Latex and hollow particles of reactive polypyrrole: preparation, properties, and decoration by gold nanospheres

Polypyrrole-coated polystyrene latex particles bearing reactive N-amino functional groups (PS-PPyNH2) were prepared by the in-situ copolymerization of pyrrole (Py) and the active amino-functionalized pyrrole (PyNH2) in the presence of 1.33 microm-diameter polystyrene (PS) latex particles. These particles were prepared by dispersion polymerization of styrene using poly(N-vinylpyrrolidone), PNVP, as a steric stabilizer. The functionalized polypyrrole-coated PS particles (PS-PPyNH2) were characterized in terms of their particle size and surface morphology using transmission electron microscopy (TEM). Infrared and X-ray photoelectron spectroscopy (XPS) detected pyrrole-NH2 repeat units at the surface of the latex particles, indicating that this monomer had indeed copolymerized with pyrrole. The core-shell structure of the PS-PPyNH2 particles was confirmed by etching the polystyrene core in THF, leading to the formation of hollow conducting polymer capsules. The PS-PPyNH2 particles were then decorated with citrate-stabilized gold nanoparticles via electrostatic interactions. Furthermore, etching of the polystyrene core resulted in the formation of gold-decorated PPyNH2 hollow capsules.     

Acetal‐functionalized polymer particles useful for immunoassays. II. Surface and colloidal characterization

Monodisperse polymer colloids with dimethyl and diethyl acetal functionalities were synthesized by a two‐step emulsion polymerization process. The first step consisted of a batch emulsion homopolymerization of styrene (St). The dimethyl and diethyl acetal functionalities were obtained by batch emulsion terpolymerization of St, methacrylic acid (MAA), and methacrylamidoacetaldehyde dimethyl acetal (MAAMA) or methacrylamidoacetaldehyde diethyl acetal (MAADA) in the second step, onto the previously formed polystyrene latex particles. The latexes were characterized by TEM and conductimetric titration, in order to obtain the particle size distribution and the amount of carboxyl and acetal groups on the surface, respectively. The chemical stability of the functionalized surface groups during the storage time was analyzed. The hydrophilic character of the surface of the polymer particles was determined by means of nonionic emulsifier titration. The colloidal stability of the synthesized latexes was studied by measuring the critical coagulation concentration (CCC) against KBr electrolyte, and the existence of a hairy layer on the surface of the latex particles was analyzed by measuring the hydrodynamic particle diameter at several electrolyte concentrations. The surface functionalized groups remained stable for 2 years. The relative hydrophilic character and the colloidal stability were affected by the pH of the medium. On the other hand, the higher the surface charge, the larger the thickness of the hairy layer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 501–511, 1999     

Synthesis of anisotropic nanoparticles by seeded emulsion polymerization

Anisotropic polystyrene nanoparticles of diameters below 0.5 microm were prepared by coating the surface of cross-linked polystyrene latex particles with a thin hydrophilic polymer layer prior to swelling the particles with styrene and then initiating second-stage free-radical polymerization. Conditions were found so that all particles had uniform asymmetry. The effect of surface chemistry on the development of particle anisotropy during seeded emulsion polymerization of sub-0.5 microm diameter particles was studied. The extent and uniformity of the anisotropy of the final particles depended strongly on the presence of the hydrophilic surface coating. Systematic variation of the degree of hydrophilicity of the surface coating provided qualitative insight into the mechanism responsible for anisotropy. Conditions were chosen so that the surface free energy favored the extrusion of a hydrophobic bulge of monomer on the hydrophilic surface of the particle during the swelling phase: the presence of a hydrophilic layer on the particle surface causes this asymmetry to be favored above uniform wetting of the particle surface by the monomer. Kinetic effects, arising from the finite time required for the seed to swell with the monomer, also play a role.     

