Fluorinated Copolyimides

The fluorinated copolyimides (including homopolyimides) are all more transparent than the nonfluorinated PMDA/ODA. The color of 10-pm-thick films changes gradually from bright yellow to colorless as the 6FDA/TFDB content increases. All these copolyimide films are also homogeneous compared with polyimide blends of 6FDA/TFDB and PMDA/TFDB. 

2 X 10 °C 6FDA/TFDB is more flexible than PMDA/TFDB, because the 

6FDA/TFDB and PMDA/TFDB homopolyimides have Tg s of 335 and over 400°C (it is not observed below 400°C by differential scanning calorimetry), respectively, and the Tg s of all that have been investigated copolyimides are above 335°C.  

It is also possible for these copolyimides to control the refractive index because 6FDA/TFDB and PMDA/TFDB have largely different values. The refractive index and birefringence of the fluorinated copolyimides are described in detail in the next section. 

---

For example, the fluorinated copoly imide with 10 mol% 6FDA/TFDB has almost the same CTE as a Si substrate. Figure 15.8 shows the TMA curves, temperature vs. elongation, of the fluorinated copolyimides with 10 mol%... 

Figure 15.7. Coefficient of thermal expansion of fluorinated copolyimides.

Figure 15.9. Decomposition temperature of fluorinated copolyimides (heating rate—10°C/min).

Low-loss, heat-resistant single-mode optical waveguides were fabricated using the fluorinated copolyimides with a high optical transparency and refractive index controllability. The high thermal stability of these waveguide materials... 

Figure 15.6. Synthesis scheme of fluorinated copolyimides prepared from 6FDA, PMDA, and TFDB.

---