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Redox chemistry of organometallic poly(ferrocenylsilane) polymers (soluble in organic or aqueous environment) is discussed. Poly(ferrocenyldimethylsilane) (PFDMS) was oxidized in CH 2 Cl 2 solution with different oxidants. Oxidation was accomplished with stepwise increasing amounts of ferric chloride (FeCl 3 ), iodine (I 2 ) and tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBPA Áþ SbCl À 6 ). The process was followed by UV-visible spectroscopy. Mixed-valence salts with different Fe(III)/Fe(II) ratios were obtained. The oxidation products were characterized by Mo¨ssbauer spectroscopy, which proved to be a very valuable tool to analyze mixed valence ferrocenyl compounds. Mo¨ssbauer analysis demonstrated that 100% oxidation could be achieved with TBPA AE + . Decamethylferrocene (DMFC) was found to be a suitable reducing agent for the oxidized polymer. The reduction process was monitored by UV-visible spectroscopy. The polymer was characterized by gel permeation chromatography (GPC) following the oxidation/reduction cycle and evidence of some fragmentation of the chains was observed. A water-soluble PFS polycation was successfully oxidized with FeCl 3 for pH values between 4 and 5. Ascorbic acid (vitamin C) was found to completely reduce the oxidized water-soluble polymer.

This work is to fabricate thermo responsive nanofibers of which the thermo response temperatures could be easily tuned, and of which the fibrous shapes could be maintained after heating-cooling cycles in aqueous solution. The nanofibers were further fabricated into a nonwoven mat with size-variable pores for temperature controlled release of a model drug, Erlotinib. The thermo responsive nanofibers were electrospun from the copolymers of PMMA-co-PVCL (synthesized from MMA and PVCL, and had different LCSTs) by changing the solvents and the ratio of initiator/monomer. FT-IR and 1 H NMR were used for molecular structural characterization; UV-vis spectra were used for LCST measurement; SEM and metalloscope were used to determine the optimal electrospinning parameters and to observe the shape maintaining abilities of the nanofibers after the heating-cooling recycles. Then, anti-cancer drug, Erlotinib, was incorporated into PMMA/PVCL nanofibers (represent as 'model I'), or put in a drug reservoir and covered with the PMMA/PVCL electrospinning mat (presented as 'model II'). UV-vis spectra were used to study the drug release behavior of each model. Results indicate that in model I, drug release was "switch on" below LCST, and "switch off" above LCST; in model II, drug release was faster above LCST than below LCST.

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