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With the aim of accessing colloidally stable, fiberlike, π-conjugated nanostructures of controlled length, we have studied the solution self-assembly of two asymmetric crystalline-coil, regioregular poly(3-hexylthiophene)- b-poly(2-vinylpyridine) (P3HT- b-P2VP) diblock copolymers, P3HT23- b-P2VP115 (block ratio=1:5) and P3HT44- b-P2VP115 (block ratio=ca. 1:3). The self-assembly studies were performed under a variety of solvent conditions that were selective for the P2VP block. The block copolymers were prepared by using Cu-catalyzed azide-alkyne cycloaddition reactions of azide-terminated P2VP and alkyne end-functionalized P3HT homopolymers. When the block copolymers were self-assembled in a solution of a 50 % (v/v) mixture of THF (a good solvent for both blocks) and an alcohol (a selective solvent for the P2VP block) by means of the slow evaporation of the common solvent; fiberlike micelles with a P3HT core and a P2VP corona were observed by transmission electron microscopy (TEM). The average lengths of the micelles were found to increase as the length of the hydrocarbon chain increased in the P2VP-selective alcoholic solvent (MeOH< iPrOH< nBuOH). Very long (>3 μm) fiberlike micelles were prepared by the dialysis of solutions of the block copolymers in THF against iPrOH. Furthermore the widths of the fibers were dependent on the degree of polymerization of the chain-extended P3HT blocks. The crystallinity and π-conjugated nature of the P3HT core in the fiberlike micelles was confirmed by a combination of UV/Vis spectroscopy, photoluminescence (PL) measurements, and wide-angle X-ray scattering (WAXS). Intense sonication ( iPrOH, 1 h, 0 °C) of the fiberlike micelles formed by P3HT23- b-P2VP115 resulted in small (ca. 25 nm long) stublike fragments that were subsequently used as initiators in seeded growth experiments. Addition of P3HT23- b-P2VP115 unimers to the seeds allowed the preparation of fiberlike micelles with narrow length distributions ( Lw/ Ln <1.11) and lengths from about 100-300 nm, that were dependent on the unimer-to-seed micelle ratio. [ABSTRACT FROM AUTHOR]

In this work, we designed copolymer microgels by the copolymerisation of N-vinylcaprolactam (VCL) and two acrylamides ( N-isopropylacrylamide (NIPAAm) and N-isopropylmethacrylamide (NIPMAAm)) under precipitation conditions in aqueous phase. In synthesis protocols, the ratio between monomers was varied from 1:5 to 5:1 mol/mol. By NMR and Raman spectroscopy, we determined the chemical composition of PVCL/NIPAAm and PVCL/NIPMAAm copolymer microgels reflecting the initial monomer ratio in the reaction mixture. The hydrodynamic radii of PVCL/NIPAAm microgels are around 375 nm (at 25 °C) and do not vary with the copolymer composition. On the contrary, for PVCL/NIPMAAm microgels, the size decreases from 450 to 250 nm with an increase of the VCL amount in copolymer structure. The heterogeneity of the microgel structure in terms of the distribution of the monomer units was probed by H transverse magnetization relaxation NMR, showing that the VCL, NIPAAm and NIPMAAm units are unorderly distributed in the colloidal networks. The investigation of volume phase transition temperature (VPTT) for copolymer microgels was performed using dynamic light scattering, NMR and differential scanning calorimetry. It has been found that PVCL/NIPAAm microgels show VPTT around 35 °C independently from the copolymer composition; however, PVCL/NIPMAAm particles exhibit a nonlinear increase of VPTT from 34 to 45 °C as the NIPMAAm fraction in copolymer structure increases. [ABSTRACT FROM AUTHOR]

