Paper Number
PO48                         My Program 

Session
Poster Session

Title
Characterizing dynamic gelation of thermoresponsive microfibrillated cellulose using Multiple Particle Tracking microrheology (MPT) and bulk rheology

Presentation Date and Time
October 16, 2024 (Wednesday) 6:30

Track / Room
Poster Session / Waterloo 3 & 4

Authors (Click on name to view author profile)

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

Author and Affiliation Lines (in printed abstract book)
Mehrnoosh Afshang1, Kelly M. Schultz1, Seth Lindberg2 and Marco Caggioni2
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; real-world rheology

Text of Abstract
Microfibrillated cellulose (MFC) has potential applications as a rheological modifier to tune rheology and induce phase transitions in products. Our research repurposes MFC from paper waste into consumer products. MFC is non-ionic, allowing easy modification for various formulations. This work characterizes thermoresponsive MFC by grafting a thermoresponsive polymer, Jeffamine M2005 (LCST~16°?), onto the MFC surface. This thermoresponsive colloid enables control over the degree of degradation or gelation by equilibrating the material at a specific temperature, which enables characterization of the structure and rheology of the material. We use multiple particle tracking microrheology (MPT) and bulk rheology to measure the rheological properties and structure of thermoresponsive MFC during sol-gel transitions. MPT measures the Brownian motion of particles to calculate rheological properties. For thermoresponsive MFC, below the polymer LCST the material is in the sol phase and the polymer is in good solvent conditions. Above the LCST, the polymer is in poor solvent conditions, causing fiber aggregation and gelation. Using MPT, we measure the evolving material properties as temperature changes. Analyzing MPT data with time-cure superposition determine the critical transition temperature(TC) and the critical relaxation exponent, identifying the state and network structure during phase transition. The measured Tc is 15.5±1.0?, indicating that the structure of the polymer on MFC is similar to that in solution. Bulk rheology measures a transition from viscous fluid to elastic solid as temperature increases below the entanglement concentration(c**). Above c**, elastic behavior is measured across all temperatures due to the initial entangled network structure and an increase in elastic moduli above TC. This information can be used in future design of consumer products that require specified structure during temperature changes and enable precise delivery from these materials across different length scales.