Vapor‐Based Synthesis of Poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] and Its Use for Biomimetic Surface Modifications

Summary: The vapor‐based synthesis and characterization of a reactive polymer, poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] ( 1 ), have been reported. The reactive polymer coating enables the immobilization of oligosaccharides via the chemoselective aldehyde‐hydrazide coupling reaction.

     

Linear Azo Polymer Containing Conjugated 5,5′‐Azodisalicylic Acid Segments in the Main Chain: Synthesis,Characterization, and Degradation

Summary: Copolymers of poly(ethylene oxide) (PEO) and 5,5′‐azodisalicylic acid (Olsalazine, OLZ) were synthesized and evaluated by hydrolysis and in‐vitro biodegradation with azoreductase. It was found that changing the molecular weight of the PEO blocks affected the loading ratio of OLZ, and resulted in significant differences in the hydration and degradability of the copolymers. These novel azo‐containing copolymers can be used in colon‐specific drug delivery.

Release of 5‐ASA from OLZ and PEO‐OLZ copolymers incubated with rat cecum content in the presence of benzyl viologen and α‐D ‐glucose.     

Dewetting Process of Polyelectrolyte Multilayer Films in Hot Water

Summary: We analyzed quantitatively the effects of temperature on the morphologic evolution of the desorption process in hot water measured ex situ by atomic force microscopy. The morphology of the hole that forms with immersion of the polyelectrolyte film in hot water has characteristics similar to those from polymer dewetting processes near the glass transition temperature. The hole diameter immediately reaches a maximum in the desorption process while the number of holes increases linearly with time.

AFM images of the morphology of PEM film after immersion in hot water 60 min.     

Evolution and Operating Experiences with Different Drop‐On‐Demand Systems

Summary: We describe the development of different drop‐on‐demand systems particularly for applications for the liquid handling of biopolymers. Different designs of drop‐on‐demand systems developed by the authors are described. Experiments with these systems show the applicability for pipetting different liquids with different properties. Commercially available systems are also tested. A comparison of the different approaches leads to a discussion of the best fields of application of the different approaches or, alternatively, to the potential further development of the drop‐on‐demand technologies.

Principle setup of the print heads.     

Polyimide/Diamond Nanocomposites: Microstructure and Indentation Behavior

Polyimide/diamond nanocomposites have been synthesized from 4,4′‐diaminodiphenyl ether (ODA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). All the polyimides show non‐crystalline X‐ray diffraction. The frequent occurrence of particular interatomic distances (R) denoted by the non‐crystalline X‐ray diffraction maxima are determined. An ultramicro‐indentation technique is employed to evaluate the effects of nano‐diamond particles on the indentation behavior of polyimides. Indentation size effect is observed and discussed.

     

Tandem RAFT Polymerization and Click Chemistry: An Efficient Approach to Surface Modification

PS grafted silica nanoparticles have been prepared by a tandem process that simultaneously employs RAFT polymerization and click chemistry. In a single pot procedure, azide‐modified silica, an alkyne functionalized RAFT agent and styrene are combined to produce the desired product. As deduced by thermal gravimetric and elemental analysis, the grafting density of PS on the silica in the tandem process is intermediate between analogous “grafting to” and “grafting from” techniques for preparing PS brushes on silica. Relative rates of RAFT polymerization and click reaction can be altered to control grafting density.

     

Rheology and Physical Properties of Polyethylene/Polyethylene‐Ionomer Blends and their Clay Nanocomposites

Rheological and solid‐state physical properties of blends containing high‐density polyethylene (HDPE) and a polyampholyte derivative (PE‐g‐PA) are assessed along with their onium ion‐exchanged montmorillonite clay (NR‐MM) nanocomposites. Strong deviations from the log‐additivity rule of zero‐shear viscosity, combined with synergistic behavior in tensile moduli, are consistent with a multi‐phase blend morphology. While this affects clay dispersion in filled blends, PE‐g‐PA/HDPE based nanocomposites are shown to exhibit a favorable balance between material stiffness and ductility.

     

The β Phase Formation Limit in Two Poly(9,9‐di‐n‐octylfluorene) based Copolymers

Random copolymers of poly(9,9‐di‐n‐octylfluorene) (PF8) incorporating 0, 8, 12, 15, and 20% dibenzothiophene (DBT), and copolymers with 2, 5, 8, 12, and 15% dibenzothiophene‐S,S‐dioxide (S‐unit) were synthesised. Absorption and emission spectra of thin films indicate that the DBT system shows a linear decrease of toluene vapour induced β phase with increasing DBT content to a 20% cutoff, whilst in the S‐unit copolymers the β phase is present up to 12% co‐monomer content, and at 15% the characteristic absorption peak is absent or masked. These results demonstrate the limits, in thin films, at which the β phase can be formed in widely used PF8 copolymer systems for device applications and clearly show that it is practical to use copolymers having electron or hole transport units in the polyfluorene backbone and still be able to form efficient β phase emission sites.

