Self‐organization on three length scales is exhibited by a block copolymer of styrene and an oligothiophene‐bearing isoprene in cast films. For example, a phase‐separated nanostructure consisting of π‐conjugated oligothiophene molecules is self‐aligned perpendicular to the substrate, as revealed in a TEM image of a section through the film (see picture).

No abstract

We studied the morphology development of ternary immiscible blends through an interfacial reaction between components. This phenomenon was observed in two ternary blend systems; one is composed of polyamide(6) (PA6), polycarbonate (PC), and poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), and the other is composed of PA6, PC, and polystyrene (PS), where PA6 forms the continuous matrix in both blend systems. Maleinated SEBS (SEBS-gMA) or maleinated PS (PS-gMA) is incorporated with its unmodified polymer (un-SEBS and un-PS, respectively) at various ratios into the blends of PA6/PC. The blends of PA6/PC/un-SEBS and PA6/PC/un-PS show a similar phase formation in which the two dispersed polymers are stuck together in a PA6 matrix. The use of the maleinated polymers instead of their unmodified polymers in the blends of PA6/PC changes the phase formation drastically. The maleinated polymers react with amine end groups of PA6 at the interface during the melt mixing. Through this interfacial reaction, the domains of the maleinated polymers are dispersed in the PA6 matrix at about 100 nm in diameter, and at the same time the maleinated polymers encapsulate the PC domains. This means that the interfacial reaction induces the change of the formation of the domains composed of two dispersed phases. That is, the interfacial reaction changes the formation from “stack formation”, where the two dispersed polymers are stuck together, to “capsule formation”, where the PC domains are encapsulated by the other phase. Moreover, when both the unmodified and its maleinated polymers are incorporated together in a variety of ratios, the encapsulation by SEBS onto the PC domains gradually becomes incomplete as the ratio of the unmodified SEBS increases, whereas the encapsulation by PS of the PC is complete even when un-PS and PS-gMA are incorporated together. We discuss this morphology development in terms of the change of interfacial tensions between PA6 and maleinated polymers through the interfacial reaction. We assumed that the reduction of interfacial tension through the interfacial reaction is the driving force for this morphology development.

We present a simple dry process to create nanoscale arrangements of metal nanoparticles within block copolymer films. This process involves only one step such that the vapor of palladium(II) acetylacetonato (Pd(acac)2) is exposed to a polymer film in a nitrogen atmosphere at 180 °C for periods up to 2 h. The Pd(acac)2 vapor penetrates into the film and then is decomposed and reduced to a metallic state to form nanoparticles therein. When block copolymer films having nanoscale microdomain structures are used, the metal complex is selectively reduced in one of the phases to give nanoscale arrangements of the metal particles that reflect the microdomain structure of the used block copolymer. In symmetric diblock copolymers of poly(styrene)-block-poly(methyl methacrylate) (PS-b-PMMA), Pd(acac)2 is selectively reduced in the PS lamellae to yield Pd nanoparticles with the average diameter ranging from 3 to 4 nm with a narrow size distribution, depending on the molecular weight. As a result, the Pd nanoparticles are arranged in a periodic lamellar manner within the film. In an asymmetric diblock copolymer having an alcohol group in the side chain of one of the blocks, poly(styrene)-block-poly(hydroxylated polyisoprene) (PS-b-PIOH), where the PIOH block forms spherical domains in the PS matrix, the Pd particles are selectively assembled in the PIOH domains, not in the PS phase. This approach would be of general applicability to any block copolymers, and the particles should be assembled in the phase having relatively stronger reducing power. The vapor of the metal complex can penetrate into the film deeply, and thus the arrangements of the particles are in a three-dimensional array within a film. Co(acac)2 is also evaluated and gives Co nanoparticles within the PIOH domains in the PS-b-PIOH film as does as Pd(acac)2. Electron spectroscopic imaging and electron energy loss spectroscopy on an energy-filtering transmission electron microscope were performed for nanoscale chemical analysis to investigate the reaction products of Co(acac)2 within the polymer films in detail.

No abstract