Preparation and characterization of poly(imide siloxane) block copolymers based on diphenylthioether dianhydride isomer mixtures

Abstract

A series of poly(imide siloxane) block copolymers were prepared based on diphenylthioether dianhydride isomer mixtures (m-TDPA), 4,4′-oxydianiline (ODA) and bis(γ-aminopropyl)polydimethylsiloxane (APPS). The ODA and m-TDPA composed the hard segment, while the APPS and m-TDPA composed the soft segment. The hard segment length was kept constant, while the soft segment lengths were varied with varying the APPS contents. The copolymers had inherent viscosities range from 0.37 to 0.51 dL g−1, and their weight-average molecular weights and number-average molecular weights were in the range of 45 000–52 600 and 21 300–27 000, respectively. All copolymers were readily soluble in many organic solvents, and could afford flexible films via solution casting. The cast films exhibited mechanical properties with tensile strengths at break of 26.7–86.2 MPa, elongations at break of 9.9–112.2%, and tensile moduli of 0.12–2.15 GPa, depending on the soft segment length. The films also exhibited low water uptakes in the range of 0.18–0.68 wt.%. Furthermore, the copolymers showed high glass transition temperatures derived from the hard segments in the range of 196–225 °C, and good thermal stability with almost no weight loss up to 350 °C under nitrogen atmosphere and 335 °C under air atmosphere.