Characterisation of heterogeneity and spatial autocorrelation in phase separating mixtures using Moran’s I

Research output: Contribution to journalArticle

Authors

  • Emma S. Thompson
  • Pieter Saveyn
  • Marc Declercq
  • Joris Meert
  • Vincenzo Guida
  • Charles D. Eads
  • Eric S. J. Robles

Colleges, School and Institutes

External organisations

  • Procter & Gamble Brussels Innovation Center
  • Procter & Gamble Company
  • Procter & Gamble Company, Newcastle Innovation Center

Abstract

In complex colloidal systems, particle-poor regions can develop within particle-rich phases during sedimentation or creaming. These particle-poor regions are overlooked by 1D profiles, which are typically used to assess particle distributions in a sample. Alternative methods to visualise and quantify these regions are required to better understand phase separation, which is the focus of this paper. Magnetic resonance imaging has been used to monitor the development of compositional heterogeneity in a vesicle-polymer mixture undergoing creaming. T2 relaxation time maps were used to identify the distribution of vesicles, with vesicle-poor regions exhibiting higher T2 relaxation times than regions richer in vesicles. Phase separated structures displayed a range of different morphologies and a variety of image analysis methods, including first-order statistics, Fourier transformation, grey level co-occurrence matrices and Moran’s I spatial autocorrelation, were used to characterise these structures, and quantify their heterogeneity. Of the image analysis techniques used, Moran’s I was found to be the most effective at quantifying the degree and morphology of phase separation, providing a robust, quantitative measure by which comparisons can be made between a diverse range of systems undergoing phase separation. The sensitivity of Moran’s I can be enhanced by the choice of weight matrices used.

Details

Original languageEnglish
Pages (from-to)180-187
JournalJournal of Colloid and Interface Science
Volume513
Early online date1 Nov 2017
Publication statusPublished - 1 Mar 2018

Keywords

  • magnetic resonance imaging (MRI) , nuclear magnetic resonance (NMR) , relaxation time contrast , phase separation , creaming , spatial autocorrelation , depletion gels