Hidekazu Sugimori

Phase Transition and Phase Transformation in Block Copolymer Nanoparticles

Block copolymer nanopaticles were prepared from the mixture solutions containing good/poor solvents by a simple evaporation process. The block copolymers formed disorder, unidirectionally stacked lamellar, and onion-like structures in nanoparticles depending on preparation temperatures. Thermal annealing induced the disorder-order phase transition and order-order phase transformation in the block copolymer nanoparticles, even though the annealing temperature is lower than the of one polymer segment. The unusual thermal behaviors suggest that the glass transition temperature of the block copolymer is decreased by the effect of nanoparticle, whose surface areas are larger than their volumes.

Three-dimensional observation of confined phase-separated structures in block copolymer nanoparticles

The effect of confinement on microphase-separated structures of a diblock copolymer is investigated in nanoparticles serving as a three-dimensional (3D) confinement system. We succeeded in preparing nanoparticles having various types of complex structures from hydrophobic diblock copolymers by a simple solvent evaporation method. The detailed 3D structural analysis of the nanoparticles by transmission electron microtomography (TEMT) revealed that complex structures were found only to form in the nanoparticle surface region, the thickness of which corresponded to the single-molecule length of the block copolymer in the bulk state. These results indicate that 3D confinement fundamentally affects block copolymer self-assemblies most strongly in the surface region of nanoparticles but only weakly in the central region.

Structural characterization of the Fddd phase in a diblock copolymer thin film by electron microtomography

A 3-dimensional Fddd network structure of a polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer (Mn = 31500, fPI = 0.645) was observed for the first time in real space by transmission electron microtomography (TEMT). In a 650 nm thick film of the PS-b-PI thin film on a silicon wafer, the Fddd phase was developed after annealing at 215 °C for 24 h. The single network structure consists of the connected tripodal units of minor PS block domains. The {111}Fddd plane, the densest plane of the minor PS phase, was found to orient parallel to the film plane. The transitional structure from the wetting layer at the free surface to the internal {111}Fddd plane via a perforated layer structure was also observed.

Direct Three-Dimensional Observations of Order-Order Transition from Gyroid to Cylindrical Structures in a Block Copolymer

An order-order transition (OOT) from the bicontinuous double-gyroid (G) structure to the hexagonally-packed cylindrical (C) structure in a poly(styrene-block-isoprene) (SI) block copolymer was investigated by transmission electron microtomography (TEMT). The coexistence of the G and C microdomains during the OOT was observed. The boundary structures between the G and C microdomains were directly three-dimensionally visualized. It was found that the {220} plane of the G structure changed to the {110} plane of the newlygenerated C structure, consistent with Matsen’s prediction from his computer simulations based on self-consistent field (SCF) theory.

Polymer nanotechnology applied to polymeric nano-soft-materials

We have been developing new techniques to evaluate polymer nano-alloys and nano-composites. This nanotechnology can be classified into nano-three dimensional (3D) measurement, nano-physical properties evaluation systems, and nano-spectroscopy. As for the nano-3D measurement, we developed polymer oriented energy-filtered 3D transmission electron microscopy. With this method, we can access important 3D structural and elemental information that cannot be obtainable from ordinary TEM. Nano-physical properties evaluation systems were also established by developing atomic force microscopy force-distance curve measurement. The distribution of mechanical properties such as Youngs modulus and adhesive energy was quantitatively obtained on high lateral resolution. These methods give new pieces of information unobtainable by the conventional techniques on polymer nanotechnology. Several results are shown here.