Block Copolymer Nanodomains Research Articles

Graphoepitaxial cylindrical block copolymer nanodomains evaluated as bit patterned media template

To utilize self-assembled block copolymer structures to fabricate the template of bit patterned media, two basic issues of block copolymer nanodomains need to be considered: (a) size uniformity and (b) position accuracy. The manipulation of domain position was achieved here by graphoepitaxy of cylindrical block copolymer domains in a topographic trench pattern. Trench surface may be neutralized to guarantee the perpendicular orientation of cylindrical domains on the trench bottom surface and domain alignment along the trench sidewall. The size distributions of cylindrical domains on both flat surface and topographically patterned surface have been analyzed and the correlation between the size distribution and the local-range order is addressed. The distributions of the domain size and domain position-related parameters, such as the dot spacing along the axis (parallel to the trench edge) and across the axis, have been investigated as a function of the number of domain rows in the trench. Qualitatively, line edge roughness or linewidth roughness of trenches attributes to the larger variation of spacing across the axis. Finally, a surface trench without neutralization pretreatment was found to enable the graphoepitaxy of block copolymer domains with an areal density >1 Tdot/in.2.

Thermodynamic Confinement and α-Helix Persistence Length in Poly(γ-benzyl-l-glutamate)-b-poly(dimethyl siloxane)-b-poly(γ-benzyl-l-glutamate) Triblock Copolymers

The structure and the associated dynamics of a series of poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) (PBLG-b-PDMS-b-PBLG) triblock copolymers were investigated using small- and wide-angle X-ray scattering, NMR, transmission electron microscopy, and dielectric spectroscopy, respectively. The structural analysis revealed phase separation in the case of the longer blocks with defected alpha-helical segments embedded within the block copolymer nanodomains. The alpha-helical persistence length was found to depend on the degree of segregation; thermodynamic confinement and chain stretching results in the partial annihilation of helical defects.

Nanocellular Structures in Block Copolymers with CO2-philic Blocks Using CO2 as a Blowing Agent: Crossover from Micro- to Nanocellular Structures with Depressurization Temperature

Uniform nanocellular structures are successfully formed within the spherical nanodomains of CO2-philic fluorinated blocks in Poly[styrene-block-4-(perfluorooctylpropyloxy)styrene] (PS−PFS) and Poly[styrene-block-perfluorooctylethyl methacrylate] (PS−PFMA) monoliths using supercritical (SC) carbon dioxide (CO2). The nanocells have a very small surface area, indicative of the closed cell structure. Temperature of depressurization (Td) is the key to the uniform nanocellular formation in the CO2-philic block nanodomains: Td must be well below the glass transition temperature (Tg) of the skeleton PS domains in the presence of CO2. As Td is raised and approaches Tg, the nanocellular structure crosses over to the microcellular structure on the order of micrometers, which is the typical cell structure formed via the conventional foaming mechanism. Two independent cell formation mechanisms coexist when Td is in the vicinity of Tg. The nanocells have upper limit diameter of ca. 40 nm, which is apparently determined by the balance between the expansion of nanocells and diffusion of CO2 either into the growing microcells or to the surface to evaporate. When Td is set above Tg, we simply find conventional microcells only slightly smaller than those formed in homopolystyrene, which are indicative of the negligible effect of block copolymer nanodomains in the conventional process.