Nanostructured magnetic thin films from organometallic block copolymers: pyrolysis of self-assembled polystyrene-block-poly(ferrocenylethylmethylsilane).

The pyrolysis of cylinder-forming samples of the diblock copolymer polystyrene-block-poly(ferrocenylethylmethylsilane) (PS-b-PFEMS) in bulk and in thin films has confirmed that these materials are useful for the generation of semi-ordered arrays of C/SiC ceramics containing Fe nanoparticles which are derived from the organometallic domains. In many cases, the ceramic mass yields were predictable and produced ceramics bearing a monomodal distribution of iron nanoparticles due to the nanoscaled structure of the preceramic PFEMS domains. The pyrolysis of thin films stabilized by cross-linking the PS domains with UV light demonstrated high areal yields, improved shape retention, and the presence of cylinder-centered magnetic nanoparticles.

Anionic ring-opening polymerization of a strained phosphirene: a route to polyvinylenephosphines.

A strained 1-phenyl-2,3-dimethylphosphirene undergoes anionic ring-opening polymerization upon initiation with n-butyl lithium at ambient temperature to yield polyvinylenephosphine, an unsaturated organophosphorus polymer.

Photocontrolled living polymerizations.

Living polymerizations involve the creation of polymer chains without significant irreversible chain transfer or chain termination. Such processes are widely used to access well-defined macromolecular materials with controlled architectures, such as block and star polymers. Although this concept was first realized for anionic polymerizations in the 1950s, many key recent advances have been made, most notably in the area of radical polymerization. Here, we report a living photopolymerization that involves photoexcited monomers. Exposure of metal-containing ferrocenophane monomers to Pyrex-filtered light from a mercury lamp (lambda>310 nm) or to bright sunlight in the presence of an anionic initiator leads to living polymerizations, in which the conversion and molecular weight of the resulting polymer can be controlled by the irradiation time. Photoirradiation selectively weakens the iron-cyclopentadienyl bond in the monomer, allowing the use of moderately basic and highly functional-group-tolerant initiators. The polymerization proceeds through attack of the initiator and propagating anion on the iron atom of the photoexcited monomer and, remarkably, the polymerization rate decreases with increasing temperature. Block copolymer formation is possible when the light source is alternately switched on and off in between sequential addition of different monomers, providing unprecedented, photocontrolled access to new types of functional polymers.