Polyamic acid ester

A polyamide ester composition comprising a plurality of different polyamide esters, each independently comprising recurring units represented by the following formula (I):

• wherein:
• each X independently represents a tetravalent aromatic group having 6 to 32 carbon atoms,
• each Y independently represents a divalent organic group having 4 to 30 carbon atoms, and
• each R independently represents a monovalent group containing an olefinic double bond,
• said plurality of different polyamide esters collectively containing, as said tetravalent aromatic groups X, the following two types of groups:
• 15 to 70 mole %, based on the total molar amount of said tetravalent aromatic groups X, of a tetravalent benzene group (II) represented by the following formula (II):
• 15 to 50 mole %, based on the total molar amount of said tetravalent aromatic groups X, of a tetravalent diphenyl ether group (III) represented by the following formula (III):
• with the proviso that the total amount of said tetravalent benzene group (II) and said tetravalent diphenyl ether group (III) is at least 50 mole %, based on the total molar amount of said tetravalent aromatic groups X,
• said polyamide ester composition being adapted to be converted to a polyimide composition in a coating form when a solution of said polyamide ester composition in a solvent for said polyamide ester composition is applied onto a silicon substrate to form a polyamide ester composition coating and heated at 350° C. for 2 hours in a nitrogen atmosphere, said polyimide composition coating exhibiting a residual stress of 33 MPa or less as measured with respect to a 10 μm-thick polyimide composition coating formed on said silicon substrate.