Koji Ishizu

Architecture of nanostructured polymers

Abstract This paper reviews the synthesis and properties of nanostructural polymers with different macromolecular architecture. Special emphasis is placed on hyperbranched polymers, rod-like macromolecules and polymer brushes. Hyperbranched polymers were prepared by various types of living radical mechanisms of functionalized vinyl monomers and showed hard sphere-like behavior in dilute solution with increasing degree of branching. This reflected on the compact nature of the hyperbranched macromolecules. Rod-like macromolecules were prepared by crosslinking cylindrical microdomains of block copolymers in the solid state or cylindrical micelles in solution. In general, polymer brushes were prepared by homopolymerization or copolymerization of macromonomers. Both solutions of rod-like macromolecules and polymer brushes formed a unimolecule structure even in high concentration. Thus, the particular chemical structures of rod-like macromolecules and polymer brushes were influenced significantly by densely branched side chains.

Synthesis of hyperbranched polymers by self‐addition free radical vinyl polymerization of photo functional styrene

The hyperbranched polystyrenes are prepared by the self-addition free radical vinyl polymerization of N,N-diethylaminodithiocarbamoylmethyletyrene (DTCS). DTCS monomers play an important role in this polymerization system as an inimer that is capable of initiating living radical polymerization of the vinyl group. The compact nature of the hyperbranched macromolecules is demonstrated by viscosity measurements compared to the linear analogues.

Synthesis and microphase-separated structures of star-block copolymers

Abstract Highly branched star-shaped polymers such as (AB) n stars of asymmetric diblock arms, star homopolymers, and gradient-modulus stars led to hierarchical structure transformation of cubic lattices in film formation. The ordered microphase-separated morphologies for A n B n and A m B n stars were quite different from those that occurred in the corresponding linear block copolymer systems. Thus, the particular chemical structures of star-block copolymers were influenced significantly by incompatibility effects.

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.

Organic nanoparticle (hyperbranched polymer)-dispersed photopolymers for volume holographic storage

We report on the use of hyperbranched polymers (HBPs) acting as mobile organic nanoparticles doped in methacrylate photopolymers for highly efficient volume holographic recording. Two types of reduced HBPs having the average size of 10nm are synthesized. The diffraction efficiency near 100% in the green (532nm) and substantive polymerization-shrinkage suppression in this photopolymer system are demonstrated. Periodic assembly of HBPs under holographic exposure is also observed.

Introduction of colloidal silver into a poly(2-vinyl pyridine) microdomain of microphase separated poly(styrene-b-2-vinyl pyridine) film

Abstract Colloidal silver was introduced into microphase separated poly(styrene- b -2-vinyl pyridine) diblock copolymer film by reduction of silver iodide. It was possible to localize silver in only poly(2-vinyl pyridine) phases in the microphase separated film. The polystyrene phases did not contain silver. The presence of silver in the film was confirmed by transmission electron microscopy.

Synthesis of microspheres with ‘hairy-ball’ structures from poly(styrene-b-2-vinyl pyridine) diblock copolymers

Monodispersed microspheres with ‘hairy-ball’ structures were synthesized by crosslinking poly(2-vinyl pyridine) spherical microdomains in poly(styrene-b-2-vinyl pyridine) [P(S-b-2Vp), Mn = 3.2 × 105, 2Vp = 15.5 mol%] diblock copolymer film cast from 1,1,2-trichloroethane solution. The yield of the microspheres increased to 80.8 wt% with increasing reaction time. The number-average external diameter of the microspheres was 50 nm and the microspheres were stiff and truly spherical. After crosslinking, the number-average diameter of the P2Vp ball (Dn) decreased to 24 nm from the Dn of the starting block copolymer film (30.3 nm). This was due to the removal of the uncrosslinked block copolymer chains by purification of the crosslinked products. From the g.p.c. measurement with refractive index and u.v. double detected at 254 nm, the surface property of the microspheres was found to be very similar to that of PS. PS chains were expanded on the P2Vp ball, and the observed and theoretical degrees of stretching of the microsphere (1.13 and 1.12, respectively) were in good agreement.

Core-shell type polymer microspheres prepared from poly(styrene-b-methacrylic acid)—1. Synthesis of microgel

Polymer microspheres with poly(methacrylic acid) (PMMA) core and poly(styrene) shell were synthesized from poly(styrene-b-methacrylic acid) (SAI, Mn = 5.35 × 104, methacrylic acid = 19.7 mol%) by casting from dioxane with hexamethylenediamine and N,N′-dicyclohexyl carbodiimide as the crosslinking reagents. The optimum amounts of the crosslinking reagents (C = [NH2]/[COOH]) were between 20 and 40 mol%. From the results of transmission electron microscopy and turbidimetric titration, the microsphere SA1-20M prepared with C = 20 mol% had a soft PMAA core and was flattened on the carbon substrate. The PMAA core of microsphere SA1-40M with C = 40 mol% was hard. From turbidimetric titration in the THF/water system, it was found that the soft microsphere SA1-20M was more swollen than SA1-40M.

Novel synthesis and characterization of cyclic polystyrenes

Abstract To overcome some experimental difficulties, a new approach to cyclic polystyrenes with narrow molecular weight distribution is proposed. The well-defined α,ω-dibromobutyl polystyrene was prepared by direct coupling of the polystyryl dianion with a large excess of 1,4-dibromobutane. End-to-end ring closure of the α,ω-dibromobutyl polystyrene was performed by interfacial condensation between the aqueous phase (hexamethylene diamine) and the organic toluene phase (polystyrene precursor). The limited field of reactions such as at the interface was very effective for ring closure. The conversion of cyclic polymers was very high (more than 80%) at polystyrene precursor concentration of 10 −3 M. The hydrodynamic size of the cyclic polymers was substantially less than that of the corresponding linear precursor.

Microsphere synthesis of polypyrrole by oxidation polymerization

Abstract Polymer microspheres were synthesized by oxidation polymerization of pyrrole (Py) with functional poly(vinyl alcohol) having pendent Py groups (PVA-P) or poly(vinyl alcohol) (PVA) as an emulsifier in various solvent media. In this polymerization system, PVA-P acted not only as a comonomer but also as a stabilizer. The diameter (submicrometre range) of the polymer microspheres decreased with increasing PVA concentration in the medium. Polypyrrole (PPy) microspheres had a very narrow particle size distribution ( D W / D n . The particles stabilized with PVA-P were smaller than the corresponding particles stabilized with PVA. The use of PVA-P as an emulsifier was favourable to the formation of micelles with Py monomers. The electrical conductivity of the PPy particles was in the range 10−5–10−1 S cm−1, depending on the amount of dopant.