Based on their rigid‐rod structure all‐conjugated, rod‐rod block copolymers show a preferred tendency to self‐assemble into low‐curvature vesicular or lamellar nanostructures independent from their specific chemical structure and composition. This unique and attractive behaviour is clearly illustrated in a few examples of such all‐conjugated block copolymers. The resulting nanostructured heteromaterials may find applications in electronic devices or artificial membranes.
A two‐armed polymer with a crown ether core self‐assembles to produce macroporous films with pores perpendicularly reaching through the film down to the substrate. A possible assembling mechanism is discussed. The pore size can be conveniently adjusted by changing the solution concentration. These through‐hole macroporous films provide a template for fabricating an array of Cu nanoparticle aggregates.
Anionic conjugated polymer (PFP‐SO) was assembled with a novel enzymatic substrate 6‐O‐modified PNP‐β‐galactoside ( 1 ) for sensitive multiplex enzyme detections. The PFP‐SO/ 1 /lipase/β‐galactosidase system has two chemical input signals which are Input 1 (lipase) and Input 2 (β‐galactosidase), and output optical signals such as fluorescence emission at 416 nm or 450 nm. Four types of logic gates, including YES, INH, NAND and AND, were successfully constructed and utilized for multiplex detections of lipase and β‐galactosidase in one tube.
Polymer‐encapsulated silver nanoparticles were synthesized and sterically stabilized by a new core‐shell type system consisting of poly(S‐alt‐MA)‐graft‐PMMA copolymer that acts as a scaffold for the synthesis of size confined nanoparticles. The graft copolymer is synthesized via ambient temperature ATRP using the CuBr/PMDETA catalytic system at ambient temperature. The graft copolymer is hypothesized to function as a scaffold with the anhydride part interacting strongly with the silver ions, while the PMMA graft functions as a polymer brush that stabilizes the dispersion and prevents the particle aggregation due to a ‘polymer brush effect’. UV absorption and TEM studies confirm that the synthesized silver composite particles have a core‐shell structure.
Rapidly shrinking poly(N‐isopropyl acrylamide) (PNIPAM) hydrogels are prepared by crosslinking with self‐assembled nanogels that consist of cholesteryl‐ and methacryloyl‐substituted pullulan (CHPMA). The CHPMA nanogel (Rh = 26.4 nm) was used as a crosslinker for a hydrophilic nanodomain. Transmission electron microscopy images of the nanogel‐crosslinked PNIPAM hydrogel reveal a well‐defined nanoporous structure. The nanogel‐crosslinked PNIPAM hydrogel shows rapid shrinking based on its structure. The shrinking half‐time was ≈2 min, which is about 3 400 times faster than that of a PNIPAM hydrogel crosslinked by methylene(bisacrylamide).
This paper describes the synthesis of narrowly distributed block copolymers consisting of a hole conducting triarylamine block and an anchor block via RAFT polymerization. The anchor block is thereby introduced via a reactive ester approach. Block copolymers with dopamine anchor groups bind to oxidic semiconductors like TiO2, SnO2, and ZnO. Thus, it becomes possible to cover inorganic electron conducting (acceptor) nanomaterials with a corona of an organic hole conducting (donor) polymer like poly(triphenylamine), giving new hybrid materials. The poly(triphenylamine) grafted to inorganic nanorods allows the preparation of stable nanorod dispersions in appropriate solvents. At higher concentration the nanorods form liquid crystalline phases in various solvents and in a low Tg oligotriphenylamine matrix. This offers the potential to orient semiconducting inorganic nanorods in a hole conducting polymer matrix by self‐assembly.
We report the synthesis of a series of block copolymers consisting of a rod‐like semiconducting poly(2,5‐di(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene) (DEH‐PPV) block and a flexible poly(lactic acid) (PLA) block that can be selectively degraded under mild conditions. Such selectively degradable block copolymers are designed as self‐assembling templates for bulk heterojunction donor–acceptor layers in organic solar cells. A lamellar microphase‐separated domain structure was identified for block copolymers with PLA volume fractions between 29 and 79% in bulk and thin films using SAXS, TEM, and AFM. Depending on the ratio of the two blocks we find either lamellae oriented parallel or perpendicular to the substrate in thin films.
Summary: A novel non‐aqueous emulsion system, consisting of cyclohexane as the continuous and acetonitrile as the dispersed phase, is described. Stabilization of the system can be achieved by using polyisoprene‐block‐poly(methyl methacrylate) copolymers as emulsifiers. The suitability of this system for performing water‐sensitive, catalytic, and oxidative polymerizations and polycondensations is demonstrated by the synthesis of poly(3,4‐ethylenedioxythiophene), poly(thiophene‐3‐yl‐acetic acid), and polyacetylene. In all cases spherical nanoparticles with diameters as small as 23 nm can be obtained.
Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end‐functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl‐modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.g., miktoarm star polymers) is summarized and potential applications as well as future perspectives are discussed.
