Star Block Copolymers Research Articles

Amphiphilic Fluorine-Containing Block Copolymers as Carriers for Hydrophobic PtTFPP for Dissolved Oxygen Sensing, Cell Respiration Monitoring and In Vivo Hypoxia Imaging with High Quantum Efficiency and Long Lifetime.

New amphiphilic star or multi-arm block copolymers with different structures were synthesized for enabling the use of hydrophobic oxygen probe of platinum (II)-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) for bioanalysis. The amphiphilic star polymers were prepared through the Atom Transfer Radical Polymerization (ATRP) method by using hydrophilic 4-arm polyethylene glycol (4-arm-PEG) as an initiator. Among the five block copolymers, P1 series (P1a, P1b, and P1c) and P3 possess fluorine-containing moieties to improve the oxygen sensitivity with its excellent capacity to dissolve and carry oxygen. A polymer P2 without fluorine units was also synthesized for comparison. The structure-property relationship was investigated. Under nitrogen atmosphere, high quantum efficiency of PtTFPP in fluorine-containing micelles could reach to 22% and long lifetime could reach to 76 μs. One kind of representative PtTFPP-containing micelles was used to detect the respiration of Escherichia coli (E. coli) JM109 and macrophage cell J774A.1 by a high throughput plate reader. In vivo hypoxic imaging of tumor-bearing mice was also achieved successfully. This study demonstrated that using well-designed fluoropolymers to load PtTFPP could achieve high oxygen sensing properties, and long lifetime, showing the great capability for further in vivo sensing and imaging.

Effect of Ionic Liquids as Cosurfactants on Photoinduced Electron Transfer in Tetronic Micelles.

This study investigates the role of varying alkyl chain lengths of a series of surface-active 1-alkyl-3-methylimidazolium tetrafluoroborate ([C nMIm][BF4], n = 4, 6, and 10) ionic liquids (ILs) as cosurfactants in modifying the micellar characteristics of a tetronic star-block copolymer, T1304, and the consequent effects on bimolecular photoinduced electron transfer (PET) reactions carried out in these T1304-IL mixed micellar systems. Using coumarin 153 as the probe dye and following ground-state absorption, steady-state fluorescence, and time-resolved emission measurements, the micropolarity, microviscosity, and solvent relaxation dynamics in the micellar palisade layer have been revealed both in pure T1304 and in T1304-IL systems. With increasing alkyl chain length of the ILs, the palisade layer of the micelles gradually becomes more polar and less viscous, suggesting better incorporation of the longer alkyl chain length ILs as cosurfactants into the T1304 micelles. The bimolecular PET reactions, involving 7-aminocoumarins as acceptors and N, N-dimethylaniline as the donor, are considerably modulated in T1304 micelles by the presence of the ILs, the effect being more prominent for ILs with longer alkyl chain lengths. In all of the micellar systems, correlations of the electron transfer (ET) kinetics with the reaction exergonicity (-Δ G0) show clear Marcus inversion (MI) behavior where onsets of MI invariably appear at significantly lower exergonicities, suggesting the involvement of a two-dimensional ET mechanism. Interestingly, the Marcus correlations display significant variations, namely, enhanced reaction rates and gradual shift in the onset of MI toward higher exergonicity, as longer alkyl chain length ILs are sequentially introduced as cosurfactants. From the observed results, it is convincingly realized that 1-alkyl-3-methylimidazolium-based ILs can be used satisfactorily as cosurfactants in tetronic star-block copolymer solutions to modulate PET reactions very significantly for their better utilizations in suitable applied areas.

AB2-type miktoarm poly(l-lactide)-b-poly(N-acryloylmorpholine) amphiphilic star block copolymers as nanocarriers for drug delivery

In this study, a series of amphiphilic AB2-type miktoarm star block copolymers consisting of hydrophobic poly(l-lactide) (PLLA) as a A arm and hydrophilic poly(N-acryloylmorpholine) (PNAM) as two B arms were synthesized via the combination of ring opening polymerization and xanthate-mediated reversible addition-fragmentation chain transfer polymerization. Resultant polymers were analyzed by 1H NMR spectroscopy and gel permeation chromatography. Aggregation properties of the amphiphilic miktoarm star block copolymers were studied by fluorescence spectroscopy, transmission electron microscopy and dynamic light scattering. Doxorubicin (DOX) was successfully loaded into the miktoarm star block copolymer micelles and the DLC and DLE of the DOX-loaded micelles increased (9.4 to 13.6% and 55.6 to 78.7%) with an increase in the hydrophilic PNAM chain length of the miktoarm star block copolymer. The result revealed that DOX release was enhanced as the pH reduced from 7.4 to 6.4 and the rate of release slightly increased with increasing the PNAM hydrophilic chain length of the micelles.

