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Published April 1, 2020 | Supplemental Material
Journal Article Open

Addressing the challenges of modeling the scattering from bottlebrush polymers in solution


Small‐angle scattering measurements of complex macromolecules in solution are used to establish relationships between chemical structure and conformational properties. Interpretation of the scattering data requires an inverse approach where a model is chosen and the simulated scattering intensity from that model is iterated to match the experimental scattering intensity. This raises challenges in the case where the model is an imperfect approximation of the underlying structure, or where there are significant correlations between model parameters. We examine three bottlebrush polymers (consisting of polynorbornene backbone and polystyrene side chains) in a good solvent using a model commonly applied to this class of polymers: the flexible cylinder model. Applying a series of constrained Monte‐Carlo Markov Chain analyses demonstrates the severity of the correlations between key parameters and the presence of multiple close minima in the goodness of fit space. We demonstrate that a shape‐agnostic model can fit the scattering with significantly reduced parameter correlations and less potential for complex, multimodal parameter spaces. We provide recommendations to improve the analysis of complex macromolecules in solution, highlighting the value of Bayesian methods. This approach provides richer information for understanding parameter sensitivity compared to methods which produce a single, best fit.

Additional Information

Published 2020. This article is a U.S. Government work and is in the public domain in the USA. Issue Online: 07 April 2020; Version of Record online: 19 February 2020; Manuscript accepted: 02 February 2020; Manuscript revised: 27 January 2020; Manuscript received: 19 December 2019. Funding Information: European Union Horizon 2020. Grant Number: 654000; National Science Foundation. Grant Number: DMR‐0520547; National Research Council Research Associateship Program.

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