Ferrocene-functionalized polymer polymerization

Synthesis of ferrocene-functionalized polymer brushes on a gold substrate by simultaneous SI-ATRP and click chemistry. (Reprinted with permission from Xu et al. 2010. One-Pot Preparation of "Ferrocene-Functionalized Polymer Brushes on Gold Substrates by Combined Surface-Initiated Atom Transfer Radical Polymerization and "Click Chemistry." Langmuir 26 (19) 15376-15382, copyright (2010) American Chemical Society.)... 

Schematic illustration of the two strategies used in the preparation of ferrocene-functionalized polymer brushes (a) hydroxyl groups of the PHEMA brushes activated by CDl, followed by coupling with FCNH2 and (b) epoxy groups of the PGMA brushes underwent direct ring-opening reaction with FcNHj. (Reprinted with permission from Wu et al. 2009. Electrochemical Biosensing Using Amplification-by-Polymerization. Analytical Chemistry 81 (16) 7015-7021, copyright (2(X)9) American Chemical Society.)...

Graphical representation of the preparation of ferrocene-functionalized polymer brush arrays via SI-ROMP by DPN. (Reproduced from Liu et al. 2(X)3. Surface and site-specific ring-opening metathesis polymerization initiated by dip-pen nanolithography. Angewandte Chemie-lnternational Edition 42 (39) 4785-4789 with permission from Wiley.)... 

A comprehensive summary of the syntheses and applications of the ferrocene polymer brushes has been presented. Ferrocene-functionalized polymer brushes covalently bonded or physisorbed on solid substrate surfaces can be readily prepared via well-known surface modification techniques, such as surface-initiated polymerizations, reaction of the end-functional groups of polymer chains with substrate surfaces, and host-guest interaction. These electroactive polymer brushes have found applications in biosensors, anion-exchange chromatography, and redox-controlled modification of surface wetting properties. 

Xu, L. Q., D. Wan, H. F. Gong, K. G. Neoh, E. T. Kang, and G. D. Fu. 2010. Qne-p>ot preparation of ferrocene-functionalized polymer brushes on gold substrates by combined surface-initiated atom transfer radical polymerization and "dick chemistry." 26 (19) 15376-15382. 

Pittman and coworkers reported a number of ferrocene-functionalized polymers in the 1960s and 1970s that not only included the synthesis but also the properties of these polymers. " In particular, the bulk and solution polymerization of vinylferrocene along with the physical, chemical, and electrical properties of many polymers and copolymers were studied. The copolymerization of vinyl-ferrocene with styrene was reported by Frey and co-workers in 1999, using living radical initiator 2,2,6,6-tetramethyl-l-pyperidinyl-l-oxy (TEMPO). The polymers obtained by this method were block copolymers with narrow polydis-persities. 

Kim B-Y, Ratcliff EL, Armstrong NR, Kowalewski T, Pyun J (2010) Ferrocene functional polymer brushes on indium tin oxide via surface-initiated atom transfer radical polymerization. Langmuir 26 2083-2092... 

In the synthesis of ferrocene-functionalized polypyrrole systems, numerous derivatives are readily obtained by substitution at either the 3-position of the ring or on the nitrogen of the pyrrole prior to polymerization. It was reported that polymers with both metallic properties and enhanced solubility may be synthesized by judicious derivatization and choice of polymerization conditions, such as a variety of processing solvents [67, 68]. 

Plenio and co-workers synthesized and polymerized of l-iodo-2-methoxymethyl-3-ethynylferrocene and l-iodo-2-(A,lV-dimethylamino methyl)-3-ethynylferrocene to give 1,3-linked ferrocene-acetylene polymers.176,177 These polymers were synthesized by Sonogahira coupling reactions. These polymers showed optical activity176 or possessed functionalized side chains.177,178 Scheme 2.28 shows the reaction of diiodoferrocenes with diethynyl monomers.178,179 The palladium-catalyzed reactions led to polymers 93a,b, which when doped with iodine displayed semiconducting properties. The iodine-oxidized polymer 93a displayed an electrical conductivity of 1.3 X 10 4S/cm. 

Le Floch and co-workers isolated ferrocene-containing polythiophenes for use in deoxyribonucleic acid (DNA) detection.230 The reaction between thiophene 160 and the functionalized ferrocene 161 gave the ferrocene functionalized polythiophene in a quantitative yield (Scheme 2.43). Polymerization in the presence of FeCl3 led to a water-soluble polymer containing a cationic side chain and an electroactive ferrocene moeity. These polymers showed a DNA detection limit of 5 X10-10M. 

The polycondensation of acetylene-substituted metallocenes has yielded polymers containing backbone aUcyne bridges. The synthesis of l-iodo-2-methoxy-methyl-3-ethynylferreocene and l-iodo-2-(N,N-dimethylamino methyl)-3-ethynyl-ferreocene was reported by Plenio and coworkers. Polymerization of these ferrocene-based complexes gave rise to soluble bimodal 1,3-linked ferrocene-acetylene polymers. Polymers exhibiting optical activity or functionalized sidechains were produced via Sonogashira coupling reactions. 

Polymerization of organoiron monomers has also resulted in the production of liquid crystalline polymers containing ferrocene units in their sidechains. " Scheme 6 illustrates Deschenaux s free-radical synthesis of ferrocene functionalized thermotropic liquid crystalline polymethacrylates Monomer 31 and its corresponding polymer 32 exhibited enantiotropic smectic A and C phases. 

Schrock, Wrighton, and coworkers have reported that ring-opening metathesis polymerization (ROMP) of norbomene monomers fhnctionalized with ferrocenyl groups allowed for the isolation of polymers such as 55-58. Alternatively, polynorbornenes capped with ferrocenyl units could be produced by using a molybdenum initiator functionalized with ferrocene. When this polymerization reaction was terminated through the addition of octamethyl-ferrocenecarboxaldehyde, low molecular weight polymers such as 58 were isolated. 

Our general synthetic route for incorporating metal-metal bonds into polymer backbones is based on the step polymerization techniques for incorporating ferrocene into polymer backbones (6,23-28). Step polymers of ferrocene can be made by substituting the cyclopentadienyl (Cp) rings with appropriate functional groups, followed by reaction with appropriate di nctional organic monomers (e.g., eq 2) (29-31). 

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

Condensation polymerization of functional ferrocenes generally yields medium- or low-molecular-weight polymers with broad molecular-weight distributions.12 For example, ferrocenylcarbinol, 6.9, has been condensation-polymerized to polymers 6.10 and 6.11 in the presence of boron trifluoride etherate or zinc chloride (reaction (5)).910 Species 6.11... 

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