Phase transitions in cellulose microfibril dispersions by high-energy mechanical deagglomeration

Area of Science:

• Materials Science
• Polymer Chemistry
• Colloid Science

Background:

• Cellulose microfibrils, particularly bacterial cellulose (BC), are known for their unique structural properties.
• Dispersions of cellulose microfibrils often form aggregates or gels, limiting their applications.
• Controlling the dispersion and structure of microfibrils is crucial for advanced material development.

Purpose of the Study:

• To investigate the structural transitions of bacterial cellulose (BC) dispersions.
• To explore the effect of sodium carboxymethyl cellulose (CMC) on BC microfibril aggregation and dispersion.
• To induce and characterize colloidal liquid crystalline structures in BC/CMC systems.

Main Methods:

• High-energy mechanical deagglomeration of bacterial cellulose (BC) networks.
• Addition of sodium carboxymethyl cellulose (CMC) to BC dispersions.
• ζ potential measurements to assess surface charge and interactions.
• Microscopy and phase analysis to observe structural changes and ordering.

Main Results:

• Dispersions exhibited gel-sol and direct gel-colloidal liquid crystalline structure transitions.
• Increasing the CMC/BC weight ratio led to transitions from aggregates to single microfibril dispersions.
• At higher concentrations, liquid crystalline ordering, reminiscent of nematic gels, was observed.
• Increased CMC content resulted in more homogeneous microstructures.

Conclusions:

• High-energy deagglomeration in the presence of CMC effectively transitions BC systems from aggregates to single microfibril dispersions.
• The study demonstrates the formation of nematic gel-type structures in cellulose microfibril dispersions.
• This method offers a pathway to control the microstructure and properties of cellulose-based materials.