Direct adhesive measurements between wood biopolymer model surfaces

Area of Science:

• Materials Science
• Polymer Science
• Biophysics

Background:

• Understanding dry adhesion in biopolymer systems is crucial for material applications.
• Wood biopolymers, including cellulose, glucomannan, and lignin, are fundamental components of wood.
• Characterizing their adhesive interactions provides insights into material properties and potential modifications.

Purpose of the Study:

• To quantify the dry adhesion of an all-wood biopolymer system using Johnson-Kendall-Roberts (JKR) contact mechanics.
• To compare the adhesion properties of cellulose with other major wood biopolymers.
• To investigate the role of surface energy and roughness in biopolymer adhesion.

Main Methods:

• Surface modification of polydimethylsiloxane (PDMS) hemispheres with Cellulose I model surfaces via layer-by-layer assembly.
• Preparation of flat cellulose, glucomannan, and lignin model surfaces on silicon dioxide substrates.
• Measurement of dry adhesion using Johnson-Kendall-Roberts (JKR) contact mechanics.
• Calculation of surface energy components using contact angle measurements.

Main Results:

• The work of adhesion and adhesion hysteresis were similar for cellulose, glucomannan, and lignin model surfaces.
• Surface energy calculations revealed comparable dispersive surface energy components across all tested biopolymer models.
• The dispersive component was the dominant factor in the overall surface energy.
• Measured JKR work of adhesion was lower than predicted by contact angle measurements, attributed to surface roughness and potential overestimation of surface energies.

Conclusions:

• Interactions between major wood biopolymers (cellulose, glucomannan, lignin) exhibit similar adhesion characteristics.
• Dispersive forces play a significant role in the surface energy of these biopolymers.
• Surface roughness and contact angle measurement limitations affect the precise determination of adhesion work in these systems.