Paper Number
SM39 

Session
Polymers Solutions, Melts, and Blends

Title
Understanding solvation of cellulose in ionic liquids by time dissolution evolution (TiDE) rheometry

Presentation Date and Time
October 13, 2021 (Wednesday) 4:10

Track / Room
Track 1 / Ballroom 5

Authors (Click on name to view author profile)

  1. Owens, Crystal E. (MIT)
  2. Sanchez, Pablo (University of Vigo)
  3. Du, Jianyi (Massachusetts Institute of Technology)
  4. Hart, A. John (MIT, Mechanical Engineering)
  5. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Crystal E. Owens1, Pablo Sanchez2, Jianyi Du1, A. John Hart1 and Gareth H. McKinley1
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA; 2University of Vigo, Vigo, Pontevedra 36310, Spain

Speaker / Presenter 
Owens, Crystal E.

Keywords
experimental methods; applied rheology; non-Newtonian fluids; polymer solutions; rheology methods

Text of Abstract
Cotton-based textiles are produced, used, and scrapped at unprecedented rates. However, due to strong interchain hydrogen-bonding interactions, the main ingredient of cotton - cellulose - does not dissolve in common solvents. While this promotes durability, it hinders recyclability, and over 80% of all cotton-based goods end up in landfills. As a possible remedy, ionic liquids have been shown to disrupt hydrogen bonds and progressively solvate cellulose so that liquid solutions can be processed and, ideally, re-spun into new cotton threads to form new textiles.

In this work, we monitor the dissolution of cotton-based textiles in 1-ethyl-3-methyl-imidazolium acetate (EMIMOAc) from chopped fiber to homogeneous dispersion using small amplitude oscillatory shear (SAOS) rheometry. We seek a quantitative description through a method of reduced variables analogous to time-temperature superposition. However, dispersions of rigid H-bonded cellulose fibers in ionic liquid are not “solvo-rheologically simple,” hence standard shifting is invalid. Instead, we outline a new method of Time Dissolution Evolution (TiDE) to understand and predict this cellulose rheology over a wide range of weight concentrations (0.5 = c = 12%). The time-evolving SAOS measurements are well-described using systematic regression to the Baumgaertel-Schausberger-Winter (BSW) relaxation spectrum to extract the evolution of the underlying material relaxation times. This results not only in kinetic information but also in observability of the majority of the material relaxation spectrum. The kinetic data can further be compared with polarized microscopy of the same dissolutions, and to prior published data for low-concentration solutions. This approach is particularly valuable for otherwise hard-to-access high-concentration and "gel-like" regimes that are required for economical cellulose regeneration. The resulting solvent-specific information is useful to guide processing of cellulose into new synthetic fibers, and to inform limits to recycling.