Grafting of amino functional monomer onto initiator-modified polystyrene particles

Polystyrene nanoparticles with grafted chains of an amino functionalized polymer were prepared by a two-step polymerization process. In the first step, the polystyrene seed particles were synthesized by the conventional batch emulsion polymerization using terpolymer HAS (hydroperoxide monomer, acrylic acid, and styrene) as a surface-active initiator. The surface of the obtained particles contains carboxyl groups, which are responsible for the latex stability, and residual undecomposed hydroperoxide groups. Therefore, in the second step, an amino functional monomer was grafted onto the hydroperoxide modified polystyrene particles by a "grafting from" approach. X-ray photoelectron spectroscopy, NMR, and scanning electron microscopy were used to examine the surface of the amino functionalized particles. The amount of incorporated amino groups onto the particles was determined by fluorescenometric titration. In general, the number of amino groups on the particle surface increased with the increase of the functional monomer content in the reaction mixture. The incorporation of the functional monomer was also confirmed by electrophoretic measurements. Final particles possess amphoteric character due to the presence of amino and carboxyl groups on the surface. Adsorption of human immunoglobulins G onto the amino functionalized particles was studied as a function of pH and ionic strength. The covalent binding of human IgG was performed using the glutaraldehyde preactivation method. The immunoreactivity of the latex-IgG complex was examined by the latex agglutination test.     

Synthesis of gold–poly(methyl methacrylate) core–shell nanoparticles by surface‐confined atom transfer radical polymerization at elevated temperature

Surface‐confined atom transfer radical polymerization was used to prepare gold nanoparticle–poly(methyl methacrylate) core–shell particles at elevated temperature. First, gold nanoparticles were prepared by the one‐pot borohydride reduction of tetrachloroaurate in the presence of 11‐mercapto‐1‐undecanol (MUD). MUD‐capped gold nanoparticles were then exchanged with 3‐mercaptopropyltrimethoxysilane (MPS) to prepare a self‐assembled monolayer (SAM) of MPS on the gold nanoparticle surfaces and subsequently hydrolyzed with hydrochloric acid. The extent of exchange of MUD with MPS was determined by NMR. The resulting crosslinked silica‐primer layer stabilized the SAM of MPS and was allowed to react with the initiator [(chloromethyl)phenylethyl] trimethoxysilane. Atom transfer radical polymerization was conducted on the Cl‐terminated gold nanoparticles with the CuCl/2,2′‐bipyridyl catalyst system at elevated temperature. The rates of polymerization with the initiator‐modified gold nanoparticles exhibited first‐order kinetics with respect to the monomer, and the number‐average molecular weight of the cleaved graft polymer increased linearly with the monomer conversion. The presence of the polymer on the gold nanoparticle surface was identified by Fourier transform infrared spectroscopy and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3631–3642, 2005     

Synthesis of P(AA‐SA)/ZnO composite latex particles via inverse miniemulsion polymerization and its application in pH regulation and UV shielding

Poly(acrylic acid‐co‐sodium acrylate)/zinc oxide, P(AA‐SA)/ZnO, composite latex particles were synthesized by inverse miniemulsion polymerization. The ZnO nanoparticles were prepared by hydrothermal synthesis and undergone oleic acid (OA) surface treatment. The X‐ray diffraction pattern and FT‐IR spectra characterized the crystal structure and functional groups of OA‐ZnO nanoparticles. An appropriate formulation in preparing P(AA‐SA) latex particles, ensuring the dominant in situ particle nucleation and growth, was developed in our experiment first. Sodium hydroxide was chosen as a costabilizer, because of its ability to increase the deprotonation of acylic acid and enhance the hydrophilicity of monomer, acrylic acid besides providing osmotic pressure. The growth mechanism of P(AA‐SA)/ZnO composite particles was proposed. The OA‐ZnO nanoparticles were adsorbed on or around the surface of P(AA‐SA) latex particles by hydrophobic interaction, thus enhanced the interfacial tension over latex particles. The P(AA‐SA)/ZnO composite latex particles owned better thermal stability than pure latex particles. The pH regulation capacity was excellent for both ZnO and P(AA‐SA) particles. Combining P(AA‐SA) and ZnO nanoparticles into composite particles, the performance in pH regulation and UV shielding was discussed from our experimental results. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8081–8090, 2008     

