Patent ID: 8617657

Claim:
A method of making a block polyimide copolymer containing a first small block copolymer segment, the first small block copolymer segment having a molecular weight of up to 1000 grams/mol, and a second larger block segment, the method comprising: (a) reacting a first aromatic acid dianhydride with an aromatic diamine in a molar ratio from about 10:100 to about 33:100 respectively with an excess amount of diamine to obtain said small block copolymer segments having a molecular weight of up to 1000 grams/mol of said first aromatic dianhydride with an amine end chain and an excess amount of diamine; (b) reacting said small block copolymer and said excess amount of diamine with a second acid dianhydride in such a quantity that a total aromatic acid dianhydride and a total aromatic diamine are equimolar to obtain a precursor solution containing said first small block copolymer segment and said second larger block segment; (c) forming a film, laminate or coating on a substrate from said precursor solution at room temperature by using solvent; and (d) cyclodehydrating said film, laminate, or coating on said substrate by imidization to obtain said block polyimide copolymer film; in which the block polyimide copolymer has a tensile strength greater than 120 megapascals (MPa) and a pull strength on said substrate greater than 10 megapascals (MPa).