New heat resistant poly (thiourea-amide-imide)s derived from 1-(1,3-dioxo-2-(4-aminophenyl) isoindolin-5-yl)carbonyl-3-(4-aminophenyl) thiourea for high performance applications

Abstract

Novel heat-resistant and organosoluble poly(thiourea-amide-imide)s (PTAIs) were synthesized through the condensation of trimellitic anhydride chloride (TMAC)-derived imide ring bearing diamine (1-(1,3-dioxo-2-(4-aminophenyl)isoindolin-5-yl)carbonyl-3-(4-aminophenyl) thiourea) with various diacid chlorides. Physical properties of PTAIs including crystallinity, organosolubility, thermal properties, flame retardancy, solution viscosity along with molecular weights were investigated. Accordingly, polymers bearing phenylthiourea moieties displayed an amorphous nature and were readily soluble in amide solvents having ηinh of 1.11–1.37 dL g−1. Moreover, gel permeation chromatography measurements revealed Mw around 76 869–80 391. Thermal stability of these polymers was ascertained via 10% weight loss temperatures around 517–544°C in an inert atmosphere. Furthermore, glass transition temperatures of PTAIs were found to be 286–292°C. Limiting oxygen index (LOI) measurements indicated that new copolymers were efficiently flame retardant as compared to several reported materials. Hence, incorporation of thiourea functionalities into the polymer backbone was demonstrated to be an effective way to enhance their thermal properties and flame retardancy.