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Three-armed star-shaped poly(ester amine) was synthesized by Michael addition polymerizations of equal molar ratio of ethylene glycol diacrylate (EGDA) and piperazine (PZ) in the presence of a small amount of multifunctional monomer, 1,3,5-triacryloylhexa-hydro-1,3,5-triazine (TT) in CHCl3. When the polymerization proceeded almost completely, the molecular weight of the polymers formed were determined by the feed molar ratio of difunctional monomer to multifunctional monomer, and the molecular weight distribution (Mw/Mn) approached the theoretical value (Mw/Mn =1+1/f). The mechanism of the polymerization was investigated by 1H NMR and Gel permeation chromatography (GPC). The monomer concentration and the molar ratio of difunctional monomers/multifunctional monomer played an important role in the polymerization.

Aqueous solution of micelles prepared from novel PS-b-PNIPAM with fluorescent group CEA at the junction between two blocks displays logical responsive switches on temperature and fluorescence; at lower temperature, stretching of PNIPAM chains causes high mobility of CEA leading to formation of more excimer species; at higher temperature, shrinking of PNIPAM chains isolates the fluorescent groups between the core and shell, resulting in fewer excimer species.

A facile strategy for control of the polymer topologies can be achieved simply by tuning the feed molar ratio of catalyst to transfer agent in the controlled radical polymerization.

Cellulose-graft-poly(N,N-dimethylamino-2-ethyl methacrylate) (cellulose-g-PDMAEMA) copolymers were prepared by homogeneous atom transfer radical polymerization (ATRP) under mild conditions. Cellulose macroinitiator was successfully synthesized by direct acylation of cellulose with 2-bromopropionyl bromide in a room temperature ionic liquid (RTIL), 1-allyl-3-methylimidazolium chloride. Copolymers were obtained via ATRP of N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) with CuBr/pentamethyldiethylenetriamine (PMDETA) as catalyst and N,N-dimethylformamide (DMF) as solvent without homopolymer byproduct. The grafting copolymers were characterized by (1)H NMR, FT-IR, and TGA measurements. The results confirmed that PDMAEMA had been covalently bonded to cellulose backbone. Furthermore, the assemblies or aggregates formed by cellulose-g-PDMAEMA copolymers in water were studied at various concentrations, temperatures, and pH values by means of UV, DLS, TEM, and AFM. The results indicate that the copolymers had the pH- and temperature-responsive properties similar to the expected stimuli-responses by PDMAEMA. The synthetic strategy presented here could be employed in the preparation of other novel biomaterials from a variety of polysaccharides.

Linear poly(ethylenimine)-graft-poly(ethylene glycol)s (LPEI-g-PEG) with various degrees of grafting and molecular weights were synthesized by Michael addition reaction of LPEI with methoxy poly(ethylene glycol) acrylate. The graft copolymers display pH-sensitive behaviors, and pH variation of the copolymer solution induced the aggregation of graft copolymers, forming the micelles with different sizes. The dynamic light scattering method was used to study the effects of ionic strength, chain composition and pH on hydrodynamic radius. With solvent evaporation of the micelles solution, various morphologies were formed.

