Assembly of Anionic Conjugated Polymer with 6‐O‐Modified PNP‐β‐Galactoside for Fluorescence Logic‐signal‐based Multiplex Detections of Enzymes

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.

     

Influence of Microwave Irradiation on the Lipase‐Catalyzed Ring‐Opening Polymerization of ε‐Caprolactone

Summary: The microwave (MW)‐assisted lipase‐catalyzed ring‐opening polymerization of ε‐caprolactone in boiling solvents was investigated for the first time. In case of boiling toluene or benzene the MW‐assisted reaction proceeded significantly slower compared to oil bath heating. On the other hand, using boiling diethyl ether as solvent, an increase of the polymerization rate due to MW irradiation was found. Yield, molecular weight measurements, and MALDI‐TOF analysis supported the results.

Reactivity of the MW‐assisted ring‐opening polymerization of ε‐caprolactone compared with conventional thermal heating in different solvents.     

A New Chemo‐Enzymatic Route to Side‐Chain Liquid‐Crystalline Polymers: The Synthesis and Polymerization of 6‐(4‐Methoxybiphenyl‐4′‐oxy)hexyl Vinyl Hexanedioate

A novel synthetic method combining chemo and enzymatic synthesis strategies was employed to prepare a vinyl acetate type monomer, 6‐(4‐methoxybiphenyl‐4′‐oxy)hexyl vinyl hexanedioate (VA‐LC). Homo‐ and copolymers of VA‐LC with maleic anhydride (MAn) were prepared by conventional free radical polymerization using 2,2′‐azobisisobutyronitrile (AIBN) and 1,1′‐azobis (cyclohexane carbonitrile) (AHCN) as an initiator at 95 and 60 °C, respectively. The thermal properties of the generated polymeric material were investigated by differential scanning calorimetry (DSC), and the optical texture was inspected by polarizing optical microscopy (POM). While the monomer VA‐LC does not exhibit liquid‐crystalline properties, poly(VA‐LC), and the alternating copolymer of VA‐LC with maleic anhydride both displayed such properties.

     

Microwave Accelerated Polymerization of 2‐Phenyl‐5,6‐dihydro‐4H‐1,3‐oxazine: Kinetics and Influence of End‐Groups on Glass Transition Temperature

Summary: The ring‐opening polymerizations of 2‐phenyl‐5,6‐dihydro‐4H‐1,3‐oxazine (PhOZI) with methyl tosylate (MeOTs) and butyl iodide (BuI) as initiators were performed in refluxing butyronitrile. Reaction kinetics under microwave irradiation was compared with conventional oil bath heating. The polymerization rates, under microwave irradiation, showed an acceleration by a factor of 1.8 (independently from the used initiator). The investigation of the thermal properties of the obtained poly(N‐benzoyl‐trimethyleneimine) showed the influence of molecular weight and end‐groups on the glass transition temperature.

The ring‐opening polymerizations of 2‐phenyl‐5,6‐dihydro‐4H‐1,3‐oxazine performed in refluxing butyronitrile.     

Multi‐Morphological Complex Aggregates Formed from Amphiphilic Poly(ethylene oxide)‐block‐Polydimethylsiloxane‐block‐Poly(ethylene oxide) Triblock Copolymers

Summary: Amphiphilic triblock copolymers (PEO_x‐b‐PDMS_y‐b‐PEO_x) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.

TEM images of the vesicles formed from PEO‐b‐PDMS‐b‐PEO.     

3‐Ethylated N‐Vinyl‐2‐pyrrolidone with LCST Properties in Water

The monomer 3‐ethyl‐1‐vinyl‐2‐pyrrolidone ( 3 ) and the homopolymer poly(3‐ethyl‐1‐vinyl‐2‐pyrrolidone) ( 5 ) have been synthesized. Polymer 5 is soluble in water and shows a critical temperature (T_c) of 27 °C. The presence of cyclodextrin causes a slight shift of the T_c. The lower critical solution temperature (LCST) could be varied between 27 and 40 °C by copolymerization with N‐vinyl‐2‐pyrrolidone. A linear correlation between the T_c and the copolymer composition is observed.

     

pH‐Responsive PEG‐Poly(β‐amino ester) Block Copolymer Micelles with a Sharp Transition

Summary: A pH‐sensitive block copolymer is synthesized by step polymerization and its pH‐sensitive micellization‐demicellization behavior is studied. This polymer has a hydrophilic MPEG (shell) and hydrophobic but pH‐sensitive poly(β‐amino ester) (core), which can form a self‐assembled micelle. As confirmed by fluorescence spectroscopy and dynamic light scattering (DLS), this polymer shows a sharp pH‐sensitive micellization‐demicellization behavior. It is confirmed that the pH sensitivity is affected by the molecular weight ratio between the MPEG and poly(β‐amino ester).

Plots of the intensity ratio I₃₃₇/I₃₃₄ (from pyrene excitation spectra): a) vs. pH for copolymer samples and b) vs. log (concentration) for M1.     

Copolymerization of Ethylene and 10‐Undecen‐1‐ol using a Montmorillonite‐Intercalated Metallocene Catalyst: Synthesis of Polyethylene/Montmorillonite Nanocomposites with Enhanced Structural Stability

Summary: Ethylene and 10‐undecen‐1‐ol have been successfully copolymerized by an organically modified montmorillonite (OMMT)‐intercalated metallocene catalyst, Et[Ind]₂ZrCl₂, activated by methylaluminoxane (MAO). The obtained hydroxy‐functionalized polyethylene (PE‐OH)/OMMT nanocomposites exhibit enhanced structural stability as compared with the neat PE‐based ones, with no significant collapse of the nanocomposite structure being detected by WAXD examination after high‐temperature processing. The simultaneous polyolefin functionalization provides an effective and convenient solution to stabilize the PE/MMT nanocomposite structure formed by in‐situ polymerization.

