The conformation of a single poly(methyl methacrylate) (PMMA) chain was studied by scanning near-field optical microscopy (SNOM). Here we discuss the conformation of PMMA in the confined geometry of the thin film with a thickness less than the unperturbed chain dimension in the bulk state. The direct observation by SNOM was performed for individual fluorescence-labeled PMMA chains dispersed in the thin films of the unlabeled PMMA prepared by the spin coating and Langmuir-Blodgett techniques. We examined the effect of the constraint in the height direction on the radius of gyration in the direction parallel to the film surface, R xy , i.e., the chain dimension normal to the confinement. In the thickness range of 1-100 nm, R xy in an ultra-thin film was not significantly altered from that in the bulk state, indicating that the PMMA chain has lowered interchain entanglement in the ultra-thin film. Polymer thin films have been widely used in various fields (e.g., coatings and adhesives) and have been extensively explored from both the fundamental and applied points of view. The physical properties of the polymeric thin film differ from those in the three-dimensional bulk state when the thickness is less than the unperturbed dimension of the polymer chain.1-8 The effect of the interaction between the polymer chain and the interface is a crucial factor to determine the characteristic properties of the thin film. As well as the interface effect, the effect of the reduced degree of freedom of a polymer chain due to the spatial confinement is also important. The properties of the individual chain and the interaction among the surrounding chains would be altered from the bulk state. The conformation of the single polymer chain is one of the most fundamental issues to understand the physics of the polymer thin film; therefore, it has attracted much attention and has been extensively studied by many researchers. The scaling theory predicted that the radius of gyration, R g , of the polymer chain with the degree of polymerization of N would be expressed as R g $ N 0:5 for the two-dimensional chain, indicating that the two-dimensional chain would be segregated. 9 Computer simulation studies have shown that for the polymer chain restricted between two walls separated by less than the bulk R g the chain dimension parallel to the surface is not dependent on the gap between the walls and that the value of R g is scaled by a factor of $ 0:5 in the two-dimensional limit. [10][11][12][13][14][15] Although the experimental method to study the conformation of the polymer chain in the ultra-thin film is limited because of the weak signal from the low sample volume, the small angle neutron scattering (SANS) is a powerful technique to probe the chain conformation. Kraus et al. studied the chain morphology of polystyrene (PS) in the thin film of the regular and deuterated PS by SANS experiments. 16 The radius of gyration, R g , in the parallel direction to the film surface increased with the decrease of the film thickness for the thicknes...

The experiments described here were designed to characterize the location and orientation of a single homopolymer chain embedded in a block copolymer lamella. We used scanning near-field optical microscopy (SNOM) to image individual perylene-labeled poly(methyl methacrylate) (PMMA-Pe) chains sparsely distributed in lamellar phases formed by poly(styrene-b-methyl methacrylate) (PS−PMMA). By calculating the center of mass (CM) of the PMMA-Pe chain, we found that the homopolymer chains were distributed throughout the PMMA-rich domain layers, with the maximum CM population at the domain centers. The orientation of the homopolymer chains is dependent on the location of the CM of the homopolymer in the PMMA block domain. If the CM locates at the domain center, the homopolymer chain prefers an orientation parallel with the lamella. If the CM is close to the block interface, the homopolymer chain tends to orient itself perpendicularly to the interface. This location dependence of chain orientation is likely the result of the rotational freedom of PMMA-Pe chains in the PMMA-rich domains of the PS−PMMA block copolymer lamella.

Polymer nanoporous materials with periodic cylindrical holes were fabricated from microphase‐separated structure of diblock copolymers consisting of a radiation‐crosslinking polymer and a radiation‐degrading polymer through simultaneous crosslinking and degradation by γ‐irradiation. A polybutadiene‐block‐poly(methyl methacrylate) (PB‐b‐PMMA) diblock copolymer film that self‐assembles into hexagonally packed poly(methyl methacrylate) cylinders in polybutadiene matrix was irradiated with γ‐rays. Solubility test, IR spectroscopy, and TEM and SEM observations for this copolymer film in comparison with a polystyrene‐block‐poly(methyl methacrylate) diblock copolymer film revealed that poly(methyl methacrylate) domains were removed by γ‐irradiation and succeeding solvent washing to form cylindrical holes within polybutadiene matrix, which was rigidified by radiation crosslinking. Thus, it was demonstrated that nanoporous materials can be prepared by γ‐irradiation, maintaining the original structure of PB‐b‐PMMA diblock copolymer film. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5916–5922, 2007

The phase-separated structure of poly(isobutyl methacrylate)-block-poly(octadecyl methacrylate) (PiBMA-b-PODMA) monolayer and single poly(isobutyl methacrylate) (PiBMA) chain dispersed therein were investigated by scanning near-field optical microscopy (SNOM), which enabled us to observe with high spatial resolution beyond the diffraction limit of light. The conformation of the individual homo-PiBMA chains was quantitatively evaluated from the fluorescence intensity distribution. We found that the homo-PiBMA chains were almost located at the center of the PiBMA domain. The homo-PiBMA chain was oriented itself depending on its location in the PiBMA domain. When the homo-PiBMA chain locates at the center of the PiBMA domain, it tends to orient itself in the direction parallel to the interface between the two microdomains. When the homo-PiBMA chain locates near the interface, it orients itself in the direction perpendicular to the interface.

Poly(methacrylate)s labeled with perylene diimide (PDI) derivatives were synthesized. The dye moiety was selectively introduced by appropriate molecular design at (1) the chain end, (2) the center segment of the main chain, and (3) the whole chain contour. The bright fluorescence from PDI allows the direct observation of the single polymer chain with a high signalto-noise ratio. The three-dimensional orientation of the chain segment and the conformation of the polymer chains were successfully observed at the single molecule level.