We describe the synthesis of an end-functionalized copolymer of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) by reversible addition-fragmentation chain transfer (RAFT) polymerization. To control the polymer composition, the faster reacting monomer (NMS) was added slowly to the reaction mixture beginning 30 min after initating the polymerization (ca. 16% HPMA conversion). One RAFT agent, based on azocyanopentanoic acid, introduced a -COOH group to the chain at one end. Use of a different RAFT agent containing a 4-amino-1,8-naphthalimide dye introduced a UV-vis absorbing and fluorescent group at this chain end. The polymers obtained had molecular weights of 30 000 and 20 000, respectively, and contained about 30 mol% NMS active ester groups. On décrit la synthèse d'un copolymère fonctionnalisé aux extrémités du N-(2-hydroxypropyl)méthacrylamide (HPMA) et de méthacrylate de N-hydroxysuccinimide (NMS) par polymérisation impliquant une addition et une fragmentation radicalaire avec transfert de chaîne (AFRT). Dans le but de contrôler la composition du polymère, le monomère qui réagit le plus rapidement (NMS) est additionné lentement au mélange réactionnel 30 min après que la polymérisation a été initiée (conversion approximative de 16 % du HPMA). Un agent AFRT à base d'acide azocyanopentanoïque permet d'introduire un groupe -COOH à une extrémité de la chaîne. L'utilisation d'un agent AFRT différent, contenant un colorant 4-amino-1,8-naphtalimide, introduit un groupe fluorescent et absorbant dans l'UV-vis à l'extrémité de la chaîne. Les polymères obtenus possèdent respectivement des poids moléculaires de 30 000 et 20 000 et ils contiennent approximativement 30 mol% de groupes esters du NMS. [ABSTRACT FROM AUTHOR]

Non-spherical nanostructures derived from soft matter and with uniform size—that is, monodisperse materials—are of particular utility and interest, but are very rare outside the biological domain. We report the controlled formation of highly monodisperse cylindrical block copolymer micelles (length dispersity ≤ 1.03; length range, ∼200 nm to 2 µm) by the use of very small (∼20 nm) uniform crystallite seeds that serve as initiators for the crystallization-driven living self-assembly of added block-copolymer unimers with a crystallizable, core-forming metalloblock. This process is analogous to the use of small initiator molecules in classical living polymerization reactions. The length of the nanocylinders could be precisely controlled by variation of the unimer-to-crystallite seed ratio. Samples of the highly monodisperse nanocylinders of different lengths that are accessible using this approach have been shown to exhibit distinct liquid-crystalline alignment behaviour. [ABSTRACT FROM AUTHOR]

Thermoplastic olefins (TPOs) are an important class of material used in the automotive industry. They are blends of isotactic polypropylene (iPP) and a polyolefin impact modifier. Chlorinated polyolefin (CPO) is a polymer used as an adhesion promoter to promote the paintability of TPO. The synthesis of a coumarin dye-labeled chlorinated (21.8 wt% Cl) maleated polypropylene (CPO), HY dye-labeled MEBR (maleated ethylene-butene copolymer with 28 wt% butene), and CPO (21.8 wt% Cl) was described. They were introduced as tracers into iPP/EBR9 (ethylene-butene copolymer with 9 wt% butene), iPP/CPO, EBR9/CPO binary, and iPP/EBR9/CPO ternary blends. The annealing effect on morphologies of the blends was examined by laser scanning confocal fluorescent microscopy (LSCFM). LSCFM revealed that the annealing caused phase coarsening in iPP/CPO and iPP/EBR blends, but had no obvious effect on the morphology of EBR/CPO blends, while in iPP/EBR/CPO ternary blends, iPP and EBR formed a completely separate domain, iPP and CPO formed their own domains EBR was distributed in the CPO domains. The morphology of iPP, EBR, and CPO binary blends was further investigated by SEM. SEM images showed that EBR and CPO interpenetrated each other on the nanometer scale in EBR/CPO blends, while obvious phase separation was observed in iPP/CPO and iPP/EBR blends. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) results showed that iPP and EBR, iPP and CPO crystallized respectively in binary blends, while there was a new population of crystals formed in EBR/CPO blend. Further exploration by dynamic mechanical analysis (DMA) revealed that there were two β relaxation transitions in iPP/CPO and iPP/EBR blends, and only one β relaxation transition with a small shoulder in EBR/CPO blends. Thus, we concluded that iPP/EBR and iPP/CPO blends are immiscible; the EBR/CPO blend is miscible in the melt and partially miscible in solid state, which is in agreement with the predictions based on calculations of the results by binary interaction energy density ( B ij- Bc). Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Mixed micelles formed by co‐assembly of pairs of block copolymers (BCPs) can develop novel morphologies and generate useful properties not accessible from homomicelles. For micelles consisting of two different polymers in the corona, identifying the location of the corona chains is a critical part of morphology characterization. Coronal segregation in mixed micelle is often characterized by transmission electron microscopy in combination with selective staining of individual polymers. In this study, Karstedt's catalyst is used for selective Pt(0)‐olefin coordination staining of polyisoprene (PI) and poly(methylvinylsiloxane) (PMVS) corona chains in the presence of poly(dimethylsiloxane) (PDMS) corona chains in cylindrical mixed micelles with a crystalline poly(ferrocenyldimethylsilane) (PFS) core. Previous experiments using OsO4 as a stain did not enable visualization of nanoscale coronal segregation in mixed micelles obtained from co‐assembly of PFS‐b‐PI and PFS‐b‐PDMS, as well as PFS‐b‐PMVS and PFS‐b‐PDMS. Karstedt's catalyst can be used as a staining agent for visualizing nanoscale coronal segregation in core‐crystalline comicelles through Pt(0)‐olefin coordination. [ABSTRACT FROM AUTHOR]

