Waterproof-breathable films from multi-branched fluorinated cellulose esters

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Chemistry

Background:

• Cellulose, a renewable biopolymer, is extensively researched for sustainable material development.
• Fluorinated compounds offer unique properties like hydrophobicity and chemical resistance.
• Combining cellulose with fluorinated moieties can lead to novel materials with enhanced characteristics.

Purpose of the Study:

• To synthesize and characterize novel cellulose ester films.
• To investigate the effect of incorporating a multibranched fluorinated carboxylic acid (BRFA) on cellulose properties.
• To evaluate the morphological, thermal, mechanical, and surface properties of the resulting cellulose-BRFA materials.

Main Methods:

• Esterification of cellulose with BRFA at varying molar ratios (1:0, 10:1, 5:1, 1:1).
• Morphological and optical analysis (film transparency and texture).
• Nuclear Magnetic Resonance (NMR) for degree of substitution (DS) determination.
• Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) spectroscopy for chemical confirmation.
• Differential Scanning Calorimetry (DSC) for thermal analysis.
• Mechanical testing to assess behavior shift from rigid to ductile.
• Wettability, breathability, and water uptake measurements.

Main Results:

• Transparent and flat cellulose-BRFA films were formed at 10:1 and 5:1 molar ratios, while the 1:1 ratio yielded translucent, rough films.
• NMR confirmed esterification with calculated DS values of 0.06, 0.09, and 0.23 for the 10:1, 5:1, and 1:1 ratios, respectively.
• DSC showed a single glass transition at -11 °C, indicating amorphous polymer behavior.
• Increasing DS shifted mechanical properties from rigid to ductile and soft.
• Wettability was comparable to PTFE and PVDF.
• Breathability and water uptake were suitable for textile applications.

Conclusions:

• Cellulose esterification with BRFA produces novel materials with tunable properties.
• The degree of substitution significantly influences film morphology and mechanical behavior.
• These cellulose-BRFA films exhibit promising characteristics for applications requiring fluoropolymer-like wettability and textile-compatible breathability.