The self‐assembly of two types of linear ABA triblock copolymers confined in cylindrical nanopores is studied using simulated annealing. The effects of pore size and block copolymer chain architecture on morphology, chain conformations and bridging fraction are investigated. For the bulk cylinder‐forming copolymers, novel structures such as helices and stacked toroids form, which depend sensitively on the pore size. Several significant differences between the two types of copolymers are predicted and explained based on the differences in their chain conformations and chain architectures. A simple model is proposed to explain the mean square radius of gyration for the bridge and loop chains.
Furan ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).
We report here a facile synthesis of high performance electro‐active polymer actuator based on a sulfonated polyimide with well‐defined silver electrodes via self‐metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer‐metal composite actuators. Also, the self‐metallized silver electrodes exhibit outstanding metal‐polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion‐based actuators.
Urchin‐like PANI microspheres with an average diameter of 5–10 µm have been successfully prepared. Their surfaces consist of highly oriented nanofibers of ≈30 nm diameter and 1 µm length. The solvent composition plays an important role in the formation process of urchin‐like PANI microspheres. The structure of the products has been characterized by FT‐IR, UV‐vis, and XRD. To investigate the self‐assembly of urchin‐like PANI microspheres, the effect of polymerization time on the morphology of the products has been studied. The morphological evolution process indicates that the urchin‐like microspheres originate from the self‐assembly of nanoplates, which then grow into urchin‐like microstructures with nanofibers on the surface.
A series of novel temperature and pH responsive block copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM) and poly(L ‐lysine) (PLL) were synthesized. The effect of pH and the length of PLL on the lower critical solution temperature (LCST) of PNIPAM, and the self‐assembly of these PLL‐based copolymers induced by temperature and pH changes were investigated by the cloud point method, dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM). These PNIPAM‐b‐PLL copolymers can self‐assemble into micelle‐like aggregates with PNIPAM as the hydrophobic block at acidic pH and high temperatures; and at alkaline pH and low temperatures, they can self‐assemble into particles with PLL as the hydrophobic block. The copolymers may have potential applications in biotechnological and biomedical areas as drug release carriers.
An organosilane with an alkyne group at the non‐condensable end, [(2‐propynylcarbamate)propyl]triethoxysilane, has been synthesized. Condensation of this organosilane with tetraethoxysilane can be achieved by a co‐condensation strategy to produce silica nanoparticles with surface alkyne functionality. The size and uniformity of size distribution of the silica nanoparticles are influenced by varying the concentration of the added organosilane. The alkyne‐functionalized silica nanoparticles are coupled directly with azide‐modified polymers by ‘click chemistry’ to yield organic–inorganic hybrid nanomaterials.
We describe an enzyme‐responsive polymeric vehicle, which is of great interest in controlled drug delivery, biosensing, and other related areas. The polymer synthesized using lipase as catalyst in DMSO has a favorable molecular structure that is quickly hydrolyzed by lipase in aqueous phase, and allows a fast release of encapsulated molecules.
The complex formation of oppositely charged surfactants with some polypeptides is known to induce β‐sheet or helix formation. Here, we report on the complex formation of cylindrical brush polymers with poly(L ‐lysine) side chains and sodium dodecylsulfate (SDS). With increasing amount of added surfactant the cylindrical polymers first adopt a helical conformation with a pitch of approximately 14–24 nm followed by a spherically collapsed structure before eventually precipitation occurs. CD measurements suggest that the helix formation of the cylindrical brush polymers is driven by the hydrophobicity of the β‐sheets formed by the PLL side chain–SDS complexes.
Combinations of synthetic and natural macromolecules offer a route to new functional materials. While biological and polymer chemistry may not be natural bedfellows, many researchers are focusing their attention on the benefits of combining these fields. Recent advances in living radical polymerization have provided methods to build tailor‐made macromolecular moieties using relatively simple processes. This has led to a plethora of block copolymers, end‐functional polymers and polymers with a whole range of biological recognition abilities. This review covers work carried out until late 2006 combining living radical polymerization with proteins and peptides in the rapidly‐expanding field of bioconjugation.
We describe the preparation and characterization of uniaxial magnetic gels. Fibril formation of the embedded magnetic particles generates easily detectable magnetic and optical anisotropies. A finite magnetization is frozen‐in and leads to a ferromagnetic‐like response in small homogeneous external magnetic fields. We present, for the first time, frequency dependent measurements of the shear modulus G′. Despite their optical and magnetic anisotropy, the gels are mechanically isotropic.
The time‐dependent G′ for a ferrogel in the parallel orientation in a homogeneous field of 200 mT. 相似文献
We report the simple one‐pot synthesis of size tunable zinc oxide nanoparticles (ZnO NPs) out of an organometallic ZnO precursor using the self‐assembly of solution phase polystyrene‐block‐poly(2‐vinylpyridine) micelles. The resulting hybrid material could be deposited on various substrates in a straightforward manner with the NPs showing size‐dependent absorption and photoluminescence due to the quantum‐size effect. We compare the results to the assembly of preformed NPs which are selectively incorporated in the poly(2‐vinylpyridine) core of the micelles due to the high affinity of ZnO to vinylpyridine.
