Polyimide/ladder-like polysilsesquioxane hybrid films: Mechanical performance, microstructure and phase separation behaviors

• Published in: Composites. Part B, Engineering Vol. 56; pp. 808 - 814
• Main Authors: Zhang, Lili, Tian, Guofeng, Wang, Xiaodong, Qi, Shengli, Wu, Zhanpeng, Wu, Dezhen
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2014; Elsevier
• Subjects: A. Polymer–matrix composites (PMCs); Applied sciences; B. Interface/interphase; B. Mechanical properties; B. Surface properties; Exact sciences and technology; Inorganic and organomineral polymers; Phase separation; Physicochemistry of polymers; Properties and characterization; A. Polymer–matrix composites (PMCs); B. Mechanical properties; B. Surface properties; B. Interface/interphase; Phase separation; Polyimide; Polymer blends; Property composition relationship; Silsesquioxane polymer; A. Polymer―matrix composites (PMCs); Mechanical properties; Tensile property; Experimental study; Glass transition temperature; Heterogeneous mixture; Structure composition relationship; Thermal properties; Dynamic mechanical properties; Morphology
• ISSN: 1359-8368; 1879-1069
• DOI: 10.1016/j.compositesb.2013.08.042

To obtain the polyimide (PI) hybrid films with silicon (Si)-enriched surface as well as excellent mechanical properties, Si-containing PI hybrid films were prepared by the incorporation with ladder-like polyphenylsilsesquioxane (ph-LPSQ) and ladder-like poly(nitrophenyl)silsesquioxane (nph-LPSQ) into PI through a casting method. The morphologies, surface structure, and phase separation behaviors of the hybrid films were investigated, and the mechanical and dynamic mechanical properties were also evaluated. For the PI/nph-LPSQ films, no evident phase separation was observed according to the SEM results, even when the nph-LPSQ content reached 30wt%, which resulted in mechanical properties improved by increasing the nph-LPSQ content. Nevertheless, silicon/carbon ratios on the surface are much higher than those calculated in bulk. For PI/ph-LPSQ films, ph-LPSQ particles with the diameter of microscale were observed. The phase separation was found to take place during the period of solvent evaporation, and the mechanical properties decreased with the increase of the ph-LPSQ content. However, such phase separation favors the enrichment of Si on the films surface, and the silicon/carbon ratios on the surface are two times higher than those of the PI/nph-LPSQ films. The Tgs of the two series hybrid films were improved because of the incorporation of rigid ladder-like polysilsesquioxane (LPSQ).