Poly Ferrocenyldimethylsilane Research Articles

Crystallization-Driven Self-Assembly of Amphiphilic Triblock Terpolymers With Two Corona-Forming Blocks of Distinct Hydrophilicities

We report the synthesis and studies of self-assembly in solution of two related polyferrocenyldimethylsilane (PFS) ABC triblock terpolymers (TTPs), in which the BC blocks are amphiphilic comb diblo...

Structure Formation of Metallopolymer-Grafted Block Copolymers

Microphase separation drives the structure formation in block copolymers. Here, functional metallopolymer-grafted diblock copolymers consisting of polystyrene-block-polyisoprene (PS-b-PI) as polymer backbone featuring low molar mass polyferrocenyldimethylsilane (PFS) and polyvinylferrocene (PVFc) are synthesized via an iterative anionic grafting-to polymerization strategy. PS-b-PI block copolymers having about 30 mol % 1,2-polyisoprene moieties are subjected to platinum-catalyzed hydrosilylation reaction for the introduction of chlorosilane groups. The Si–Cl moieties are shown to efficiently react with the active metallopolymers yielding block-selective metallopolymer-grafted copolymers with 34 vol % PVFc and 43 vol % PFS as evidenced by 1H NMR spectroscopy as well as size exclusion chromatography. The microphase separation of the functional metallopolymer-grafted block copolymers is evidenced via TEM measurements revealing fascinating morphologies. The structure formation of the PVFc-grafted block copoly...

Hierarchical Polymer-Carbon Nanotube Hybrid Mesostructures by Crystallization-Driven Self-Assembly.

Multistep crystallization-driven self-assembly has great potential to enable the construction of sophisticated hybrid mesostructures. During the assembly procedure, each step modifies the properties of the overall structure. Here, we demonstrate the flexibility and efficiency of this approach by preparing polymer-carbon nanotube (CNT) hybrid mesostructures. We started by growing polyferrocenyldimethylsilane (PFS) homopolymer crystals onto multiwalled CNTs. This first step facilitated the redispersion of the coated CNTs in both polar (2-propanol) and nonpolar (decane) solvents. In the second step of hybrid construction, a unimer solution of a PFS block copolymer was added into the PFS-CNT solution. The PFS coating on the CNT initiated the growth of elongated micelles, resulting in structures that resembled hairy caterpillars. PFS-b-P2VP (P2VP = poly-2-vinylpyridine) micelles were grown from the surface of PFS-CNT hybrids in 2-propanol, and PFS-b-PI (PI = polyisoprene) micelles were grown from these hybrids in decane. These micelles, by transmission electron microscopy were seen to have an unusual wavy kinked structure, very different from the uniform smooth structures normally formed by both block copolymers. For hybrids with PFS-b-PI micelles, cross-linking of the micelle coronas locked the whole structure in place and allowed us to use the partial oxidation of PFS components to grow metal nanoparticles in the core of these micelles. We finally investigated the influence of the corona-forming block used to grow the micelles on the wettability of films made from these mesostructures. Films formed with CNT hybrids grafted with PFS-b-PI micelles were superhydrophobic (contact angle, 152°). In contrast, the surface of the films was much more hydrophilic (contact angle, 54°) when they were prepared from CNT hybrids grafted with PFS-b-P2VP micelles.

Branched micelles by living crystallization-driven block copolymer self-assembly under kinetic control.

We have found that the width and shape (from rectangular to elliptical, to almost circular in cross-section) of the crystalline core of fiberlike micelles of polyferrocenyldimethylsilane (PFDMS) diblock copolymers can be varied by altering the degree of polymerization of PFDMS, and also the chemistry of the complementary corona-forming block. This enabled detailed studies of living crystallization-driven self-assembly (CDSA) processes that involved the addition of unimers with a short, crystallizable core-forming PFDMS block to a seed solution of short micelles with a large diameter crystalline core, derived from block copolymers with a longer PFDMS block. The morphology of resultant micelles was found to be highly dependent on the polarity of the solvent and temperature. For example, linear micelles were formed in less polar solvents (which are moderately poor solvents for PFDMS) and/or at higher temperatures. In contrast, the formation of branched structures could be "switched on" when the opposite conditions were used. Thus, the use of more polar solvents (which are very poor solvents for PFDMS) and ambient or subambient temperatures allowed the formation of branched micelles and block comicelles with variable and spatially distinct corona chemistries, including amphiphilic nanostructures. Rapid crystallization of added unimers at the seed micelle termini under nonequilibrium self-assembly conditions appears to facilitate the formation of the branched micellar structures as a kinetically trapped morphology. This is evidenced by the transformation of the branched micelles into linear micelles on heating at elevated temperatures.