Self-Alignment of Cylinder-Forming Silicon-Containing Block Copolymer Films

Well-ordered perpendicular cylinders of star-block copolymers (BCPs) composed of polystyrene and poly(dimethylsiloxane) blocks with high aspect ratio can be achieved by using a combination of architecture effect (entropy effect) and surface air plasma treatment (enthalpy effect). An interesting morphological evolution from disordered texture to hexagonally packed cylinders with perpendicular orientation has been observed, in which perpendicular cylinders are initiated at the top surface and bottom substrate of the thin film, followed by a self-alignment process, resulting in span-thru cylinders through the thin film. The self-alignment process is systematically examined by a combination of real space imaging using transmission electron microscopy, reciprocal space imaging using grazing incidence small-angle X-ray scattering, and three-dimensional tomography. The experimental results reveal a unique mechanism for the formation of highly ordered BCP thin films via surface-induced nucleation of perpendicular...

Synthesis of miktoarm star-shaped and inverse star-block copolymers by a combination of ring-opening polymerization and click chemistry

Abstract Based on the combination of the “arm-first” and “core-first” strategies, the miktoarm star-shaped copolymer PLLA2PCL2 and the inverse star-block copolymer (PCL-b-PLLA)2-core-(PCL-b-PLLA)2 were designed and synthesized by the combination of ring-opening polymerization (ROP) and a click reaction. The miktoarm star-shaped copolymer PLLA2PCL2 was synthesized by a click reaction of an azido macroinitiator PLLA2(N3)2 and HC≡C-PCL. The inverse star-block copolymer (PCL-b-PLLA)2-core-(PCL-b-PLLA)2 was synthesized by a click reaction of an azido macroinitiator (PCL-b-PLLA)2(N3)2 and HC≡C-PCL-b-PLLA. The structures of these star polymers were confirmed by nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy and gel permeation chromatograph (GPC). The inverse star-block copolymer could be used to study the potential relationship between polymer structure and properties, which has a unique structure and good crystallization properties.

Synthesis of a double-hydrophilic star-block copolymer by aqueous SET-LRP and its dual-stimuli responses

The synthesis of a well-defined dual-responsive double-hydrophilic star-block copolymer by single-electron-transfer living radical polymerization (SET-LRP) in aqueous solution is reported. Conditions for iterative block formation have been optimized for an N-isopropylacrylamide three-armed star-shaped polymer, which was prepared with DP = 120–360 with full conversion in < 30 min with polydispersity index (Ð) < 1.18. To demonstrate this approach for true block stimuli-responsive copolymer materials, a well-defined block polymer containing N-isopropylacrylamide, dimethylaminoethyl methacrylate, and N-vinylpyrrolidone has been prepared in high purity, with purification only required in the final step. The Ð after each chain extension was below 1.20. The polymer has been characterized by FTIR spectroscopy, 1H NMR spectrometry, and gel permeation chromatography. The responsive behaviors of the block-star copolymer have been studied by turbidity measurements, dynamic light scattering, and transmission electron microscopy. The phase transition temperature of the star-block copolymer increased with decreasing pH. At pH 3.0, the copolymer displayed weak thermo-responsive behavior. At higher pH (8.6 and 10.0), the star-block copolymer showed a strong thermal response and formed spherical micelles and vesicles.

Synthesis of an (AB)4-type Star Block Copolymer of L-lactide and Cyclohexene Oxide from a Tetra-Arm Telechelic Macrophotoinitiator