Hydrazine‐functionalized latexes

The noncommercial functional monomer 4‐vinylbenzyl hydrazine (VBH) was synthesized and subsequently copolymerized with styrene (St) by means of different batch and semicontinuous seeded emulsion polymerization processes, so as to obtain hydrazine‐functionalized nanoparticles. The effect of pH, surfactant and initiator amounts, ratio VBH/St, reaction temperature, and ratio acetone/water were studied. Due to the amphiphilic character of VBH at acid pH, the hydrazine groups of the functionalized comonomer were masked with acetone to form hydrazone groups. Secondary nucleations were avoided by using the protected VBH comonomer; however, a decreased radical efficiency achieving limited conversion was observed. Controlling the cationic initiator concentration, complete conversions together with the neat growth of the seed particles were obtained in the semicontinuous seeded emulsion polymerization of styrene and VBH protected with acetone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6201–6213, 2009     

Tailoring of carboxyl‐decorated magnetic latex particles using seeded emulsion polymerization

In this research, submicron and carboxyl‐functionalized magnetic latex particles were elaborated by using seeded emulsion polymerization technique in presence of oil‐in‐water (o/w) magnetic emulsion as seed. The polymerization conditions were optimized in order to get well‐defined latex particles with magnetic core and polymer shell bearing carboxylic (–COOH) functionality. Starting from (o/w) magnetic emulsion as seed, synthesis process was performed by copolymerization of styrene (St) monomer with the cross‐linker divinylbenzene (DVB) in presence of 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as a carboxyl‐bearing initiator. The prepared magnetic latex particles were first characterized in terms of particle size, chemical composition, morphology, magnetic properties, magnetic content, and colloidal stability using various techniques, e.g. particle size analyzer using dynamic light scattering (DLS) technique, Fourier transform infrared, transmission electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, and zeta potential measurements as a function of pH of the dispersion media, respectively. The prepared magnetic latex particles were then used as second seed for further functionalization with methacrylic acid (MAA) in order to enhance carboxylic groups on the magnetic particle's surface. The results showed that final magnetic latex particles possessed spherical morphology with core‐shell structure and enriched carboxylic acid functionality. More importantly, they exhibited superparamagnetism with high magnetic content (58.42 wt%) and high colloidal stability, which considered as the main requirements for their application in the biomedical diagnostic domains. Copyright © 2017 John Wiley & Sons, Ltd.     

Polymerization of styrene with ionic comonomer,nonionic comonomer,or both

Nanosized polystyrene latexes with high polymer contents were obtained from an emulsifier-free process by the polymerization of styrene with ionic comonomer, nonionic comonomer, or both. After seeding particles were generated in an initial emulsion system consisting of styrene, water, an ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2-hydroxyethyl methacrylate (HEMA)], and potassium persulfate, most of the styrene monomer or a mixture of styrene and HEMA was added dropwise to the polymerizing emulsion over 6 h. Stable latexes with high polystyrene contents (≤25%) were obtained. The latex particle weight-average diameters were largely reduced (41 nm) by the continuous addition of monomer(s) compared with those (117 nm) obtained by the one-pot polymerization method. Latex particles varied from about 30 to 250 nm in diameters, whereas their molar masses were within 10⁴ to 10⁵ g/mol. The effect of the comonomer concentration on the number of polystyrene particles per milliliter of latex and the weight-average molar masses of the copolymers during the polymerization are discussed. The surface compositions of the latex particles were analyzed by X-ray photoelectron spectroscopy, which indicated that the surface of the latex particles was significantly enriched in NaSS, HEMA, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1634–1645, 2001     

Functional colloidal particles stabilized by layered silicate with hydrophilic face and hydrophobic polymer brushes

In this study, we describe a new strategy for producing narrowly dispersed functional colloidal particles stabilized by a nanocomposite with hydrophilic clay faces and hydrophobic polystyrene (PS) brushes on the edges. This method involves preparation of polymer brushes on the edges of clay layers and Pickering suspension polymerization of styrene in the presence of the nanocomposites. PS brushes on the edges of clay layers were prepared by atom transfer radical polymerization. X‐ray diffraction and thermogravimetric analysis results indicated that PS chains were grafted to the edges of clay platelets. Transmission electron microscope results showed that different morphologies of clay‐PS particles could be obtained in different solvents. In water, clay‐PS particles aggregated together, in which PS chains collapsed forming nanosized hydrophobic domains and hydrophilic clay faces stayed in aqueous phase. In toluene, clay‐PS particles formed face‐to‐face structure. Narrowly dispersed PS colloidal particles stabilized by clay‐PS were prepared by suspension polymerization. Because of the negatively charged clay particles on the surface, the zeta potential of the PS colloidal particles was negative. Positively charged poly(2‐vinyl pyridine) (P2VP) chains were adsorbed to the surface of PS colloidal particles in aqueous solution at a low pH value, and gold nanoparticles were prepared in P2VP brushes. Such colloidal particles may find important applications in a variety of fields including waterborne adhesives, paints, catalysis of chemical reactions, and protein separation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1535–1543, 2009     