Abstract: Single lap shear adhesion measurements on model isotactic polypropylene and thermoplastic polyolefin (TPO) substrates which sandwich a chlorinated polyolefin (CPO) show similar values of the fracture strength, as determined from the stress at break, but much larger deformation at break for the substrates that contain a copolymer of ethylene with 9wt% butane (EBR9) as an impact modifier. We also found for sections cut from a large format (300×100mm) plaque of TPO12 (12wt% EBR9), that the fracture energy increased as a function of distance from the gate. ATR-FTIR measurements on these sections indicated that there was a variation in the EBR content in the near-surface region of the substrate, and that stronger adhesion correlated with an increase of EBR content at or near the surface. [Copyright &y& Elsevier]

Nucleated self-assembly in selective solvents of core-crystalline block copolymers (BCPs) is a special case of living supramolecular polymerization, leading to rodlike micelles of controlled and uniform length. For the crystallization-driven self-assembly of PFS-containing BCPs (PFS = polyferrocenyldimethylsilane), the formation of block comicelles by sequential addition of different BCPs is well-established. But there are only a few examples of living copolymerization, the simultaneous addition of pairs of BCPs with different corona-forming chains. At present, relatively little is known about the competitive kinetics of different BCPs crystallizing on a common seed. Here we report a systematic study of the competitive seeded growth kinetics of pairs of linear PFS-containing BCPs and show that one can manipulate the kinetics to control the morphology of the comicelles. We found that the seeded-growth kinetics of the individual BCP unimer dominates the coassembly behavior and thus the morphology of the corona. Patchy comicelles with microphase-segregated corona chains are formed when the epitaxial growth rates of the two different BCPs on the common seed are similar. In contrast, factors that lead to dissimilar growth rates (long corona-forming blocks or introduction of charges on corona-forming chains) promote large-scale separation of the corona blocks, leading to block comicelles. Because the termini of the comicelles remain living, they can further direct the growth of unimers, resulting in hierarchical block comicelles with patchy blocks and single-component (homo) blocks. Furthermore, the patchy comicelles can be loaded with either gold or platinum nanoparticles, generating organic-inorganic hybrid materials with potential application in catalysis. [ABSTRACT FROM AUTHOR]

