Synthesis and characterization of highly transparent poly(amide-imide)s and polyimides with high glass transition temperature

Abstract

The synthesis and properties of highly transparent poly(amide-imide) and polyimide with high glass transition temperature are reported in this dissertation. Recently, as the need for flexible displays has grown, research have tended to focus on high temperature polymers for electronic devices. Due to the inherent chemical structural limitations of the polymer main chain, currently available engineering plastics cannot meet the heat-resistant characteristics required for plastic substrates, so studies are being conducted to increase the optical properties of high performance polymers with high thermal properties. In the case of high temperature polymers, however, the factors that improve optical characteristics are also negatively related to high thermal properties, thus enhancing transparency frequently has a negative impact on the glass transition temperature and the coefficient of thermal expansion. To address this trade-off relationship, the microstructure of the polymer must be fine-tuned in the beginning stage of monomer design. The thesis begins with the general introduction of high temperatrue polymers, as well as polyimides and poly(amide-imide)s. In Chapter 2, we explored strategies to alleviate disadvantages by reducing the flexibility of aliphatic rings, which is known to improve transparency of polymeric paterials, but to decrease thermal stability. In Chapter 3, a novel trimellitic anhydride containing a trifluoromethyl group was synthesized and its influence on the polymer was studied. In Chapter 4, a dianhydride monomer having a polycyclic structure was synthesized and the effect of the polycyclic structure on the physical properties of the polymer was studied. In chapter 5, we designed and synthesized a new dicarboxylic acid monomer including polycyclic structures and examined the relationship between structural modification and polymer characteristics through comparative analysis with previous studies.