Ultrahigh molecular weight polyethylene produced by a bis(phenoxy‐imine) titanium complex supported on latex particles

The applicability of latex particle supports for non‐Cp type metallocene catalysts for ethylene polymerization is presented. Polystyrene latex particles were prepared by miniemulsion polymerization and functionalized with poly(ethyleneoxide)chains and pyridyl groups on the surface. These latex particles were chosen to demonstrate that a support with nucleophilic substituents on the surface can act as a carrier for a (phenoxy‐imine) titanium complex (titanium FI‐catalyst) to produce ultrahigh molecular weight polyethylene (UHMWPE). The composition of the support, the concentration of pyridyl groups on the surface, and the crosslinking of the support were optimized to provide a system where the FI‐catalyst resulted in the formation of polyethylene with a M_w of more than 6,000,000 and a relatively narrow molecular weight distribution of 3.0 ± 0.5. High activities for long polymerization times greater than 6 h resulted in a catalyst system exhibiting productivities of up to 15,000 g PE/g cat. or 7,000,000 g PE/g Ti. The resulting polymer properties showed that nucleophilic groups on the latex particle support did not negatively impact the catalyst by blocking the active site but instead created a stable environment for the titanium catalyst. In particular, pyridyl groups on the surface of the latex particle stabilized the catalyst system probably by trapping trimethylaluminium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3103–3113, 2006     

A kinetic investigation of surfactant‐free emulsion polymerization of styrene using laponite clay platelets as stabilizers

We report the kinetics and mechanism of soap‐free emulsion polymerization of styrene using laponite platelets as stabilizers. The polymerization was initiated by potassium persulfate and the latex particles were stabilized by laponite platelets dispersed in water. Laponite adsorption on the polymer particles was enhanced by the addition of poly(ethylene glycol) monomethylether methacrylate (PEGMA). Particle nucleation can be described using the classical homogeneous nucleation mechanism followed by coagulation of unstable precursors. Oligomeric radicals formed in the water phase become insoluble and precipitate on the laponite surface leading to primary precursor particles composed of a few polymer chains and one or several clay platelets. Mature latex particles are then generated by coagulation and growth of the previously formed precursor particles. Both the nucleation and initial aggregation rates increased in the presence of PEGMA. Calorimetric monitoring of the polymerization allowed estimating the heat produced by the reaction and the monomer conversion. Hence, using the monomer material balance, the number of radicals in the polymer particles could be estimated precisely. The average number of radicals per particle, $ \bar n $ , was found to be high in the range 3–6. This result was attributed to strong attractive interactions between the growing radicals and the clay surface. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis of amino‐functionalized latex particles by a multistep method

Cationic latex particles with surface amino groups were prepared by a multistep batch emulsion polymerization. In the first one or two steps, monodisperse cationic latex particles to be used as the seed were synthesized, and in the third step, two different amino‐functionalized monomers [aminoethylmethacrylate hydrochloride (AEMH) and vinylbenzylamine hydrochloride (VBAH)] were used to synthesize the final functionalized latex particles. 2,2′‐Azobisisobutyramidine dihydrochloride was used as the initiator, and different concentrations of two quaternary ammonium emulsifiers with hydrophobic chains of different lengths were examined. To characterize the final latexes yields were obtained gravimetrically, and particle size distributions and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The amount of amino groups was determined by fluorimetry. The effect of the amino‐functional monomer used on the final latexes and the colloidal behavior of the system were studied. The influence of the different conditions utilized to synthesize the latexes on the colloidal stability of the particles was evaluated in terms of the Fuchs stability ratio and electrophoretic mobility. High yields of the amino‐functional monomers were obtained. Surface amino, amidine, and quaternary ammonium groups provided the cationic character. The colloidal stability behavior of the products obtained was compatible with their cationic character. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2929–2936, 2001     

