Atsushi Goto

Temperature‐Selective Dual Radical Generation from Alkyl Diiodide: Applications to Synthesis of Asymmetric CABC Multi‐Block Copolymers and Their Unique Assembly Structures

Temperature-selective radical generation from a newly designed alkyl diiodide (I-R2 -R1 -I) was studied. R1 -I and I-R2 had different reactivities for generating alkyl radicals in the presence of a tetraoctylammonium iodide (ONI) catalyst. Taking advantage of the temperature selectivity, we used the alkyl diiodide as a dual initiator in ONI-catalyzed living radical polymerization to uniquely synthesize CABC non-symmetric multi-block copolymers. Because of their non-symmetric structure, CABC multi-block copolymers form unique assemblies, that is, Janus-type particles with hetero-segment coronas and flower-like particles with hetero-segment petals.

Use of poly(methyl methacrylate) with an unsaturated chain end as a macroinitiator precursor in organocatalyzed living radical block polymerization

Poly(methyl methacrylate) (PMMA) with an unsaturated chain end (PMMA–Y) was transformed into PMMA–iodide (PMMA–I) in situ in the organocatalyzed living radical polymerization of butyl acrylate; the generated PMMA–I acted as a macroinitiator to successfully generate a PMMA–PBA–I block copolymer, where PBA is poly(butyl acrylate). The use of PMMA–Y overcomes the drawback of the direct use of the isolated PMMA–I, i.e. its general lack of long-term stability upon storage, and thus significantly improves the ease of operation. This method is highly suitable for practical use. A quantitative mechanistic study on the transformation of PMMA–Y into PMMA–I was also conducted.

Synthesis of transition-metal-free and sulfur-free nanoparticles and nanocapsules via reversible complexation mediated polymerization (RCMP) and polymerization induced self-assembly (PISA)

NaI-catalyzed reversible complexation mediated living radical polymerization (RCMP) was combined with polymerization induced self-assembly (PISA) to generate self-assemblies. Poly(methacrylic acid) (PMAA) and poly(methyl methacrylate) (PMMA) were used as hydrophilic and hydrophobic segments, respectively, to generate self-assemblies. Micelles (nano-particles), worms (nano-cylinders), and vesicles (nano-capsules) were generated in ethanol at 5–9 wt% solid content. The self-assemblies were also fixed (crosslinked) by using a cross-linkable divinyl monomer, i.e., ethylene glycol dimethacrylate (EGDMA), as a co-monomer in the hydrophobic segment. NaI-catalyzed RCMP is a heavy-metal-free and sulfur-free synthetic method. The nano-particles, cylinders, and capsules obtained through the RCMP/PISA process are highly attractive for biomedical, healthcare, cosmetics, and agrochemical release applications.

Versatile preparation of surface-skinless particles of epoxy resin-based monoliths using a well-defined diblock copolymer surfactant

Epoxy resin-based monoliths, possessing a bicontinuous structure that consists of a porous channel and a resin skeleton, have a broad range of applications such as chromatography; however, the preparation of spherical particles has been limited so far. This is the first report on a versatile and facile preparation method for surface-skinless monolithic particles with micrometer diameters by polymerization-induced phase separation in an oil-in-oil emulsion system. The key to success is the addition of a well-defined block copolymer surfactant, compatible for both the dispersed and continuous phases in suspension polymerization. In essence, the volume ratio and length of the block copolymers are crucial to control the stability of the emulsion and the suppression of the unwanted skin layer on the surface of the produced particles. The present work represents a new direction for versatile and large-scale preparation of monolithic particles, including silicates and polyacrylates, with several surface properties.

Facile Fabrication of Concentrated Polymer Brushes with Complex Patterning by Photocontrolled Organocatalyzed Living Radical Polymerization

Photocontrolled surface-initiated reversible complexation mediated polymerization (photo-SI-RCMP) was successfully applied to fabricate concentrated polymer brushes with complex patterning structures. Positive-type patterned polymer brushes were obtained by photo-SI-RCMP under visible light (550(±50)u2005nm) using photomasks. A particularly interesting finding was that negative-type patterned polymer brushes were also obtainable in a facile manner. A nonspecial UV light (250-385u2005nm) enabled the preparation of pre-patterned initiator surfaces in a remarkably short time (1u2005min), leading to negative-type patterned polymer brushes. Based on this unique selectivity between visible and UV light, the combination of two patterning techniques enabled the preparation of complex patterned brushes, including diblock copolymers, binary polymers, and functional binary polymers, without multistep immobilization of one or more initiators on the surfaces.