Synthesis and Characterization of Poly(imide siloxane) (PIS) Copolymer and PIS-Inorganic Oxide Hybrid Nanocomposites

• Main Authors: Kuan-Pin Chen, 陳觀彬
• Other Authors: Wen-Chang Liaw
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/32304548426413422968

博士 === 國立雲林科技大學 === 工程科技研究所博士班 === 95 === In this article, we focus on three part of this dissertation; (1). The influence of diphenyl siloxane on morphology and physical properties in the poly (imide siloxane)(PIS) copolymer. (2). Preparation and properties of poly(imide siloxane) (PIS) segmented copolymer / silica (SiO2) hybrid nanocomposites. (3). Preparation and characterization of poly (imide siloxane) (PIS) �} titania (TiO2) hybrid nanocomposites by sol-gel processes. In the first part of this dissertation, we synthesized the various numbers of diphenyl-siloxane groups were incorporated in α,ω-bis(aminopropyl)polydimethylsiloxane (APPS) to prepar α,ω-bis(aminopropyl)polydimethyl diphenylsiloxane (APPPS) random oligomers of three differet number-average molecular weights. These APPPS oligomers were with 3,3’,4,4’-bezonphenone tetracarboxylic dianhydride (BTDA) and 2-2’-bis 4-(3-aminophenoxy)phenyl〕sulfone (m-BAPS), to synthesize a series of APPPS containing poly (imide siloxane) (PIS) copolymers. The critical point of microphase separation was found at 8.0, 4.3 and 2.1 mol% for Mn of 547, 772 and 1210 g/mol, respectively). Microstructural studies showed that when the APPPS contens was less than the critical point of phase separation, the APPPS domains were solvated in the PI matrix and formed a microscopically homogenous phase, and consequently a smooth surface. Whereas at higher mole concentration of APPPS, they are more likely to diffuse out of the PI matrix and aggregate, thus forms a distinct domain and lead to an unsmoothed surface, which they called “island”. In other hand, the long chain polysiloxane segments tend to have higher cohesive energy than short ones, and should be more likely to segregate from the PI phase and form separate domains. In the Tg study, at mole ratios higher than critical point, two Tgs (Tg1 and Tg2) were observed, for all three different molecular weights of APPPS. Tg1 appeared in the low temperature region: -100 to -50℃; and Tg2 appeared in the high temperature region: 200 to 255 ℃. Tg1, if observed, in all cases, virtually remained unchanged and coincided with the Tg of APPPS before copolymerization. On the other hand, Tg2 decreased upon increasing content of the APPPS.Consenquently, diphenyl -siloxane significantly improved compatibility between polyimide and polysiloxane segments. Physical studies showed that the introduction of diphenyl siloxane changed the thermal stabilities and mechanical properties of the PIS copolymers. The second part of this dissertation, we first synthesized the random copolymer, vinyl-containing α,ω-bis(aminopropyl) polydimethyldiphenyl siloxane, APPPVS) (Mn = 850 g/mol), which was used as the flexible segments in the PIS copolymers. This APPPVS was copolymerized with BTDA /m-BAPS to form the PAAVS solution. The obtained copolymer solution was then added with TMVS, TEOS, and AIBN. When the free-radical reaction was initiated, sol-gel reaction, and thermal imidization took places as well. It is expected that the TMVS molecules will provide an opportunity of covalent bond formation between the inorganic SiO2 and the PIS matrix. In FTIR and 1H, 29Si-NMR spectra were shown that a three-dimensional Si-O-Si network has formed like Q4 and T3 in the hybrid films. In microstructure study, when SiO2 content was less than 12wt%, the particle size of SiO2 was smaller than 100 nm. At this nanocomposite level, the film is visually transparent. The particle size increased from 100 nm to 2000 nm at 30 wt% and the films were opaque. The nanosized SiO2 particles played a key role in affecting important features and rendered special properties to optical transparency and improved mechanical as well as thermal properties in PIS/SiO2 hybrid nanocomposites. The third part of this dissertation, PIS copolymer synthesized in this section was characterized by the observed coexisting two segments: the PI segment and polydimethyldiphenylsiloxane segment, and the latter were specially featured with the introduction of a diphenyl group for improved homogeneity. The TiO2 network was synthesized from a titanium precursor and the reaction was controlled by adding chelating agent (acetylactone, acac) to chelate with titanium ion, and to reduce the gelation rate. The FTIR and XPS spectrum confirmed the Ti�{O�{Ti bonding and provided the evidence of the presence of the TiO2 in the PIS matrix. The PIS/TiO2 hybrid nanocomposite films have good optical transparency, even at high TiO2 content (up to 20wt�s) by UV-visible measurement. The TiO2 network is well dispersed in the PIS matrix with particle diameters smaller than 50 nm at high TiO2 content of 20wt�s, as was confirm by TEM morphological analysis. The in situ incorporation of TiO2 together with the adoption of coupling agent significantly enhanced the material’s Young’s modulus, which increased with increasing TiO2 content. The presence of TiO2 rendered the material brittleness and consequently lowered its tensile strength, elongation at break and thermal stability. This reason could be the TiO2 was metal oxide-catalyzed that oxidative decomposition pathways in the composite.