*2.2. Dyeing of PI Fibers*

Dyeing experiments were carried out on an Ahiba IR dyeing machine (Datacolor, Lawrenceville, NJ, USA). PI fibers were dyed at a liquor-to-material ratio of 20:1 with 5% of disperse and basic dyes (owf) by adding 50 g/L of swelling agents. The temperature of the dyebath was raised to 130 ◦C at a rate of 2 ◦C/min, and held for 60 min. When the dyeing was complete, the temperature was lowered to 85 ◦C, and the dyed PI fibers were taken out for washing. The PI fibers dyed with basic dyes were washed by soaping with 2 g/L of soaping agen<sup>t</sup> at 85 ◦C for 20 min, and the PI fibers dyed with disperse dyes were washed by reduction cleaning with 2 g/L of hydrosulphite and 2 g/L of sodium hydroxide at 85 ◦C for 20 min. All the dyed PI fibers were rinsed thoroughly with fresh water and dried under ambient conditions.