Immobilization of RAFT agents on silica nanoparticles utilizing an alternative functional group and subsequent surface‐initiated RAFT polymerization

Silica–polystyrene core‐shell particles were successfully prepared by surface‐mediated reversible addition fragmentation chain transfer (RAFT) polymerization of styrene monomer from the surfaces of the silica‐supported RAFT agents. Initially, macro‐RAFT agents were synthesized by RAFT polymerization of γ‐methacryloxypropyltrimethoxysilane (MPS) in the presence of chain transfer agents (CTAs). Immobilization of CTAs onto the silica surfaces was then performed by reacting silica with macro‐RAFT agents via a silane coupling. Grafting of polymer onto silica forms core‐shell nanostructures and shows a sharp contrast between silica core and polymer shell in the phase composition. The thickness of grafted‐polymer shell and the diameter of core‐shell particles increase with the increasing ratio of monomer to silica. A control experiment was carried out by conventional free radical emulsion copolymerization of MPS‐grafted silica and styrene under comparable conditions. The resulting data provide further insight into the chemical composition of grafted‐polymers that are grown from the silica surface through RAFT process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 467–484, 2009     

Preparation and characterization of biotinylated and enzyme‐immobilized heterobifunctional latex particles as nanobio devices

A novel biotinylated and enzyme‐immobilized nanobio device was prepared with heterobifunctional composite latex particles. Hemispherical poly(glycidyl methacrylate‐co‐divinylbenzene)/polystyrene [P(GMA‐DVB)/PSt] particles with epoxy and hydroxyl groups were prepared by soap‐free seeded emulsion polymerization with P(GMA‐DVB) seed particles. Hydroxyl groups were introduced to PSt chain terminals in the seeded stage by adding 2‐mercaptoethanol as a chain‐transfer agent. To obtain the desired hemispherical structure particles, we studied the effects of the preswelling process, the type and amount of solvents added in the seeded polymerization step, the weight ratio of the secondary monomer (styrene) to the seed particle (M/P), and the type of initiators. Under suitable conditions, heterobifunctional P(GMA‐DVB)/PSt was obtained, which was confirmed by observing the binding of streptavidin–colloidal gold with transmission electron microscopy (TEM). To obtain biotinylated and enzyme‐immobilized particles, 5‐(N‐succinimidyloxycarbonyl)pentyl D‐biotinamide was first reacted with the hydroxyl group on the PSt domain of the particle. Pyruvate kinase (PK) was then directly immobilized to the biotinylated particles through a reaction with the epoxy group in the PGMA domain. The monolayer of PK on the latex particle surface was considered to be formed by covalent binding. The activity of immobilized PK was almost conserved, even after being stored at 4 °C for 48 days. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 562–574, 2005     

Surface modification of iron oxide nanoparticles by a phosphate‐based macromonomer and further encapsulation into submicrometer polystyrene particles by miniemulsion polymerization

A new strategy relying on the use of a phosphate‐based macromonomer (PAM200) to modify the surface of iron oxide nanoparticles was developed for the synthesis of submicrometer polystyrene (PS) magnetic particles. First, iron oxide nanoparticles were synthesized using the coprecipitation of ferrous and ferric salts in alkaline medium. Besides the classical oleic acid (OA)/octane‐based ferrofluid, styrene‐based ferrofluids were elaborated with either OA or PAM200 as the stabilizer. In all cases, maghemite (γ‐Fe₂O₃) was clearly identified, with nanoparticles rather spherical in shape but exhibiting broad particle size distribution (PSD). Both OA and PAM200 led to stable maghemite‐based ferrofluids showing superparamagnetic properties. Further use of these ferrofluids in styrene miniemulsion polymerization resulted in inhomogeneous distribution of maghemite among and inside the polymer particles with OA‐based ferrofluids, whereas PAM200/styrene‐based ferrofluids led to magnetic particles with homogeneous distribution of maghemite inside PS particles. Broad PSD and small nonmagnetic particles were however observed. The true mechanisms operating in these systems are still to elucidate, but this study validates PAM200 as an efficient compatibilizing agent between hydrophilic maghemite and hydrophobic PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 327–340, 2008     

Effect of an anionic monomer on the pickering emulsion polymerization stabilized by titania hydrosol