     

Simple Patterning of Cells on a Biocompatible Nonchemically Amplified Resist

Summary: A simple lithographic process in conjunction with a novel biocompatible nonchemically amplified photoresist material was successfully used for cell patterning. UV light irradiation on selected regions of the nonchemically amplified resist film renders the exposed regions hydrophilic by the formation of carboxylic groups. Mouse fibroblast cells were found to be preferentially aligned and proliferated on the UV light exposed regions of the nonchemically amplified resist film where carboxylic groups were present.

Schematic representation of the simplified lithographic process used for cell patterning.     

Pressure,the Critical Factor Governing Final Microstructures of Cured Rubber/Clay Nanocomposites

Summary: The changes in both local intercalated structures and spatial distribution states of organoclays (OC) in rubber/clay nanocomposites (RCNs) caused by vulcanization were monitored by using WAXD and TEM, and the corresponding mechanism was studied. It was first discovered that the pressure was the critical factor determining the final microstructures of cured RCNs. The cured RCNs with fine dispersion could be obtained through vulcanization under atmospheric pressure.

TEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).     

The Role of Oxidation in the Migration Mechanism of Layered Silicate in Poly(propylene) Nanocomposites

Summary: Evidence of clay migration from the core to the surface of poly(propylene)/montmorillonite nanocomposites is provided. A three‐ to fivefold increase in the clay concentration of the surface is obtained during isothermal heating in oxidative atmosphere. The mechanism of migration is investigated by means of attenuated total reflectance Fourier transform infrared spectrometry. It is shown that oxygen plays a fundamental role in the migration mechanism.

ρ_Si versus c for the annealed samples.     

Amphiphilic Multi‐Arm Block Copolymer Based on Hyperbranched Polyester,Poly(L‐lactide) and Poly(ethylene glycol) as a Drug Delivery Carrier

A novel type of biodegradable/biocompatible amphiphilic hyperbranched copolymer (H40‐PLA‐b‐MPEG) was synthesized. Its micellar properties were studied by DLS, fluorescence spectroscopy and TEM. The drug release profile showed that the H40‐PLA‐b‐MPEG micelles provide an initial burst release, followed by a sustained release of the entrapped hydrophobic model drug over a period of 4 to 58 h. The copolymer degraded hydrolytically within 6 weeks under physiological conditions. The MTT assay showed no obvious cytotoxicity against a human endothelial cell line at a concentration range of 0–400 µg · mL⁻¹. These results indicate that the H40‐PLA‐b‐MPEG micelles have great potential as hydrophobic drug delivery carriers.

     

Large‐Scale Synthesis of Necklace‐Like Single‐Crystalline PbTiO3 Nanowires

Summary: We show in this communication that large‐scale necklace‐like single‐crystalline tetragonal perovskite PbTiO₃ nanowires can be obtained via a simple electrospinning method. The morphology and the crystal structure are investigated by SEM, XRD, and HRTEM. The length of the necklace‐like PbTiO₃ nanowires is from tens to several tens of micrometers, the wider the diameter of it is between 100 and 200 nm and the thinner the part is between 20 and 50 nm. The necklace‐like PbTiO₃ nanowires exhibit high surface photovoltage under the action of external electric field, which is probably applicable in displaying photoelectric devices of heterojunction structure.

SEM image of the electrospinning necklace‐like PbTiO₃ nanowires.     

New Polylactide/Layered Silicate Nanocomposite: Nanoscale Control Over Multiple Properties

The preparation, characterization, materials properties, crystallization behavior and biodegradability of a polylactide (PLA)/organically modified layered silicate nanocomposite is described. Wide‐angle X‐ray diffraction and high‐resolution TEM analyses confirmed that intercalated stacked and disordered/exfoliated mica layers coexist in the nanocomposite. The nanocomposite showed improved materials properties and crystallization behavior with a simultaneous improvement in biodegradability as compared to neat PLA.

Degree of biodegradation (i.e. CO₂ evolution) of neat PLA and PLACN4 under compost conditions.     

Organically Modified Layered Titanate: A New Nanofiller to Improve the Performance of Biodegradable Polylactide

Summary: The preparation and characterization of a new type of nanocomposite material that is based on biodegradable polylactide (PLA) and organically modified layered titanate, is reported. Layered titanate, modified with a N‐(cocoalkyl)‐N,N‐[bis(2‐hydroxyethyl)]‐N‐methylammonium cation, was used as a new nanofiller (OHTO) for the nanocomposite preparation. Wide‐angle X‐ray diffraction and transmission electron microscopy (TEM) analyses confirmed that titanate layers were intercalated and nicely distributed in the PLA matrix. The materials properties of neat PLA improved remarkably after nanocomposite preparation.

UV/vis transmission spectra of neat PLA and a nanocomposite.