Molecular dynamics of rigid rod polymers

• Published in: Polymer (Guilford) Vol. 34; no. 8; pp. 1588 - 1601
• Main Authors: Farmer, B.L., Chapman, B.R., Dudis, D.S., Adams, W.W.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.1993; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; molecular dynamics; Organic polymers; PBO; PBZT; persistence length; Physicochemistry of polymers; polyphenylene; PPP; Properties and characterization; rigid rod polymers; Structure, morphology and analysis; polyphenylene; PPP; rigid rod polymers; PBZT; molecular dynamics; PBO; persistence length; Benzoxazole derivative polymer; Molecular flexibility; Phenylene derivative polymer; Simulation; Molecular dynamics method; Phenylene polymer; Aromatic polymer; Theoretical study; Benzothiazole derivative polymer; Rigid chain
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/0032-3861(93)90314-Z

Molecular dynamics (MD) calculations have been used to study the behaviour of isolated rigid rod molecules of poly( p-phenylene), poly( p-phenylene benzobisthiazole) and poly( p-phenylene benzobisoxazole). The molecular mechanics force field was initially modified to improve agreement between minimized structural geometries and available X-ray data, as well as results from semiempirical molecular orbital calculations. The MD simulations show the molecules to be surprisingly flexible, with changes in end-to-end distances as large as 16%. An examination of the energies (calculated by various methods) associated with out-of-plane bending deformation, suggests that the rigid rod polymers may in fact be even more flexible than the simulations indicate. The results provide rationalizations for the relatively short persistence lengths measured in solution and for bending observed in high-resolution electron micrographs of these materials.