A multi-step reaction process was applied for the synthesis of a novel and well-defined star-shaped telechelic macrophotoinitiator with four poly(L-lactide) (PLLA) arms bearing photoinitiating benzoin groups at the chain ends (PLLA-PI)4. To achieve this, 2,2-bis(hydroxymethyl)-1,3-propanediol was used as the initiator which constitutes the core of the star-shaped polymeric scaffold. Benzoin photoreactive end groups of the telechelic (PLLA-PI)4, capable of entering into further polymerization, allowed its use as a prepolymer in photoinduced free radical promoted cationic polymerization with cyclohexene oxide (CHO) monomer at l=350 nm to produce an (AB)4-type star-shaped block copolymer composed of both esteric L-lactide and etheric cyclohexene oxide chains on each arm, (PLLA-PCHO)4. Structural analysis and characterization of all intermediate and final compounds were done by a series of analytical and spectral methods. Molecular weights of the prepared polymers up to telechelic macrophotoinitiator (PLLA-PI)4 were determined based on 1H-NMR (Mn H-NMR), GPC (Mn exp) analyses and theoretical calculations (Mn theo) and were found to be in good agreement with each other. The thermal behaviors of the polymers synthesized were investigated by thermogravimetric and differential thermal analysis (TG/DTA). The melting temperature for (PLLA-PCHO)4 was found higher compared to the other homo-type polymers in the literature. The thermogravimetric (TG) analyses showed that introduction of the thermally stable PCHO segment into the structure via photopolymerization increased its stability shifting its decomposition temperature to the higher values compared to the prepolymers.

Rotation Dynamics of Star Block Copolymers under Shear Flow.

Star block-copolymers (SBCs) are macromolecules formed by a number of diblock copolymers anchored to a common central core, being the internal monomers solvophilic and the end monomers solvophobic. Recent studies have demonstrated that SBCs constitute self-assembling building blocks with specific softness, functionalization, shape and flexibility. Depending on different physical and chemical parameters, the SBCs can behave as flexible patchy particles. In this paper, we study the rotational dynamics of isolated SBCs using a hybrid mesoscale simulation technique. We compare three different approaches to analyze the dynamics: the laboratory frame, the non-inertial Eckart’s frame and a geometrical approximation relating the conformation of the SBC to the velocity profile of the solvent. We find that the geometrical approach is adequate when dealing with very soft systems, while in the opposite extreme, the dynamics is best explained using the laboratory frame. On the other hand, the Eckart frame is found to be very general and to reproduced well both extreme cases. We also compare the rotational frequency and the kinetic energy with the definitions of the angular momentum and inertia tensor from recent publications.

Synthesis, self-assembly and micellization characteristics of choline alkanoate ionic liquids in association with a star block copolymer

Herein, alkyl chain dependent self-assembly of choline carboxylate ionic liquids (ILs) and their effect on micellar characteristics of a star block copolymer (Tetronic®T1304) are reported. The ILs showed good aqueous solubility (low Kraft point) and formed spherical micelles. Small angle neutron scattering (SANS) analyses revealed a reduction in the critical micelle concentration (CMC) and elevation in the aggregation number (Nagg) upon increasing alkyl chain length of ILs. More importantly, ILs demonstrated good biocompatibility in murine erythrocytes and A549 cells, irrespective of the chain length.Furthermore, the effect of IL addition on micellar behaviour of T1304 was examined through thermal and scattering studies. We observed alkyl chain dependent increase in the cloud point (CP), critical micellization temperature (CMT), micelle size (Rh, Rc, Rhs) and Nagg. In association with T1304, long chain ILs (n = C12–C18) formed charged mixed micelles with a lower Nagg which showed enhanced solubilization of quercetin, a hydrophobic drug. Mixed micelles, composed with such biocompatible ILs, can further be tuned to explore their drug delivery applications.

Microfluidic-assisted nanoprecipitation of (PEGylated) poly (d,l-lactic acid-co-caprolactone): Effect of macromolecular and microfluidic parameters on particle size and paclitaxel encapsulation

In this work we evaluate the effect of polymer composition and architecture of (PEGylated) polyesters on particle size and paclitaxel (PTX) loading for particles manufactured via microfluidic-assisted, continuous-flow nanoprecipitation using two microfluidic chips with different geometries and mixing principles.We have prepared poly (d,l-lactic acid-co-caprolactone) (PLCL) from ring-opening polymerization (ROP) of LA and CL mixtures and different (macro) initiators (namely, 1-dodecanol, a MeO-PEG-OH, and a 4-armed star PEG-OH), rendering polyesters that vary in monomer composition (i.e. LA/CL ratios) and architecture (i.e. linear vs 4-armed star). Continuous-flow nanoprecipitation was assayed using two microfluidic chips: a cross-flow chip with a X-shaped mixing junction (2D laminar flow focusing) and a micromixer featuring a Y-shaped mixing junction and a split and recombine path (2D laminar flow focusing convinced with stream lamination for faster mixing). Nanoparticle formulations were produced with Z-average sizes in the range of 30–160 nm, although size selectivity could be seen for different polymer/chip combinations; for instance, smaller particles were obtained with Y-shaped micromixer (30–120 nm), specially for the PEGylated polyesters (30–50 nm), whereas the cross-flow chip systematically produced larger particles (80–160 nm). Loading of the anti-cancer drug paclitaxel (PTX) was also heavily influenced not only by the nature of the polyester, but also by the geometry of the microfluidic chip; higher drug loadings were obtained with the cross-flow reactor and the star block copolymers. Finally, decreasing the LA/CL ratio generally had a positive effect on drug loading.

