Simulation of polymerization induced phase separation in model thermosets.

Area of Science:

• Materials Science
• Polymer Chemistry
• Computational Chemistry

Background:

• Polymerization induced phase separation (PIPS) is crucial for thermoset material properties.
• Understanding PIPS requires models that capture complex molecular interactions and kinetics.
• Thermoset systems with varying crosslinker properties present unique phase separation challenges.

Purpose of the Study:

• To investigate PIPS in a three-component thermoset using molecular dynamics simulations.
• To develop and utilize a new coarse-grained thermoset model.
• To explore the influence of crosslinker characteristics (T_g, chain length) on PIPS.

Main Methods:

• Development of a coarse-grained thermoset model with distinct crosslinker types.
• Molecular dynamics simulations at the cure temperature.
• Systematic variation of crosslinker chain length (short and long) and reaction rates.

Main Results:

• PIPS was observed for a long, high T_g (rubbery) crosslinker at slow reaction rates, forming nanoscale domains.
• A short, high T_g crosslinker did not exhibit PIPS under similar conditions.
• Simulation results successfully reproduced recent experimental observations.

Conclusions:

• Slow reaction rates are essential for enabling diffusion and achieving PIPS in thermosets.
• Crosslinker chain length significantly impacts the occurrence of PIPS.
• The secondary amine reaction rate must be sufficiently slow to prevent PIPS.