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The concept of initiators for continuous activator regeneration (ICAR) in atom transfer radical polymerization (ATRP) is introduced, whereby a constant source of organic free radicals works to regenerate the Cu(I) activator, which is otherwise consumed in termination reactions when used at very low concentrations. With this technique, controlled synthesis of polystyrene and poly(methyl methacrylate) (Mw/Mn < 1.2) can be implemented with catalyst concentrations between 10 and 50 ppm, where its removal or recycling would be unwarranted for many applications. Additionally, various organic reducing agents (derivatives of hydrazine and phenol) are used to continuously regenerate the Cu(I) activator in activators regenerated by electron transfer (ARGET) ATRP. Controlled polymer synthesis of acrylates (Mw/Mn < 1.2) is realized with catalyst concentrations as low as 50 ppm. The rational selection of suitable Cu complexing ligands {tris[2-(dimethylamino)ethyl]amine (Me6TREN) and tris[(2-pyridyl)methyl]amine (TPMA)} is discussed in regards to specific side reactions in each technique (i.e., complex dissociation, acid evolution, and reducing agent complexation). Additionally, mechanistic studies and kinetic modeling are used to optimize each system. The performance of the selected catalysts/reducing agents in homo and block (co)polymerizations is evaluated.

Atom transfer radical polymerization (ATRP) has been successfully extended to an ab initio emulsion system using a "two-step" procedure, in which the final emulsion polymerization system was formed by adding monomer to an ongoing microemulsion ATRP. The newly developed AGET (activators generated by electron transfer) initiation technique was employed in the first stage of this ab initio ATRP. It allows using oxidatively stable Cu(II) species that is reduced in situ by ascorbic acid. The surfactant concentration in the final emulsion system was efficiently decreased to approximately 2 wt % (approximately 10 wt % vs monomer) by decreasing the catalyst concentration and changing the ratio of the monomer added at the microemulsion stage to the monomer added during the second stage. This two-step procedure avoids the necessity of transporting catalysts through the aqueous media during polymerization, resulting in a controlled emulsion polymerization, as evidenced by a linear first-order kinetic plot and formation of a polymer with a relatively narrow molecular weight distribution (Mw/Mn = 1.2-1.4). The polymerization typically reached 70-90% monomer conversion in 5-6 h. The resulting polymer had high chain-end functionality and was successfully chain extended to form in situ block copolymers by adding the second monomer to an ongoing emulsion polymerization. The stable latex from the ab initio emulsion ATRP had a particle size approximately 120 +/- 10 nm.

A new methodology for the synthesis and functionalization of nanometer-sized colloidal particles consisting of well-defined, water-soluble, functional polymers with narrow molecular weight distribution (M(w)/M(n) < 1.3) was developed, utilizing atom transfer radical polymerization (ATRP) of water-soluble monomers in an inverse miniemulsion. The optional introduction of a disulfide-functionalized cross-linker allowed for the synthesis of cross-linked (bio)degradable nanogels. Dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements indicated that these particles possessed excellent colloidal stability. ATRP in inverse miniemulsion led to materials with several desirable features. The colloidal particles preserved a high degree of halogen chain-end functionality, which enabled further functionalization. Cross-linked nanogels with a uniformly cross-linked network were prepared. They were degraded to individual polymeric chains with relatively narrow molecular weight distribution (M(w)/M(n) < 1.5) in a reducing environment. Higher colloidal stability, higher swelling ratios, and better controlled degradability indicated that the nanogels prepared by ATRP were superior to their corresponding counterparts prepared by conventional free radical polymerization (RP) in inverse miniemulsion.

Covalent carbon-carbon bonds are hard to break. Their strength is evident in the hardness of diamonds and tensile strength of polymeric fibres; on the single-molecule level, it manifests itself in the need for forces of several nanonewtons to extend and mechanically rupture one bond. Such forces have been generated using extensional flow, ultrasonic irradiation, receding meniscus and by directly stretching a single molecule with nanoprobes. Here we show that simple adsorption of brush-like macromolecules with long side chains on a substrate can induce not only conformational deformations, but also spontaneous rupture of covalent bonds in the macromolecular backbone. We attribute this behaviour to the fact that the attractive interaction between the side chains and the substrate is maximized by the spreading of the side chains, which in turn induces tension along the polymer backbone. Provided the side-chain densities and substrate interaction are sufficiently high, the tension generated will be strong enough to rupture covalent carbon-carbon bonds. We expect similar adsorption-induced backbone scission to occur for all macromolecules with highly branched architectures, such as brushes and dendrimers. This behaviour needs to be considered when designing surface-targeted macromolecules of this type-either to avoid undesired degradation, or to ensure rupture at predetermined macromolecular sites.

