Cellulose acetate aerogels
Mechanically strong, biodegradable and reusable aerogels are disclosed, which can be made with a cross-linked cellulose ester, and which exhibit a low density and high porosity. The aerogels disclosed herein may be used as sorbent materials and can be modified with a hydrophobic and/or oleophilic agent.
1. An aerogel comprising a cross-linked cellulose ester having a degree of substitution of from about 1.0 to about 2.8, and further comprising a hydrophobic agent,
wherein the aerogel has a bulk density of from about 15 mg/cc to about 85 mg/cc, and
wherein the cellulose ester is a (C 1 -C 10 )alkyl-C(O)-functionalized cellulose.
2. The aerogel of claim 1 , wherein the degree of substitution of the cellulose ester is from about 1.8 to about 2.6.
3. The aerogel of claim 1 , wherein the cellulose ester is cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate or a combination thereof.
4. The aerogel of claim 1 , wherein the cellulose ester is cross-linked via an ester, ether or urethane linkage.
5. The aerogel of claim 4 , comprising a cross-linking agent at from about 1 wt. % to about 15 wt. %.
6. The aerogel of claim 4 , comprising the cellulose ester at from about 85 wt. % to about 99 wt. %.
7. The aerogel of claim 5 , wherein the cross-linking agent is selected from at least one of a C 7 -C 20 aromatic anhydride, a (C 5 -C 20 )cycloalkyl anhydride, a bis(halo(C 1 -C 3 )alkyl)-(C 5 -C 20 )aromatic, a bis(halo(C 1 -C 3 )alkyl)(C 3 -C 7 )cycloalkyl, a bis(isocyanato(C 1 -C 3 )alkyl)(C 5 -C 20 )aromatic, or a bis(isocyanato(C 1 -C 3 )alkyl)(C 3 -C 7 )cycloalkyl.
8. The aerogel of claim 7 , wherein the cross-linking agent is pyromelletic dianhydride (PMDA).
9. The aerogel of claim 1 , wherein the aerogel has the capacity to absorb at least about 20 grams of water per gram of aerogel.
10. The aerogel of claim 1 , wherein the hydrophobic agent is selected from at least one of a C 2 -C 20 alkyl silane, a C 3 -C 7 cycloalkyl silane, an aromatic silane, an (C 2 -C 20 )alkyl, a (C 3 -C 7 )cycloalkyl, an (C 2 -C 20 )alkyl urethane, a (C 3 -C 7 )cycloalkyl urethane, an (C 2 -C 20 )alkyl ester, a (C 3 -C 7 )cycloalkyl ester, an (C 2 -C 20 )alkyl carbonate, a (C 3 -C 7 )cycloalkyl carbonate or any mixture thereof.
11. The aerogel of claim 10 , wherein the hydrophobic agent is a C 5 -C 10 alkyl silane.
12. The aerogel of claim 1 , wherein the aerogel exhibits at least one of the following:
(a) a porosity equal to or greater than 90%,
(b) a maximum compressive stress of from about 50 kPa to about 400 kPa,
(c) a maximum strain of from about 15% to about 100%,
(d) a compression modulus of from about 20 kPa to about 500 kPa,
(e) a pore size average diameter of from about 20 μm to about 100 μm,
(f) a Brunauer-Emmett-Teller (BET) of from about 2 m 2 /g to about 5 m 2 /g, and
(g) a surface tension of from about 30 mN/m to about 60 mN/m.
13. The aerogel of claim 1 , wherein the aerogel adsorbs at least about 20 grams of oil per gram of aerogel.
14. The aerogel of claim 13 , wherein the aerogel adsorbs at least about 10 grams of oil per gram of aerogel after 5 cycles of adsorption and compression.
15. The aerogel of claim 13 , wherein the ratio of oil:water capable of being adsorbed per gram of aerogel is from about 1:5 to about 1:50.
16. An aerogel comprising:
a cross-linked cellulose ester, wherein the cellulose ester is cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate or a combination thereof;
a cross-linking agent; and
a hydrophobic agent,
wherein the aerogel has a bulk density of from about 1 mg/cc to about 500 mg/cc, and wherein the aerogel has a BET of from about 2 m 2 /g to about 5 m 2 /g, an average diameter pore size of from about 20 um to about 100 um, or a combination thereof.
17. The aerogel of claim 16 , wherein the hydrophobic agent is selected from at least one of a C 2 -C 20 alkyl silane, a C 3 -C 7 cycloalkyl silane, an aromatic silane, an (C 2 -C 20 )alkyl, a (C 3 -C 7 )cycloalkyl, an (C 2 -C 20 )alkyl urethane, a (C 3 -C 7 )cycloalkyl urethane, an (C 2 -C 20 )alkyl ester, a (C 3 -C 7 )cycloalkyl ester, an (C 2 -C 20 )alkyl carbonate, a (C 3 -C 7 )cycloalkyl carbonate or any mixture thereof.