Aqueous Processing of Mechanically Robust, Dense Films from Carboxymethyl Cellulose-Based Coacervates

Area of Science:

• Materials Science
• Polymer Chemistry
• Biotechnology

Background:

• Development of sustainable, high-performance films from natural and synthetic polymers is crucial for advanced applications.
• Polyelectrolyte complexes (PECs) offer tunable properties but require optimized processing conditions.
• Antimicrobial properties in materials are increasingly sought after for public health and safety.

Purpose of the Study:

• To fabricate free-standing carboxymethyl cellulose (CMC) and poly-(diallyldimethylammonium chloride) (PDADMAC) films via all-aqueous processing.
• To investigate the influence of salt concentration on polyelectrolyte complex (PEC) formation and film properties.
• To evaluate the mechanical performance and antimicrobial activity of the fabricated CMC/PDADMAC films.

Main Methods:

• Screening of CMC/PDADMAC complexation using turbidity measurements in the presence of NaCl or KBr.
• Rheological testing to optimize PEC conditions for blade casting.
• Aqueous phase separation (APS) for film formation, followed by SEM, DMA, and tensile testing for characterization.

Main Results:

• Coacervation of CMC/PDADMAC required an excess of PDADMAC, resulting in positively charged complexes.
• Films exhibited dense morphology and high Young's moduli (436–975 MPa), with salt concentration affecting surface stability and mechanical strength.
• All CMC/PDADMAC films demonstrated significant antimicrobial activity, inactivating approximately 50% of tested bacteria (E. coli, S. aureus).

Conclusions:

• Sustainable all-aqueous processing enables the fabrication of robust, cationic biopolymer films from CMC and PDADMAC.
• The inherent positive charge of the films confers contact-killing antimicrobial properties.
• These films hold promise for applications in membranes, packaging, and antimicrobial coatings.