Self‐Assembling Nanomaterials using Magnetic Nanoparticles Modified with Polystyrene Brushes

Magnetic nanomaterials have been studied in order to generate novel nanocomposites that display both the magnetic properties of the nanoparticles and the ability to self‐assemble of the amorphous block copolymer matrix. Towards this goal, iron oxide magnetic nanoparticles have been modified with PS brushes by ATRP in order to improve both the dispersion and the affinity of the nanoparticles with one of the blocks of a polystyrene‐block‐polybutadiene‐block‐polystyrene block copolymer. This method of preparation of nanocomposites opens new strategies for the generation of magnetic nanomaterials. The samples are characterized using DSC and atomic and magnetic force microscopies.

     

Nanostructured Thermosetting Systems from Epoxidized Styrene Butadiene Block Copolymers

Summary: Nanostructured thermosetting materials were prepared by modification of an epoxy resin with 30 wt.‐% epoxidized polystyrene‐block‐polybutadiene copolymer (PS‐b‐PepB). The copolymer self‐assembles into a well‐defined hexagonal nanoordered structure, of around 30‐nm diameter, thus establishing its use as structure‐directing agent to generate nanostructured thermosetting materials. The study confirms pathways towards tailoring interactions between thermosetting matrices and immiscible block copolymers by using the concept of functionalization to build nanostructured polymer matrices.

Structure of diglycidyl ether of bisphenol‐A/4,4′‐methylenebis(3‐chloro 2,6‐diethylaniline) cured blend containing 30 wt.‐% PS‐b‐PepB61 block copolymer.     

Polyoxazoline Thermoresponsive Micelles as Radionuclide Delivery Systems

Thermoresponsive polymer micelles are promising drug and radionuclide carriers with a strong passive targeting effect into solid tumors. We have synthesized ABA triblock copolymers poly[2‐methyl‐2‐oxazoline‐block‐(2‐isopropyl‐2‐oxazoline‐co‐2‐butyl‐2‐oxazoline)‐block‐2‐methyl‐2‐oxazoline]. These polymers are molecularly dissolved in aqueous millieu below the cloud point temperature (CPT) of the thermoresponsive central block and above CPT form polymer micelles at CMC 5–10 × 10^?5 g · mL^?1 with diameter ≈200 nm. The phenolic moiety introduced into the copolymer allowed radionuclide labeling with iodine‐125 ongoing in good yield with sufficient in vitro stability under model conditions.

     

Block‐Copolymer‐Assisted Solubilization of Carbon Nanotubes and Exfoliation Monitoring Through Viscosity

Summary: The use of the block copolymers polystyrene‐block‐poly(ethylene oxide) and poly(methyl methacrylate)‐block‐poly(ethylene oxide) is described to assist the direct solubilization of single‐walled carbon nanotubes (SWNTs) into water under ultrasonic irradiation. As compared to surfactants and homopolymers, the block copolymer systems may offer the potential of additional unique morphologies through self‐assembly. TEM and AFM analyses of solution‐cast samples indicate exfoliation and wetting of the SWNTs by the block copolymer. With increasing duration of ultrasonic irradiation, an increase in solution viscosity is initially found, which suggests that it is a convenient indicator of the progress of exfoliation of the SWNTs. With continued intense ultrasonic irradiation, the solution viscosity may decrease apparently because of damage/breakage of the SWNTs.

Schematic of the interaction of the PMMA‐b‐PEO block copolymer with the single‐walled carbon nanotubes and the specific viscosity of the system in aqueous solution as a function of sonication time: results from using an ultrasound bath (‐‐‐‐▪‐‐‐‐) or an ultrasound horn (—▴—).     

pH/Thermosensitive Hydrogels Formed at Low pH by a PMMA‐PAA‐P2VP‐PAA‐PMMA Pentablock Terpolymer

A poly(methyl methacrylate)‐block‐poly(acrylic acid)‐block‐poly(2‐vinyl pyridine)‐block‐poly(acrylic acid)‐block‐poly(methyl methacrylate) (PMMA‐PAA‐P2VP‐PAA‐PMMA), pentablock terpolymer has been synthesized by anionic polymerization with sequential addition of monomers and studied in aqueous media at low pH. The system exhibits combined properties and adopts the behavior of ‘telechelic’ polyelectrolytes and that of double hydrophilic polyampholytes. This complex behavior leads to the pentablock terpolymer forming a pH and temperature sensitive reversible hydrogel at very low polymer concentration.

     

A New Approach to Thick Films of a Block Copolymer with Ordered Surface Structures

Summary: A unique and simple method to prepare films with various ordered nanoscopic cylindrical patterns on the surface is reported. Various solutions of gemini surfactants with different spacers were used as a nanotemplate, on which thick polymer films were fabricated by the supramolecular assembly of a native or chemically modified polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene (SEBS) triblock copolymer. At the air/polymer surface, normal oriented cylindrical nanodomains formed by poly(ethylene/butylene) (PEB) block associates surrounded by polystyrene (PS) blocks are exhibited. While at the polymer/surfactant solution interface, parallel cylindrical nanodomains formed by PEB block stripes alternating with PS block stripes are observed. The ordered structure of the surface can be adjusted by changing the surfactant and the chemical nature of the polymer. In a special case using Gemini 16‐1‐Ph‐1‐16 and SEBS chemically modified with 2 wt.‐% maleic anhydride, a nearly perfect hexagonal ordered structure is obtained.