Liang Qiu, Chun-Yan Hong, Cai-Yuan Pan Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui, People’s Republic of China Abstract: Redox- and pH-sensitive branched star polymers (BSPs), BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAIGP)ns, have been successively prepared by two steps of reversible addition–fragmentation chain transfer (RAFT) polymerization. The first step is RAFT polymerization of 2-(N,N-dimethylaminoethyl)methacrylate (DMAEMA) and p-(methacryloxyethoxy)benzaldehyde (MAEBA) in the presence of divinyl monomer, 2,2'-dithiodiethoxyl dimethacrylate (DTDMA). The resultant branched polymers were used as a macro-RAFT agent in the subsequent RAFT polymerization. After hydrolysis of the BSPs to form BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAGP)ns (BSP-H), the anticancer drug doxorubicin (DOX) was covalently linked to branched polymer chains by reaction of primary amine of DOX and aldehyde groups in the polymer chains. Their compositions, structures, molecular weights, and molecular weight distributions were respectively characterized by nuclear magnetic resonance spectra and gel permeation chromatography measurements. The DOX-loaded micelles were fabricated by self-assembly of DOX-containing BSPs in water, which were characterized by transmission electron microscopy and dynamic light scattering. Aromatic imine linkage is stable in neutral water, but is acid-labile; controlled release of DOX from the BSP-H-DOX micelles was realized at pH values of 5 and 6, and at higher acidic solution, fast release of DOX was observed. In vitro cytotoxicity experiment results revealed low cytotoxicity of the BSPs and release of DOX from micelles in HepG2 and HeLa cells. Confocal laser fluorescence microscopy observations showed that DOX-loaded micelles have specific interaction with HepG2 cells. Thus, this type of BSP micelle is an efficient drug delivery system. Keywords: RAFT polymerization, controlled release, doxorubicin, branched star polymer, pH-sensitive

A new type of polymer dispersed liquid crystal (PDLC) composite film has been made by polymerizing the mixture of di-methacrylates, methacrylates containing various groups and E-7. It was found that the long chain alkyl and mesogenic groups in methacrylate monomers greatly affected the saturation and threshold voltages and response time. The sharpness could be improved by addition of methacrylate monomers containing long chain alkyl and 4-butoxylbisphenyl based mesogenic group in appropriate ratios.

Lanthanide complexes have wide applications in biochemical research and biomedical imaging. We have designed and synthesized a new class of macrocyclic lanthanide chelates, Ln/DTPA-PDA-C(n), for cell labeling and magnetic resonance imaging (MRI) applications. Two lipophilic Gd3+ complexes, Gd/DTPA-PDA-C(n) (n = 10, 12), labeled a number of cultured mammalian cells noninvasively at concentrations as low as a few micromolar. Cells took up these agents rapidly and showed robust intensity increases in T1-weighed MR images. Labeled cells showed normal morphology and doubling time as control cells. In addition to cultured cells, these agents also labeled primary cells in tissues such as dissected pancreatic islets. To study the mechanism of cellular uptake, we applied the technique of diffusion enhanced fluorescence resonance energy transfer (DEFRET) to determine the cellular localization of these lipophilic lanthanide complexes. After loading cells with a luminescent complex, Tb/DTPA-PDA-C10, we observed DEFRET between the Tb3+ complex and extracellular, but not intracellular, calcein. We concluded that these cyclic lanthanide complexes label cells by inserting two hydrophobic alkyl chains into cell membranes with the hydrophilic metal binding site facing the extracellular medium. As the first imaging application of these macrocyclic lanthanide chelates, we labeled insulin secreting beta-cells with Gd/DTPA-PDA-C12. Labeled cells were encapsulated in hollow fibers and were implanted in a nude mouse. MR imaging of implanted beta-cells showed that these cells could be followed in vivo for up to two weeks. The combined advantages of this new class of macrocyclic contrast agents ensure future imaging applications to track cell movement and localization in different biological systems.

The Monte Carlo method has been applied to simulate the process of the self-assembling of amphiphilic diblock copolymers in a selective solvent. The simulations illustrated that the aggregates morphologies of A-b-B diblock copolymers in solution strongly depend on the length of corona-forming segments, i.e., with the decrease of the corona-forming segments, the transition of spherical micelles to rodlike aggregates occurs, which are in accord with the experimental results of Eisenberg and co-workers [Science 268, 1728 (1995); Macromolecules 32, 2239 (1999); 31, 3509 (1998); 29, 6359 (1996); 31, 9399 (1998)].

