Representing Structural Isomer Effects in a Coarse-Grain Model of Poly(Ether Ketone Ketone)

Area of Science:

• Materials Science
• Polymer Physics
• Computational Chemistry

Background:

• Thermoplastic carbon-fiber composites are crucial in aerospace due to their processing and performance advantages.
• Predicting polymer matrix structure during processing is challenging due to long polymer relaxation times.
• Existing coarse-grained polymer models have limited transferability across different thermodynamic states.

Purpose of the Study:

• To develop and validate a minimal coarse-grained model for poly(etherketoneketone) (PEKK), an aerospace thermoplastic.
• To enable accurate prediction of PEKK structure-property relationships during processing.
• To achieve significant computational speedups compared to traditional simulation methods.

Main Methods:

• Utilized multistate iterative Boltzmann inversion to derive transferable potentials for PEKK.
• Introduced tabulated EKK angle potentials to account for terephthalic (T) and isophthalic (I) acid precursor ratios.
• Validated the model against rheological experiments, including glass transition, chain relaxation, and melting temperatures.

Main Results:

• The developed coarse-grained PEKK model shows transferability across relevant thermodynamic states.
• Glass transition temperature was found to be independent of the T/I ratio, while chain relaxation and melting temperature are dependent.
• Achieved a 15x performance speedup compared to united atom (UA) representations.

Conclusions:

• A simple, validated coarse-grained model for PEKK has been successfully developed.
• The model facilitates the study of thermoplastic processing-structure-property-performance relationships in aerospace applications.
• This computational approach enhances the efficiency of simulating complex polymer dynamics.