Morphology of grain boundaries observed during order-order transition at the perforated layer (PL)/gyroid interface was investigated by electron tomography in a polystyrene-block-polyisoprene (SI)/polystyrene (hS) blend. As a general result, 3D analysis shows the nonrelated orientation of the growing gyroid phase relative to the consumed PL grain: a nonepitaxial transition. This is a predictable result due to the nucleation of PL and gyroid grains in the sponge phase, with random orientation. In few cases, however, epitaxy was observed with part of the PL phase orientation conserved by the growing gyroid, a rare situation potentially resulting from the nucleation of the gyroid grain into the PL phase, or from the lucky match between both grain orientations. For both epitaxial and nonepitaxial grain boundaries, the PI and PS phases were found continuous through the grain boundary. For nonepitaxial transitions, connections were observed at the grain boundary between the otherwise independent PI gyroid networks. These networks remain independent through epitaxial transitions, each of them being connected, with a regular pattern, to one out of two perforated layers. With clarification of these complex morphologies, electron tomography demonstrates again its usefulness for polymer science.
We successfully developed a method to control the introduction of Pd nanoparticles selectively into the poly(2-vinylpyridine) (P2VP) microdomains of polyisoprene-block-poly(2-vinylpyridine) (PI-b-P2VP) diblock copolymer. The technique consists of three steps: (i) cross-linking of P2VP microdomains with diiodobutane (DIB), (ii) immersion of the cross-linked film in the mixture of palladium diacetate (Pd(acac) 2 ), benzyl alcohol, and toluene, and (iii) annealing the immersed and dried film at 230 °C for 30 min. With this method, we could generate Pd nanoparticles with considerably uniform size (5.5 nm) by in situ reduction of the Pd ions solely within the P2VP microdomains without disturbing the regular microdomain structure of PI-b-P2VP diblock copolymer. We employed 3D electron tomography to analyze the location and the size of the Pd nanoparticles and demonstrated its capability in the analysis of nanoparticle/block copolymer systems.
We made a 3D median filter to remove noises and to smooth out the 3D image obtained by electron tomography and we examined its effectiveness. We applied the filter to the 3D reconstructed data obtained for the cylindrical microdomain structure of a SIS triblock copolymer by using an ordinary conventional electron microscope and showed that a clear 3D image could be obtained . KEY WORDS Electron Tomography/3D Median Filter/Block Copolymer/Microphase Separation/
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