic diblock copolymers by interfacial condensation

Abstract The well-defined α,ω-dibromopropyl polyisoprene-block-polystyrene-block-polyisoprene copolymer was prepared by coupling of corresponding triblock dianion end-capped with 1,2-diphenylethylene with a large excess of 1,3-dibromopropane. End-to-end ring closure of the α,ω-dibromopropyl triblock copolymer was performed by interfacial condensation between the aqueous phase (1,6-diaminohexane) and the organic phase (difunctional triblock copolymer). The limited field of reactions such as at the interface was very effective for ring closure. In the strongly segregated state, the lamellar domain spacing of cyclic diblock copolymer was smaller than that of linear A–B diblock copolymer with the same molecular weight.

Cross-linking reaction of poly(4-vinylpyridine) cylindrical microdomains of poly(α-methylstyrene)-block-poly(4-vinylpyridine) films and characterization of soluble ribbon-like nanopolymers

Abstract The ribbon-like nanopolymers were prepared by the cross-linking reaction of poly(α-methylstyrene)-block-poly(4-vinylpyridine) (PMS-block-P4VP) diblock copolymer films exhibiting P4VP cylindrical microdomains with the vapour of 1,4-dibromobutane in the solid state. It was indicated from the transmission electron microscopy (TEM) and the small-angle X-ray scattering (SAXS) that these cross-linked products had a structure of ribbon-like nanopolymers. It was found from the curve fitting on the static light scattering (SLS) intensity that such nanopolymers were in agreement with the conformation of the Gaussian model.

Synthesis of core–shell type microsphere with reactive seed microspheres

Monodispersed poly(methyl methacrylate) (PMMA) particles (seed microspheres) were synthesized with the living radical initiators, tetramethylthiuram disulfide, or p-xylene dimethyldithiocarbamate by suspension polymerization in water media with and without divinyl benzene as a crosslinker. Monodispersed spherical microspheres with PMMA core–polyacrylamide shells were synthesized by UV irradiation to the seed microsphere–acrylamide aqueous solution. The content and the molecular weight of the polyacrylamide shell chain were controlled by changing the acrylamide feed and irradiation time of the UV light. The microspheres became dispersible to water after the UV irradiation.

Architecture of hybrid structures on starpolymers formed by polymerization-induced phase separation

Polyisoprene (PI) star polymers with many arms formed a body-centred cubic (BCC) structure near the overlap threshold (C*) in solution. After the PI stars (arm number n above about 90) revealed a superlattice of BCC structure in vinyl monomers (methyl methacrylate, styrene and t-butyl acrylate), the hybrid structures were constructed by locking the ordered superlattice into a solid matrix by means of free radical polymerization of the vinyl monomers. The morphologies of the polymerization-induced phase separation depended strongly on the arm number, propagation rate of the vinyl monomers, and the addition of chain transfer or cross-linking agents.

Structural ordering of gradient-modulus star copolymers in solution and in bulk film

Abstract Gradient-modulus stars (arm number n = 19–289, polystyrene = 44 mol%) were prepared by cross-linking poly(isoprene-b-isoprene/styrene-b-styrene) tapered block monoanions with divinylbenzene. Structural orderings of stars were investigated through the small-angle x-ray scattering in benzene and through the transmission electron microscopy measurements. All of the star samples formed a lattice with a body-centered-cubic structure near the overlap threshold (C*). In the star specimens with arm numbers n < 67, this structure changed to the lamellae in the bulk film. In the star specimen with n = 289, it showed an interesting tendency for the spherical structure to be maintained with the dimension of the unimolecular micelle even in the bulk film.