Macromolecular Rapid Communications

Xie, Jingwei; Li, Xiaoran; Xia, Younan

doi: 10.1002/marc.200890045pmid: N/A

Cover: Electrospinning is a powerful tool for generating one‐dimensional nanostructured materials for a range of biomedical applications including controlled release, drug delivery, and tissue engineering. The cover shows images of the schematic of electrospinning setup (upper left), cells with elongated and irregular shape (upper left and down left), and ordered and disordered neurites' outgrowth patterns (upper right and down right) on an aligned and randomly electrospun nanofiber mat. Further details can be found in the article by J. Xie, X. Li, and Y. Xia* on page 1775.

doi: 10.1002/marc.200890046pmid: N/A

Xie, Jingwei; Li, Xiaoran; Xia, Younan

doi: 10.1002/marc.200800381pmid: 20011452

Electrospinning has been exploited for almost one century to process polymers and related materials into nanofibers with controllable compositions, diameters, porosities, and porous structures for a variety of applications. Owing to its high porosity and large surface area, a non‐woven mat of electrospun nanofibers can serve as an ideal scaffold to mimic the extracellular matrix for cell attachment and nutrient transportation. The nanofiber itself can also be functionalized through encapsulation or attachment of bioactive species such as extracellular matrix proteins, enzymes, and growth factors. In addition, the nanofibers can be further assembled into a variety of arrays or architectures by manipulating their alignment, stacking, or folding. All these attributes make electrospinning a powerful tool for generating nanostructured materials for a range of biomedical applications that include controlled release, drug delivery, and tissue engineering.

Mantzaridis, Christos; Pispas, Stergios

doi: 10.1002/marc.200800402pmid: N/A

We report here on the formation of hybrid compound block copolymer micelles encapsulating gold nanoparticles, utilizing a direct and general preparation method. The giant hybrid compound micelles are structured with micelles of PS‐b‐P2VP with gold nanoparticles in their P2VP core and PI‐b‐PS chains as the outer part of the compound micelles. The gold nanoparticles were produced using gold ion‐loaded PS‐b‐P2VP micelles as a nanoreactor, in a PS selective solvent (toluene), by the subsequent reduction of gold ions. The synthesis of the gold nanoparticles was monitored by UV‐vis spectroscopy. The gold containing micelles were then encapsulated in larger micelles of PI‐b‐PS copolymer, by successive utilization of toluene and heptane with the intermediate evaporation of toluene. The nanoassembly of the compound materials comprised a PI corona and a PS compound core, with P2VP/Au0 domains, and was characterized using UV‐vis spectroscopy, dynamic light scattering and transmission electron microscopy.

Cho, Eun Seon; Hong, Sung Woo; Jo, Won Ho

doi: 10.1002/marc.200800457pmid: N/A

A new pH sensor based on carbon nanotubes (CNTs), which consist of a fluorescent molecule and a CNT attached to each chain end of a pH sensitive polysulfonamide, respectively, is synthesized, and its pH sensitivity is examined in terms of the fluorescent quenching efficiency of the CNT. The pH sensitive polymeric linker shows an abrupt conformational change between an expanded coil structure and a collapsed globule structure, which results in the drastic on‐and‐off fluorescent quenching efficiency because of the change in the distance between the fluorophore and CNT. This CNT‐based sensor responds to a small change in pH with well‐defined on‐and‐off behavior, and also shows an excellent reversibility against pH change, which explains its feasibility to be widely used in the areas of biological and environmental applications.

Yi, Hunan; Johnson, Richard G.; Iraqi, Ahmed; Mohamad, David; Royce, Richard; Lidzey, David G.

doi: 10.1002/marc.200800440pmid: N/A

A series of donor/acceptor carbazole copolymers comprising alternating 6,7‐diphenyl‐4,9‐bis‐(thiophen‐2‐yl)‐(1,2,5)thiadiazolo(3,4‐g)quinoxaline and 3,6‐dimethyl‐9‐alkyl‐9H‐carbazole repeat units (P1), or 3,6‐dimethyl‐9‐triarylamino‐9H‐carbazole repeat units (P2), or 9‐triarylamino‐9H‐carbazole repeat units (P3) has been prepared following Suzuki polymerization procedures. P3 absorbs light up to 1 200 nm and has an energy gap of 1.1 eV, while P1 and P2 have energy gaps of 1.3 and 1.25 eV, respectively. Photovoltaic cells with ITO/PEDOT:PSS/P3:PCBM (1:1 w/w)/Ca showed an open‐circuit voltage of 0.4 V under white light illumination, power conversion efficiency of 0.61%, and short‐circuit current of 5.2 mA · cm−2.

Zhao, Changwen; Zhuang, Xiuli; He, Chaoliang; Chen, Xuesi; Jing, Xiabin

doi: 10.1002/marc.200800494pmid: N/A

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.

Zhang, Kai; Zou, Yang; Xu, Xichen; Gong, Shaolong; Yang, Chuluo; Qin, Jingui

doi: 10.1002/marc.200800521pmid: N/A

Two new carbazole derivatives with the oxadiazole moiety substituted at the 9 position of carbazole have been facilely synthesized by an aromatic nucleophilic substitution reaction of arylamine and fluoroarenes. Alternating copolymers with spirobifluorene were then prepared by a Suzuki coupling reaction. Spirobifluorene units together with the bulky oxadiazole pendant significantly enhance the morphological stability of the copolymers. An increased π‐electron delocalization in P2 with 2,7‐coupling of carbazole results in a decrease of absorption and phosphorescence emission energies as compared to P1 with 3,6‐coupling of the carbazole. The bandgaps and energy levels of the polymers can be tuned by different coupling positions between carbazole and the spirobifluorene moieties.

Manceau, Matthieu; Rivaton, Agnès; Gardette, Jean‐Luc

doi: 10.1002/marc.200800421pmid: N/A

We studied the role that singlet oxygen plays in the solid‐state photochemistry of poly(3‐hexylthiophene) (P3HT). The photosensitized formation of singlet oxygen by solid‐state P3HT and its subsequent reactivity on the polymer were investigated. Using a fluorescent probe, it was found that singlet oxygen (1O2) could be produced by irradiation of P3HT by photosensitization, with no oxidation of the polymer. In addition, 1O2 was directly formed on P3HT via a chemical reaction, again with no oxidation of the polymer. These results give strong evidence that 1O2 is not the principal photo‐oxidative degradation intermediate of P3HT, which conflicts with previous reports.

Radhakrishnan, Bindushree; Constable, Andrew N.; Brittain, William J.

doi: 10.1002/marc.200800435pmid: N/A

The in situ formation of functionalized silica nanoparticles is reported. The reactive stabilizers used in the study, (3‐(2‐bromoisobutyryl)propyl)triethoxysilane and (3‐(2‐bromoisobutyryl)propyl)ethoxydimethylsilane, have an atom transfer radical polymerization (ATRP) initiator at the noncondensable end. Condensation with tetraethoxysilane yields silica nanoparticles with a surface‐immobilized initiator. The size of these functionalized silica nanoparticles can be controlled by varying the time of initiator addition and initiator concentration. The silica particle sizes ranged from 10 to 300 nm. With the initiator functionalized silica nanoparticles, ATRP synthesis was performed with styrene, tert‐butyl acrylate, and methyl acrylate to produce organic–inorganic nanomaterials.