Silica nanotubes with controlled diameters and lengths were fabricated by a template-directed method. Nanowires composed of poly(2-dimethylaminoethyl methacrylate)-block-polystyrene (PDMAEMA–PS), which were fabricated by RAFT dispersion polymerization of styrene in methanol using PDMAEMA as a macro-RAFT agent, were used as sacrificial templates. The diameter of the polymeric nanowires can be adjusted by changing the degree of polymerization (DP) of the hydrophilic PDMAEMA block. As the chain length of the hydrophilic PDMAEMA block increases, the DP of the PS block for formation of the nanowires increases, leading to the diameter increase of the corresponding nanowires. Moreover, the polymeric nanowires with controlled lengths and diameters of the core and the shell can be fabricated on a large scale through polymerization-induced self-assembly and reorganization, conveniently. The weak polyelectrolyte, PDMAEMA shell, is an ideal nanoreactor for deposition of silica to form hybrid nanowires. Silica nanotubes were prepared by calcination of the hybrid nanowires.

This study proposes a unified method for a wide variety of image composition tasks. The proposed method is developed by constraining the responses of a set of filters to a target image. Each filter describes an attribute of the target image. Also, each attribute field is assumed to be equal to the corresponding attribute field of an input source. The constraints imposed by all those attributes are weighted heterogeneously and formulated into a minimisation problem. For different tasks, the required attributes (e.g. gradient, texture and colour constraints) can be specified by different sources (e.g. from a given image, constructed from several images or specified by users). The framework is flexible and can be configured to meet a variety of image editing tasks. To validate the effectiveness of this method, a variety of applications have been presented, including face data illumination removal, remote-sensing images fusion, texture transfer, multi-focus image fusion, seamless texture tiling and text layer transfer. The experimental results illustrate that the proposed method is effective in performance for the presented image editing tasks with comparisons to classical methods for the specified tasks.

Multi-block copolymers with well-controlled numbers of blocks and block chain length are synthesized for the first time using a 'polyinitiator'.

In this paper, in order to solve the interface-trap issue and enhance the transconductance induced by high-k dielectric in metal—insulator—semiconductor (MIS) high electron mobility transistors (HEMTs), we demonstrate better performances of recessed-gate Al2O3 MIS-HEMTs which are fabricated by Fluorine-based Si3N4 etching and chlorine-based AlGaN etching with three etching times (15 s, 17 s and 19 s). The gate leakage current of MIS-HEMT is about three orders of magnitude lower than that of AlGaN/GaN HEMT. Through the recessed-gate etching, the transconductance increases effectively. When the recessed-gate depth is 1.02 nm, the best interface performance with τit = (0.20−1.59) μs and Dit = (0.55−1.08) × 1012 cm−2 eV−1 can be obtained. After chlorine-based etching, the interface trap density reduces considerably without generating any new type of trap. The accumulated chlorine ions and the N vacancies in the AlGaN surface caused by the plasma etching can degrade the breakdown and the high frequency performances of devices. By comparing the characteristics of recessed-gate MIS-HEMTs with different etching times, it is found that a low power chlorine-based plasma etching for a short time (15 s in this paper) can enhance the performances of MIS-HEMTs effectively.

Addition of PS into St monomer can accelerate the SI-ATRP and the PS chains were grown to high molecular weight in a short time from silica nanoparticles and carbon nanotubes.

Selectivity for the Diels-Alder cycloaddition reaction of the electron-rich diene with single-walled carbon nanotubes was first investigated. This chemistry is a complete departure from the curvature-dependent reactivity based on the carbon pyramidalization angle.

A novel strategy for preparation of multiple nanostructural materials, which is the creation of such materials directly from controlled radical dispersion polymerization in one pot, has been developed. In the formation of polymeric nanomaterials, the chain length ratio of the hydrophobic to hydrophilic blocks is altered continuously, which induces two phase transitions, phase separation to form spherical micelles and re-organization of the resulting spheres to yield multiple morphologies including nanorods, nanotubes, vesicles and doughnuts. This is quite different from self-assembly of the block copolymer in a selective solvent, where nature and solubility parameter of the solvents are changed. In the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in methanol using poly(4-vinylpyridine) as macro RAFT agent, the resultant polymeric nanomaterials with various morphologies coexisted generally, however, uniform nanowires and vesicles could be prepared by appropriately selecting concentration of monomer and feed ratio, as well as by strict control of reaction conditions. One advantage of this strategy is that the nanomaterials with a concentration as high as 0.5 g mL−1 can be achieved, this provides possibility for studying extensive applications of the various nanomaterials.