Atom transfer radical polymerization (ATRP) equilibrium constants (K(ATRP)) were determined using modified Fischer's equations for the persistent radical effect. The original Fischer's equations could be used only for low conversion of Cu(I) to X-Cu(II) and consequently for relatively low values of K(ATRP). At higher conversion to X-Cu(II) (>10%) and for larger values of K(ATRP) (>10(-)(7)), modified equations that take into account the changes in catalyst and initiator concentrations should be used. The validity of new equations was confirmed by detailed kinetic simulations. UV-vis spectrometric and GC measurements were used to follow the evolution of X-Cu(II) species and the initiator concentration, respectively, and to successfully determine values of K(ATRP) for several catalysts and alkyl halides. The effect of structure on reactivities of ATRP components is presented.

Long-range orientational order in monolayers of brush-like macromolecules was achieved during spreading of a polymer melt on the surface of highly oriented pyrolytic graphite. The combination of wetting-induced flow and epitaxial adsorption of poly(n-butylacrylate) side chains on graphite led to the formation of large domains of uniaxially oriented rodlike molecules. The domain size varied from ca. 1 to 10 microm which is noticeably larger than the submicrometer-sized mosaic domains typically observed upon adsorption from solution. The increase in the degree of order is attributed to the flow-enhanced diffusion of the macromolecules within spreading monolayers which facilitates the epitaxial alignment of the large macromolecules. The diffusion coefficient was shown to increase linearly with the spreading rate. Even though the ordering occurred during flow, no correlation was observed between the molecular orientation and the flow direction. Thus, the role of the flow was not to induce the molecular orientation but to facilitate the intrinsic ordering process. This finding can inspire and lead to new strategies for constructing large scale ordered structures on surfaces.

Reactive zero valent iron nanoparticles can degrade toxic nonaqueous phase liquids (NAPL) rapidly in contaminated groundwater to nontoxic products in situ, provided they can be delivered preferentially to the NAPL/water (oil/water) interface. This study demonstrates the ability of novel triblock copolymers to modify the nanoiron surface chemistry in a way that both promotes their colloidal stability in aqueous suspension and drives their adsorption to the oil/water interface. The ability of the copolymers to drive adsorption is demonstrated by the ability of copolymer-modified iron nanoparticles, but not the unmodified iron nanoparticles, to stabilize oil-in-water emulsions.

We have developed a novel technique to synthesize near-uniform protein-polymer conjugates by initiating atom transfer radical polymerization of monomethoxy poly(ethylene glycol)-methacrylate from 2-bromoisobutyramide derivatives of chymotrypsin (a protein-initiator). Polymerization initiated from the monosubstituted protein-initiator resulted in the conjugate containing a single, near-monodisperse polymer chain per protein molecule with polydispersity index 1.05. Increasing the number of conjugated 2-bromoisobutyramide initiators per molecule of protein increased the molecular weights and polydispersity indices of the final protein-polymer conjugates. The generic nature of this technique was demonstrated by initiating polymerization of nonionic, cationic, and anionic monomers from the protein-initiator. Protein-polymer conjugates synthesized by this novel technique retained 50-86% of the original enzyme activity. The technique described herein should be useful in synthesizing well-defined protein-polymer conjugates exhibiting a wide range of physical and chemical properties.

