Atom-transfer radical-polymerisation

Methyl methacrylate (MMA) and sodium styrene sulfonate (SSNa) are water-soluble. These polymers behave like a low MW surfactant as they form micelles in aqueous solution in which the hydrophobic part is directed towards the centre and the hydrophilic part is situated on the periphery of the micelle. Owing to such features, amphiphilic block copolymers have wide-ranging applications in drugs, pharmaceuticals, coatings, cosmetics and paints. They also exhibit very high antibacterial activities. Oikonomou and co-workers used ATRP to prepare amphiphilic block copolymers, consisting of polymethyl methacrylate (PMMA) and poly (sodium styrene sulfonate) (PSSNa) blocks [18]. The synthesis methods are described below. 

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Abstract Over the past decade significant advances have been made in the fields of polymerisation, oligomerisation and telomerisation with metal-NHC catalysts. Complexes from across the transition series, as well as lanthanide examples, have been employed as catalysts for these reactions. Recent developments in the use of metal-NHC complexes in a-olefin polymerisation and oligomerisation, CO/olefm copolymerisation, atom-transfer radical polymerisation (ATRP) and diene telomerisation are discnssed in subsequent sections. 

There are a number of reports of NHC complexes of mid-late transition metals being used as catalysts for atom transfer radical polymerisation (ATRP) of acrylates and styrene. Grubbs reported Fe(II) complexes of a simple monodentate carbene. 

TEMPO combines with the radical chain and keeps the concentration of the growing radical chain low, such that the recombination of radicals is suppressed. This type of radical polymerisation is called Atom Transfer Radical Polymerisation (ATRP). It has the properties of a living polymerisation, as the molecular weight increases steadily with time and one can make block polymers this way by adding different monomers sequentially. 

Synthesis of New Polymeric Surfactants and Dispersants Via Atom Transfer Radical Polymerisation at Ambient Temperature... 

Atom Transfer Radical Polymerisation (ATRP) was discovered independently by Wang and Matyjaszewski, and Sawamoto s group in 1995. Since then, this field has become a hot topic in synthetic polymer chemistry, with over 1000 papers published worldwide and more than 100 patent applications filed to date. ATRP is based on Kharasch chemistry overall it involves the insertion of vinyl monomers between the R-X bond of an alkyl halide-based initiator. At any given time in the reaction, most of the polymer chains are capped with halogen atoms (Cl or Br), and are therefore dormant and do not propagate see Figure 1. 

Figure 1 General reaction scheme for Atom Transfer Radical Polymerisation (A TRP)...

The Cu(II)/Cu(I) redox system added as bromide has recently been used to prepare well-defined polymers (controlled molecular weight, reduced poly-dispersity, terminal functionalities). One of the most successful methods to make well-defined polymers is atom transfer radical polymerisation (ATRP)18 ... 

Polymer brushes are polymers tethered to a surface via one end. The connection to the surface can be covalent or non-covalent, and the brushes can be made via grafting to or grafting from the surface. In the past few years, there has been considerable interest in the growth of polymer brushes via surface-initiated polymerisations from (patterned) initiator-functionalised SAMs.62,63 For example, we have recently shown that surface confined Atom Transfer Radical Polymerisations (ATRP) in aqueous solvents leads to rapid and controlled... 

Development of ATRP (Atom Transfer Radical Polymerisation) by Wang, Matyjaszewski and Sawamoto... 

The general mechanism in atom transfer radical polymerisation is depicted in Scheme 8.11. The main difference to conventional radical polymerisation is in the presence of a metal complex. Free radicals are generated from reaction between the initiator (such as an organic halide) and the metal species which further controls the reaction by reversibly transforming the free radicals into a dormant species.1"6 However, it ought to be pointed out that in ATRP contrary to, for example, Ziegler-Natta-type catalysts, the polymerisation does not take place at the metal centre. 

AFM=atomic force microscopy ATRP=atom transfer radical polymerisation PEO=poly(ethylene oxide)... 

Nitroxide-mediated CRP has been investigated for use in emulsion polymerisation systems, but with mixed the results. " Atom transfer radical polymerisation (ATRP) offers greater scope than nitroxide-mediated CRP in that it is less discriminating in terms of the monomers that can be used. However, there are few reports of work on adapting ATRP to heterogeneous systems. " Given the established requirements for control of these polymerisations, both nitroxide-mediated CRP and ATRP suffer from problems brought about by... 

Scheme 9.2 Schematic example of the atom transfer radical polymerisation technique to prepare an adduct from an alkyl halide (R-X) and an alkene (CH2 = CHY). Mf2 is the transition metal Mtn+1 is the oxidised transition metal X is a halogen and R is a radical.

A corresponding principle applies to controlled radical polymerisation performed in quite a number of modes such as nitroxide-mediated polymerisation (NMP), atom transfer radical polymerisation (ATRP), reversible addition fragmentation chain transfer (RAFT) or catalytic chain transfer (CCT) reactions. All of these variants of controlled radical polymerisation lead to well-defined architectures with the particular advantage that a much larger number of monomers are suitable and the reaction conditions are much less demanding than those of living ionic polymerisation reactions. 

Figure 2.3 ATRP current status and future perspectives. ARGET activator regenerated by electron transfer, eATRP electron-atom transfer radical polymerisation, ICAR initiators for continuous activator regeneration and SARA supplemental activator and reducing agent. Reproduced with permission from K.Matyjaszewski, Macromolecules, 2012,45,10,4015.

N-(3 -aminopropyl)methacrylamide (3-Aminopropyl)triethoxysilane Activator regenerated by electron transfer Antimicrobial susceptibility test(ing) American Society for Testing and Materials Adenosine triphosphate Atom transfer radical polymerisation Blood brain barrier Bilayer fragment(s)... 

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