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Optimizing Self-Consistent Field Theory Block Copolymer Models with X-Ray Metrology



Adam F. Hannon, Daniel Sunday, Alec Bowen, Gurdaman Khaira, Jiaxing Ren, Paul Nealey, Juan de Pablo, Regis J. Kline


A block copolymer self-consistent field theory (SCFT) model is used for direct analysis of experimental X-ray scattering data obtained from thin films of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) made from directed self-assembly. In a departure from past work that reconstructed the real space structure using simple geometric shapes, we build on recent work that has relied on physics-based models to determine shape profiles and extract thermodynamic processing information from the scattering data. More specifically, an SCFT model, coupled to a covariance matrix adaptation evolutionary strategy (CMAES), is used to find the set of simulation parameters for the model that best reproduces the scattering data. The SCFT model is complex enough to capture the essential physics of the copolymer self-assembly but simple enough to quickly produce structure profiles needed in inversely fitting the scattering data. The accuracy of the model in producing a matching scattering profile is assessed, and improvements to the model are proposed to more accurately recreate the experimental results. Comparisons are made of predicted parameters from the model fits with measured parameters via additional experimental methods and with predicted parameters from direct particle-based simulations of the same model, which allows one to include the effects of fluctuations. The Flory-Huggins interaction parameter found for PS-b-PMMA agrees with reported ranges for this material. These results show the potential for directly using physics-based models in the analysis of spectral based experiments.
Molecular Systems Design and Engineering


block copolymers, directed self-assembly, X-ray scattering, self-consistent field theory, theoretically informed coarse-grained simulations


Hannon, A. , Sunday, D. , Bowen, A. , Khaira, G. , Ren, J. , Nealey, P. , de Pablo, J. and Kline, R. (2018), Optimizing Self-Consistent Field Theory Block Copolymer Models with X-Ray Metrology, Molecular Systems Design and Engineering, [online], (Accessed April 14, 2024)
Created February 11, 2018, Updated October 12, 2021