Monomer diffusion into static and evolving polymer networks during frontal photopolymerisation.

Area of Science:

• Polymer Science
• Materials Science
• Chemical Engineering

Background:

• Frontal photopolymerisation (FPP) solidifies liquid monomers into polymers using light, with applications in 3D printing and lithography.
• The process involves an evolving polymer network interacting with a surrounding monomer bath, leading to potential swelling.
• Understanding monomer diffusion into the polymer network is crucial for controlling material properties.

Purpose of the Study:

• To investigate the conditions and mechanisms of monomer diffusion and swelling in frontal photopolymerisation.
• To develop and validate a theoretical model that predicts network growth and swelling.
• To explore the relationship between light intensity, monomer diffusion, and polymer network formation.

Main Methods:

• Decoupling growth and swelling by immersing pre-formed polymer networks in monomer baths at varying temperatures.
• Utilizing a nonlinear poroelastic model for theoretical predictions of network thickness.
• Conducting FPP propagation experiments under swelling conditions and analyzing the impact of light intensity.

Main Results:

• Experimental measurements of network thickness closely matched predictions from the poroelastic model.
• Swelling unexpectedly increased with higher incident light intensity for a fixed exposure time.
• A novel FPP model incorporating mass transport and network mechanics accurately described experimental data.

Conclusions:

• Monomer diffusion significantly influences polymer conversion profiles and generates stresses during FPP.
• The developed model provides insights into swelling mechanisms and material property development.
• This predictive capability allows for the fabrication of gradient materials with tailored mechanical properties and controlled stress.