Addressing the challenges of modeling the scattering from bottlebrush polymers in solution. Issue 7 (19th February 2020)

• Record Type: Journal Article
• Authors: Sunday, Daniel F.; Martin, Tyler B.; Chang, Alice B.; Burns, Adam B.; Grubbs, Robert H.
• Is Part Of: Journal of polymer science. Volume 58:Issue 7(2020)
• Page Start: 988
• Page End: 996
• Publication Date: 2020-02-19
• Subjects: Bayesian analysis -- bottlebrush -- neutron scattering -- small‐angle scattering; Polymers -- Periodicals; Polymerization -- Periodicals; Polymerization; Polymers; Periodicals; 547.7
• DOI: 10.1002/pol.20190289
• Languages: English
• ISSNs: 2642-4150

Abstract

Abstract: 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. Abstract : Scattering experiments are used to connect the structure of a polymer to the resulting conformation, but the interpretation of the scattering from complex macromolecules can be challenging. In this article, the authors address some of the difficulties in characterizing the conformation of bottlebrush polymers in solution. They provide recommendations which will enable more reliable interstudy comparisons of materials, such as the use of Bayesian approaches for mapping parameter correlations.