The study of metallopolymers has blossomed into a mature field over the last few decades. Especially, polyferrocenylsilane (PFS) chemistry has taken a tremendous leap and continues to raise intense interest. Since the discovery of thermal ring-opening polymerization (ROP) of sila[1]ferrocenophanes, PFSs have been also accessed by anionic, cationic, transition-metal-catalyzed, and photolytic anionic ROP methodologies. A plethora of synthetic strategies have been devised, enabling access to a wide variety of copolymers, polyelectrolytes, and nanostructured materials. The distinctive physical properties and functions of many PFS-based polymers have been explored, leading to their apt exploitation in technical applications. Therefore, it is conceivable that PFS-related platforms might be indispensable nano-objects in the near future, as they stand on the verge of a new generation of sophisticated materials.

Controlled polymerization of hexamethylcyclotrisiloxane was achieved by carrying out the polymerization first at room temperature to about 50% conversion and then at -20 °C until complete conversion in order to avoid side reactions. The poly(dimethylsiloxane)s produced show narrow molecular weight distributions (M w/Mn e 1.1). Using this approach, a model linear triblock copolymer PS-b-PDMSb-PS, as well as 3-miktoarm star co-and terpolymers of the (PDMS)(PS)2 and (PDMS)(PS)(PI) type, where PS is polystyrene, PI is polyisoprene, and PDMS is poly(dimethylsiloxane), have been prepared.

No abstract

The equilibrium melting temperature, Tm,0, of poly(ferrocenyl dimethylsilane) (PFDMS) is re‐investigated using two PFDMS homopolymers and a PS‐b‐PFDMS copolymer (PS: polystyrene). The melting temperatures of samples crystallized at different crystallization temperatures, Tc, were found to depend in a nonlinear fashion on Tc. Consequently, the Hoffmann–Weeks approach fails in determining Tm,0. The more reliable Gibbs–Thomson approach results in a Tm,0 = (215 ± 11) °C for the PFDMS homopolymers, and a Tm,0 = (179 ± 5) °C for the PFDMS microphases in the lamellar PS‐b‐PFDMS diblock copolymer.magnified image

Metallopolymere haben sich in den letzten Jahrzehnten zu einem ergiebigen Forschungsgebiet entwickelt. Besonders die Polyferrocenylsilan(PFS)‐Chemie hat sich dabei rasant entwickelt. Nach Entdeckung der thermischen Ringöffnungspolymerisation (ROP) von Sila[1]ferrocenophanen konnten Polyferrocenylsilane bald auch durch anionische, kationische, übergangsmetallkatalysierte und photolytische anionische ROP zugänglich gemacht werden. Hiervon ausgehend wurden unterschiedlichste weiterführende Synthesestrategien ausgearbeitet, die Zugang zu einer breiten Palette an Copolymeren, Polyelektrolyten und nanostrukturierten Materialien eröffnen. Die physikalischen Eigenschaften PFS‐basierter Polymere sowie die mit ihnen realisierbaren Funktionen wurden erforscht und können jetzt in technischen Anwendungen genutzt werden.

The synthesis of block copolymers with a high degree of molecular and compositional homogeneity has facilitated researchers in understanding properties such as morphology, 1,2 dynamics, 3 adsorption, 4,5 and rheology. 6 Furthermore, block copolymers have found useful applications 7 and are potential candidates for many others. 8 The most powerful method for the synthesis of block copolymers is the sequential addition of monomers by anionic polymerization. Unfortunately, there are pairs of polymeric blocks, such as poly(dimethylsiloxane) (PDMS) and polymethacrylates (PMA), that cannot be prepared by this procedure, because the nucleophilicity of the living polymeric blocks does not match the electron affinity of the other monomer. To overcome this problem, Hogen-Esch et al. 9 prepared an -OH endcapped poly(methyl methacrylate) (PMMA) using an R-OH protected initiator. In a second step, the -OH group was transformed, after deprotection, to -OLi group and used to initiate the polymerization of hexamethylcyclotrisiloxane (D 3 ). Although the block copolymers prepared are well-defined, the weak point of this methodology is the instability of the -C-O-Si-group that connects the two blocks. Other methods have been reported for the synthesis of PDMS-b-PMA by combining anionic with group transfer, 10 atom transfer radical, 11 or free radical polymerization. 12 The above procedures (refs 10-12) lead to materials with high molecular and compositional polydispersity.An alternative and perhaps more versatile approach for the synthesis of block copolymers would be one that employs a linking agent with two different functional groups (heterofunctional linking agent). The reactivity of the two groups should be different toward dissimilar macroanions. On the basis of the greater reactivity of the -Si(Me) 2 -Cl than -Ph-CH 2 -Cl group toward silicon-oxygen nucleophiles, 13 we are proposing 2-(chloromethylphenyl)ethyldimethylchlorosilane (CMPDMS) as an efficient heterofunctional linking agent for the synthesis of well-defined block copolymers of PDMS and poly(tert-butyl methacrylate) (PTBMA) or poly(2-vinylpyridine) (P2VP).Experimental Section. a. Equipment and Materials. n-Butyllithium (1.6 M) in hexanes, hexamethylcyclotrisiloxane (D 3 ) (98%), 2-vinylpyridine (98%), tertbutyl methacrylate (99%), (CH 3 ) 3 SiCl (99%), benzene (99%), tetrahydrofuran (THF) (99%), CsI (99.999%), and LiCl (99%) were purchased from Aldrich. CMPDMS (98%), a mixture of para and meta isomers, was purchased from ABCR. Purification of monomers and solvents to the standards required for anionic polymerization has been described in detail elsewhere. 14 s-BuLi was prepared in vacuo from s-butyl chloride and lithium dispersion. Addition and removal of the reagents were performed using break-seals and constrictions. 14 CMPDMS was purified by fractional distillation under high vacuum (10 -6 Torr).Size exclusion chromatography (SEC) experiments were carried out at 25°C in two different setups. In the first a Waters model 510 pump, a Waters model 410 differential ...

Chemoselective stepwise coupling between living polymers and a heterobifunctional linking agent is shown to be a versatile, facile, and efficient methodology for block copolymer synthesis. This protocol is based on the quantitative formation of the end‐functionalized precursor in the first coupling step. In this proof‐of‐concept study, we investigate the behavior of specific macroanions, prepared through living anionic polymerization (LAP). Nevertheless, the applicability range is becoming exceptionally wide upon transformation reactions, e.g., by tailoring the chain‐termini nucleophilicity via endcapping. This novel protocol will considerably expand the limits of LAP, rendering viable the construction of advanced and tailor‐made materials via an effortless pathway.magnified image

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.