Polystyrene (PS) nanocomposite particles with high titania content are prepared by Pickering emulsion polymerization. A self‐made titania hydrosol modified by an anionic monomer sodium styrene sulfonate (NaSS) is used as a stabilizer and photocatalyst. The stability of the emulsion system is greatly improved by the electrostatic interaction between negatively charged NaSS and positively charged titania nanoparticles. The nanocomposite spheres with the diameter of around 120 nm are highly charged, indicating titania‐rich surfaces of latex particles. It is also proven by the field‐emission transmission electron microscope and field‐emission scanning electron microscope images. The well‐defined core‐shell structure of the obtained PS/titania composite particles is confirmed by the formation of fragile hollow titania nanospheres after thermogravimetric analysis tests. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5728–5736, 2009     

Synthesis of azide‐functionalized nanoparticles by microemulsion polymerization and surface modification by click chemistry in aqueous medium

Stable translucent aqueous suspensions of azide‐functionalized cross‐linked nanoparticles (NPs), with diameters in the 15–20 nm range, were prepared using two synthetic approaches. Copolymerization of azidomethylstyrene (VBN₃), styrene, and divinylbenzene in various oil‐in‐water microemulsions led to NPs with modulable azide contents (0.53–0.78 mmol/g) and surface over volume distributions. Surface modifications of reactive NPs bearing chlorobenzyl groups, produced by microemulsion copolymerization of vinylbenzylchloride, with sodium azide led to azido‐coated NPs with high densities of peripheral groups (0.13–0.45 mmol/g). It is shown that the nature of the surfactant used for the preparation of the microemulsion has an impact on the incorporation of VBN₃ in the polymer particles as well as on the surface reaction yield. The azide‐functionalized NPs were used as clickable polymeric scaffolds for the grafting of sparingly water‐soluble dansyl and fluorescein derivatives through copper(I)‐catalyzed azide‐alkyne cycloaddition in water in the presence of surfactants as solubilizing agents to produce fluorescent NPs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Gold nanoshells on polystyrene cores for control of surface plasmon resonance

A method is presented for synthesizing core-shell structures consisting of monodisperse polystyrene latex nanospheres as cores and gold nanoparticles as shells. Use of polystyrene spheres as the core in these structures is advantageous because they are readily available commercially in a wide range of sizes, and with dyes or other molecules doped into them. Gold nanoparticles, ranging in size from 1 to 20 nm, are prepared by reduction of a gold precursor with sodium citrate or tetrakis(hydroxymethyl)phosphonium chloride (THPC). Carboxylate-terminated polystyrene spheres are functionalized with 2-aminoethanethiol hydrochloride (AET), which forms a peptide bond with carboxylic acid groups on their surface, resulting in a thiol-terminated surface. Gold nanoparticles then bind to the thiol groups to provide up to about 50% coverage of the surface. These nanoparticles serve as seeds for growth of a continuous gold shell by reduction of additional gold precursor. The shell thickness and roughness can be controlled by the size of the nanoparticle seeds as well as by the process of their growth into a continuous shell. By variation of the relative sizes of the latex core and the thickness of the gold overlayer, the plasmon resonance of the nanoshell can be tuned to specific wavelengths across the visible and infrared range of the electromagnetic spectrum, for applications ranging from the construction of photonic crystals to biophotonics. The position and width of the plasmon resonance extinction peak are well-predicted by extended Mie scattering theory.     

Pluronics‐Stabilized Gold Nanoparticles: Investigation of the Structure of the Polymer–Particle Hybrid

Hybrid gold–polymer nanoparticles are obtained by self‐assembly of amphiphilic copolymers (Pluronics) in solutions containing preformed gold nanoparticles (diameter ca. 12 nm). Dynamic light scattering, TEM, cryo‐TEM, and small‐angle neutron scattering experiments with contrast variation are used to characterize the structure of the gold–polymer particles. Five Pluronics (F127, F68, F88, F108, P84) with different molecular weights and hydrophilic/hydrophobic balances are investigated. Gold nanoparticles are individually embedded within globules of polymer, even under conditions for which Pluronics micelles do not form in solution. The hybrid particles are several tens of nanometers in size (larger than micelles of the corresponding Pluronics), and the size can be tuned by changing the temperature.