Topology Affecting Block Copolymer Nanoassemblies: Linear Block Copolymers versus Star Block Copolymers under PISA Conditions

Linear and star block copolymer (BCP) nanoassemblies of [poly(4-vinylpyridine)-block-polystyrene]n ([P4VP-b-PS]n) with different arm numbers have been synthesized by RAFT dispersion polymerization under formulation of polymerization-induced self-assembly (PISA). All RAFT dispersion polymerizations employing mono- and multifunctional macromolecular chain transfer agents proceed with similar polymerization kinetics. The size and/or morphology of [P4VP-b-PS]n nanoassemblies are firmly correlative to arm number n, and star [P4VP-b-PS]n BCPs have more complex morphology than the linear counterpart. Several interesting morphologies of star BCPs including small-sized vesicles and porous nanospheres have been synthesized, and they are compared with those of the linear counterpart. Our research indicates that topology is a significant parameter to dedicate the size and morphology of star BCP nanoassemblies under PISA conditions.

Structural Studies of Three-Arm Star Block Copolymers Exposed to Extreme Stretch Suggests a Persistent Polymer Tube.

We present structural small-angle neutron scattering studies of a three-armed polystyrene star polymer with short deuterated segments at the end of each arm. We show that the form factor of the three-armed star molecules in the relaxed state agrees with that of the random phase approximation of Gaussian chains. Upon exposure to large extensional flow conditions, the star polymers change conformation resulting in a highly stretched structure that mimics a fully extended three-armed tube model. All three arms are parallel to the flow, one arm being either in positive or negative stretching direction, while the two other arms are oriented parallel, right next to each other in the direction opposite to the first arm.

Tetronic Star Block Copolymer Micelles: Photophysical Characterization of Microenvironments and Applicability for Tuning Electron Transfer Reactions.

Detailed photophysical investigations have been carried out using a probe dye, coumarin-153 (C153), to understand the microenvironments of micelles formed by the newly introduced Tetronic star block copolymers, T1304 and T1307, having the same poly(propylene oxide) (PPO) block size but different poly(ethylene oxide) (PEO) block sizes. Ground state absorption, steady-state fluorescence, and time-resolved fluorescence measurements have been used to estimate the micropolarity, microviscosity, and solvation dynamics within the two micelles. To the best of our knowledge, this is the first report on these important physicochemical parameters for this new class of the star block copolymer micelles. Our results indicate that T1307 micelle offers a relatively more polar and less viscous microenvironment in the corona region, compared to T1304. The effect of the two micellar systems has subsequently been investigated on the bimolecular photoinduced electron transfer (ET) reactions between coumarin dyes (electron acceptors) and aromatic amines (electron donors). On correlating the energetics and kinetics of the ET reactions, clear Marcus inversion (MI) behavior is observed in both of the micellar media. Interestingly, the ET rates for all of the donor-acceptor pairs are much higher in T1307 than in T1304, and the onset of MI also appears at a relatively higher exergenocity (-Δ G0) in the former micelle (∼0.45 eV for T1307) than the latter (∼0.37 eV for T1304). The effect of added NaCl salt studied selectively in T1307 micelle shows that the ET rate decreases significantly along with a shift in the onset of MI toward lower exergenocity region, so that in the presence of 2 M NaCl the system becomes quite comparable to T1304. On the basis of the observed results, it is realized that the micropolarity and hence the dynamics of the ET process can be tuned very effectively either by changing the constitution of the star block copolymer or by using a suitable additive as a modifier of the micellar microenvironment.

Directed Self-Assembly of Star-Block Copolymers by Topographic Nanopatterns through Nucleation and Growth Mechanism.

