*2.5. Introduction of Distant Hydroxyl Groups to Polyimide*

To obtain PI4 initiator (Figure 8, see Result and Discussion section), an azide-alkyne cycloaddition was carried out between the azide groups of PI3 (Figure 8) and the acetylene groups of propargyl alcohol. The typical synthesis was as follows. A sample of PI3 macroinitiator (0.25 g, 0.32 mmol per initiating group) (Figure 8) was placed in a 25 mL Schlenk flask equipped with a magnetic stirrer. Propargyl alcohol (92.9 μL, 1.6 mmol) and PMDETA (66.7 μL, 0.32 mmol) were added, and then DMF (4 mL, 0.052 mol) was added using a syringe. The solvent and syringes were purged with argon. The flask was sealed with a rubber septum, and the mixture was stirred until the powder was completely dissolved. Then, three freeze−pump−thaw cycles (evacuation for 15 min) were carried out, after which the flask was filled with argon. After opening the septum, CuBr (0.0457 g, 0.32 mmol) was added to the reaction mixture in an argon flow, after which the flask was closed again with the septum, three more freeze−pump−thaw cycles (evacuation for 15 min) of the reaction mixture were carried out, the flask was filled with argon and thermostated in an oil bath, placed on a magnetic stirrer with a temperature regulator at 50 ◦C overnight. Then the reaction mixture was cooled to room temperature and the product was precipitated into methanol. Residual copper was disposed of by changing the

precipitant and reprecipitation from DMF. The filtered powder was dried under vacuum at 50 ◦C.

### *2.6. Synthesis of Linear Homopolymer PCL with Terminal Alkyne Groups*

The synthesis was carried out by ROP of CL in a solution in toluene using propargyl alcohol as an initiator. A typical synthesis procedure is as follows: Propargyl alcohol (51 μL, 0.89 mmol), ε-caprolactone (1.97 mL, 17.8 mmol), and toluene (2.52 mL, 23.7 mmol) were added to a 10 mL Schlenk flask equipped with a magnetic stirrer. Then three freeze−pump−thaw cycles (evacuation for 15 min) were carried out, after which the flask was filled with argon. Then, 0.08 mL (0.25 mmol) of Sn(Oct)2 was introduced in an argon flow into the reaction, after which the flask was closed again with a septum, three more freeze−pump−thaw cycles (evacuation for 15 min) of the reaction mixture were carried out, the flask was filled with argon and thermostated in the oil bath, placed on a magnetic stirrer with a temperature controller, at 100 ◦C for a specified time (3 h) and at 80 ◦C overnight. Upon completion of polymerization, the reaction mixture was cooled to room temperature and diluted with methylene chloride. The resulting solution was passed through a silica gel column to purify the product from catalyst and monomer impurities. The solution was then concentrated on a rotary evaporator and the product was precipitated into cooled petroleum ether. The polymer was dried under vacuum at 30 ◦C.

#### *2.7. Synthesis of Grafted Copolyimides PI-g-PCL*

To obtain the targeted copolymers, two approaches were used. The first approach consisted in ROP of CL on a macroinitiator with distant hydroxyl groups ("graft from"). A typical experiment was as follows. A 10 mL Schlenk flask equipped with a magnetic stirrer was charged with 0.05 g (0.054 mmol per initiating group) of PI4 macroinitiator (Figure 8), sealed with a rubber septum, and then 3 mL (26.9 mmol) of ε-caprolactone was introduced in an argon flow. The mixture was thermostated at 130 ◦C in an oil bath. After complete dissolution of the initiator, 0.123 mL (0.38 mmol) of Sn(Oct)2 was introduced into the flask in an argon flow, and the reaction mixture was thermostated for a preset time. The molar ratio of PI4/CL was 1/500. The amount of Sn(Oct)2 was 5 wt.% in relation to the monomer. Upon completion of polymerization, the reaction mixture was rapidly cooled to room temperature and diluted with methylene chloride. The resulting solution was passed through a silica gel column to purify the product from catalyst and monomer impurities. The solution was then concentrated using a rotary evaporator and the product was precipitated into cooled petroleum ether. The polymer was dried under vacuum at 30 ◦C.

The second approach was to carry out an azide-alkyne cycloaddition between the azide groups PI3 macroinitiator (Figure 8) and the alkyne groups of linear PCL. A typical reaction was carried out as follows. A weighed portion of PI3 macroinitiator (0.05 g, 0.064 mmol per initiating group) (Figure 8), PCL (0.447 g, 3.9 mmol per initiating group), and PMDETA (13 μL, 0.064 mmol) was placed in a 25-mL Schlenk flask equipped with a magnetic stirrer, then DMF (3.7 mL, 47.8 mmol) was added using a syringe. The solvent and syringes were purged with argon. The flask was sealed with a rubber septum, and the mixture was stirred until the powder was completely dissolved. Then, three freeze−pump−thaw cycles (evacuation for 15 min) were carried out, after which the flask was filled with argon. After opening the septum, CuBr (0.009 g, 0.064 mmol) was added to the reaction mixture in an argon flow, after which the flask was closed again with the septum, three more freeze−pump−thaw cycles (evacuation for 15 min) of the reaction mixture were carried out, the flask was filled with argon and thermostated in an oil bath placed on a magnetic stirrer with a temperature regulator, at 50 ◦C overnight. After that the reaction mixture was quickly cooled to room temperature and diluted two times with THF. To remove copper salts from the mixture, it was passed through a column filled with Al2O3, then

concentrated using a rotary evaporator, and precipitated into cooled petroleum ether. The filtered powder was dried under vacuum at 30 ◦C.
