Membrane comprising self-assembled block copolymer and process for producing the same by hybrid casting (Ib)
Disclosed are membranes formed from self-assembling diblock copolymers of the formula (I): wherein R 1 -R 4 , n, and m are as described herein, which find use in preparing porous membranes. Embodiments of the membranes contain the diblock copolymer that self-assembles into a cylindrical morphology. Also disclosed is a method of preparing such a membrane which involves hybrid casting a polymer solution containing the diblock copolymer to obtain a thin film, followed by evaporation of some of the solvent from the thin film, and coagulating the resulting this film in a bath containing a nonsolvent or poor solvent for the diblock copolymer.
1. A method of preparing a porous membrane comprising a diblock copolymer of the formula (I):
wherein:
R 1 is a C 1 -C 22 alkyl group optionally substituted with a substituent selected from halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro, or a C 3 -C 11 cycloalkyl group, optionally substituted with a substituent selected from alkyl, halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro;
R 2 is a C 6 -C 20 aryl group or a heteroaryl group, optionally substituted with a substituent selected from hydroxy, amino, halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro;
one of R 3 and R 4 is a C 6 -C 14 aryl group, optionally substituted with a substituent selected from hydroxy, halo, amino, and nitro, and the other of R 3 and R 4 is a C 1 -C 22 alkoxy group, optionally substituted with a substituent selected from carboxy, amino, mercapto, alkynyl, alkenyl, halo, azido, and heterocyclyl; and
n and m are independently about 10 to about 2000;
wherein the volume fraction of the monomeric unit bearing R 2 to that of the monomeric unit bearing R 1 is about 2.3 to about 5.6:1;
wherein the porous membrane has cylindrical morphology;
the method comprising:
(i) dissolving the diblock copolymer in a solvent system to obtain a polymer solution;
(ii) coating the polymer solution onto a substrate;
(iii) evaporating at least a portion of a solvent from the coating obtained in (ii);
(iv) immersing the coating from (iii) into a coagulation bath; and
(v) washing the porous membrane obtained in (iv).
2. The method of claim 1 , wherein R 1 is a C 10 -C 18 alkyl group, optionally substituted with a substituent selected from halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro.
3. The method of claim 1 , wherein R 2 is a phenyl group, optionally substituted with a substituent selected from hydroxy, amino, halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro.
4. The method of claim 1 , wherein R 3 is phenyl.
5. The method of claim 1 , wherein R 4 is a C 1 -C 6 alkoxy group.
6. The method of claim 1 , wherein n is about 10 to about 200 and m is about 50 to about 2000.
7. The method of claim 1 , wherein n is about 83 to about 190 and m is about 675 to about 1525.
8. The method of claim 1 , wherein n is about 105 and m is about 870.
9. The method of claim 1 , wherein the diblock copolymer of formula (I) has the following structure:
10. The method of claim 1 , wherein the solvent system includes a solvent or a mixture of solvents selected from halogenated hydrocarbons, ethers, amides, and sulfoxides.
11. The method of claim 1 , wherein the solvent system includes a solvent or a mixture of solvents selected from dichloromethane, 1-chloropentane, chloroform, 1,1-dichloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran, 1,3-dioxane, and 1,4-dioxane.
12. The method of claim 1 , wherein the polymer solution contains about 10 to about 35% by weight of the diblock copolymer.
13. The method of claim 1 , wherein the substrate is selected from glass, silicon wafer, metal plate, plastic film, woven or nonwoven fabric, and a plastic film coated on a glass substrate or on or a silicon wafer.
14. The method of claim 1 , wherein the substrate is porous.
15. The method of claim 1 , wherein the coagulation bath comprises a nonsolvent or poor solvent for the diblock copolymer.
16. The method of claim 15 , wherein the nonsolvent or poor solvent is selected from alcohols, alkanes, water, dimethylsulfoxide, and mixtures thereof.
17. A porous membrane prepared by the method of claim 1 .
18. The porous membrane of claim 17 , which is an asymmetric membrane comprising a first layer and a second layer, the first layer comprising the diblock copolymer and ordered pores in a cylindrical morphology continuously extending to the second layer comprising the diblock copolymer in a network of porous structure in which micro and macro channels are connected so as to provide a tortuous path for fluid flow.
19. The porous membrane of claim 18 , wherein the first layer has a thickness of about 50 to about 200 nm and the second layer has a thickness of about 100 μm to about 300 μm.