Acrylate-based block copolymers, synthesized by atom transfer radical polymerization (ATRP) processes, were evaluated as drug delivery matrices for the controlled release of paclitaxel from coronary stents. The polymers were multiblock copolymers consisting of poly(butyl acrylate) or poly(lauryl acrylate) soft blocks and hard blocks composed of poly(methyl methacrylate), poly(isobornyl acrylate), or poly(styrene) homo- or copolymers. Depending on the ratio of hard to soft blocks in the copolymers, coating formulations were produced that possessed variable elastomeric properties, resulting in stent coatings that maintained their integrity when assessed by scanning electron microscopy (SEM) imaging of overexpanded stents. In vitro paclitaxel release kinetics from coronary stents coated with these copolymers typically showed an early burst followed by sustained release behavior, which permitted the elution of the majority of the paclitaxel over a 10-day time period. It was determined that neither the nature of the polyacrylate (n-butyl or lauryl) nor that of the hard block appeared to affect the release kinetics of paclitaxel at a loading of 25% drug by weight, whereas some effects were observed at lower drug loading levels. Differential scanning calorimetry (DSC) analysis indicated that the paclitaxel was at least partially miscible with the poly(n-butyl acrylate) phase of those block copolymers. The copolymers were also evaluated for sterilization stability by exposing both the copolymer alone and copolymer/paclitaxel coated stents to e-beam radiation at doses of 1-3 times the nominal dose used for medical device sterilization (25 kGy). It was found that the copolymers containing blocks bearing quaternary carbons within the polymer backbone were less stable to the radiation and showed a decrease in molecular weight as determined by gel-permeation chromatography. Conversely, those without quaternary carbons showed no significant change in molecular weight when exposed to 3 times the standard radiation dose. There was no significant change in drug release profile from any of the acrylate-based copolymers after exposure to 75 kGy of e-beam radiation, and this was attributed to the inherent radiation stability of the poly(n-butyl acrylate) center block.

Fully sulfonated poly(styrenesulfonate) brushes were grown from the surface of colloidal silica particles and used to prepare stable trichloroethylene-in-water and heptane-in-water Pickering emulsions. These particles were highly charged and colloidally stable in water but could not be dispersed in trichloroethylene or heptane. Both two-phase (emulsion plus neat water) and three-phase (emulsion separating neat oil and water phases) systems were observed, with water-continuous emulsion phases in all cases. Emulsion phases containing as much as 83% (v/v) oil were stable for over six months. Poly(styrenesulfonate)-grafted particles were very efficient emulsifiers; stable emulsion phases were prepared when using as little as 0.04 wt% particles. The emulsifying effectiveness of the poly(styrenesulfonate)-grafted silica particles can be attributed to the hydrophobicity of the vinylic polymer backbone that makes this highly charged polyelectrolyte unusually surface active at the oil/water interface.

The phase state of a series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octadecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated in bulk and on surfaces using small-angle X-ray scattering and atomic force microscopy, respectively. The mean-field theory was employed to construct the bulk phase diagram. Excellent agreement was found between the bulk and surface morphologies as well as for the domain spacing (domain spacing scaled as d approximately equal to N(0.64)), suggesting that the strong polymer-polymer interactions in bulk are also the dominant interactions on surfaces.

A new type of flow fingering instability was observed in monolayer-thick polymer films as they spread on a solid substrate. Tracing the movement of individual molecules by atomic force microscopy enabled us to follow the development of the flow instability on the molecular level and to understand the underlying physical mechanism. The fingering instability was observed to be triggered by conformational changes of brushlike macromolecules in response to the pressure gradient driving the flow.

Mesoporous carbons were synthesized from polyacrylonitrile (PAN) using ordered and disordered mesoporous silica templates and were characterized using transmission electron microscopy (TEM), powder X-ray diffraction, nitrogen adsorption, and thermogravimetry. The pores of the silica templates were infiltrated with carbon precursor (PAN) via polymerization of acrylonitrile from initiation sites chemically bonded to the silica surface. This polymerization method is expected to allow for a uniform filling of the template with PAN and to minimize the introduction of nontemplated PAN, thus mitigating the formation of nontemplated carbon. PAN was stabilized by heating to 573 K under air and carbonized under N2 at 1073 K. The resulting carbons exhibited high total pore volumes (1.5-1.8 cm3 g(-1)), with a primary contribution of the mesopore volume and with relatively low microporosity. The carbons synthesized using mesoporous templates with a 2-dimensional hexagonal structure (SBA-15 silica) and a face-centered cubic structure (FDU-1 silica) exhibited narrow pore size distributions (PSDs), whereas the carbon synthesized using disordered silica gel template had broader PSD. TEM showed that the SBA-15-templated carbon was composed of arrays of long, straight, or curved nanorods aligned in 2-D hexagonal arrays. The carbon replica of FDU-1 silica appeared to be composed of ordered arrays of spheres. XRD provided evidence of some degree of ordering of graphene sheets in the carbon frameworks. Elemental analysis showed that the carbons contain an appreciable amount of nitrogen. The use of our novel infiltration method and PAN as a carbon precursor allowed us to obtain ordered mesoporous carbons (OMCs) with (i) very high mesopore volume, (ii) low microporosity, (iii) low secondary mesoporosity, (iv) large pore diameter (8-12 nm), and (v) semi-graphitic framework, which represent a desirable combination of features that has not been realized before for OMCs.