Block copolymers (BCPs) with a short crystallizable poly(ferrocenyldimethylsilane) (PFS) core-forming block self-assemble in selective solvents to afford cylindrical micelles, the ends of which are active to further growth via a process termed living crystallization-driven self-assembly (CDSA). We now report studies of the CDSA of a series of crystalline-brush BCPs with C6 (BCP6), C12 (BCP12), and C18 (BCP18) n-alkyl branches that were prepared by the thiol—ene functionalization of PFS-b-PMVS (PMVS = poly(methylvinylsiloxane)). Although the increased n-alkyl brush length of BCP12 and BCP18 hindered micelle growth, the increased intercoronal chain repulsion could be alleviated by their coassembly with linear PFS-b-PMVS. When the coassembly was initiated by short cylindrical seed micelles, monodisperse block comicelles of controllable length with “patchy” coronal nanodomains were accessible. TEM and AFM analysis of micelles prepared from BCP18 and PFS-b-PMVS were found to provide complementary characterization in that the OsO4-stained PMVS coronal domains were observed by TEM, whereas the brush block domains of BCP18 (which displayed greater height) were detected by tapping mode AFM. The results showed that the coassembly afforded a gradient structure, with an initial bias for the growth of the linear BCP over that of the more sterically demanding brush BCP, which was gradually reversed as the linear material was consumed. This represents the first example of living gradient CDSA, a process reminiscent of a living covalent gradient copolymerization of two different monomers. Although other possible explanations exist, simulations based on a statistical model indicated that the coronal nanodomains detected likely result from a segmented, gradient comicelle architecture that arises as a consequence of: (i) different rates of addition of BCP unimer to the micelle termini, and (ii) a cumulative effect resulting from steric hindrance associated with the brush block. [ABSTRACT FROM AUTHOR]

The solution self-assembly of block copolymers with aπ-conjugated,crystalline, core-forming block represents a facile strategy towardthe preparation of semiconducting nanowires with potential for high-techapplications. In this study, two asymmetric block copolymers basedon regioregular poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate)(PMMA), namely P3HT40-b-PMMA520(6a) and P3HT40-b-PMMA1100(6b) (block ratios = 1:13 and 1:27.5, respectively)were prepared via atom transfer radical polymerization (ATRP) froma P3HT macroinitiator. The solution self-assembly of the P3HT-b-PMMA block copolymers was subsequently studied under avariety of experimental conditions. Short, fiber-like micelles resultedwhen THF (common solvent for P3HT and PMMA) solutions of the blockcopolymer were dialyzed against ethyl acetate and n-butyl acetate (selective solvents for PMMA). The electronic propertiesof the fiber-like micelles obtained coupled with wide-angle X-rayscattering studies confirmed that the cores of the aggregates werecrystalline and suggested that growth occurs via a crystallization-drivenpathway. The average lengths of fiber-like micelles were shown toincrease relative to those obtained from dialysis versus the PMMAselective solvent, when THF was slowly evaporated from mixtures containing n-butyl acetate and P3HT-b-PMMA unimers,thereby limiting the rate of P3HT aggregation. Furthermore, the formationof only relatively short (mainly under 200 nm, always <1 μm)fiber-like micelles in these studies, even when the ratio of THF/alkylacetate was controlled carefully via dialysis or evaporation, indicatedthat homogeneous nucleation of P3HT-b-PMMA blockcopolymers is relatively facile. This behavior differs significantlyfrom that detected for other block copolymers such as polyferrocenylsilane-basedmaterials that undergo crystallization-driven self-assembly to formcylinders with lengths of up to 10 μm under analogous conditions. [ABSTRACT FROM AUTHOR]

Abstract: This article describes a systematic study of ion release, carried out on lanthanide-encoded polystyrene-co-methacrylic acid (P(S-MAA)) and polystyrene-co-acrylic acid (P(S-AA)) copolymer particles, which were synthesized by two-stage or three-stage dispersion polymerizations. These particles with different levels of lanthanide (Ln) ion content and containing several different types of Ln ions were dispersed in normal buffer media, namely 2-(N-morpholino)ethanesulfonic acid (MES), phosphate buffered saline solution (PBS), ammonium acetate (AmAc) and buffers containing strong chelating molecules like ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA). Traditional inductively coupled plasma mass spectrometry (ICP-MS) was employed to follow the loss of ions into the aqueous medium as a function of time. The release behavior of the Ln ions were compared. In MES and PBS buffers at neutral pH, and AmAc at pH 9.0, there was essentially no significant loss of Ln ions from the particles to the buffer. When the chelating agents EDTA or DTPA were present in the buffer, the loss of Ln ions was more prominent, but less than 15% after 8 weeks under stirring. The differences among the different samples were small. Considering the ability of EDTA and DTPA to remove Ln ions from the particles and the fact of minimal ion release in the presence of PBS buffer, we infer that the ion loss is a more active process involving the EDTA or DTPA molecules. The main conclusion is that in the absence of strong chelating agents, these particles are stable against ion leakage, even upon prolonged storage and stirring. This is of great importance for their application in bead-array biological assays based on mass cytometry detection. [Copyright &y& Elsevier]

