Coating solutions and crosslinked polymer films
In a first aspect, a coating solution includes a soluble polymer and a crosslinking precursor. The soluble polymer includes an imide group. The crosslinking precursor includes a first amine group that is either reactive or passivated towards crosslinking and one or more additional amine groups, wherein the one or more additional amine groups has been passivated towards crosslinking such that the crosslinking precursor can be chemically converted, thermally converted, photo-converted or dissociated to form at least two reactive amines. In a second aspect, a process for forming a polymer film includes: (a) casting a coating solution, (b) activating the crosslinking precursor using an external stimulus to form at least two reactive amines and crosslink the polymer, and (c) drying the polymer film. The coating solution includes a soluble polymer, including an imide group, and a crosslinking precursor.
1. A coating solution comprising:
a soluble polymer comprising an imide group; and
a crosslinking precursor comprising:
a first amine group that is either reactive or passivated towards crosslinking; and
one or more additional amine groups, wherein the one or more additional amine groups has been passivated towards crosslinking by forming a moiety selected from the group consisting of carbamates, N-aryl amines, N,N-diaryl amines, benzyl amines, amides, sulfonamides, ammonium salts made from acids and silyl derivatives, such that the crosslinking precursor is un-reactive towards the soluble polymer having an imide group upon initial introduction and after activation, the crosslinking precursor can be chemically converted, thermally converted, photo-converted or dissociated to form at least two reactive amines.
2. The coating solution of claim 1 , wherein a carbamate is thermally cleavable.
3. The coating solution of claim 2 , wherein the thermally cleavable carbamate comprises a passivating group selected from the group consisting of tert-butyloxycarbonyl, fluorenylmethoxycarbonyl, and benzyl carbamate.
4. The coating solution of claim 1 , wherein a carbamate is photo-cleavable and a photo-cleavable carbamate is selected from the group consisting of 3,5-dimethoxybenzyl carbamate, m-nitrophenyl carbamate, and o-nitrobenzyl carbamate.
5. The coating solution of claim 1 , wherein an amide is selected from the group consisting of formamide, trifluoroacetamide, trichloroacetamide, chloroacetamide, phenylacetamide, 3-phenylpropanamide, 3-pyridylcarboxamide, N-benzoylphenylalanyl, and benzamide.
6. The coating solution of claim 1 , wherein an amide can be thermally cleaved, chemically cleaved, photo-cleaved, dissociated or a mixture thereof.
7. The coating solution of claim 1 , wherein:
an ammonium salt is made from an acid selected from the group consisting of acetic acid, butyric acid, pivalic acid, hydrochloric acid, and sulfuric acid; and
the ammonium salt can be thermally dissociated to form a reactive amine.
8. The coating solution of claim 1 , wherein the crosslinking precursor is selected from a single multi-functional precursor, a combination of multiple single-functional precursors, or a mixture thereof.
9. The coating solution of claim 1 , wherein the soluble polymer is selected from the group consisting of polyimides, poly(amide-imides), poly(ether-imides), poly(ester-imides), copolymers comprising amide, ester or ether groups, and mixtures thereof.
10. The coating solution of claim 1 , further comprising a filler selected from the group consisting of nanoparticles, colorants, matting agents, submicron particles, thermally conductive fillers, electrically conductive fillers and mixtures thereof.
11. The coating solution of claim 10 , wherein a colorant comprises low conductivity carbon black.