Large-scale alignment of lamellae in thin films of diblock copolymers containing polyacrylonitrile and poly(n-butyl acrylate) was achieved by casting copolymer solution on a silicon substrate moved away at a constant speed from the casting nozzle (zone-casting). Grazing incidence small-angle X-ray scattering revealed that the lamellae, which were perpendicular to the substrate, were also aligned over macroscopic scale in the direction perpendicular to the casting direction. Such long-range ordered block copolymer films were then converted by pyrolysis into nanostructured carbons, with excellent preservation of lamellar morphology and orientation.

A new initiating/catalytic system for atom transfer radical polymerization (ATRP) is reported. This system starts with alkyl halides as initiators and transition metal complexes in their oxidatively stable state (e.g., Cu(II)Br2/ligand) as catalysts. The activators are generated by electron transfer (AGET) without involvement of initiating organic radicals. AGET ATRP has a significant advantage over simultaneous reverse and normal initiation (SR&NI) ATRP, because it provides a simple route for synthesizing pure polymers with complex architectures such as star copolymers, block copolymers, etc. Furthermore, AGET ATRP can be also successfully carried out in miniemulsion. Homopolymers and pure block copolymers were successfully synthesized via ATRP in miniemulsion using AGET ATRP. The final products were analyzed via two-dimensional chromatography, which combines high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). The resulting chromatograms showed that pure linear block copolymers and star block copolymers were prepared without the presence of any homopolymers.

We measured the form factor of bottle-brush macromolecules under good solvent conditions with small-angle neutron scattering and static light scattering. The systems under investigation are brushes, synthesized via the grafting-from route, built from a poly(alkyl methacrylate) backbone to which poly(n-butyl acrylate) side chains are densely grafted. The aim of our work is to study how the systematic variation of structural parameters such as the side chain length and backbone length change the conformation of the polymer brushes in solution. All spectra can be consistently described by a model, considering the bottle-brush polymers as flexible rods with internal density fluctuations. Parameters discussed are (1) the contour length per main chain monomer l(b), (2) the fractal dimension of the side chains Ds, as well as (3) the fractal dimension D, and (4) the Kuhn length lambdak of the overall brush. l(b)=0.253+/-0.008 nm is found to be independent of the side chain length and equal to the value found for the bare main chain, indicating a strongly stretched conformation for the backbone due to the presence of the side chains. The fractal dimension of the side chains is determined to be Ds=1.75+/-0.07 which is very close to the value of 10.588 approximately 1.70 expected for a three-dimensional self-avoiding random walk (3D-SAW) under good solvent conditions. On larger length scales the overall brush appears to be a 3D-SAW itself (D=1.64+/-0.08) with a Kuhn-step length of lambdak=70+/-4 nm. The value is independent of the side chain length and 46 times larger than the Kuhn length of the bare backbone (lambdak=1.8+/-0.2 nm). The ratio of Kuhn length to brush diameter lambda(k)d>or=20 determines whether lyotropic behavior can be expected or not. Since longer side chains do not lead to more persistent structures, lambda(k)d decreases from 8 to 4 with increasing side chain length and lyotropic behavior becomes unlikely.

Spreading of a polymer drop on a solid substrate was monitored with molecular resolution. Three characteristic rates, i.e., the spreading rate of the precursor film D(spread)=(3.9+/-0.2)x10(3) nm(2)/s, the flow-induced diffusion rate of molecules within the film D(induced)=1.3+/-0.1 nm(2)/s, and the thermal diffusion coefficient of single molecules D(therm)>D(induced), the plug flow of polymer chains was identified as the main mass-transport mechanism of spreading with an insignificant contribution from the molecular diffusion.

