# US 8,785,589 B1 · Azobenzene-containing glassy polyimides capable of photo-induced large-angle bending and methods of making the same

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- Number: US 8,785,589 B1
- Document ID: US8785589B1
- Status: Granted
- Kind: B1
- Application number: 13/866,551
- Filed: 2013-04-19
- Granted: 2014-07-22
- Earliest claimed: 2012-04-20
- Assignees: The United States of America as represented by the Secretary of the Air Force
- Applicants: The United States of America, as Represented by the Secretarty of the Air Force
- Inventors: Loon-Seng Tan; David Huabin Wang; Kyung Min Lee; Timothy J. White
- Web page: https://patentgrep.com/patent/US8785589B1

## CPC

- C07C 245/08: with the two nitrogen atoms of azo groups bound to carbon atoms of six-membered aromatic rings, e.g. azobenzene
- C07C 217/90: the oxygen atom of at least one of the etherified hydroxy groups being further bound to a carbon atom of a six-membered aromatic ring, e.g. amino-diphenylethers
- C07F 9/5325: {Aromatic phosphine oxides or thioxides (P-C aromatic linkage)}
- C08G 73/1085: {Polyimides with diamino moieties or tetracarboxylic segments containing heterocyclic moieties}
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

## Abstract

Cross-linked polyimides based on a novel crosslinker and methods of making the same. The general structure of these heat-resistant and amorphous polyimides is shown as follows: in which n, m, and l denote the degrees of polymerization (DP) of each arm and the linking group R′ is one of the following moieties: —C(CF3)2—, —O—, —SO2—, >C(═O), —OPh-C(CH3)2-PhO-, -(Ph)C(CF3)—, or a direct bond (—). Films (cantilevers) comprising cross-linked polyimides according to the present invention demonstrate photodirected bending upon exposure to linearly polarized light.

## Claims

### Claim 1

A cross-linked polyimide having three branches and the following general structure:
wherein n, m, and l are degrees of polymerization of each of the three branches of the cross-linked polyimide; and wherein R′ is selected from the group consisting of —C(CF3)2—, —O—, —SO2—, >C(═O), —OPh-C(CH3)2-PhO-, -(Ph)C(CF3)—, a direct bond (—), and mixtures thereof.

### Claim 2 (depends on 1)

The cross-linked polyimide of claim 1 wherein n, m, and l are equal.

### Claim 3 (depends on 1)

The cross-linked polyimide of claim 1 wherein at least one of n, m, and l are not equal.

### Claim 4 (depends on 1)

The cross-linked polyimide of claim 1 wherein n, m, and l are from about 2 to about 20.

### Claim 5 (depends on 2)

The cross-linked polyimide of claim 2 wherein n, m, and l are from about 3 to about 15.

### Claim 6 (depends on 1)

A method for making the crosslinked polyimide of claim 1 comprising the following steps:
dissolving a bis(phthalic anhydride) compound having a general structure:
and 1,3-bis(3-aminophenoxy)benzene in N,N-dimethylacetamide to form a solution;
stirring the solution under a nitrogen atmosphere at room temperature to form a poly(amic acid) oligomer solution comprising poly(amic acid) oligomers, the poly(amic acid) oligomers further comprising terminal anhydride groups;
adding a tris(azobenzene-amine) cross-linker to the poly(amic acid) oligomer solution, wherein the tris(azobenzene-amine) cross-linker has a general structure:
wherein for meta-azo substitution, R is equal to H, and for para-azo substitution, R is selected from the group consisting of H, F, Cl, CF3, and CH3;
allowing the tris(azobenzene-amine) cross-linker to dissolve in the poly(amic acid) oligomer solution to form a poly(amic acid) sol-gel precursor; and
curing the poly(amic acid) sol-gel precursor to crosslink and imidize the poly(amic acid) sol-gel precursor to form the crosslinked polyimide.

### Claim 7 (depends on 6)

The method of claim 6 wherein a molar ratio of the bis(phthalic anhydride) compound to the 1,3-bis(3-aminophenoxy)benzene is from about 1.00:0.92 to about 1.00:0.55.

### Claim 8 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 2,2-bis(phthalic anhydride)-1,1,1,3,3,3-hexafluoroisopropane.

### Claim 9 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 4,4′-oxydiphthalic anhydride.

### Claim 10 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 3,3′,4,4′-benzophenonetetracarboxylic dianhydride.

### Claim 11 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride.

### Claim 12 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.

### Claim 13 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 4,4′-(2,2,2-trifluoro-1-phenylethylidene)diphthalic anhydride.

### Claim 14 (depends on 6)

The method of claim 6 wherein the bis(phthalic anhydride) compound is 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride.