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Tailoring Pore Size and Chemical Interior of near1 nm Sized Pores in a Nanoporous Polymer Based on a Discotic Liquid Crystal

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ABSTRACT

A triazine based disc shaped moleculewith two hydrolyzable units,imine and ester groups, was polymerized via acyclic diene metathesisin the columnar hexagonal (Colhex) LC phase. Fabricationof a cationic nanoporous polymer (pore diameter ∼1.3 nm) linedwith ammonium groups at the pore surface was achieved by hydrolysisof the imine linkage. Size selective aldehyde uptake by the cationicporous polymer was demonstrated. The anilinium groups in the poreswere converted to azide as well as phenyl groups by further chemicaltreatment, leading to porous polymers with neutral functional groupsin the pores. The pores were enlarged by further hydrolysis of theester groups to create ∼2.6 nm pores lined with −COONasurface groups. The same pores could be obtained in a single stepwithout first hydrolyzing the imine linkage. XRD studies demonstratedthat the Colhex order of the monomer was preserved afterpolymerization as well as in both the nanoporous polymers. The porousanionic polymer lined with −COOH groups was further convertedto the −COOLi, −COONa, −COOK, −COOCs,and −COONH4 salts. The porous polymer lined with−COONa groups selectively adsorbs a cationic dye, methyleneblue, over an anionic dye.

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Schematic illustrationsof the pore surface engineering of theporous polymers: (a) Hydrolysis of the imine linkage of the nativepolymer using DMF:HCl (11:1 v/v) to fabricate the porous polymer,Pore-NH3Cl. The amino groups in the pores reacted withdifferent aldehydes, (b) benzaldehyde (where X = H), benzene-1,3,5-tricarboxaldehyde(where X = CHO), and (c) the template aldehyde, Triz-3CHO, to transformback to the original polymer. (d) The ammonium groups in the poresof Pore-NH3Cl were converted to diazonium salt (−N2Cl) by reacting with aqueous NaNO2/HCl solutionat 0–5 °C for 1 h. (e, f) Pore-N2Cl was furtherreacted with NaN3 and H3PO2 in waterand THF, respectively, at 21 °C to fabricate porous polymerswith neutral azide (−N3) and phenyl (−Ph)groups at the pore surface (Pore-N3 and Pore-Ph), respectively.(g) The ester groups present in the inner core of Pore-NH3Cl were successfully hydrolyzed using 1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h to furnish a porous polymer containinganionic −COONa groups at the pore surface. (h) Pore-COONa couldbe directly obtained in one step by reacting the native polymer with1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h.(i) Pore-COONa was converted to a porous polymer with −COOHgroups at the pore surface (Pore-COOH) by reacting with ethanolicHCl solution for 10–12 min at ambient condition. (j) Treatmentof Pore-COOH with hydroxides salt of Li+, Na+, K+, Cs+, and NH4+ resultedin the formation of Pore-COOM (where M = Li, Na, K, Cs, and NH4).
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fig3: Schematic illustrationsof the pore surface engineering of theporous polymers: (a) Hydrolysis of the imine linkage of the nativepolymer using DMF:HCl (11:1 v/v) to fabricate the porous polymer,Pore-NH3Cl. The amino groups in the pores reacted withdifferent aldehydes, (b) benzaldehyde (where X = H), benzene-1,3,5-tricarboxaldehyde(where X = CHO), and (c) the template aldehyde, Triz-3CHO, to transformback to the original polymer. (d) The ammonium groups in the poresof Pore-NH3Cl were converted to diazonium salt (−N2Cl) by reacting with aqueous NaNO2/HCl solutionat 0–5 °C for 1 h. (e, f) Pore-N2Cl was furtherreacted with NaN3 and H3PO2 in waterand THF, respectively, at 21 °C to fabricate porous polymerswith neutral azide (−N3) and phenyl (−Ph)groups at the pore surface (Pore-N3 and Pore-Ph), respectively.(g) The ester groups present in the inner core of Pore-NH3Cl were successfully hydrolyzed using 1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h to furnish a porous polymer containinganionic −COONa groups at the pore surface. (h) Pore-COONa couldbe directly obtained in one step by reacting the native polymer with1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h.(i) Pore-COONa was converted to a porous polymer with −COOHgroups at the pore surface (Pore-COOH) by reacting with ethanolicHCl solution for 10–12 min at ambient condition. (j) Treatmentof Pore-COOH with hydroxides salt of Li+, Na+, K+, Cs+, and NH4+ resultedin the formation of Pore-COOM (where M = Li, Na, K, Cs, and NH4).

Mentions: Performing XRD on the films showed thatthe diffraction pattern of the porous polymer was the same as thenative polymer film. However, the lattice spacing, d100, increased from 4.21 to 4.39 nm upon removal of thetemplate, which we attributed to the reduction of the cross-link densityand concomitant stress relaxation (Figure 4c). This result indicates structural integrityand the formation of nanopores with an estimated pore diameter of∼1.3 nm (Figure 3, path a, and Figure S4).