Environment-controlled scanning force microscopy allowed us to study adsorption and desorption of single poly(methacrylate)-graft-poly(n-butyl acrylate) brush molecules on mica in real time. The molecules transform reversibly from a two-dimensional, extended wormlike state to a compact globular state. The dynamics of the conformational transition was sufficiently slow in order to allow its observation by scanning force microscope in real time. The reversible transformation is effected by coadsorption of water or ethanol, the latter introduces the collapse. Adsorbing ethanol and water from the vapour atmosphere results in a change of the surface properties of mica, either favouring adsorption or desorption of the graft polymer. When the extended, tightly adsorbed poly(n-butyl acrylate) brush molecules are exposed to ethanol vapour, the macromolecules swell and contract to form compact globules. Exchanging the ethanol vapour to a humid atmosphere caused the molecules to extend again to a wormlike two-dimensional conformation. Coexistence of collapsed and extended strands within the same molecule indicates a single-molecule first-order transition in agreement with observations on Langmuir films previously reported.

We describe a technique to visualize and effect in real time motion and conformational transitions of single macromolecules. Two steps are involved. First, scanning force microscopy (SFM) was applied to detect in situ conformational transitions of single polymer molecules adsorbed on a substrate surface. Secondly, these changes were induced by controlled variations of environmental conditions in a microscope environmental chamber. In particular, we have revealed that exposure of a substrate with adsorbed macromolecules to vapours of different nature was able to increase molecular mobility and to stimulate conformational transitions of the polymer chains on the surface. Realization of SFM observation in a variable vapour environment was not as difficult as in liquid media. Variations of the vapour composition affected the oscillation dynamics of the cantilever with the scanning probe only to a small extent, and did not impede continuation of the scanning procedure. In fact, the characteristic times of the observed conformational changes were large enough (minutes to dozens of minutes) for sampling images repeatedly. Although recording of an SFM image was slow and required several minutes, we were able to visualize step-by-step the successive stages of the slow conformational transformation of the macromolecules adhering to the substrate, i.e. to investigate a molecular response to the environment changes in real time. Here, we studied the reversible collapse-decollapse transitions of cylindrical poly(methacrylate)-graft-poly(n-butyl acrylate) brush-like macromolecules exposed to different vapours. Single macromolecules on mica tended to assume a compacted globular conformation when exposed to the vapour of compounds, which due to their amphiphilic nature adsorb on mica and lower the surface energy of the substrate (e.g. alcohols). By contrast, the macromolecules adopted extended two-dimensional worm-like conformations in the vapours of compounds having high values of surface tension (such as water). In our opinion, the reason for the observed tendency was a competition in spreading on the substrate surface between the macromolecules and the co-adsorbed vapour molecules. If the brush-like macromolecules succeeded in the spreading, they acquired an extended conformation. Otherwise they collapsed to globuli in order to reduce the surface area per macromolecule. Thus, the enhanced mobility of synthetic macromolecules on a substrate observed in a vapour environment in combination with the possibility to manipulate the macromolecular conformation via changes in a vapour phase and the ability to visualize the transitions of the macromolecules individually, provides challenging prospects for SFM studies on the dynamics of single molecules under applied external stimuli.

Individual molecules of multiarm starlike molecular brushes were visualized by atomic force microscopy. In the studied series of brushes, the number of arms varied from one for a linear chain to four, while the length of the side chains was kept approximately constant. Molecular visualization provided a unique opportunity for independent size characterization of the brush arms separately from that of the entire molecule. In agreement with the Schulz-Flory theory for chain coupling, the polydispersity of the total length was significantly lower than that of the arm length. The variation in polydispersity had an effect on molecular ordering. Lateral compression of the starlike brushes caused a transition from an extended dendritic-like conformation to a compact disklike conformation. In contrast to one-, two-, and three-arm brushes, the four-arm molecules with a lower polydispersity index of 1.04 demonstrated local hexagonal order.