Synthesis and crystallization-driven solution self-assembly of polyferrocenylsilane diblock copolymers with polymethacrylate corona-forming blocks

In order to increase the range of coronal chemistries available for crystallization-driven self-assembly protocols a series of highly asymmetric diblock copolymers comprising a crystallizable polyferrocenyldimethylsilane (PFS) block and a polymethacrylate coblock (poly(tert-butylmethacrylate) (PtBMA), poly(n-butylmethacrylate) (PnBMA), and poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA), block ratios PFS core : corona = 1 : 14–1 : 21) were synthesized by sequential living anionic polymerization. Self-assembly of these block copolymers in acetone yielded cylindrical micelles with a crystalline PFS core (confirmed by wide-angle X-ray scattering) and a polymethacrylate corona. The cylindrical micelles were fragmented by sonication and the short micelles were successfully used as “seed initiators” to grow longer monodisperse cylindrical micelles with controlled lengths from added unimers via crystallization-driven living self-assembly. Block co-micelles were also prepared by the sequential addition of unimers with a different coronal block to pre-existing cylinders.

Electrospun nanofibers of polyferrocenylsilanes with different substituents at silicon

The strained silicon-bridged [1]ferrocenophane Fe(η-C5H4)2SiBuMe was prepared via a facile chloride substitution reaction at the bridging atom of a readily available SiMeCl-bridged [1]ferrocenophane precursor. Thermal ring-opening polymerization of Fe(η-C5H4)2SiBuMe and Fe(η-C5H4)2SiMe2 afforded polyferrocenyldimethylsilane (PFDMS) and polyferrocenylbutylmethylsilane (PFBMS), respectively. Polyferrocenylsilane nanofibers were fabricated by electrospinning polymer solutions in 90wt% tetrahydrofuran and 10wt% N,N-dimethylformamide at room temperature. The effect of processing parameters such as concentration of polyferrocenylsilanes solution, applied voltage, and working distance on the diameter and morphology of resulting nanofibers were investigated. Electron diffraction patterns from polymer nanofibers revealed that PFS fibers exhibit different orientation owing to variance of the side groups at silicon.

Study on the Electrochemical Behavior of Poly(ferrocenylsilane) Films

The electrochemical behavior of polyferrocenyldimethylsilane (PFDMS) films and polyferrocenylmethylphenylsilane (PFMPS) films deposited on a glassy carbon electrode in 1.0 M aqueous LiClO4 was investigated by means of cyclic voltammetry (CV). The influences of supporting electrolyte concentration, temperature, film thickness, and the molecular structure of the polymer on the electrode process are discussed. In 1.0 M aqueous LiClO4, the electrochemical processes of two polymer films on glassy carbon electrodes were complex and have a low rate of electron transport and mass diffusion. At routine sweep rates, quasi-reversible or irreversible CV processes of the films were observed, but at slow sweep rates, nearly reversible CV waves were recorded. Below 0.05 M, the concentration of the supporting electrolyte had a considerable effect on the CV behavior of the film, especially on the oxidation wave, that is, the kinetics of film oxidation was limited by the counterion flow into the polymer phase. Elevated temperature increased the rate of the electrode process and improved the reversibility of the film electrode process. The diffusion rate of the active species in the film electrode process was reduced with the film thickness. Furthermore, the molecular structure of the polymer had a notable influence on the electrochemical behavior of the films. The phenyl groups in PFMPS hobbled the chain mobility in the polymer and restricted the surface charge transfer and the active species diffusion so that the kinetic parameters of the PFMPS films, especially the surface transfer coefficient αnα, were found to be smaller than those corresponding to the PFDMS films. The shapes of the CV peaks of the PFMPS films were broader, the peak potentials for both cathodic and anodic peaks were more positive, and the peak separation ΔEp was larger.