Thermal fluctuation and elasticity of lipid vesicles interacting with pore-forming peptides.

The thermal fluctuation and elasticity of dioleoyl-phosphocholine large unilamellar vesicle interacting with pore-forming peptide, melittin, were investigated by neutron spin-echo measurements. The relaxation behavior of the membrane fluctuation with different peptide to lipid molar ratio P/L can be divided into three regions, resulting from characteristic changes of the effective bending modulus κ(˜) of the membrane which includes the effects of internal dissipation within the membrane. At low P/L, melittin is adsorbed parallel to the surface of membrane and κ(˜) decreases significantly due to perturbation of hydrocarbon chain packing. At a critical P/L, melittin forms pores in the membrane and κ(˜) starts to increase slightly due to high pore rigidity. At higher P/L where the repulsive interpore interaction becomes significant, κ(˜) increases rapidly.

Thermally switchable one- and two-dimensional arrays of single-walled carbon nanotubes in a polymeric system.

Fabrication of highly ordered arrays of single-walled carbon nanotubes (SWNTs) has been of great interest for a wide range of potential applications. Here, we report thermally switchable one- and two-dimensional arrays of individually isolated SWNTs formed by cooperative self-assembly of functionalized SWNTs and a block copolymer/water system. Small-angle X-ray scattering measurements reveal that when the block copolymer/water system is in an isotropic phase, two-dimensional hexagonal arrays of SWNTs are formed by depletion attraction, and when the block copolymer/water system is in a lamellar phase, one-dimensional lattices of SWNTs intercalated in the polar regions of the polymeric lamellar structure are formed by entropically driven segregation and two-dimensional depletion attraction. These two SWNT arrays are thermally interchangeable, following the temperature-dependent phase behavior of the block copolymer/water system.

Highly ordered self-assembly of 1D nanoparticles in phospholipids driven by curvature and electrostatic interaction.

Self-assembly of 1D nanoparticles such as carbon nanotubes or nanorods into highly ordered superstructures using various interactions has been of great interest as a route toward materials with new functionalities. However, the phase behavior of 1D nanoparticles interacting with surrounding materials, which is the key information to design self-assembled superstructures, has not been fully exploited yet. Here, we report for the first time a new phase diagram of negatively charged 1D nanoparticle and cationic liposome (CLs) complexes in water that exhibit three different highly ordered phases, intercalated lamellar, doubly intercalated lamellar, and centered rectangular phases, depending on particle curvature and electrostatic interactions. The new phase diagram can be used to understand and design new highly ordered self-assemblies of 1D nanoparticles in soft matter, which provide new functionalities.