We have grown an antimicrobial polymer directly on the surfaces of glass and paper using atom transfer radical polymerization (ATRP). The method described here results in potentially permanent nonleaching antibacterial surfaces without the need to chemically graft the antimicrobial material to the substratum. The tertiary amine 2-(dimethylamino)ethyl methacrylate was polymerized directly onto Whatman #1 filter paper or glass slides via atom transfer radical polymerization. Following the polymerization, the tertiary amino groups were quaternized using an alkyl halide to produce a large concentration of quaternary ammonium groups on the polymer-modified surfaces. Incubating the modified materials with either Escherichia coli or Bacillus subtilis demonstrated that the modified surfaces had substantial antimicrobial capacity. The permanence of the antimicrobial activity was demonstrated through repeated use of a modified glass without significant loss of activity. Quaternary amines are believed to cause cell death by disrupting cell membranes allowing release of the intracellular contents. Atomic force microscopic imaging of cells on modified glass surfaces supports this hypothesis.

Amphiphilic random, gradient, and block copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and n-butyl methacrylate (BMA) were synthesized by atom transfer radical polymerization (ATRP) in water/2-propanol mixtures using a methoxy-poly(ethylene glycol) (MPEG) (M(n) = 2000) macroinitiator. Kinetic studies indicate that the copolymerization is well controlled with molecular weights increasing linearly with conversion. Copolymers with molecular weights up to M(n) = 34000 and low polydispersities (M(w)/M(n) = 1.11-1.47) were prepared. The reactivity ratios were calculated for the copolymerizations catalyzed by CuBr/bpy, (r(DMAEMA) = 1.07, r(BMA) = 1.24). The thermosensitivity and aggregation properties of the random, gradient, and block copolymers significantly depended on the architecture of the copolymers. The lower critical solution temperature of MPEG-b-PDMAEMA(84) was 38 degrees C (5 wt % in water).

Three controlled/living radical polymerization processes, atom transfer radical polymerization (ATRP), reversible addition-fragmentation transfer (RAFT) polymerization, and nitroxide-mediated polymerization (NMP), were investigated for the polymerization of N,N-dimethylacrylamide in the presence of Lewis acids known to enhance isotacticity, such as yttrium trifluoromethanesulfonate (Y(OTf)(3)) and ytterbium trifluoromethanesulfonate (Yb(OTf)(3)). Poly(N,N-dimethylacrylamide) with controlled molecular weight, low polydispersity (M(w)/M(n) < 1.2), and a high proportion of meso dyads ( approximately 85%) was prepared by ATRP (with initiating system methyl 2-chloropropionate/CuCl/Me(6)TREN) and RAFT (with cumyl dithiobenzoate transfer agent) in the presence of Y(OTf)(3). The combination of NMP (using N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide, SG1) and a Lewis acid complexation technique led to less precise control over chain architecture and microstructure ( approximately 65% meso dyads), as compared to RAFT/Y(OTf)(3) or ATRP/Y(OTf)(3). The latter two systems were used for the first one-pot synthesis of stereoblock copolymers by radical polymerization. Well-defined stereoblock copolymers, atactic-b-isotactic poly(N,N-dimethylacrylamides), were obtained by adding Y(OTf)(3) at a given time to either RAFT or ATRP polymerizations, initially started without the presence of the Lewis acid.

Absolute-molecular-weight distribution of cylindrical brush molecules were determined using a combination of the Langmuir Blodget (LB) technique and Atomic Force Microscopy (AFM). The LB technique gives mass density of a monolayer, i.e., mass per unit area, whereas visualization of individual molecules by AFM enables accurate measurements of the molecular density, i.e., number of molecules per unit area. From the ratio of the mass density to the molecular density, one can determine the absolute value for the number average molecular weight. Assuming that the structure of brush molecules is uniform along the backbone, the length distribution should be virtually identical to the molecular weight distribution. Although we used only brush molecules for demonstration purpose, this approach can be applied for a large variety of molecular and colloidal species that can be visualized by a microscopic technique.