Polymerization-induced self-assembly and re-organization (PISR) was used to prepare polymeric nanostructured materials with a variety of morphologies. Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in a selective solvent, methanol, was carried out using cyanoisopropyl dithiobenzoate-terminated poly(2-dimethylaminoethyl methacrylate) (PDMAEMA-DBT) as the macro chain transfer agent and stabilizer for investigation of the factors influencing the formation of morphologies. Various morphologies, including spherical micelles, nanostrings, vesicles and large compound vesicles, with different shapes were obtained by changing the feed ratios and reaction conditions. The sequential morphologic transitions from spherical micelles to nanostrings, to vesicles and to large compound vesicles via increasing the chain length ratio of the hydrophobic block to the hydrophilic one in the same system were observed for the first time. This approach can be performed at a high concentration, thus it can be scaled up for the reproducible preparation of nanostructured materials in a relatively high volume.

The preparation of exquisite hierarchical worm-like silica nanotubes by a simple sol–gel method is successfully achieved for the first time. Poly(2-(dimethylamino)ethyl methacrylate)-grafted multiwall carbon nanotubes (MWNT-g-PDMAEMA) were used as a sacrificial template, subsequent hydrolysis and polycondensation of tetraethoxysilane-produced MWNT–silica nanocomposites with lots of silica nanowires arranged on their surfaces. The length of the silica nanowires can be controlled by the deposition time of silica. After the templates were removed by calcination in air, hierarchical worm-like silica nanotubes with some of the characteristics of mesoporous materials, such as large surface area, multiple pore distribution and large pore volume, were obtained.

A simple and facile strategy has been developed for synthesis of nanomaterials via polymerization in high concentration; multiple morphologies can be created and tuned just by variation of the feed ratio and reaction conditions.

A facile and versatile method to prepare mesoporous core-shell nanostructures with a reversibly switchable nanoshell is reported. Reversible addition-fragmentation chain transfer (RAFT) functionalities were anchored to the exterior surface of mesoporous silica nanoparticles (MSNs), forming RAFT agent coated MSNs. RAFT polymerization was then conducted to graft a poly(acrylic acid) (PAA) shell onto the exterior surface of MSNs, producing novel smart nanocontainers with a MSN as the container and a pH-responsive PAA nanoshell as a smart nanovalve. The PAA nanovalve can control the access of guest molecules to and from the MSN nanocontainer. This core-shell nanostructure should have potential applications in drug and gene delivery.

Two new pyrrolidino[60]fullerene derivatives 2 and 4 with unsaturated bond were synthesized by [60]fullerene reacted with sarcosine and aldehydes 1 and 3 refluxing in toluene and characterized by FTIR, FD-mass, 1 HNMR, 13 CNMR and UVVis spectra

The formation of ring-shaped structures in an H-shaped block copolymer [a poly(ethylene glycol) backbone with polystyrene branches, i.e., (PS)2PEG(PS)2] thin film was investigated when it was annealed in saturated PEG-selective acetonitrile vapor. Our results clearly indicate that ring formation is determined by the initial morphology of the spin-coated film, the solvent vapor selectivity and the environmental temperature of the solvent-annealing process. Only the films with the initial core–shell cylindrical structure in strongly PEG-selective acetonitrile vapor could form the ring-shaped structures. Environmental temperature has an influence on the formation mechanisms. It was proven that the rings arising from the core–shell cylindrical structure of the pristine spin-coated (PS)2PEG(PS)2 film were caused by the migration of the PEG shells to the top surface in the process of PEG-selective vapor annealing at the environmental temperature of 15 °C. While at a higher environmental temperature (25 °C), the degree of swelling of the film and the chains’ mobility increased and the formation mechanism of the rings in this situation was similar to that in dilute solution.

