Paper Number
PO95 

Session
Poster Session

Title
Phase behavior and rheology of microgel-surfactant mixtures

Presentation Date and Time
October 12, 2022 (Wednesday) 6:30

Track / Room
Poster Session / Riverwalk A

Authors (Click on name to view author profile)

  1. Chaub, Arnaud (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry, and Materials)
  2. Goujard, Sarah (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry, and Materials)
  3. Suau, Jean-Marc (Coatex SAS)
  4. Cloitre, Michel (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry and Materials)

Author and Affiliation Lines (in printed abstract book)
Arnaud Chaub1, Sarah Goujard1, Jean-Marc Suau2 and Michel Cloitre1
1Molecular, Macromolecular Chemistry, and Materials, ESPCI Paris - PSL, Paris 75005, France; 2Coatex SAS, Genay, France

Speaker / Presenter 
Chaub, Arnaud

Keywords
colloids; glasses; jammed systems; microscopy; surfactants

Text of Abstract

Stimuli-responsive microgels are colloidal particles made of cross-linked polymeric networks that undergo a volume transition in response to changes in pH, temperature, or solvent quality. A wide-spread trigger of microgels in industrial applications is pH. Crosslinked acrylic acid or alkyl acrylate/methacrylic acid microgels swell by a large amount when the carboxylic functions borne by the polymer network are ionized. pH-sensitive microgels suffer from their sensitivity to ionic strength variations and from the fact that the optimum rheology is reached at high pH, which is detrimental to their use many applications.

Here we explore another strategy that consists in triggering the swelling of microgels by the addition of surfactants which adsorb onto the polymeric network and induce swelling. The great challenge is to control and model the volume transition and the rheological properties in terms of the enthalpic, entropic and electrostatic interactions that develop between the polymeric network and the guest molecules. We address this question in the case of alkyl acrylate/methacrylic acid copolymers carrying negative charges. Blending microgels with anionic surfactants produces a rich phase diagram encompassing liquid, glassy, jammed, metastable, and reentrant liquid states [1]. When cationic surfactants are used, initially swollen microgels successively deswell until they fully collapse and precipitate due to attractive interactions. An excess of surfactant reswells the microgels and restabilizes the suspensions due overcharging. We rationalize the rheological properties of the nanocomposites in each domain of the state diagrams, which provides exquisite solutions for designing new rheology modifiers.

[1] Sarah Goujard et al 2021 J. Phys.: Condens. Matter 33 404003