The development of new controlled/living radical polymerization processes, such as Atom Transfer Radical Polymerization (ATRP) and other techniques such as nitroxide mediated polymerization and degenerative transfer processes, including RAFT, opened the way to the use of radical polymerization for the synthesis of well-defined, complex functional nanostructures. The development of such nanostructures is primarily dependent on self-assembly of well-defined segmented copolymers. This article describes the fundamentals of ATRP, relevant to the synthesis of such systems. The self-assembly of block copolymers prepared by ATRP is illustrated by three examples. In the first, block copolymers of poly(butyl acrylate) with polyacrylonitrile phase separate, leading to spherical, cylindrical or lamellar morphologies, depending on the block copolymer composition. At a higher temperature, polyacrylonitrile block converts to nanostructured carbon clusters, whereas poly(butyl acrylate) block serves as a sacrificial block, aiding the development of designed nanostructures. In the second example, conductive nanoribbons of poly(n-hexylthiophene) surrounded by a matrix of organic polymers are formed from block copolymers prepared by ATRP. The third example describes an inorganic-organic hybrid system consisting of hard nanocolloidal silica particles (approximately 20 nm) grafted by ATRP with well-defined polystyrene-poly(benzyl acrylate) block copolymer chains (approximately 1000 chains per particle). Silica cores in this system are surrounded by a rigid polystyrene inner shell and softer polyacrylate outer shell.

Arrays of graphitic carbon nanoclusters were obtained by pyrolysis of nanoscale phase-separated block copolymers of polyacrylonitrile and poly(n-butyl acrylate). Upon heating in an inert atmosphere to temperatures ranging from approximately 400 to 1200 degrees C, polyacrylonitrile domains were converted into carbon nanoclusters, maintaining the overall shape and spacing, whereas the poly(n-butyl acrylate) phase was sacrificed. Preservation of the original nanoscale morphology of a block copolymer was possible only if pyrolysis was preceded by oxidation at temperatures of approximately 230 degrees C, in analogy with thermal stabilization of polyacrylonitrile precursor in the process used in the manufacturing of carbon fibers. Preorganization of the carbon precursor through self-assembly in block copolymers of polyacrylonitrile appears to be an attractive and robust strategy for templated synthesis of well-defined nanostructured carbon materials.

A general method for the determination of the activation (ka), deactivation (kd), and initiation (ki) rate constants in atom transfer radical processes is reported. The method involves the monomer trapping techniques and the analytical solution of the persistent radical effect. For tert-butyl 2-bromopropionate, using ATRP catalyst [CuI(dNbpy)2][Br] and methyl methacrylate in CH3CN at 22 degrees C, the values of ka, kd, and ki were determined to be (9.4 +/- 0.6) x 10-3 M-1 s-1, (8.5 +/- 1.2) x 106 M-1 s-1 and (5.5 +/- 0.9) x 104 M-1 s-1, respectively. The determined initiation rate constant was in good agreement with the literature value (6.0 x 104 M-1 s-1), confirming the validity of the proposed approach. For methyl 2-bromopropionate, under the same conditions, ka, kd, and ki values were found to be (26 +/- 5.9) x 10-3 M-1 s-1, (29 +/- 7.3) x 106 M-1 s-1, and (5.7 +/- 1.6) x 104 M-1 s-1, respectively.

The crystal structure of a novel compound Cu(II)(dNbpy)Br(2) (dNbpy = 4,4'-di(5-nonyl)-2,2'-bipyridine), which is used in the reverse atom transfer radical polymerization, is reported. Cu(II)(dNbpy)Br(2) crystallizes in the triclinic P1 space group with a = 12.5283(11) A, b = 15.0256(14) A, c = 17.7900(16) A, alpha = 90.350(2) degrees, beta = 99.360(2) degrees, gamma = 107.937(2) degrees, and Z = 2. The Cu(II) center in the complex has a distorted square planar geometry and is coordinated by two nitrogen atoms of a single dNbpy ligand (Cu-N = 2.011(7) and 2.022(7) A) and two bromine atoms (Cu-Br = 2.3621(14) and 2.3567(13) A). The similarity of the absorption spectra in the solid state and in solution suggested that the geometry of the complex remained unchanged upon dissolution. In the presence of dNbpy, Cu(II)(dNbpy)Br(2) undergoes Br substitution to form ionic [Cu(II)(dNbpy)(2)Br](+)[Br](-). DeltaH degrees and DeltaS degrees values for this equilibrium were negative and dependent on the polarity of the medium. It was found that, under the typical polymerization conditions (T > or =90 degrees C and the total copper concentration in the range 1.0 x 10(-2)-1.0 x 10(-1) M), Cu(II)Br(2) and 2 equiv of dNbpy will predominantly form the neutral Cu(II)(dNbpy)Br(2) complex. In a polar medium under the same conditions, [Cu(II)(dNbpy)(2)Br](+)[Br](-) is preferred.

