POLYIMIDE-BASED BLOCK COPOLYMER

摘要

PROBLEM TO BE SOLVED: To provide a copolymer containing plural polyimide blocks having specific recurring unit in the molecule, having a plurality of good properties difficult to get at the same time by conventional means and useful as a constituent component of an agent for forming a liquid crystal orientation film. SOLUTION: This copolymer contains (A) a 1st polyimide block having a recurring unit of the formula I or the formula II (R<1> is a tetravalent organic group; Q<1> is a bivalent organic group; X is H or a univalent organic group; (m) and (n) are each the number of recurring units) and (B) a 2nd polyimide block bonded to the component A, having a structure different from that of the component A and containing a recurring unit of the formula III or the formula IV (R<2> is a tetravalent alicyclic group; Q<2> is a bivalent alicyclic group or a bivalent aromatic group; X is H or a univalent organic group; (p) and (q) are each the number of recurring units) and has a logarithmic viscosity (ηln) of 0.1-2dL/g. The copolymer can be produced e.g. by preparing a polyamic acid prepolymer having amino group on molecular terminal as a starting raw material.