Polyimides, coating composition formed therefrom and use thereof

1. A coating composition comprising at least 1% of polyimide (PI), based on the total weight of the composition, and a hardening agent having 2 to 6 functional groups capable of reacting with —COOH,

wherein the polyimide (PI) has a structure represented by Formula (I):

wherein:

A, C and E are the same or different and are each independently a tetravalent organic group, and if n is greater than 1, each C is the same or a different tetravalent organic group;

each B is the same or different, and is independently a divalent organic group; and

n is an integer greater than 0, and

wherein the 2 to 6 functional groups of the hardening agent are selected from the group consisting of an oxazolyl group, a benzoxazinyl group, and a mixture thereof.

2. The coating composition according to claim 1 , wherein A, C and E are respectively a tetravalent organic group selected from the group consisting of the following groups:

wherein:

each X is independently hydrogen, halogen, a linear or branched C 1 -C 4 perfluoroalkyl group, or a linear or branched C 1 -C 4 alkyl group; and

A 1 and B 1 are each independently a covalent bond, a linear or branched C 1 -C 4 alkyl group, a linear or branched C 1 -C 4 perfluoroalkyl group, an alkoxy group, silanyl, oxygen, sulfur, carbonyl, a carboxylate group, sulfonyl, phenyl, biphenyl, fluorenyl, or

 wherein J is —O—, —SO 2 —, —CH 2 —, —C(CF 3 ) 2 , and —C(CH 3 ) 2 .

3. The coating composition according to claim 2 , wherein A, C and E are respectively a tetravalent organic group selected from the group consisting of the following groups:

wherein Z is hydrogen or halogen.

4. The coating composition according to claim 3 , wherein A, C and E are respectively a tetravalent organic group selected from the group consisting of the following groups:

5. The coating composition according to claim 1 , wherein B is respectively a divalent organic group selected from the group consisting of the following groups:

wherein:

each R 17 is independently H, a C 1 -C 4 alkyl group, a C 1 -C 4 perfluoroalkyl group, methoxy, ethoxyl, halogen, —OH, —COOH, —NH 2 , or —SH;

each a is independently an integer of 0 to 4;

each b is independently an integer of 0 to 4; and

R 18 is a covalent bond or is selected from the following groups:

wherein:

c and d are each independently an integer of 0 to 20;

R 17 and a are as defined above;

R 19 is —S(O) 2 —, —C(O)—, a covalent bond, or a linear or branched C 1 -C 18 alkyl group;

each R 20 is independently H, methyl, ethyl, or phenyl;

each R 21 is independently a C 1 -C 20 alkyl group or a cyclic alkyl group;

each m is independently an integer of 1 to 20; and

e and f are each independently an integer greater than 0.

6. The coating composition according to claim 5 , wherein B is respectively a divalent organic group selected from the group consisting of the following groups:

wherein:

each a is independently an integer of 0 to 4; and

each Z is independently hydrogen, methyl, trifluoromethyl or halogen.

7. The coating composition according to claim 6 , wherein B is respectively a divalent organic group selected from the group consisting of the following groups:

8. The coating composition according to claim 1 , wherein n is an integer of 1 to 100.

9. A flexible device, comprising a thin film formed by the coating composition according to claim 1 .

10. The coating composition according to claim 1 , wherein the hardening agent is (1,3-bis(4,5-dihydrooxazol-2-yl)benzene).