Exploring the ordering mechanism and dynamics of self-assembled block copolymer (BCP) thin films under confined conditions are highly essential in the application of BCP lithography. In this study, it is aimed to examine the self-assembling mechanism and kinetics of silicon-containing 3-arm star-block copolymer composed of polystyrene (PS) and poly(dimethylsiloxane) blocks as nanostructured thin films with perpendicular cylinders and controlled lateral ordering by directed self-assembly using topographically patterned substrates. The ordering process of the star-block copolymer within fabricated topographic patterns with PS-functionalized sidewall can be carried out through the type of secondary (i.e., heterogeneous) nucleation for microphase separation initiated from the edge and/or corner of the topographic patterns, and directed to grow as well-ordered hexagonally packed perpendicular cylinders. The growth rate for the confined microphase separation is highly dependent upon the dimension and also the geometric texture of the preformed pattern. Fast self-assembly for ordering of BCP thin film can be achieved by lowering the confinement dimension and also increasing the concern number of the preformed pattern, providing a new strategy for the design of BCP lithography from the integration of top-down and bottom-up approaches.

Star Block-Copolymers in Shear Flow.

Star block-copolymers (SBCs) have been demonstrated to constitute self-assembling building blocks with specific softness, functionalization, shape, and flexibility. In this work, we study the behavior of an isolated SBC under a shear flow by means of particle-based multiscale simulations. We systematically analyze the conformational properties of low-functionality stars, as well as the formation of attractive patches on their corona as a function of the shear rate. We cover a wide range of system parameters, including functionality, amphiphilicity, and solvent quality. It is shown that SBCs display a richer structural and dynamical behavior than athermal star polymers in a shear flow [ Ripoll Phys. Rev. Lett. , 2006 , 96 , 188302 ], and, therefore, they are also interesting candidates to tune the viscoelastic properties of complex fluids. We identify three factors of patch reorganization under shear that lead to patch numbers and orientations depending on the shear rate, namely, free arms joining existing patches, fusion of medium-sized patches into bigger ones, and fission of large patches into two smaller ones under high shear rates. Because the conformation of single SBC is expected to be preserved in low-density bulk phases, the presented results are a first step in understanding and predicting the rheological properties of semidilute suspensions of this kind of polymers.

Synthesis of water soluble metalloporphyrin-cored amphiphilic star block copolymer photocatalysts for an environmental application

Two series of water-soluble metalloporphyrin-cored amphiphilic star block copolymers were synthesized by controlled radical polymerizations such as atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer (RAFT), which gave eight amphiphilic block copolymer arm chains consisting of poly(n-butyl acrylate-b-poly(ethylene glycol) methyl ether methacylate) (PnBA-b-PEGMEMA, Mn,GPC = 78,000, Mw/Mn = 1.2, 70 wt% of PPEGMEMA) and poly(styrene-b-2-dimethylamino ethyl acrylate) (PS-b-PDMAEA, Mn,GPC = 83,000, Mw/Mn = 1.2, 67 wt% of PDMAEA), yielding porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 and porphyrin(Pd)-(PS-b-PDMAEA)8, respectively. Obtained metalloporphyrin polymer photocatalysts were homogeneously solubilized in water to apply to the removal of chlorophenols in water, and was distinguished from conventional water-insoluble small molecular metalloporphyrin photocatalysts. Notably, we found that the water-soluble star block copolymers with hydrophobic–hydrophilic core–shell structures more effectively decomposed the chlorophenol, 2,4,6-trichlorophenol (2,4,6-TCP), in water under visible light irradiation (k = 1.39 h−1, t1/2 = 0.5 h) in comparison to the corresponding water-soluble star homopolymer, because the hydrophobic core near the metalloporphyrin effectively captured and decomposed the hydrophobic chlorophenols in water.

A Comparative Study on Micellar and Solubilizing Behavior of Three EO-PO Based Star Block Copolymers Varying in Hydrophobicity and Their Application for the In Vitro Release of Anticancer Drugs.

The temperature and pH dependent self-assembly of three star shaped ethylene oxide-propylene oxide (EO-PO) block copolymers (Tetronics® 304, 904 and 908) with widely different hydrophobicity was examined in aqueous solutions. Physico-chemical methods viz. viscosity, cloud point, solubilization along with thermal, scattering and spectral techniques shows strongly temperature and salt dependent solution behavior. T304 possessing low molecular weight did not form micelles; moderately hydrophilic T904 remained as micelles at ambient temperature and showed micellar growth while very hydrophilic T908 formed micelles at elevated temperatures. The surface activity/micellization/solubilization power was favored in the presence of salt. The copolymers turn more hydrophilic in acidic pH due to protonation of central ethylene diamine moiety that hinders micelle formation. The solubilization of a model insoluble azo dye 1-(o-Tolylazo)-2-naphthol (Orange OT) and hydrophobic drugs (quercetin and curcumin) for copolymer solutions in aqueous and salt solutions are also reported. Among the three copolymers, T904 showed maximum solubility of dye and drugs, hence the in vitro release of drugs from T904 micelles was estimated and the effect on cytotoxicity of loading the drugs in T904 micelles was compared with the cytotoxicity of free drugs on the CHO-K1 cells. The results from the present work provide a better insight in selection of Tetronics® for their application in different therapeutic applications.

