Method for pore sealing of porous materials using polyimide langmuir-blodgett film
Method for pore sealing a porous substrate, comprising: forming a continuous monolayer of a polyimide precursor on a liquid surface, transferring said polyimide precursor monolayer onto the porous substrate with the Langmuir-Blodgett technique, and imidization of the transferred polyimide precursor monolayers, thereby forming a polyimide sealing layer on the porous substrate. Porous substrate having at least one surface on which a sealing layer is provided to seal pores of the substrate, wherein the sealing layer is a polyimide having a thickness of a few monolayers and wherein there is no penetration of the polyimide into the pores.
1. A method for pore sealing a porous substrate, comprising:
(a) forming a continuous monolayer of a polyimide precursor on a liquid surface; and
(b) transferring said polyimide precursor monolayer onto the porous substrate with the Langmuir-Blodgett technique, wherein the porous substrate is an ultra-low κ dielectric material having a dielectric constant κ lower than 2.3 and the porous substrate has a pore size of 1 to 5 nm;
and further comprising:
(c) imidization of the transferred polyimide precursor monolayers, thereby forming a polyimide sealing layer on the porous substrate.
2. The method according to claim 1 , wherein both forming said continuous monolayer of said polyimide precursor on the liquid surface and transferring said polyimide precursor monolayer onto the porous substrate with said Langmuir-Blodgett technique are repeated a number of times, so that said sealing layer on said porous substrate comprises a plurality of said monolayers.
3. The method according to claim 2 , wherein said sealing layer has a thickness lower than 5 nm.
4. The method according to claim 1 , wherein the polyimide precursor is polyamic acid alkylamine salt.
5. The method according to claim 1 , wherein the sealing layer does not penetrate into pores of the porous substrate.
6. The method according to claim 1 , wherein the dielectric constant κ is lower than 2.1.
7. The method according to claim 1 , wherein the porous substrate has an average pore size of 2 nm.
8. The method according to claim 1 , wherein the porous substrate is a porous organosilicate.
9. The method according to claim 8 , wherein the porous organosilicate comprises SiOCH material having a κ-value of 2.3 and an average pore size of 2 nm.