Journal
ADVANCED FUNCTIONAL MATERIALS
Volume 28, Issue 19, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.201706226
Keywords
block copolymers; grazing-incidence small-angle X-ray scattering; solvent vapor annealing; thin films; vapor mixtures
Categories
Funding
- Deutsche Forschungsgemeinschaft [PA 771/10-2]
- DANSCATT (Danish Centre for the Use of Synchrotron X-ray and Neutron Facilities)
- MaMaSelf (Master in Materials Science Exploring Large Scale Facilities) master program
- National Science Foundation [DMR-1332208]
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Solvothermal vapor annealing at elevated temperature is applied to a thin film from a cylinder-forming polystyrene-block-poly(dimethyl siloxane) (PS-b-PDMS) diblock copolymer. At this, the film is swollen in the vapor of n-heptane (highly selective for PDMS). This vapor is stepwise replaced by the vapor of toluene (weakly selective for PS). The morphologies are investigated using in situ, real-time grazing-incidence small-angle X-ray scattering (GISAXS). The initial cylindrical morphology is transformed into, among others, the lamellar one. This novel type of experiments allows probing a trajectory in the state diagram of the PS-b-PDMS/n-heptane/toluene mixture. To corroborate the morphologies, they are generated by molecular simulations, and the 2D GISAXS maps are calculated using the distorted-wave Born approximation. To relate the morphologies to the solvent distribution in the two types of nanodomains, the latter is estimated from the intensities of the Bragg reflections in the 2D GISAXS maps along with the swelling ratio of the film. Comparison with the results from a similar experiment carried out at room temperature results in the same sequence of morphologies; however, at elevated temperature, more well-ordered structures are obtained. This new approach proves to be efficient to achieve a block copolymer thin film having a desired morphology and orientation.
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