We report an electrospray ionization mass spectrometric study of Cu(I) and Cu(II) bipyridine complexes employed in atom transfer radical polymerization. Mass spectra of Cu(I)Br complexed with 2 equiv. of 4,4'-di(5-nonyl)-2,2'-bipyridine (dNbpy) in toluene, methyl acrylate or styrene showed the presence of [Cu(I)(dNbpy)(2)](+) cation and [Cu(I)Br(2)](-) anion. For the Cu(II)Br(2)/2dNbpy system, [Cu(II)(dNbpy)(2)Br](+), [Cu(II)(dNbpy)Br](+), [Cu(I)Br(2)](-), [Cu(II)Br(3)](-) and [Cu(II)(dNbpy)Br(3)](-) species were observed. In addition, for mixed Cu(I)Br/2dNbpy and Cu(II)Br(2)/2dNbpy systems, the negative ion mode showed only the presence of [Cu(I)Br(2)](-) anions, which are potentially formed through halogen exchange between [Cu(II)Br(3)](-) and [Cu(I)(dNbpy)(2)](+). Copyright 2000 John Wiley & Sons, Ltd.

The effects of copper(I) and copper(II) metal centers on the atom transfer radical polymerization (ATRP) of styrene and methyl acrylate were investigated. The free-radical polymerizations were initiated by AIBN in the presence of copper(I) and copper(II) complexes. For methyl acrylate, the rate of the polymerization was reduced in the presence of CuIBr/dNbpy and CuIOTf/dTbpy but was unaffected by the presence of CuII(OTf)2/dTbpy. For styrene, under conditions which yield relatively low molecular weight polymer (16 000), no effect was observed in the presence of CuII(OTf)2/dNbpy; however, under conditions which yield high molecular weight polystyrene (50 000-100 000), the polymerization was limited in the molecular weight attainable and stopped at partial conversion. No effect was observed for the free-radical polymerization of styrene in the presence of copper(I) complexes. These results indicate that control in ATRP does not originate in interactions of growing radicals with copper complexes but in the reversible halogen atom transfer.

Copper-catalyzed atom transfer radical polymerization (ATRP) is one of the most robust and precise techniques for controlling radical polymerization. The very good control of molecular weights, polydispersities, functionalities, chain composition, and topologies unusual for radical systems combined with the application of transition metals as catalysts requires more detailed mechanistic studies and proof of the radical nature of active species. The following results are in agreement with the radical nature of ATRP: reverse ATRP, chemoselectivities similar to those for conventional radical polymerization (effect of additives and inhibitors/scavengers, reactivity ratios, transfer coefficients), regioselectivities similar to those for conventional radical polymerization (low proportion of head-to-head units and expected structure of both tail and head end groups), stereoselectivities (tacticities) similar to that in conventional radical polymerization, EPR detection of X-Mtn+1 species resulting from the persistent radical effect, and confirmation of the termination by doubling molecular weights as well as cross-linking with multifunctional initiators and inimers. In addition, it seems that, in most ATRP systems, the contribution of degenerative transfer and reversible formation of organometallic intermediates is small and a halogen atom is transferred in the concerted process rather than in a two-step process with the involvement of radical anions.

A radical polymerization process that yields well-defined polymers normally obtained only through anionic polymerizations is reported. Atom transfer radical polymerizations of styrene were conducted with several solubilizing ligands for the copper(I) halides: 4,4'-di-tert-butyl, 4,4'-di-n-heptyl, and 4,4'-di-(5-nonyl)-2,2'-dipyridyl. The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities (ratio of the weight-average to number-average molecular weights of 1.04 to 1.05). Similar results were obtained for the polymerization of acrylates.

Some Bromothymol Blue derivatives with a nitro, amino, isothiocyanato or sulfonamide group substituted on the sulfonated ring of the dibromothymolsulfonephthalein have been studied spectrometrically. All the dyes have two characteristic absorption peaks which can be used to measure pH in the physiological range. The molar absorptivities, wavelengths of maximum absorption and pK(a) values have been determined from the absorbances, and are similar for all four dyes.