Self‐Assembled Hollow Polyaniline/Au Nanospheres Obtained by a One‐Step Synthesis

Self‐assembled hollow nanosphere composites of polyaniline and Au nanoparticles (PANI‐p‐TSA/Au) were chemically synthesized from solutions containing p‐toluenesulfonic acid (p‐TSA) with the addition of gold chloride trihydrate as the oxidant. The composite materials were characterized by SEM, TEM, and a range of spectroscopic methods. Spectroscopic characterizations confirmed that the polymeric product is a form of doped PANI, while electron diffraction and X‐ray diffraction showed that elemental Au was present in the PANI‐p‐TSA/Au nanocomposites. The room temperature electrical conductivity of the PANI‐p‐TSA/Au nanocomposites was two orders of magnitude greater than a PANI‐p‐TSA obtained in the presence of ammonium persulfate as the oxidant under the same conditions.

     

Synthesis of Folic Acid Functionalized PLLA‐b‐PPEGMA Nanoparticles for Cancer Cell Targeting

Poly(L ‐lactic acid)‐block‐poly(poly(ethylene glycol) monomethacrylate) (PLLA‐b‐PPEGMA) has been prepared by the ring‐opening polymerization of lactide with a double‐headed initiator, 2‐hydroxyethyl 2′‐methyl‐2′‐bromopropionate (HMBP), followed by atom transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethacrylate (PEGMA). PLLA‐b‐PPEGMA nanoparticles with encapsulated Fe₃O₄ are prepared by a solvent evaporation/extraction technique, and then further functionalized with folic acid, a cancer targeting ligand. Our results show that such functionalized PLLA‐b‐PPEGMA nanoparticles have good potential as carriers for targeted drug delivery in cancer treatment.

     

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.

     

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.

     

A Discrete,Space Variation Model for Studying the Kinetics of Shape Deformation of Vesicles Coupled with Phase Separation

Summary: The evolution dynamics of phase separation, coupled with shape deformation of vesicles is described by using dissipative dynamic equations, specifically the time‐dependent Ginzburg‐Landau (TDGL) equations. In order to improve the numerical stability and thus to efficiently deal with a large deformation of vesicles, a new algorithm, namely the discrete space variation model (DSVM) has been developed for the first time. The algorithm is based on the variation of the discretized free‐energy functional, which is constructed in discrete membrane space, in contrast to the commonly used continuous free‐energy functional. For the sake of numerical tractability, only the cylindrical vesicles (2D), with two components, are taken into consideration to illustrate the efficiency and validity of new algorithm. The simulation results, based on the DSVM algorithm have been compared with those from both linear analysis and strong segregation theory using the continuous space free‐energy functional. It is found that the DSVM algorithm can correctly describe the coupling between the lateral phase‐separation on the vesicle membrane and the vesicle shape deformation, both for early and late stages.

A flower‐like vesicle obtained by DSVM simulation.     

Preparation of Well‐Defined Poly[(ethylene oxide)‐block‐(sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate)] Diblock Copolymers by Water‐Based Atom Transfer Radical Polymerization

Summary: Well‐defined poly[(ethylene oxide)‐block‐(sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate)] diblock copolymers [P(EO_m‐b‐AMPS_n)], have been obtained by water‐based ATRP using α‐methoxy‐ω‐(2‐methylbromoisobutyrate) poly(ethylene oxide)s (MeO‐P[EO]_m‐BrⁱB with m ranging from 12 to 113) and CuBr · 2Bpy (Bpy for 2,2′‐bipyridyl) as macroinitiator and catalytic complex, respectively. Compared to direct polymerization in water, it has been demonstrated that the water/methanol (3:1, v/v) mixture is better suited for predicting the final number‐average molar mass from the initial monomer‐to‐macroinitiator molar ratio and achieving a quite narrow polydispersity, even at high monomer conversion ( ≈ 1.4 at 80% conversion). The effect of temperature, solvent mixture composition and addition of NaCl salt on the polymerization rate and extent of control over the copolymer molecular parameters have been highlighted as well.

     

Novel C‐acylated triazole derivatives of ravuconazole,an azole antifungal agent

Novel C‐acylated triazoles were synthesized from ravuconazole via bicyclic triazole lactone. The synthesis and antifungal activity of these C‐acylated derivatives are described.     

