Microrheology of novel cellulose stabilized oil-in-water emulsions

B Medronho,A Filipe,C Costa,A Romano,B Lindman,H Edlund,M Norgren

doi:10.1016/j.jcis.2018.07.043

B Medronho, A Filipe + Show 5 more

Open Access

https://doi.org/10.1016/j.jcis.2018.07.043

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Abstract

Diffusing wave spectroscopy (DWS) is a powerful optical technique suitable to investigate turbid samples in a nondestructive and reproducible way, providing information on the static and dynamic properties of the system. This includes the relative displacement of emulsion droplets over time and changes in the viscoelastic properties. Here, novel and promising cellulose-based oil-in-water (O/W) emulsions were prepared and studied, for the first time, by DWS. Cellulose plays the role of a novel eco-friendly emulsifying agent. The hydrolysis time of cellulose was observed to affect the average size of the emulsion droplets and their stability; the longer the hydrolysis time, the more dispersed and stable the emulsions were found to be. Additionally, a good complementarity between the microrheology (DWS) and macrorheology (mechanical rheometer) data was found. Our work suggests that DWS is a highly attractive method to investigate the stability, aging and microrheology properties of cellulose-based emulsions, providing valuable insights on their microstructure. This technique is thus highly appealing for the characterization and design of novel emulsion formulations.

Highlights

Emulsions are metastable systems consisting of one liquid dispersed as small droplets in another liquid [1,2]
After the preparation of the emulsions, as described in the Material and Methods section, the average droplet size was determined by diffusing wave spectroscopy (DWS) in the backscattering mode (Fig. 2a)
The DWS assays described in this study enabled the determination of the droplet size, microrheology and revealed changes happening on the microstructure that are not accessible with conventional mechanical rheometry

Summary

Introduction

Emulsions are metastable systems consisting of one liquid dispersed as small droplets in another liquid [1,2]. Creation of an emulsion generally requires an emulsifier, which may work as a stabilizer to facilitate the dispersion formation by lowering the interfacial tension and to prevent the coalescence and flocculation of the droplets by creating a net repulsion between them. Surfactants, polymers and particles are used as emulsifier or stabilizer agents but some amphiphilic polymers, notably block copolymers, can fulfill both criteria.

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