Ion-responsive fluorescence resonance energy transfer between grafted polyacrylic acid arms of star block copolymers

Interactions between polyacrylic acid (PAA) arms of star block copolymers through metal ions were investigated by fluorescence resonance energy transfer (FRET). Dendritic polyester (DPE) core was grafted with block copolymer arms of oligo (ethylene glycol) methyl ether acrylate (OEGA) and PAA. Fluorescein o-methacrylate (FMA) or methacryloxyethyl thiocarbamoyl rhodamine B (MTR) was introduced via copolymerization to the terminated PAA blocks. The unique copolymer structure enabled FRET between PAA chains without causing precipitation, which inevitably occurs for linear PAA. Addition of metal ions such as Zn2+, Ca2+, or Na+ induced FRET, the order of which was Zn2+>Ca2+≫Na+. FRET intensity was also correlated with concentration of each ion. Furthermore, in situ FRET measurement during the hydrogel formation of the star block copolymers was performed by mixing the star block copolymers and Zn2+.

Facile Synthesis of Optically Active and Thermoresponsive Star Block Copolymers Carrying Helical Polyisocyanide Arms and Their Thermo-Triggered Chiral Resolution Ability.

A left-handed helical poly(phenyl isocyanide) bearing a norbornene unit and a Pd(II) complex on each terminus was prepared. The norbornene terminus was core cross-linked with a bisnorbornene linker via ring-opening metathesis polymerization (ROMP), yielding a star polymer carrying left-handed helical arms decorated with Pd(II) units at the exterior. The optical activities of the helical arms were maintained after the cross-linking reaction. The Pd(II) units on the surface of the star polymer were chain extended with a new phenyl isocyanide bearing three hydrophilic triethylene glycol monomethyl chains, which afforded an amphiphilic star block copolymer carrying helical arms. Such a star block copolymer showed excellent thermoresponsiveness with the lower critical solution temperature (LCST) around 55 °C. This optically active and thermoresponsive star polymer can enantioselectively capture the S-enantiomer of racemic methyl benzyl alcohol solution at a temperature lower than the LCST and precipitated when the temperature was higher than the LCST, leaving the R-enantiomer in the solution. The enantiomeric excess (ee) of the isolated enantiomer is up to 75%.

Understanding the Mechanism of Star-Block Copolymers as Nanoreactors for Synthesis of Well-Defined Silver Nanoparticles

Facile and large-scale synthesis of well-defined, thermally stable silver nanoparticles protected by polymer brushes for use in practical applications is still a challenge. Recent work has reported a nanoreactor approach that can be used to synthesize these silver nanoparticles. This approach uses amphiphilic star-block copolymers, which have a hydrophilic core surrounded by a hydrophobic exterior. These polymers thus can serve as the nanoreactors. In this study, we hypothesize that the local high concentration of silver ions in the inner hydrophilic cores of these star-block copolymers facilitates the nucleation and subsequent growth of silver nanoparticles. When all silver nanoparticles nucleate from the cores of the star-block copolymers in solution, the particle size can be controlled by the core size of the polymer. To test this hypothesis, a polyisoprene-b-poly(p-tert-butylstyrene) (PI-b-PtBS) star-block copolymer was functionalized with carboxylic acid groups using a high-efficiency, photo-initiated thiol-ene click reaction. We characterized this modified polymer using proton nuclear magnetic resonance spectroscopy, and the results indicated that ~60% of the double bonds in the polyisoprene block were successfully functionalized with carboxylic acid groups. When silver ions were added to a solution of these functionalized star-block copolymers, the negatively charged carboxylic acid groups would attract the positively charged silver ions. Subsequent reduction of these Ag+ by a tert-butylamine-borane complex at room temperature produced nanosized silver particles. However, transmission electron microscopy images showed that a significant amount of relatively large silver nanoparticles grew outside the star-block copolymer nanoreactors.