Molecular simulations of the imidization of adsorbed polyamic acid

Computer simulations have been developed to investigate the intramolecular cyclization of polyimides (i.e., imidization, the conversion of the precurs or polyamic acid into polyimide). Imidization was examined as a function of time, temperature, and presence or absence of a silica substrate. To do th is, the essential results of quantum mechanical studies were incorporated i nto a molecular dynamics simulation. Molecular dynamics simulations were us ed to determine the conformational properties of the polymer chain and to s imulate the imidization reaction when the conformational criteria establish ed by quantum mechanical methods were met. In agreement with experiments, i midization occurred in two distinct stages, and increased temperatures were shown to produce higher extents of imidization. Finally, the interfacial c hains exhibited more complete imidization than the isolated chains. These r esults not only support the proposed molecular rationale behind the kinetic models of imidization but also demonstrate that only local chain motions a re necessary for imidization to occur.