Taewook Ryu

Synthesis and Characterization of Polycarbonate Copolymers Containing Benzoyl Groups on the Side Chain for Scratch Resistance

The purpose of this study was to enhance the scratch resistance of polycarbonate copolymer by using 3,3′-dibenzoyl-4,4′-dihydroxybiphenyl (DBHP) monomer, containing benzoyl moieties on the ortho positions. DBHP monomer was synthesized from 4,4′-dihydroxybiphenyl and benzoyl chloride, followed by the Friedel-Craft rearrangement reaction with AlCl3. The polymerizations were conducted following the low-temperature procedure, which is carried out in methylene chloride by using triphosgene, triethylamine, bisphenol-A, and DBHP. The chemical structures of the polycarbonate copolymers were confirmed by 1H-NMR. The thermal properties of copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry, and also surface morphologies were assessed by atomic force microscopy. The scratch resistance of homopolymer film (100 μm) changed from 6B to 1B, and the contact angle of a sessile water drop onto the homopolymer film also increased.

Studies of Grafted and Sulfonated Spiro Poly(isatin-ethersulfone) Membranes by Super Acid-Catalyzed Reaction

Spiro poly(isatin-ethersulfone) polymers were prepared from isatin and bis-2,6-dimethylphenoxyphenylsulfone by super acid catalyzed polyhydroxyalkylation reactions. We designed and synthesized bis-2,6-dimethylphenoxyphenylsulfone, which is structured at the meta position steric hindrance by two methyl groups, because this structure minimized crosslinking reaction during super acid catalyzed polymerization. In addition, sulfonic acid groups were structured in both side chains and main chains to form better polymer chain morphology and improve proton conductivity. The sulfonation reactions were performed in two steps which are: in 3-bromo-1-propanesulfonic acid potassium salt and in con. sulfuric acid. The membrane morphology was studied by tapping mode atomic force microscope (AFM). The phase difference between the hydrophobic polymer main chain and hydrophilic sulfonated units of the polymer was shown to be the reasonable result of the well phase separated structure. The correlations of proton conductivity, ion exchange capacity (IEC) and single cell performance were clearly described with the membrane morphology.