The AFM micrograph and associated FFT (inset) of the morphology of a SEBS thick film formed on a 16‐1‐Ph‐1‐16 solution to give a nearly perfect hexagonal ordered structure.     

Selective and Sequential Re‐Assembly of Patterned Block Copolymer Thin Film for Fabricating Polymeric,Inorganic, and Their Composite Nanostructured Arrays

We report that the nanostructures of poly(styrene‐block‐4‐vinylpyridine) block copolymer (PS‐b‐P4VP) thin film on a wafer substrate can be re‐assembled by sequential vapor treatment using selected solvents. Metal or other inorganic nanoparticles that were randomly pre‐loaded inside or on the surface of PS‐b‐P4VP thin film could be pulled to the rim of PS and P4VP along with the movements of PS and P4VP blocks during the treatment. As a result, the patterned polymeric or inorganic/polymer composite nanoisland and nanoring arrays were fabricated.

     

Transparent and Conductive Polyethylene Oxide Film by the Introduction of Individualized Single‐Walled Carbon Nanotubes

It is demonstrated that an optically transparent and electrically conductive polyethylene oxide (PEO) film is fabricated by the introduction of individualized single‐walled carbon nanotubes (SWNTs). The incorporated SWNTs in the PEO film sustain their intrinsic electronic and optical properties and, in addition, the intrinsic properties of the polymer matrix are retained. The individualized SWNTs with smaller diameter provide high transmittance as well as good electrical conductivity in PEO films.

     

Ring and Disk‐Like CdSe Nanoparticles Stabilized with Copolymers

CdSe nanoparticles stabilized with the amphiphilic diblock copolymer polystyrene‐block‐poly(4‐vinylpyridine) were spread from toluene dispersion on the water surface. Monolayers could be transferred onto solid substrates using the Langmuir‐Blodgett technique. By means of atomic force and scanning electron microscopy highly symmetric ring and disk‐like structures with diameters ranging between 150 nm and 1200 nm were observed.

AFM image of a mixed monolayer of copolymer 12 and CdSe nanoparticles stabilized with polystyrene‐block‐poly(4‐vinylpyridine).     

Block Copolymer Micelles with Near Infrared Metal Phthalocyanine Dyes for Laser Induced Writing

A route has been developed to disperse metal‐containing phthalocyanine dyes in a non‐polar medium based on amphiphilic block copolymer micelles of poly[styrene‐block‐(4‐vinylpyridine)] (PS‐b‐P4VP) and poly[styrene‐block‐(acrylic acid)] (PS‐b‐PAA) copolymers. Polar P4VP and PAA efficiently encapsulate cobalt(II ), manganese(II ), and nickel(II ) phthalocyanine dyes by axial coordination of nitrogen and µ‐oxo bridged dimerization with the transition metals, respectively. Good dispersion of the dyes is confirmed by the linear enhancement of Q‐bands in UV–vis absorption spectra with dye concentration. A thin monolayered PS‐b‐P4VP micelle film that contained a nickel(II ) phthalocyanine dye which efficiently adsorbs a laser beam on a localized area to generate a local heat higher than the glass transition temperatures of both blocks. One‐dimensional laser writing on the dye‐containing film allows the fabrication of a few submicrometer wide line patterns in which the self‐assembled nanostructure of the block copolymer is modified by the directional heat arising from laser scanning.

     

Preparation of Magnetite Nanoparticles Coated with an Amphiphilic Block Copolymer: A Potential Drug Carrier with a Core‐Shell‐Corona Structure for Hydrophobic Drug Delivery

Summary: The synthesis of magnetic magnetite nanoparticles coated with amphiphilic block copolymers of poly(ethyl methacrylate)‐block‐poly(2‐hydroxyethyl methacrylate) for use as new potential carriers for hydrophobic drug delivery is reported. The results show that a new core‐shell‐corona structural material is obtained with a very narrow molecular weight distribution of the hydrophobic segment (PDI = 1.10). UV‐Vis results show that 37% of progesterone is released from the nanoparticles after 22 h, much slower than free release (99% after 14 h), which demonstrates that the presence of the hydrophobic segment can effectively control the release of hydrophobic drugs.

