Study of the Dynamic Process of Enhancing the Stability of Conjugated Polymer Solutions and Films Induced by an External Electric Field

Taking the classic red light conjugated polymer MEH-PPV material as a representative, aiming at the common problem, that is, its degradation over time in the natural environment, which leads to unstability of the solution and film, a new idea and method based on the self-assembly of molecular chains in solution induced by an external electric field are proposed to manipulate the condensed-state structure of molecular chains in solution and enhance the dynamic stability of its solution. Then, the stability of the film was enhanced by transferring the condensed-state structure of the solution to the film in the dynamic evolution process from the solution to the film. First, the molecular mechanism of the unstability of the MEH-PPV precursor solution with time change was explored. Then, the self-built external electric field equipment was used for enhancing the dynamic stability of the conjugated polymer MEH-PPV solution and film by induction of an external electric field. Surprisingly, it was found that the precursor solutions with different concentrations all responded significantly to the induction of an external electric field during the 30 day storage period, forming large-scale, close-packed, chain-aggregated structures. More importantly, this structure can stably exist in the process of dynamic evolution with time change, thereby enhancing the stability of the solution. Through a series of studies on the films, it was found that the chain-aggregated structure formed in the solution could be stably transferred to the film in the process of dynamic transition from the solution to the film. Under the induction of the external electric field, a large-area, compact arrangement and ordered chain structures also appeared in the films, which not only enhanced the stability of the film but also revealed that there was an internal and intrinsic physical connection between the condensed-state structures of the solution and film in the dynamic evolution process. The study also revealed the molecular mechanism of the stability enhancement for the conjugated polymer MEH-PPV solution and film induced by the external electric field.