Glass-Forming Terephthalic Esters with Lateral Phenylthio Groups and their Relaxation Behavior

Abstract

The esters of 2,5-bis(2-carboxy-phenylthio)terephthalic acid 4a-f were prepared by reaction of 2,5-bis(2-carboxy-phenylthio)terephthalic acid 2 via chloride 3 with alcohols or phenols. These novel glass-forming compounds are of the sulfur ligated “trilling” type. Two structures were established by X-ray analysis as well. The thermal behavior was characterized by DSC. In dependence of the different lateral substituents we found calorimetric glass transition temperatures (T_g ) in the range of −50°C to 85°C. The molecular dynamics were investigated by use of dielectric spectroscopy (10-²Hz-10⁹Hz). The temperature time dependence for the α-relaxation, which is associated with the glass transition, is discussed in the fragility concept of liquids.

Key Words:

• Esters of 2,5-bis(2-carboxy-phenylthio)terephthalic acid
• sulfur ligated “trillings”
• glass transition
• DSC
• dielectric relaxation
• fragility