High performance polymers

Stiff Chain Aromatic Heterocyclic Polymers

Light weight, high strength fibers and films produced from stiff chain aromatic heterocyclic polymers are good candidates for use as structural materials in advanced technological applications. Some examples of this kind of polymers we studied are

ABPBO poly-2,5-benzoxazole

ABPBT poly-2,6-benzothiazole

ABPBI poly-2,5-benzobimidazole

PBT poly-paraphenylene-benzothiazole

PBO poly-paraphenylene-benzoxazole

PBI poly-paraphenylene-benzobimidazole

Molecular mechanics and molecular dynamics methods used in studying the structure, dynamics, thermodynamics and mechanical properties of these high performance polymers. Semi-empirical solid state quantum mechanics programs are used in studying the elctronic structures of the same polymers.

Structure of PBZT Crystal.

Mechanical Properties

We subjected these polymers moderate incremental tension and compression to compute the finite difference elastic properties. [1]
Second, Extreme tensions and compressions are applied to investigate the structural transformations. [2]
Hessians for single crystals were computed using Dreiding Force field to obtain elastic constants at a single point. [1]
Harmonic theory is used to study the structural and thermodynamic stability as a function of temperature. [1, 2]
Molecular dynamics simulations on the isolated chains and in the bulk state are performed to investigate the rigidity, thermal behavior and mechanical properties[3].

Electronic Properties

Electronic structures and band gaps of PBO, PBI, and PBT are also studied using semi-empirical quantum mechanical methods. [4]

References

T. Cagin, "Mechanical Response of High Performance Polymers," in Materials Theory and Modeling, pp 321-4, 1993.
T. Cagin and W. A. Goddard, III, unpublished.
B. L. Farmer, T. Cagin, D. S. Dudis, W. W. Adams, "Molecular Modeling of Rigid Rod Polymers," in Deformation, Yield and Fracture of Polymers, 1991.
T. Cagin and D. S. Dudis, unpublished.

Collaborators

Drs. W. W. Adams, D. S. Dudis, and Profs. B. L. Farmer and W. A. Goddard, III.

tahir@wag.caltech.edu