Properties of Polyferrocenylsilanes

Polyferrocenylsilanes (PFSs) have attracted growing interest since the early 1990s. ° These materials exemplify the types of polymers accessible by the use of the novel ring-opening polymerization (ROP) approach. PFS materials can be easily fabricated and processed as films, gels, and monoliths, and have even been 

Cyclic voltammetric studies of PFSs show clear evidence for the existence of interactions between the iron atoms. Comparisons of the behavior of PFSs with other polyferrocenes indicate that the metal-metal interactions are influenced by the silicon spacer. PFSs have been found to possess interesting hole transport properties, and partial oxidation causes up to a 10 increase in electrical conductivity with values in to the semiconductor range.  

Thin films of PFS homopolymers have also attracted attention as potential protective charge dissipation coatings for dielectrics, as electrochromic materials, as sensors, and as electrode mediators. In addition, the relatively high refiactive indices of PFS derivatives make these materials of interest for applications in photonics— for example, in photonic crystals where periodic variations in refiactive index are necessary.  

ROP methods have allowed access to a wide variety of high moleodar weight polyferrocenes, of which the polyferrocenylsilanes are the prototypical example. Studies of the latter materials have provided an excellent opportunity for the systematic and detailed examination of a class of main-chain metal ontaining macromolecules representative examples are included in Table 3.1. This section surveys some of the properties of these interesting polymers. 

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Thermal ROP of silicon-bridged [1 Jferrocenophanes Thermal ROP of other strained metallocenophanes Living anionic ROP of strained metallocenophanes Transition metal-catalyzed ROP of strained metallocenophanes Other ROP methods for strained metallocenophanes Properties of polyferrocenylsilanes... 

Water-soluble polyferrocenylsilane polycations, belonging to the rare class of main chain organometallic polyelectrolytes, have been reported by us and others. "" These compounds are of interest because they combine the unusual properties of polyferrocenylsilanes with the processability of polyelectrolyte solutions, for example, enabling one to make use of ionic interactions to deposit these polymers onto substrates. Polyelectrolytes can be employed in layer-by-layer (LbL) self-assembly processes to form ultrathin multilayer films with controlled thickness and composition. ... 

Recently, we reported the first examples of well-characterized, crosslinked, swellable polyferrocenylsilanes (7). Thermal copolymerization of ferrocenophane 1 with the spirocyclic [IJferrocenophane 3 allows access to material with controlled crosslink densities. Because of the interesting properties of polyferrocenylsilanes, we identified crosslinked examples as possible candidates for stimuli-responsive gels. 

Properties of other ring-opened polymetallocenes and related materials Polyferrocenylsilane block co-polymers Polyferrocenylphosphine block co-polymers... 

Tang and coworkers have reported that pyrolyzed hyperbranched polyferro-cenylsilanes have greater ceramic yields than their linear polymeric counterparts. Manners has reported that thermally crosslinked polyferrocenylsilanes (28) possessed greater thermal stability than their linear analogs. The swelling properties of these crosslinked polymers were examined, and the solubility parameter of the corresponding linear homopolymer was determined. The pyrolysis of linear, hyperbranched, and crosslinked polyferrocenylsilanes has resulted in the production of ceramics that possess magnetic properties. " ... 

Polyferrocenylsulfides 3.32 have been prepared by the ROP of highly strained sulfur-bridged [Ijferrocenophanes and, based on electrochemical measurements, appear to possess more substantial metal-metal interactions (redox coupling A i/2>0.30 V) than the analogous polyferrocenylsilanes [73], Polyferrocenylboranes 3.34 are sensitive to moisture, which has hindered detailed studies of their properties [74],... 

It has been demonstrated that polyferrocenylsilanes possess low plasma etch rates, which can be attributed to the formation of a protective layer of involatile iron and silicon compounds. This property has been exploited with PFS block copolymers self-assembled into micelles or phase-separated thin films to deposit patterned ceramics as well as for pattern transfer to the substrate. In our research, we are interested in the direct formation of high metal content magnetic ceramic films by RIE treatment of Co-PFS in the presence of a secondary magnetic field. ... 

Cationic, anionic, and nonionic polyferrocenylsilane-based hydrogels were recently introduced [356-358]. In the case of anionic, permanently charged hydrogels, the electrochemical oxidation to ferrocenium imparts a polyampholytic behavior together with a color change. In addition, oxidation leads to shrinkage of the gel and to a loss of elasticity upon reduction, the former properties could be reached reversibly. 

The transition-metal-catalyzed ring-opening polymerization of silicon-bridged, strained, ring-tilted ferrocenophans yields polyferrocenylsilanes with intriguing properties. ... 

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