Polymers for use in electronic devices

A polyimide film comprising a repeat unit structure of Formula II

• wherein:
• Ra is the same or different at each occurrence and represents one or more tetracarboxylic acid component residues;
• and
• Rb is the same or different at each occurrence and represents one or more diamine residues;
• and further wherein:
• the polyimide film is prepared according to a method comprising the following steps in order and without repeating:
• coating a polyamic acid solution comprising one or more tetracarboxylic acid components, one or more diamine components, and one or more phosphorous-containing additives in a high-boiling, aprotic solvent onto a matrix;
• soft-baking the coated matrix;
• treating the soft-baked coated matrix at a plurality of pre-selected temperatures for a plurality of pre-selected time intervals.