Regulation of Poly(Amide‐Imide) Dimensional Stability and Melt Processability by Introduction of Siloxane Structures and Hydrogen Bonding Interactions

In order to solve the conflicting challenge of melt processability and dimensional stability in polyimides (PIs), a series of poly(amide‐imide)s (PAIs) with siloxane structures were synthesized by polycondensation of 2,2′‐(2,2′‐bis(trifluoromethyl)‐[1,1′‐biphenyl]‐4,4′‐diyl)bis(1,3‐dioxoisoindoline‐5‐carbonyl chloride) (CT‐TFDB), 4,4′‐([1,1′‐biphenyl]‐4,4′‐diylbis(oxy))bis(3‐(trifluoromethyl)aniline) (6FBAPB), 2,2′‐bis(trifluoromethyl)benzidine (TFDB), and 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (BATMS). It was found that when the BATMS content in the polymer increased, the thermoplastic processability improved while dimensional stability decreased slightly. All of the PAIs exhibited moderate glass transition temperatures ( T g ) in the range of 237°C–261°C, low minimum melt viscosities of 144–11,348 Pa·s, and good dimensional stability with coefficient of thermal expansion (CTE) values of 32.0–42.3 ppm/K. Additionally, these polymers exhibited better optical properties along with excellent mechanical properties and solubility. Taking PAI‐2‐3 with 30 mol% BATMS content as an example, compared to PAI‐2‐0, the minimum melt viscosity decreased from 10 4 to 267 Pa·s, while the CTE increased only from 32.0 to 35.5 ppm/K. These thermoplastic PAIs exhibit potential applications in the field of precision injection molding components.