We describe the synthesis, characterization, and film-forming properties of two-component nanoparticles that undergo a reversible morphology transformation in water as a function of pH. The particles consist of a high molecular weight acrylate copolymer and an acid-rich oligomer designed to be miscible with the polymer when its -COOH groups are protonated. Attaching a fluorescence resonance energy transfer (FRET) pair to components inside the nanoparticles enabled us to assess morphology at the molecular level. By inspecting changes in the donor fluorescence decay profile at different pH values, we established miscibility of the components in acidic solution but with charge-induced phase separation when the oligomers were neutralized to their carboxylate form. Complementary titration experiments revealed that the nanoparticles adopt a core-shell structure when the acid groups are deprotonated. We studied the effect of the acid-rich oligomer on the diffusion rate of the high molecular weight polymers following film formation. Our results show that the carboxylated oligomer enhanced the rate of diffusive mixing between high molecular weight molecules by more than 2 orders of magnitude. FRET measurements carried out on partially dried films using a low-resolution microscope showed that the carboxylate oligomer shell can delay coalescence for ca. 30 min after passage of the drying front. This delay is expected to help with increasing the 'open time' of latex paints, a desirable property of solvent-based paints that remains difficult to achieve with (environmentally compliant) waterborne paints. Use of ammonia as a volatile base resulted in synergistic effects: initial retardation of coalescence followed by acceleration of diffusive mixing as the ammonium salts dissociated and ammonia evaporated from the film. [ABSTRACT FROM AUTHOR]

Cylindrical block copolymer micelles with a crystalline poly(ferrocenyldimethylsilane) (PFDMS) core and a long corona-forming block are known to elongate through an epitaxial growth mechanism on addition of further PFDMS block copolymer unimers. We now report that addition of the semicrystalline homopolymer PFDMS28 to monodisperse short (ca. 200 nm), cylindrical seed micelles of PFDMS block copolymers results in the formation of aggregated structures by end-to-end coupling to form micelle networks. The resulting aggregates were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). In some cases, a core-thickening effect was also observed where the added homopolymer appeared to deposit and crystallize at the core-corona interface, which resulted in an increase of the width of the micelles within the networks. No evidence for aggregation was detected when the amorphous homopolymer poly(ferrocenylethylmethylsilane) (PFEMS25) was added to the cylindrical seed micelles whereas similar behavior to PFDMS28 was noted for semicrystalline polyferrocenyldimethylgermane (PFDMG30). This suggested that the crystallinity of the added homopolymer is critical for subsequent end-to-end coupling and network formation to occur. We also explored the tendency of the cylindrical seed micelles to form aggregates by the addition of PI-b-PFDMS (PI = polyisoprene) block copolymers (block ratios 6:1, 3.8:1, 2:1, or 1:1), and striking differences were noted. The results ranged from typical micelle elongation, as reported in previous work, at high corona to core-forming block ratios (PI-b-PFDMS; 6:1) to predominantly end-to-end coupling at lower ratios (PI-b-PFDMS; 2:1, 1:1) to form long, essentially linear structures. The latter process, especially for the 2:1 block copolymer, led to much more controlled aggregate formation compared with that observed on addition of homopolymers. [ABSTRACT FROM AUTHOR]

Abstract: Small amounts of hydrogen-bonding comonomers such as N-(2-methacryloxyethyl)ethylene urea (MEEU) are often included in latex particle synthesis to promote adhesion of latex films to metals and old surfaces. Little is known about how these monomers affect the latex film formation process. Here we examine the influence of 1–7 wt.% MEEU on butyl acrylate-methyl methacrylate copolymer latex films using fluorescence resonance energy transfer (FRET) measurements, in conjunction with donor- and acceptor-labeled latex particles, to study the rates of polymer diffusion in these films. The presence of MEEU in the copolymer leads to small increases in the polymer glass transition temperature (Tg). It also tends to retard the rate of polymer diffusion. This effect, however, is very sensitive to the humidity of the surrounding atmosphere. It appears that moisture taken up in the film minimizes the influence of MEEU groups on the rate of polymer diffusion. [Copyright &y& Elsevier]

