Gradient composition distribution in poly(2,6-dimethylphenylene oxide)/polystyrene blend nanorods

We report formation of nanorods that exhibit a gradient distribution of poly(2,6-dimethylphenylene oxide) and polystyrene (PPO and PS), i.e., the PPO weight fractions in the nanorods increase from top to bottom along the long axis of the nanorods. PPO/PS nanorods with various diameters were prepared by infiltrating porous anodic aluminium oxide (AAO) templates with polymer blend melts. Their morphology was investigated by Fourier transform infrared spectroscopy (FTIR). The gradient distribution of polymer blends in the nanopores is governed by (1) the viscosity difference between the two polymers and (2) the pore diameter. This remains true although PPO/PS blends are compatible in the segmental level. For various diameter nanorods made of PPO/PS blends, the PPO content decreased as the rod diameter became smaller owing to the increased confinement imposed by the nanopores. This leads to a higher rate of capillary rise in smaller nanopores.