Catechol functionalized polymers

Catechol is a unique and versatile adhesive molecule capable of forming reversible physical interactions and irreversible covalent bonds (Figure 10.2). In this section, various catechol chemical interactions are introduced. Additionally, various chemical modifications used to modulate catechol side chain reactivity and in the preparation of catechol-functionalized polymers are reviewed. 

The catecholate functionality of CTC should make it a more effective metal binder than is CTV, although there are few known examples. A discrete trinuclear chelate complex of deprotonated CTC with Pt(II) has been reported. The manganese hydroxide-linked MeLa tetrahedra of the type discussed in Section 4.1.2 link into a complicated 3D coordination polymer through bridging oxides and sandwich-type interactions to additional Cs + cations that occur between (MnOH)6L4 tetrahedra. ... 

Figure 10.6 Schematic representation of polymer preparation using catechol-modified and polymerizable monomers (A) and using a polymer-bound initiator to form a block copotymer (B). In the presence of bi-functional crosslinkers, potymerization forms a three-dimensional pol3mier network containing catechol (C). R represents the side chain of the monomers used to copotymerize with the catechol-functionalized monomers.

Fig ure 10.13 Chemical structures of nitrodopamine-functionalized polymer forming a cured adhesive through dimerization of the catechol side chain. The cured adhesive is degraded upon light exposure. R = polymer chain. 

Most aromatic difunctional reagents react with N3P3Cl6 to afford spirocyclic products (20,176,180,181,189,190). With catechol, the trispiro product is observed (190). This product was shown to function as a host in the formation of several inclusion adducts, including polymers (191). Ring degradation of the cyclophosphazene ring occurs in the reaction with o-amino phenol as well as in the reaction with catechol in the presence of a triethylamine (192). 

A polymer (P-DHB) (XI) based on catechol, the active functional group of enterobactin, was recently synthesised by the reaction of polyvinyl amine with the ethyl ester of 2,3-dihy-droxybenzoic acid (DHB). Only about one third of the amine groups was found to be substituted with DHB units. The formation constant of the iron(III) complex (log K = 40) is the same as that reported for the simple dimethyl amide of DHB and so there does not appear to be any appreciable chelate effect. 

The aryl silane library was also screened for their ability to function as the sole carbon source for Ralstonia eutropha A5, a wild type strain expressing a biphenyl dioxygenase (BPO) enzyme. A number of silanes were observed to support growth, including diphenylsilanes and trialkoxysilanes. Overall the study indicated the feasibility of the enzymatic conversion of arylsilanes to a novel series of silane cw-dihydrodiols and catechols. Such compounds may find application as chiral polymer precursors, intermediates for natural product synthesis and other usefol materials. 

Cosnier et al. [166] has developed electropolymerizable materials of a dicarbazole-derivative functionalized by N-hydroxysuccinimide and pentafluorophenoxy groups [166]. The subsequent chemical functionalization of the poly(dicarbazole) film was easily performed by successive immersions in aqueous enzyme and mediator solutions. These derivatized, bioactive conducting polymer films were demonstrated as sensing layers for catechol. 

Laine et al. [34] have described a process where SiOj is directly reacted with ethylene glycol and an alkali to produce reactive pentacoordinate silicates, which can be used to produce silicate materials. Laine has made stable precursor polymers (>670 K), some of which are liquid crystalline, by using catechol. Agaskar [35] has prepared organolithic macromolecular materials, which are hybrids containing silicate and organic molecules (functionalized spherosilicates) and can be used as precursors for microporous ceramic (Si-C-0) materials. 

Figure 10.4 Diversity of chemistiy structures utilized to create biomimetic adhesive polymers. Catechol side chain (A) modification alters its interfacial binding strength and reactivity. Substitution can be achieved by replacing -H at the para position with chloro-(B), nitro- (C) and hydrojyl (D) groups or a hydro)yl group at the meta position (E). The benzene ring can be substituted with a pyridine group (F). Linking the catechol with a polymer can be achieved via reaction of the amino acid (G), acid (H), or amine (I) groups. Catechol modified with a bromide propionamide Initiator to initiate polymerization (J) or functionalized with polymerizable methacrylamide (K), vinyl (L), and M-carboxyanhydride (NCA, M) groups.

---