Block copolymers consist of two or more chemically different polymers connected by covalent linkages. In solution, repulsion between the blocks leads to a variety of morphologies, which are thermodynamically driven. Polyferrocenyldimethytsilane block copolymers show an unusual propensity to forming cylindrical micelles in solution. We found that the micelle structure grows epitaxially through the addition of more polymer, producing micelles with a narrow size dispersity, in a process analogous to the growth of living polymer. By adding a different block copolymer, we could form co-micelles. We were also able to selectively functionalize different parts of the micelle. Potential applications for these materials include their use in lithographic etch resists, in redox-active templates, and as catalytically active metal nanoparticle precursors. [ABSTRACT FROM AUTHOR]

We report the creation and properties of colloidally stable shell-cross-linked cylindrical organo-metallic block copolymer micelles with adjustable length and swellability. The one-dimensional (1 D) structures with semicrystalline polyferrocenylsilane (PFS) cores and polyisoprene (PI) coronas were initially self-assembled from PI-b-PFS block copolymers in a PI-selective solvent such as hexane. The length of the cylinders could be varied from hundreds of nanometers to several tens of micrometers by adjusting solution conditions, using various solvents such as hexane, decane, or hexane/THF (or toluene) mixtures. The cylindrical micelles with vinyl groups in the PI corona were cross-linked through a Pt(0)-catalyzed hydrosilylation reaction using 1,1 ,3,3-tetramethyl disiloxane as a cross-linker at room temperature. The shell cross-linking significantly increased the stability of the micelles relative to the un-cross-linked precursors as no fragmentation was observed upon sonication in solution. In addition, the structural integrity of the micelles was also enhanced after solvent removal; a solid sample was successfully microtomed and then examined using TEM, which revealed circular cross-sections for the PI-b-PFS micelles with an average diameter of ca. 15 nm. We also discovered that shell cross-linking is a prerequisite for generating ceramic replicas through the pyrolysis of PI-b-PFS aggregates. Moreover, we were able to pattern the cross-linked micelles on a flat substrate by microfluidic techniques, generating perpendicularly crossed lines of aligned micelles. In short, the shell-cross-linked PI-b-PFS 1D organometallic aggregates are a promising new type of nanomaterial with intriguing potential applications. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution scanning transmission electron microscope (HR STEM) measurements were performed on a thermoplastic polyolefin (TPO) substrate coated with chlorinated polyolefin (CPO). This CPO was a maleated chlorinated polypropylene containing 21.8wt% Cl. The TPO investigated was a blend of high-modulus isotactic polypropylene (iPP) with a crystalline ethylene–butene copolymer (EB9) containing 9wt% butene. For these injection-molded samples, examined ca. 10mm from the mold gate, a stratified morphology found at TPO surface consisting of thin fibers of EB9 trapped in a transcrystalline iPP matrix, with crystalline lamellae propagating from the matrix across the EB9 domains. This structure was unperturbed when the plaques were coated (from tetrahydrofuran solution) with a 5μm layer of CPO, but underwent changes of increasing severity when subjected either to a dry bake at 120°C or annealing at 120°C in the presence of xylene vapor. The interfacial structure between the CPO and the TPO was probed by TEM with energy dispersive X-ray imaging (EDX). The elemental chlorine across the interface gave good fits to a tan h function, and the interface thickness increased from 23±2nm to 28±1nm upon annealing at 120°C for 30min. After annealing in the presence of xylene vapor, this value increased to 50±4nm. As reference points, we determined an interface thickness of 29±3nm for the CPO–EB interface and 15±2nm for the interface between CPO and iPP. [Copyright &y& Elsevier]

Describes a reversible tube-to-rod transition in a block copolymer micelle induced by a change in temperature for a PFS[sub40]-b-PDMS[sub480] sample in decane solution. Characteristics of polyferrocenylsilanes (PFS); Synthesis of the sample; Characteristics of the micelle structures in solution.