Tailoring Pore Size and Chemical Interior of near1 nm Sized Pores in a Nanoporous Polymer Based on a Discotic Liquid Crystal
Schematic illustrationsof the pore surface engineering of theporous polymers: (a) Hydrolysis of the imine linkage of the nativepolymer using DMF:HCl (11:1 v/v) to fabricate the porous polymer,Pore-NH3Cl. The amino groups in the pores reacted withdifferent aldehydes, (b) benzaldehyde (where X = H), benzene-1,3,5-tricarboxaldehyde(where X = CHO), and (c) the template aldehyde, Triz-3CHO, to transformback to the original polymer. (d) The ammonium groups in the poresof Pore-NH3Cl were converted to diazonium salt (−N2Cl) by reacting with aqueous NaNO2/HCl solutionat 0–5 °C for 1 h. (e, f) Pore-N2Cl was furtherreacted with NaN3 and H3PO2 in waterand THF, respectively, at 21 °C to fabricate porous polymerswith neutral azide (−N3) and phenyl (−Ph)groups at the pore surface (Pore-N3 and Pore-Ph), respectively.(g) The ester groups present in the inner core of Pore-NH3Cl were successfully hydrolyzed using 1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h to furnish a porous polymer containinganionic −COONa groups at the pore surface. (h) Pore-COONa couldbe directly obtained in one step by reacting the native polymer with1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h.(i) Pore-COONa was converted to a porous polymer with −COOHgroups at the pore surface (Pore-COOH) by reacting with ethanolicHCl solution for 10–12 min at ambient condition. (j) Treatmentof Pore-COOH with hydroxides salt of Li+, Na+, K+, Cs+, and NH4+ resultedin the formation of Pore-COOM (where M = Li, Na, K, Cs, and NH4).
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fig3: Schematic illustrationsof the pore surface engineering of theporous polymers: (a) Hydrolysis of the imine linkage of the nativepolymer using DMF:HCl (11:1 v/v) to fabricate the porous polymer,Pore-NH3Cl. The amino groups in the pores reacted withdifferent aldehydes, (b) benzaldehyde (where X = H), benzene-1,3,5-tricarboxaldehyde(where X = CHO), and (c) the template aldehyde, Triz-3CHO, to transformback to the original polymer. (d) The ammonium groups in the poresof Pore-NH3Cl were converted to diazonium salt (−N2Cl) by reacting with aqueous NaNO2/HCl solutionat 0–5 °C for 1 h. (e, f) Pore-N2Cl was furtherreacted with NaN3 and H3PO2 in waterand THF, respectively, at 21 °C to fabricate porous polymerswith neutral azide (−N3) and phenyl (−Ph)groups at the pore surface (Pore-N3 and Pore-Ph), respectively.(g) The ester groups present in the inner core of Pore-NH3Cl were successfully hydrolyzed using 1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h to furnish a porous polymer containinganionic −COONa groups at the pore surface. (h) Pore-COONa couldbe directly obtained in one step by reacting the native polymer with1 M NaOH in EtOH:H2O (23:1 v/v) at 75 °C for 12 h.(i) Pore-COONa was converted to a porous polymer with −COOHgroups at the pore surface (Pore-COOH) by reacting with ethanolicHCl solution for 10–12 min at ambient condition. (j) Treatmentof Pore-COOH with hydroxides salt of Li+, Na+, K+, Cs+, and NH4+ resultedin the formation of Pore-COOM (where M = Li, Na, K, Cs, and NH4).
Mentions: Performing XRD on the films showed thatthe diffraction pattern of the porous polymer was the same as thenative polymer film. However, the lattice spacing, d100, increased from 4.21 to 4.39 nm upon removal of thetemplate, which we attributed to the reduction of the cross-link densityand concomitant stress relaxation (Figure 4c). This result indicates structural integrityand the formation of nanopores with an estimated pore diameter of∼1.3 nm (Figure 3, path a, and Figure S4).

View Article: PubMed Central - PubMed

ABSTRACT

A triazine based disc shaped moleculewith two hydrolyzable units,imine and ester groups, was polymerized via acyclic diene metathesisin the columnar hexagonal (Colhex) LC phase. Fabricationof a cationic nanoporous polymer (pore diameter ∼1.3 nm) linedwith ammonium groups at the pore surface was achieved by hydrolysisof the imine linkage. Size selective aldehyde uptake by the cationicporous polymer was demonstrated. The anilinium groups in the poreswere converted to azide as well as phenyl groups by further chemicaltreatment, leading to porous polymers with neutral functional groupsin the pores. The pores were enlarged by further hydrolysis of theester groups to create ∼2.6 nm pores lined with −COONasurface groups. The same pores could be obtained in a single stepwithout first hydrolyzing the imine linkage. XRD studies demonstratedthat the Colhex order of the monomer was preserved afterpolymerization as well as in both the nanoporous polymers. The porousanionic polymer lined with −COOH groups was further convertedto the −COOLi, −COONa, −COOK, −COOCs,and −COONH4 salts. The porous polymer lined with−COONa groups selectively adsorbs a cationic dye, methyleneblue, over an anionic dye.

No MeSH data available.


Related in: MedlinePlus