Synthesis of an amphiphilic block polymer poly(ethyl methacrylate)‐block‐poly(2‐hydroxyethyl methacrylate) on magnetite nanoparticles and their use as potential drug carriers     

Nano Grape Formation by isotactic‐Poly(methacrylic acid)‐block‐Poly(butyl acrylate)

A novel approach is employed to produce core–corona nanospheres, which introduces a stereoregular hydrophilic part to an amphiphilic block copolymer. The resultant morphology is reported using isotactic‐poly(methacrylic acid)‐block‐poly(butyl acrylate). Infrared spectroscopy revealed a supramolecular interaction, and X ray diffraction revealed the crystallization of the outer isotactic‐poly(methacrylic acid) part. The nanostructure, which looks like a nanosized ‘grape’, was formed when nanospheres and nanofibers coexisted simultaneously and partially fused.

     

Preparation of a Polyethylene Latex by Catalytic Hydrogenation of a Polybuta‐1,4‐diene‐Based Dispersion

Summary: Fully linear polyethylene‐based latexes have been prepared by the hydrogenation of polybuta‐1,4‐diene dispersions. The latter were synthesized via dispersion ring‐opening metathesis polymerization of cycloocta‐1,5‐diene, and hydrogenated using RuCl₂(PPh₃)₃ as catalyst, without any further treatment. A high hydrogenation efficiency was achieved as demonstrated by different techniques including DSC, and ¹H NMR and FT‐IR spectroscopy. The hydrogenation process could be carried out without detrimental effect on particle size and colloidal stability as evidenced by optical microscopy and light scattering analysis.

Optical microscopy photograph of a polybutadiene‐based dispersion after hydrogenation. No change in size is observed.     

Nanoporous Network Channels from Self‐Assembled Triblock Copolymer Supramolecules

Supramolecular complexes of a poly(tert‐butoxystyrene)‐block‐polystyrene‐block‐poly(4‐vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self‐assemble into a core–shell gyroid morphology with the core channels formed by the hydrogen‐bonded P4VP(PDP)complexes. After structure formation, PDP was removed using a simple washing procedure, resulting in well‐ordered nanoporous films that were used as templates for nickel plating.

     

Multifunctional Poly(N‐vinylcarbazole)‐Based Block Copolymers and their Nanofabrication and Photosensitizing Properties

The synthesis of poly(N‐vinylcarbazole)‐based block copolymers functionalized with rhenium diimine complexes or pendant terpyridine ligands is reported. The copolymers are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and they exhibit interesting morphological properties as a result of the phase separation between different blocks. The rhenium complex polymer block may function as a photosensitizer, while the terpyridine‐containing polymer block can be used as the template for nanofabrication by selective deposition of zinc complexes.

     

Formation of Integral Asymmetric Membranes of AB Diblock and ABC Triblock Copolymers by Phase Inversion

The formation of integral asymmetric membranes from ABC triblock terpolymers by non‐solvent‐induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐b‐P2VP‐b‐PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post‐functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements.

     

Pulling Polymers on Energetically Disordered Surfaces: Molecular Dynamics Tests of Linear and Non‐linear Response

Equilibrium and non‐equilibrium molecular dynamics simulations of flexible polymer chains absorbed on heterogeneous surfaces are presented. The surfaces are flat but energetically disordered, consisting of a random mixture of weakly and more strongly absorbing sites (94 and 6%, respectively). For comparison, the two corresponding homogeneous surfaces are also simulated. This apparently weak energetic disorder can produce significant changes of the chain statistics, equilibrium dynamics, and non‐equilibrium response to a horizontal pulling force. On the disordered surfaces, the polymer–surface effective friction coefficient becomes strongly force‐dependent, as the dominant mode of motion changes from localized stick–slip events to smooth and continuous sliding. This is strongly reminiscent of the Schallamach model of rubber friction and the Maier–Göritz picture of the Payne effect in filled elastomers.

     

Au/CdS Hybrid Nanoparticles in Block Copolymer Micellar Shells

A polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) micellar structure with a P2VP core containing 5 nm CdS nanoparticles (NPs) and a PS shell formed in toluene that is a good solvent for PS block undergoes the core‐shell inversion by excess addition of methanol that is a good solvent for P2VP block. It leads to the formation of micellar shell‐embedded CdS NPs in the methanol major phase. The spontaneous crystalline growth of Au NPs on the CdS surfaces positioned at micellar shells without a further reduction process is newly demonstrated. The nanostructure of Au/CdS/PS‐b‐P2VP hybrid NPs is confirmed by transmission electron microscopy, energy‐dispersive X‐ray, and UV‐Vis absorption.

     

Synthesis and Surface Morphology of Tetraaniline‐block‐Poly(L‐lactate) Diblock Oligomers

Summary: Tetraaniline‐block‐poly(L ‐lactide) diblock oligomers are synthesized via ring‐opening polymerization. The diblock oligomers cast from an L ‐lactide selective solvent (chloroform) show spherical aggregates for the leucoemeraldine state, and ring‐like structures that are composed of much smaller spherical aggregates for the emeraldine state. The formation mechanisms of the two different surface morphologies are discussed in detail.

Surface morphology changes induced by oxidation of the aniline segment of tetraaniline‐block‐poly(L ‐lactate) and drying effects.