Paper Number
CS20                         My Program 

Session
Colloids and Suspensions

Title
Characterizing dynamic gelation of thermoresponsive microfibrillated cellulose using multiple particle tracking microrheology (MPT) and bulk rheology

Presentation Date and Time
October 15, 2024 (Tuesday) 10:30

Track / Room
Track 2 / Waterloo 4

Authors (Click on name to view author profile)

  1. Afshang, Mehrnoosh (Purdue university, Davidson school of chemical engineering)
  2. Caggioni, Marco (Procter & Gamble Co.)
  3. Lindberg, Seth (Procter & Gamble Co.)
  4. Schultz, Kelly M. (Purdue University, Davidson School of Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Mehrnoosh Afshang1, Marco Caggioni2, Seth Lindberg2 and Kelly M. Schultz1
1Davidson school of chemical engineering, Purdue university, West Lafayette, IN 47907; 2Procter & Gamble Co., West Chester, OH 45069

Speaker / Presenter 
Afshang, Mehrnoosh

Keywords
experimental methods; colloids; gels

Text of Abstract
Rheological modifiers adjust flow behavior, tune rheology and induce phase transitions in products. Microfibrillated cellulose (MFC), from paper waste, is a potential rheological modifier due to the high fiber aspect ratio, which enables the change in rheology with minimal added material. Thermoresponsive polymer, Jeffamine polyetheramine M2005, is grafted to the surface of MFC. Jeffamine M2005-MFC (JMFC) is characterized with multiple particle tracking microrheology (MPT) and bulk rheology to measure the dynamic temperature-dependent rheology during sol-gel phase transitions. MPT measures the Brownian motion of particles to calculate rheological properties. MPT data are analyzed using time-cure superposition to determine the critical transition temperature and critical relaxation exponent. The critical relaxation exponent identifies the state of the material and the fiber network structure at the phase transition. For JMFC, from 4 – 16°C the material is a sol where the colloids are stable and in good solvent conditions. From 16 – 30°C aggregates form and the material gels. The critical transition temperature is Tc=15.5±1.0?, which is within error of the lower critical solution temperature of the grafted polymer, 16?. This indicates that the structure and phase transition of the polymer on MFC is similar to that in solution. Using bulk rheology, we measure the bulk properties as a function of temperature and overlap concentration. Below the overlap concentration, that material transitions from a viscous fluid to an elastic solid as temperature increases. Above the overlap concentration, we measure elastic behavior at all temperatures due to fiber entanglement and an increase in elastic moduli above Tc. We also characterize hysteresis which cause a shift in moduli values during heating and cooling cycles due to the association-dissociation kinetics of the grafted polymer. This information can be used in future design of consumer products that require specified structure and properties during temperature changes.