Stable Aqueous Dispersion of PEGylated Nanoparticles by Polyelectrolyte Complex Formation

Stable aqueous dispersions of nanoparticles were prepared by polyelectrolyte complex formation between well‐defined poly(ethylene glycol)‐block‐poly(2‐acrylamido‐2‐methyl‐1‐propane sodium sulfonate) and poly(ethylene glycol)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] diblock copolymers. Controlled synthesis of the copolymers was achieved by water‐based atom transfer radical polymerization (ATRP). The nanoparticles were characterized by a quite narrow and monomodal size distribution as evidenced by dynamic light scattering (DLS) and confirmed by atomic force microscopy (AFM) after solution casting and freeze‐drying.

     

Polypeptide‐Shelled Poly(propylene imine) Dendrimers and Their Complexing Properties towards Copper(II) Ions

Summary: Polypeptide‐shelled poly(propylene imine) dendrimers were realized by ring‐opening polymerization of α‐amino acid N‐carboxyanhydrides, initiated by dendrimers as core molecules. Polypeptides with 2nd generation core were used as model compounds to investigate interior complexes between metal ion and surface‐modified dendrimers. Micro‐calorimetric measurements outlined the formation of approximate 1:1 complexes between Cu^II and polypeptide‐shelled dendrimers and the influence of polypeptide chain compositions on differential molar heats of complexation.

Composition of one of the polypeptides synthesized.     

Reaction of Boranes with TMS Diazomethane and Dimethylsulfoxonium Methylide. Synthesis of Poly(methylidene‐co‐TMSmethylidene) Random Copolymers

Summary: Borane reacts with TDM by a sequence of insertion and disproportionation reactions to yield tris‐(trimethylsilylmethyl)borane. No further addition of TDM occurs. Triallylborane and tris‐(4‐methoxyphenylethyl)borane initiate the copolymerization of TDM and dimethylsulfoxonium methylide. The reactions afford TMS‐substituted polymethylene oligomers. The resultant poly(methylidene‐co‐TMSmethylidene) random copolymers arise from incorporation of TMSmethylidene (CHSiMe₃) and methylidene (CH₂) groups into the growing polymer chain one carbon at a time.

Trialkylborane‐catalyzed copolymerization of trimethylsilyl diazomethane and dimethylsulfoxonium methylide.     

Addition‐Fragmentation Chain Transfer Involving Dimers of α‐Methylvinyl Monomers Studied by ESR Spectroscopy: Competition between Fragmentation and Bimolecular Termination

Detection of the adduct radical by ESR spectroscopy and after‐effect ESR measurements of the adduct radical concentrations in the photosensitized polymerization of styrene (St) in the presence of dimers of α‐methylstyrene (MSD) and methyl methacrylate have revealed that the dominant mechanism of adduct radical loss changes from bimolecular termination to fragmentation as the temperature is increased beyond 90 °C for St/MSD.

     

Synthesis of a Fluorescent Polymer Bearing Covalently Linked Thienylene Moieties and Rhodamine for Efficient Sensing

A novel conjugated polymer (RB‐PPETE) of poly[p‐(phenylene ethynylene)‐alt‐(thienylene ethynylene)] (PPETE) bearing covalently linked thienylene rings and Rhodamine B units has been synthesized and successfully used to detect metal ions. The Rhodamine B exists as a lactone, which is colorless and non‐fluorescent. Hg²⁺ ions can induce the Rhodamine group to form a ring‐opened state. The fluorescence resonance energy transfer (FRET) was demonstrated in the polymer, and in the presence of Hg²⁺ ions the excitation energy along the backbone of the conjugated polymer is transferred to the energy acceptor (Rhodamine B), which leads to a visual color change of the solution from slight yellow to orange. Meanwhile, this new system shows outstanding Hg²⁺‐selective FRET off–on type fluoroionophoric properties among the representative metal ions in tetrahydrofuran.

