RAFT Polymerization of Styrene Mediated by Ferrocenyl-Containing RAFT Agent and Properties of the Polymer Derived from Ferrocene

Synthesis of Site-specific Charged Metallopolymers via Reversible Addition-Fragmentation Chain Transfer (RAFT) Polymerization

Site-specific cobaltocenium-labeled polymers are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using cobaltocenium-labeled chain transfer agents. These chain transfer agents show counterion-dependent solubility. Based on the chemical structure of the chain transfer agents, single cobaltocenium moieties are dictated to be in predetermined locations at either the center or terminals of the polymer chains. Polymerization of hydrophobic monomers (methyl methacrylate, methyl acrylate and styrene) and hydrophilic monomers (2-(dimethylamino)ethyl methacrylate and methacrylic acid) is demonstrated to follow a controlled manner based on kinetic studies. Cobaltocenium-labeled polymers with molecular weights greater than 100,000 Da can be prepared by using a difunctional chain transfer agent. Photophysical properties, electrochemical properties, thermal properties and morphology of the cobaltocenium-labeled polymers are also investigated.

Self-assembly of amphiphilic homopolymers bearing ferrocene and carboxyl functionalities: effect of polymer concentration, β-cyclodextrin, and length of alkyl linker

Three new acrylamide monomers containing ferrocene and tert-butyl ester groups were first synthesized via multistep nucleophilic substitution reaction under mild conditions followed by reversible addition-fragmentation chain transfer (RAFT) homopolymerization to give well-defined homopolymers with narrow molecular weight distributions (M(w)/M(n) ≤ 1.36). The target amphiphilic homopolymers were obtained by the acidic hydrolysis of tert-butyoxycarbonyls to carboxyls in every repeating unit using CF3COOH. The self-assembly behaviors of these amphiphilic homopolymers bearing both ferrocene and carboxyl moieties in each repeating unit in aqueous media were investigated by transmission emission microscopy (TEM), dynamic light scattering (DLS), and atomic force microscopy (AFM). Large compound micelles with different morphologies were formed by these amphiphilic homopolymers, which consist of the corona formed by hydrophilic carboxyls and the core containing numerous reverse micelles with hydrophilic islands of carboxyls in continuous hydrophobic phase of ferrocene-based segments. The morphologies of the formed micelles could be tuned by the concentration of amphiphilic homopolymers, pH value of the solution, the length of -CH2 linker between ferrocene group and carboxyl, and the amount of β-cyclodextrin (β-CD).

Living Radical Polymerization by the RAFT Process – A Third Update

This paper provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669) and the second in December 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymerization which include reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.

Dual responsive supramolecular hydrogel with electrochemical activity

Supramolecular materials with reversible responsiveness to environmental changes are of particular research interest in recent years. Inclusion complexation between cyclodextrin (CD) and ferrocene (Fc) is well-known and extensively studied because of its reversible association-dissociation controlled by the redox state of Fc. Although there are quite a few reported nanoscale materials incorporating this host-guest pair, polymeric hydrogels with electrochemical activity based on this interactive pair are still rare. Taking advantage of our previous reported hybrid inclusion complex (HIC) hydrogel structure, a new Fc-HIC was designed and obtained with β-CD-modified quantum dots as the core and Fc-ended diblock co-polymer p(DMA-b-NIPAM) as the shell, to achieve an electrochemically active hydrogel at elevated temperatures. Considering the two independent cross-linking strategies in the network structure, i.e., the interchain aggregation of pNIPAM and inclusion complexation between CD and Fc on the surface of the quantum dots, the hydrogel was fully thermo-reversible and its gel-sol transition was achieved after the addition of either an oxidizing agent or a competitive guest to Fc.

One-pot preparation of ferrocene-functionalized polymer brushes on gold substrates by combined surface-initiated atom transfer radical polymerization and "click chemistry"

A gold substrate with surface-grafted ferrocene functional polymer brushes, or Au-g-PFTMA surface [PFTMA = poly(5-ferrocene-triazolyl methacrylate)], was prepared by a combination of surface-initiated atom transfer radical polymerization (SI-ATRP) and "click chemistry" in one pot, in the presence of 2-azidoethyl methacrylate (AzEMA), ethynyl ferrocene, CuBr catalyst, CuBr(2) deactivator, and pentamethyldiethylenetriamine ligand. Thus, SI-ATRP of AzEMA from the Au substrate (the "grafting from" process) and click chemistry of the ethynyl ferrocene to the azide functional group of AzEMA (the "grafting to" process) proceeded simultaneously to produce the functional PFTMA brushes on the Au surface. Kinetic studies suggest that the reaction involving simultaneous SI-ATRP and click chemistry is still consistent with a controlled/"living" process. The composition and physical properties of the modified gold surface were analyzed by X-ray photoelectron spectroscopy, water contact angle measurement, and cyclic voltammetry. The redox-responsive properties of the ferrocene-functionalized polymer brushes on the Au-g-PFTMA surface were demonstrated in the reversible loading-unloading step of the β-cyclodextrin polymer via host-guest interaction.