Synthesis and comparative study of thermoplastic polyetherimides derived from hydroquinone diphthalic anhydride isomers with tert-butyl group

Two isomeric dianhydride monomers, 1,4-bis(3,4-dicarboxyphenoxy)-2- tert -butylbenzene dianhydride (4,4′-TBHQDA) and 1,4-bis(2,3-dicarboxyphenoxy)-2- tert -butylbenzene dianhydride (3,3′-TBHQDA), were successfully synthesized from tert -butylhydroquinone and nitrophthalonitrile. Two series of polyetherimides (PEIs) were synthesized by chemical imidization using the above dianhydrides with four common commercially available diamines. The effects of dianhydrides with isomerization and tert -butyl group on the thermal properties, optical properties, melt processability, solubility, and mechanical properties of PEIs were systematically studied. Among them, PEI-2(a-d) derived from 3,3′-TBHQDA displayed better comprehensive performance than other PEIs, which showed well T g s at 234–261 ℃, good optical properties of 82–86 % at 450 nm, extremely low melt viscosities of 30–59 Pa·s at 400 ℃, excellent solubility and good mechanical properties (tensile modulus of 2.7–3.5 GPa, tensile strengths of 90–97 MPa and elongations at break of 3.4–4.8 %).