Synthesis of transparent poly(amide-imide)s containing alicyclic and trifluoromethyl units & new type of thermoresponsive polymers

Abstract

Over the past few years, polymer films have been actively researched to replace solid silicon based materials for flexible electronics. Due to the characteristics of electronic devices, the available polymeric film should have high transparency, such as a glass, and also good thermal properties to withstand the heating and high temperature processing issues of electronic devices. Transparent polymer films, known as crystal clear, are almost transparent to glass, but are less resistant to heat and difficult to use as electronic devices. Conversely, for most high-performance polymer films, it is not suitable for new electronic devices because of low transparency and processability. Thus it is important to take advantage of each polymer film, which can be achieved by changing the structure of a monomer unit. In this dissertation, a new series of alicyclic poly(amide-imide)s, were synthesized and analyzed to produce transparent polymer films with good thermal properties. In chapter 2,3, and 4, optical properties of polymer films have been significantly improved by inducing cyclohexane rings and compound with two trifluoromethyl groups. In addition, the resultant polymer films had a high heat resistance due to strong interaction between polymer chains, contributed by structure of poly(amide-imide)s. although alicyclic units were composed in polymers. Depending on the position and isomers of alicyclic units introduced in polymers, thermal stability and transparency of the polymer films were adjustable, and in particular, the thermal expansion characteristics varied greatly.In chapter 5 and 6 of the dissertation, new thermoresponsive polymers were described. First, self-assembly of block copolymers, containing a rigid conductive polymer and a temperature responsive polymer, was conducted in water according to temperature. Depending on the molecular weight of each polymer block, a different lower critical solution temperature was observed, and color of polymer solution was changed as increasing temperature due to increased packing distance between conjugated polymers. In chapter 6, polymers, which had thermoresponsive properties in organic solvents, not a water, was synthesized and the cause of this unusual phenomenon has been proved. Above the specific molecular weight, a lower critical solution temperature was increased with concentration of solution and molecular weight of polymers. When this polymer was incorporated as block copolymers with another polymer, temperature responsive phenomenon was also observed.