Molecular-Cluster-Assembly Method for Analysis of High-Dimensional Structures of p-Cresol Chains in Phenolic Polymers

• Published in: Macromolecular theory and simulations Vol. 22; no. 9; pp. 443 - 461
• Main Authors: Ho, Shirun, Aoyagi, Mutsumi
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.11.2013
• Subjects: Atomic structure; Composite structures; Dissociation energy; Heat of formation; Hydrogen atoms; Molecular structure; Phenol; phenolic polymers; quantum mechanics/molecular mechanics calculations; simulation; Spirals; structure
• ISSN: 1022-1344; 1521-3919
• DOI: 10.1002/mats.201300101

A new method for analyzing oriented structures of polymers and their formation processes, called “molecular‐cluster‐assembly” (MoCA), is proposed. With this method, a polymer structure is assembled by molecular clusters at local minimum‐energy states and comprised of alternating structures along variable atomic coordinates. The reduced conformational space is searched comprehensively by using a Monte Carlo method. The total energy of the polymer structure is calculated from quantum mechanics/molecular mechanics (QM/MM) energy. It has the same accuracy as full QM energy given by the Møller–Plesset (MP2) method and the fast calculation time is the same as that of the MM method. It is shown that long p‐cresol chains form self‐organized spiral structures and composite structures with both spirals and open‐rings. As phenol groups are oriented towards the inside of the long chains, more oxygen atoms located around a hydrogen atom provide a strong negative potential. It is concluded that these two kinds of oriented structures change the dissociation energy of the hydrogen atoms in the phenol groups. p‐Cresols with long chains are analyzed by the molecular‐cluster‐assembly method. The composite structures with spirals and open‐rings show minimum energies. It is revealed that the dissociation energy of the hydrogen atom located inside the composite structure increases compared to that of the first hydrogen atom surrounded by less neighboring oxygen atoms.