     

Flow‐Induced Polymer Degradation During Ink‐Jet Printing

We report for the first time evidence of flow‐induced polymer degradation during inkjet printing for both poly(methyl methacrylate) (PMMA) and polystyrene (PS) in good solvent. This has significance for the deposition of functional and biological materials. Polymers having either less than 100 kDa or greater than approximately 1 000 kDa show no evidence of molecular weight degradation. The lower boundary condition is a consequence of low Deborah Number De imposed by the printhead geometry and the upper boundary condition due to visco‐elastic damping. For intermediate molecular weights the effect is greatest at high elongational strain rate and low solution concentration with higher polydispersity polymers being most sensitive to molecular weight degradation. For low polydispersity samples, PDi ≤ 1.3, chain breakage is essentially centro‐symmetric induced either by turbulance or overstretching when the strain rate increases well beyond a critical value, that is the stretching rate is high enough to exceed the rate of relaxation. For higher polydispersity samples chain breakage is consistent with almost random scission along the chain, inferring that the forces required to break the chain are additionally transmitted either by valence bonds, i.e. network chains and junctions or discrete entanglements rather than solely by hydrodynamic interaction.

     

Gold Nanoparticles Functionalized by a Dextran‐Based pH‐ and Temperature‐Sensitive Polymer

A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.

     

Kinetic Modeling as a Tool to Understand and Improve the Nitroxide Mediated Polymerization of Styrene

Kinetic modeling is used to obtain insight in the complex interplay between reaction rates and obtained polymer properties in the SG1 and the TEMPO mediated bulk polymerization of styrene at 396 K. The increase of the viscosity during NMP is accounted for. At higher targeted chain lengths, chain transfer to dimer and transfer from nitroxide to dimer are shown to cause the experimentally observed reduced control over the average polymer properties and to result in a clear fronting of the polymer chain length distribution. The potential of kinetic modeling to design tailor‐made synthesis strategies is illustrated. Simulations indicate that careful control of the polymerization conditions allows to obtain an important improvement of the polymer properties. The approach is also applicable for NMP mediated by other alkoxyamines/nitroxides and allows to expand the application range of NMP for styrene polymerization in particular to synthesize complex polymer architectures by assembly of functionalized polymers.

     

Cross‐Linked Conjugated Polymers for Achieving Patterned Three‐Color and Blue Polymer Light‐Emitting Diodes with Multi‐Layer Structures

Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross‐linking of the main polymer chains. The cross‐linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three‐color polymer light‐emitting diodes (PLEDs) with a multi‐layer structure can be easily realized by a dry photo‐pattern in an active‐gas‐free environment. Multi‐layer blue devices with dramatically enhanced efficiency can also be achieved conveniently.

     

Synthesis of Silver Nanoparticles Using a Novel Graft Copolymer and Enhanced Particle Stability via a “Polymer Brush Effect”

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.

     

Enzyme‐Catalyzed Preparation of Aliphatic Polyesters Containing Thioester Linkages

Aliphatic polyesters containing thioester linkages were enzymatically prepared by both the copolymerization of lactone with mercaptoalkanoic acid and by the transesterification of polyesters with mercaptoalkanoic acids. The enzymatic copolymerization of ε‐caprolactone with 11‐mercaptoundecanoic acid (11MU) and 3‐mercaptopropionic acid (3MP) was performed under reduced pressure using an immobilized lipase from Candida antarctica (CA). The transesterification of poly(ε‐caprolactone) and poly[(R)‐3‐hydroxybutyrate] was carried out with 11MU and 3MP using lipase CA under reduced pressure.

     

Synthesis and Characterization of Novel Biodegradable Copolymers of 5‐Benzyloxy‐1,3‐dioxan‐2‐one and Glycolide

A series of novel biodegradable random copolymers of 5‐benzyloxy‐1,3‐dioxan‐2‐one (5‐benzyloxy‐trimethylene carbonate, BTMC) and glycolide were synthesized by ring‐opening polymerization. The copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The incorporation of BTMC units into the copolymer chains results in good solubility of the polymers in common solvents. The in vitro degradation rate can be tailored by adjusting the composition of the copolymers.

The in vitro degradation of the homopolymers and poly(BTMC‐co‐GA) copolymers.     

A Rapid Eco‐Friendly Synthesis of Poly(butylene succinate) by a Direct Polyesterification under Microwave Irradiation

Summary: A rapid and eco‐friendly synthesis of poly(butylene succinate) (PBS) using microwaves was developed in the presence of 1,3‐dichloro‐1,1,3,3‐tetrabutyldistannoxane as catalyst. To determine the optimum conditions, the effect of catalyst concentration, bulk vs. solution polymerization, reaction time, temperature, and stoichiometry of the monomers were studied. Based on the optimum conditions, PBS with a weight‐average molecular weight of 2.35 × 10⁴ was obtained in a short time of 20 min.

Synthesis of poly(butylene succinate) under microwave irradiation.