Carbon nanotubes (CNTs) have many potential applications in biological and biomedical sciences as nanoscale probes and sensors, which need CNTs to be able to respond to biologically relevant stimuli, such as pH, temperature, glucose, glutathione, various ions, enzymes and proteins, etc. This highlight examines several representative CNTs responsive to pH, temperature, glucose, ions and DNA, covering both noncovalently and covalently functionalized CNTs for advanced biosensors and bioprobes.

Amphiphilic block copolymers, poly(ethylene oxide)-b-poly(N-acryloxysuccinimide) (PEO-b-PNAS) with various molecular weights have been successfully synthesized by atom transfer radical polymerization (ATRP) of NAS using functionalized PEO (PEO-Br) as ATRP macroinitiator. The self-assembling of the block copolymers in water, which is a good solvent for PEO and a non-solvent for PNAS, yielded spherical core-shell micelles with PNAS as core and PEO as shell. The cross-linked reaction of oxysuccinimide in PNAS chains with ethylenediamine occurred in the core of micelles, and the core cross-linked micelles were formed. The flower-like and dendritic aggregates were formed by self-assembling of the core cross-linked micelles on the glass slides or silicon wafers. Longer PNAS block in the block copolymers and higher evaporation temperature formed bigger spherical particles. The optical microscope was used to follow the formation and growth of the flower-like aggregates from the colloidal solution and the main driving forces for the self-assembling are solution fluid and interactions between PEO chains.

Self-assembly morphology effects on the crystalline behavior of asymmetric semicrystalline block copolymer polystyrene-block-poly(L-lactic acid) thin film were investigated. Firstly, a series of distinctive self-assembly aggregates, from spherical to ellipsoid and rhombic lamellar micelles (two different kinds of rhombic micelles, defined as rhomb 1 and rhomb 2) was prepared by means of promoting the solvent selectivity. Then, the effects of these self-assembly aggregates on crystallization at the early stage of film evolution were investigated by in situ hot stage atomic force microscopy. Heterogeneous nucleation initiated from the spherical micelles and dendrites with flat on crystals appeared with increasing temperature. At high temperature, protruding structures were observed due to the thickening of the flat-on crystals and finally more thermodynamically stable crystallization formed. Annealing the rhombic lamellar micelles resulted in different phenomena. Turtle-shell-like crystalline structure initiated from the periphery of the rhombic micelle 1 and spread over the whole film surface in the presence of mostly noncrystalline domain interior. Erosion and small hole appeared at the surface of the rhombic lamellar micelle 2; no crystallization like that in rhomb 1 occurred. It indicated that the chain-folding degree was different in these two micelles, which resulted in different annealing behaviors.

Monodispersed nanoparticles of Ag(I)–polymer hybrids have been prepared by using designed crown-ether-centred two-armed copolymers to chelate Ag+ ions at the interface of organic–aqueous solutions. The copolymer–Ag+ complex nanoparticles, as well as the reduced copolymer–Ag nanoparticles, have been characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS). The particle size can be varied by simply changing the polymer concentration, the monomers, and/or the molecular weight. The copolymer–Ag(I) hybrids exhibit weak photoluminescence, which was substantially enhanced after the hybrids were reduced to copolymer–silver nanoparticles with UV irradiation.

Functional micelles with a poly(N-isopropylacrylamide) (PNIPAM) shell and a cross-linked poly((acrylic acid)-co-(ethylene glycol diacrylate)) core have been successfully prepared in one pot by the reversible addition–fragmentation chain transfer (RAFT) copolymerization of acrylic acid and ethylene glycol diacrylate in selective solvent using PNIPAM-SC(S)Ph as a RAFT agent. Since PNIPAM and poly(acrylic acid) are temperature- and pH-sensitive polymers, respectively, the micelles obtained should display double environmental sensitivity to temperature and pH in water.