Silver polymer complexes

The immobilisation of antibacterial coatings onto conductive materials such as stainless steel or carbon fibre used in orthopaedic implants was investigated by two methods. The formation of thin films by electrodeposition of polypyrrole doped with polyanions able to complex silver ions, and their characterisation by SEM, FTIR and microbiological testing is described. The alternative method, involving chemical grafting of a thin film of a quatemaiy ammonium polymer using a surface initiator, is also discussed. 2 refs. 

A recent XPS study [276] on the interactions between PAN films and silver cations revealed that the more reduced form of the polymer was capable of depositing silver metal from 0.1 M AgNOj. For the intrinsically more oxidized polymer with open-circuit potential greater than the formal potential of silver deposition (0.115 eV), a metal-polymer complex was formed. In a parallel development, it was found that by coupling the metal reduction process in acid solutions with an increase in the intrinsic oxidation state of a N-containing polymer, such as PAN or PPY, and the subsequent re-protonation and reduction of the intrinsically Oxidized polymer in acid media, spontaneous and sustained reduction of precious metals (such as Au and Pd) to their elemental form can be readily achieved... 

A macromolecule provides a suitable fimctional group for either complexation with metal ions of metal salts or attaching metal complexes into the macromolecular matrix through a coordination bond typical examples of the former are silver-polymer complexes, while cobalt porphyrins incorporated on a polymer backbone through coordination bonding are examples of the latter. 

In this chapter, the specific and reversible bindings of small molecules with metal complexes in macromolecules are described using the examples of silver-polymer complexes and metalloporphyrins coordinatively bound in macromolecules. Next, their structures are characterized, followed by potential applications such as gas-separation membranes and gas-carrying materials. 

Gas permeability is also one of the parameters used to detect a change in the structure of a polymer. Since paraffins, such as propane, do not have any specific interaction with silver ions and thus only permeate via normal sorption and diffusion transport, the permeability behavior of propane is mostly determined by the microstructure and chain mobility of a polymer complex. As such, the propane permeabilities of POZ films decrease rapidly with AgCp3S03 concentration, which is consistent with the results of the d-spacings and glass... 

When small molecules, such as olefins, come into contact with a metal complex in macromolecules, such as silver-polymer complexes, a significant amount of olefins are absorbed by the silver-polymer complexes. The propylene solubilities in Ag-POZ complex films ([Ag ] in AgBp4 [C=0] in POZ = 1 1, ca. 80 wt.% of AgBp4 in the polymer matrix) were plotted against the propylene pressure, as shown in Fig. 9-4 [15]. The propylene solubility in pure POZ was very small. However, the propylene solubilities in a 1 1 AgBp4-POZ complex (190 and 240 cm (STP)of propylene per 1 cm of silver-polymer complex at 50 and 190 kPa, respectively) significantly increased 100 times compared to those in pure POZ because of the chemically specific binding of propylene into silver ions. 

Figure 9-4. Solubility of propylene in solid silver-polymer complex films at 25 °C[15]. [Ag1 [C=0]=l l.

Figure 9-5. Structures of complexes of a AgBF4 2-dimethoxy ethane complex, b AgBF4 , 2-dimethoxy ethane-ethylene adduct where 1,2-dimethoxy ethane is a model compound of poly(ethylene oxide) [15]. The silver ion is coordinated by two oxygen atoms from 1,2-dimethoxy ethane and two F atoms from the anion to make silver-polymer complexes, when AgBF4 is complexed with 1,2-dimethoxy ethane. One of the two F atoms bound to the silver ion is replaced by an ethylene molecule, when one ethylene molecule approaches the complex in an ethylene environment.

Membrane performance also depends on the thickness of the selective layers of a silver-polymer complex, that is, the thinner the selective layer, the better the transport performance of the membrane. A thickness of several micrometers for the selective layer was the limitation in conventional methods used to prepare composite membranes. Based on exciting developments in the field of nanostructure science and technology, there have been several attempts to reduce the thickness of the selective layer to a nanometer length scale [41-43]. Schematic methods for preparing nano-thin selective layer membranes are generalized in Fig. 9-13, based on the use of nanometer-sized dendrimers, star... 

