Covalent Polymers Containing Discrete Heterocyclic Anion Receptors

Abstract

This chapter covers recent advances in the development of polymeric materials containing discrete heterocyclic anion receptors, and focuses on advances in anion binding and chemosensor chemistry. The development of polymers specific for anionic species is a relatively new and flourishing area of materials chemistry. The incorporation of heterocyclic receptors capable of complexing anions through non-covalent interactions (e.g., hydrogen bonding and electrostatic interactions) provides a route to not only sensitive but also selective polymer materials. Furthermore, these systems have been utilized in the development of polymers capable of extracting anionic species from aqueous environments. These latter materials may lead to advances in water purification and treatment of diseases resulting from surplus ions.

Fig. 1

Schematic representation of heterocyclic anion receptors incorporated into polymeric materials A) as additives in polymers B) via attachment as appendages on the side-chains of polymers and C) by direct incorporation into the main-chain of the polymer backbone.

Fig. 2

Cyclic polyamines of varying sizes that have been used as ionophores for phosphate-selective electrodes.

Fig. 3

Aliphatic and heteroaromatic amines used as ionophores to construct ISEs.

Fig. 4

Expanded porphyrins rubyrin and triphenylrosarin.

Fig. 5

Calix[4]pyrrole (17), dichlorocalix[2]pyrrole[2]pyridine (18), and tetrachlorocalix[4]pyridine (19). As described in the text, these anion receptors were incorporated into ISE membranes.

Fig. 6

Calix[4]pyrrole derived chemosensors from non-chromogenic dye precursors.

Fig. 7

Polyurethane films in which chemosensor 20 is embedded. PLAS solutions of anions (10 mM), bovine serum albumin (BSA), and blood plasma were applied to polymer films at pH = 7.4. This figure, which originally appeared in J. Am. Chem. Soc. 2005, 127, 8270–8271 (copyright Am. Chem. Soc.), is reproduced with permission [33].

Fig. 8

Hydrogen bonding chemosensors for anions based on pyrrole hydrogen bond donor motifs.

Fig. 9

Cyclic amine monomers 30 and 31.

Fig. 10

Polyphenylacetylenes functionalized with imidazole moieties.

Fig. 11

PPA containing naphthalimide as a pendant side-chain.

Fig. 12

Photonic ionic liquid monomer based on imidazolium.

Fig. 13

Photonic IL polymer shifts its stop gap as a function of counter anion leading from a shift from pink to blue. This figure, which originally appeared in Adv. Mater. 2008, 20, 4074–4078 (Copyright Wiley-VCH GmbH & Co. KGaA), is reproduced with permission [57].

Fig. 14

Pinacol-based boronate derivatized pyrrole monomer.

Fig. 15

Ferrocene-viologen based receptors developed for polypyrrole-based ATP²⁻ sensing.

Fig. 16

Polymer resins containing calix[4]pyrrole (45 and 46) and calix[4]pyrrole[2]thiophene (47) receptors.

Fig. 17

Calix[4]pyrrole methacrylate monomer (48), calix[4]pyrrole methacrylate homopolymer (49), calix[4]pyrrole-co-methylmethacrylate polymer (50), and the calix[4]pyrrole-co-benzocrown[5]-co-methylmethacrylate polymer (51) developed by Sessler, Bielawski, and coworkers.

Fig. 18

Aqueous solutions of water-soluble chloride salt (52) after extraction with CH₂Cl₂ (bottom layer) solutions of: a) blank with CH₂Cl₂ b) octamethylcalix[4]pyrrole c) benzo-[15]-crown-5-ether d) a mixture of octamethylcalix[4]pyrrole and benzo-15-crown[5]ether e) and polymer 51. This figure, which originally appeared in Angew. Chem. Int. Ed. 2008, 47, 9648–9652 (Copyright Wiley-VCH GmbH & Co. KGaA), is reproduced with permission [68].

Fig. 19

Thin films of DPQ copolymer 54 as they appear upon: a) Pre-exposure to HF vapors, b) post-exposure to 48% aq. HF vapors, c) 2 min after exposure to 48% aq. HF vapors, d) pre-exposure to aqueous solutions of HF (i.e., “dip-stick” method), e) after dipping film of copolymer 54 into 48% aq. HF, and f) after dipping a film of copolymer 54 into 25% aq. HF.

Fig. 20

Poly[ortho-diaminophenylene-fluorene)-co-(quinoxaline-fluorene)].

Fig. 21

Azomethine-containing conjugated polymers containing linked fluorene and quinoxaline subunits.

Fig. 22

Changes of polymer 58 upon exposure to acid gas in the solid state; (a) polymer 58 embedded onto filter paper (b) after exposure to acid vapors for 10 sec. and (c) regeneration after exposure to air for 5 min. This figure, which originally appeared in React. Funct. Polym. 2008, 68, 1696–1703 (Copyright, Elsevier) is reproduced with permission [74].

Fig. 23

DPQ-based poly(phenylene ethynylene).

Fig. 24

Structure of DPQ-based polymers used as sensors.

Fig. 25

Structures of oxadiazole-based small molecule chemosensors.

Fig. 26

Polyphenylenes containing phenol-substituted oxadiazole moieties.

Fig. 27

Small molecule model hydroxylated diquinoline control and corresponding polymer system.

Fig. 28

Carbazole containing conjugated polymers.

Scheme 1

Aza-crown ether derivative 8 developed by Umezawa et al.

Scheme 2

Synthesis of cationic polythiophene derivative containing imidazolium salts.

Scheme 3

Free radical polymerization of DPQ (53) and DIQ (55) acrylamide monomers used to generate DPQ (54) and DIQ (56) methyl methacrylate copolymers.

Scheme 4

Suzuki cross-coupling reaction to yield poly[2-(2′-hydroxyphenyl)benzoxazole] (71).

Scheme 5

Bipyridine containing polymer synthesized via Knoevenagel condensation.