Polyimide

A polyimide or a polyimide copolymer comprising a requisite structural unit of 1.about.100 mol % of recurring structural units represented by the formula (1):

• ##STR50## wherein Ar is a tetravalent radical having 6 to 27 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member, a trifluoromethyl radical is situated at the 3- or the 4-position on the pyridine nucleus, and an imide nitrogen atom is connected at the 3- or the 4-position to an ether bond, and 99.about.0 mol % of recurring structural units represented by the formula (2):
• ##STR51## wherein n is an integer of 0 to 6;
• Q is a direct bond, --O--, --S--, --CO--, --SO.sub.2 --, --CH.sub.2 --, --C(CH.sub.3).sub.2 -- or --C(CH.sub.3).sub.2 --, and when two or more bonding radicals Q connect aromatic rings to each other, the bonding radicals Q can be the same or different;
• and Ar' is a tetravalent having 6 to 27 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member;
• or said polyimide or said polyimide copolymer having at the polymer chain end a radical which is essentially unsubstituted or substituted with a radical having no reactivity with amine or dicarboxylic anhydride.

A preparation process of polyimide having a requisite structural unit consisting of one or more recurring structural units represented by the formula (1):

• ##STR52## wherein Ar is a tetravalent radical having 6 to 27 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member, a trifluoromethyl radical is situated at the 3- or the 4-position on the pyridine nucleus, and an imide nitrogen atom is connected at the 3- or the 4-position to an ether bond, comprising reacting aromatic diamine consisting essentially of one or more aromatic diamino compounds represented by the formula (3):
• ##STR53## wherein a trifluoromethyl radical is situated at the 3- or the 4-position on a pyridine nucleus, and an amino radical is connected at the 3- or the 4-position to an ether bond, with tetracarboxylic dianhydride essentially represented by the formula (4):
• ##STR54## wherein Ar is a tetravalent radical having 6 to 27 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member;
• and thermally or chemically imidizing the resultant polyamic acid.

A preparation process of a polyimide having a requisite structural unit consisting of one or more recurring structural units represented by the formula (1):

• ##STR55## wherein Ar is a tetravalent radical having 6 to 27 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member, a trifluoromethyl radical is situated at the 3- or the 4-position on the pyridine nucleus, and an imide nitrogen atom is connected at the 3- or the 4-position to an ether bond, and having at the polymer chain end thereof an aromatic ring which is essentially unsubstituted or substituted with a radical having no reactivity with amine or dicarboxylic anhydride, comprising reacting aromatic diamine consisting essentially of one or more aromatic diamino compounds represented by the formula (3):
• ##STR56## wherein positions of the trifluoromethyl radical and the amino radical is connected at the 3- or the 4-position to an ether bond, with tetracarboxylic dianhydride essentially represented by the formula (4):
• ##STR57## wherein Ar is the same as above, in the presence of aromatic dicarboxylic anhydride represented by the formula (5):
• ##STR58## wherein Z is a divalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member, or aromatic monoamine represented by the formula (6):
• Z.sub.1 --NH.sub.2 ( 6)
• wherein Z.sub.1 is a monovalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed polyaromatic radical having aromatic radicals connected to each other with a direct bond or a bridge member;
• and thermally or chemically imidizing the resultant polyamic acid.