Structure-Gas Barrier Property Relationship in a Novel Polyimide Containing Naphthalene and Amide Groups: Evaluation by Experiments and Simulations

In order to meet the increasingly stringent requirements for heat resistance and barrier properties in the packaging and electronic device encapsulation field. A high-barrier polyimide (NAPPI) contains naphthalene ring and amide group was prepared by polymerization of a novel diamine (NAPDA) and pyromellitic dianhydride. The structure and properties of diamine monomers and polymers were characterized. Results show that the NAPPI exhibits superior barrier properties with extremely low water vapor and oxygen transmission rate values of 0.14 g center dot m(-2)center dot day(-1) and 0.04 cm(3)center dot m(-2)center dot day(-1), respectively. In addition, the NAPPI presents outstanding mechanical properties and thermal stability as well. This article attempts to explore the relationship between NAPPI structure and barrier properties by combining experiment and simulation. Studies on positron annihilation lifetime spectroscopy, Wide angle X-ray diffractograms and molecular dynamics simulations prove that the NAPPI has smaller interplanar spacing and higher chain regularity. In addition, the strong chain rigidity and interchain cohesion of NAPPI due to the presence of the rigid naphthalene ring and a large number of hydrogen bond interactions formed by amide groups result in compact chain packing and smaller free volume, which reduces the solubility and diffusibility of small molecules in the matrix. In general, the simulation results are consistent with the experimental results, which are important for understanding the barrier mechanism of NAPPI.

Automated summary

The high-barrier polyimide (NAPPI) with naphthalene ring and amide group exhibits superior barrier properties, mechanical properties, and thermal stability. Experimental and simulation studies confirm that the small interplanar spacing and high chain regularity of NAPPI play a key role in its barrier properties, while the strong chain rigidity and interchain cohesion due to the presence of the rigid naphthalene ring and hydrogen bond interactions formed by amide groups result in compact chain packing and smaller free volume, reducing the solubility and diffusibility of small molecules in the matrix.