Applications of Biopolymer Microgels

Abstract

IntroductionAs a result of their structural versatility, rich dynamic behavior, biocompatibility, and sustainability, biopolymer microgels are employed in a wide range of industrial applications. Most biopolymers are linear or branched macromolecules forming microgel particles due to intermolecular binding. As was discussed in previous chapters, an essential property of microgel particles is their ability to swell, thus occupying a large volume in solution at very low-weight fractions of polymer. In the case of synthetic microgels, swelling is due to osmotic effects and the equilibrium swelling ratio is given by a balance between the entropic elasticity of the macromolecules, the polymer-solvent interactions [1-3], and, for flexible polyelectrolytes, the ionic strength and/or solution pH. By contrast, microgels of biological origin are composed of relatively rigid macromolecules; it is this intrinsic rigidity that largely determines the swelling of these biopolymer microgels.Above a critical overlap, concentrated suspensions of microgel particles behave as jammed materials [4,5], or more precisely, as soft glassy materials [6], which possess both a high elastic modulus and a yield stress. In the linear viscoelastic regime, the stress relaxation is very slow because the stress relaxes via collective rearrangements of the microgel particles. This makes microgels ideal for applications in consumer and food industries, where they are used to stabilize emulsions and suspensions and to control the rheological characteristics of the products. Microgel particles formed by biopolymers are preferred in pharmaceutical, food, and oral care industries due to their natural origin and biocompatibility [7][8][9]. In addition, microgels of biological origin have found applications in oil recovery because of their high solubility in water, low sensitivity to temperature, and high thickening potential. Biogels also find applications in drug delivery, particularly for oral [10] and ocular [11] delivery.There are other important reasons for using microgels of biological origin. First, high prices of petrochemicals make synthetic microgels, such as polyacrylates or Microgel Suspensions: Fundamentals and Applications Edited

Modeling amorphous materials: from hydrogel packings to mesoscale models

“…Particles made of hydrogels -chemically cross-linked polymeric materials which swell when they absorb water -are important in industries such as pharmaceuticals, bioengineering, agriculture, food science, and cosmetics [160,125,19,127]. Owing to their softness and the in situ tunability of their size via controlled swelling, they have also been used more recently as a test bed for basic ideas in the physics of jamming and the glass transition [3,4,10,17,18,21,22,40,39,41].…”