Small-molecule transport other than olefin and molecular oxygen facilitated transport through a metal-polymer complex containing carriers (silver ions and metalloporphyrins, respectively) has also received attention, such as nitrogen transport by a cyclopentadienylmanganese and benzenechromium complex attached to a polymer [50,51], and CO2 and H2S transport based on ion-... 

Spectroscopic and Sorption Experiments with Silver-Polymer Complexes (Section 9.2,2) [20-22]... 

Silver polymer complexes were made by dissolving a silver salt, silver triflate (AgCp3S03) or silver tetrafluoroborate (AgBFa), in a polar polymer, POZ, PVP, or PVMK. The POZ and PVMK were purchased from Aldrich Chemical Co, the PVP from Polysciences Inc. AgBFa (98%) and the AgCF3S03 (99+%) from Aldrich Chemical Co. 

For the spectroscopic and sorption experiments, the silver-polymer complex solution (20 wt.% in water) was cast on a glass plate and dried under a nitrogen atmosphere. The cast films were finally dried overnight in a vacuum at room temperature to remove any residual water. After drying completely, the films were lifted from the glass plate and FTIR measurements performed. The FTIR spectra for the solid-state interactions of the silver-PVMK complex and olefin are shown in Fig. 9-6. 

For the absorption experiments, a film was placed in a sample chamber, which had been evacuated for more than 12 h. Pure propylene gas was then introduced into the chamber and allowed to equilibrate. The solubility was obtained by measuring the difference between the initial and final pressures. Once the chamber pressure remained constant, additional gas was introduced and again allowed to equilibrate. In this incremental manner, the propylene solubility as a function of the gas pressure was observed. The solubility of propylene in the solid silver-polymer complex films is shown in Fig. 9-4. 

Silver-polymer complexes were prepared by dissolving a silver salt, AgCF3S03 or AgBF4, in a polar polymer, POZ or PVP. For the permeation experiments, an RK Control Coater was used to coat the silver-pol)mier complex solution (20 wt.% in water) onto a microporous membrane support to give composite membranes. The composite membranes were first dried at 40 °C for a day in a light-protected convection oven under nitrogen, then subsequently in a vacuum oven for a day at room temperature. The membrane samples were then cut into... 

Sakano T, Okano M, Osakada K. Preparation of triazole-fumished ferrocene derivatives and their polymer complexes of silver(I). J Inorg Organomet Polym Mater 2009 19(1) 35 5. 

A prominent FDA-approved chitin dressing is rapid deployment hemo-stat (RDH) (Marine Polymer Technologies) which costs 300 per dressing. One study shows that polymeric hber material based on P-NAG is more effective than alpha-chitin or chitosan, since these have a heterogeneous structure and are complexed with minerals and proteins. Moreover, the j3 structure (parallel orientation) of the hbers was found to be more effective than the a structure (antiparallel orientation). In another study, the hemostatic and antibacterial properties of chitosan dressings have been shown to be improved by the addition of polyphosphate polymers and silver nanoparticles respectively. One limiting factor is that all forms of chitin or chitosan bandages are not equally effective and the effectiveness varies from batch to batch. ... 

Trilialophenols can be converted to poly(dihaloph.enylene oxide)s by a reaction that resembles radical-initiated displacement polymerization. In one procedure, either a copper or silver complex of the phenol is heated to produce a branched product (50). In another procedure, a catalytic quantity of an oxidizing agent and the dry sodium salt in dimethyl sulfoxide produces linear poly(2,6-dichloro-l,4-polyphenylene oxide) (51). The polymer can also be prepared by direct oxidation with a copper—amine catalyst, although branching in the ortho positions is indicated by chlorine analyses (52). 

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