     

Carbon Nanotubes as a Ligand in Cp2ZrCl2‐Based Ethylene Polymerization

Summary: We report a simple method for tuning catalytic property of a metallocene‐based catalyst, Cp₂ZrCl₂, for ethylene polymerization by the direct adsorption of Cp₂ZrCl₂ onto multi‐walled carbon nanotubes (MWCNTs). The direct interactions between MWCNTs and the Cp rings of Cp₂ZrCl₂ controlled the polymerization behaviors, and we could generate polyethylene with an extremely high molecular weight ( = 1 000 000) at 30 °C and under 1 atm of ethylene gas.

Preparation of Cp₂ZrCl₂‐MWCNT.     

Copolymers of Intrinsic Microporosity Based on 2,2′,3,3′‐Tetrahydroxy‐1,1′‐dinaphthyl

A series of new copolymers with high molecular weight and low polydispersity, prepared from tetrahydroxydinaphthyl, tetrahydroxyspirobisindane, and tetrafluoroterephthalonitrile monomers, prevent efficient space packing of the stiff polymer chains and consequently show intrinsic microporosity. One copolymer, DNPIM‐33, has an excellent combination of properties with good film‐forming characteristics and gas transport performance, and exhibits higher selectivity than the corresponding spirobisindane‐based homopolymer PIM‐1 for gas pairs, such as O₂/N₂, with a corresponding small decrease in permeability. This work demonstrates that significant improvements in properties may be obtained through development of copolymers with intrinsic microporosity (CoPIMs) that extends the spectrum of high‐molecular‐weight ladder structures of poly(dibenzodioxane)s.

     

Poly(4‐vinylbenzoyl azide): A New Isocyanato Group Generating Polymer

4‐Vinylbenzoyl azide was synthesized from p‐vinylbenzoic acid and polymerized by free radical polymerization. The obtained polymer contained acyl azide groups which were thermally transformed to the corresponding isocyanato groups. Reactions on these polymers with ethanol, hydroxyethyl methacrylate and 1‐pyrenebutanol proceeded quantitatively. Time‐resolved FT‐IR studies of the reactions with ethanol were carried out by varying the concentration and temperature. The effect of the solvent polarity on the Curtius rearrangement was investigated.

     

Redox‐Responsive Hydrogel System Using the Molecular Recognition of β‐Cyclodextrin

Summary: We have successfully constructed a redox‐responsible hydrogel system by combination of β‐cyclodextrin (β‐CD), dodecyl‐modified poly(acrylic acid) [p(AA/C₁₂)], and a redox‐responsive guest, ferrocenecarboxylic acid (FCA). In the reduced state of FCA, the ternary mixture exhibited a gel‐like behavior, whereas, in its oxidized state, the mixture exhibited a sol behavior.

Conceptual illustration for the redox‐responsive hydrogel system.     

Reduced Graphene Oxide/Poly(3‐hexylthiophene) Supramolecular Composites

Poly(3‐hexylthiophene) (P3HT) supramolecular structures are fabricated on P3HT‐dispersed reduced graphene oxide (RGO) monolayers and surfactant‐free RGO monolayers. P3HT is able to disperse RGO in hot anisole/N,N‐dimethylformamide solvents, and forms nanowires on RGO surfaces through a RGO induced crystallization process. The TEM and AFM investigation of the resultant P3HT/RGO composites shows that P3HT nanowires grow from RGO, and connect individual RGO monolayers. Raman spectroscopy confirms the interaction between P3HT and RGO, which allows the manipulation of the RGO electrical properties. Such a bottom‐up approach provides interesting graphene‐based composites for nanometer‐scale electronics.

     

An Improved Catalytic Method for Alkoxyamine Synthesis – Functionalized and Biradical Initiators for Nitroxide‐Mediated Radical Polymerization

Mn(salen)Cl was applied as a low‐cost catalyst for the formation of alkoxyamines from nitroxides and substituted styrenes. These “unimolecular initiators” for nitroxide‐mediated radical polymerization (NMRP) were synthesized using 2,2,6,6‐tetramethyl‐1‐piperidine‐1‐oxyl and 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐oxyl. Functionalized alkoxyamines were obtained from 4‐vinylbenzyl chloride and 4‐vinylbenzyl alcohol. The divinyl compound 1,2‐bis(4‐vinylphenyl)ethane was converted to an alkoxyamine monomer and to bisaminooxy compounds, which can be used as “biradical initiators” for NMRP.

Formation of alkoxyamines using Mn(salen)Cl as the catalyst.     

Supramolecular Thermoresponsive Hyperbranched Polymers Constructed from Poly(N‐Isopropylacrylamide) Containing One Adamantyl and Two β‐Cyclodextrin Terminal Moieties

Poly(N‐isopropylacrylamide) (PNIPAM) oligomer containing one adamantyl (AD) and two β‐cyclodextrin (β‐CD) moieties at the chain terminals, AD‐PNIPAM‐(β‐CD)₂, was synthesized by atom transfer radical polymerization (ATRP) and successive click reactions. In aqueous solution, AD‐PNIPAM‐(β‐CD)₂ spontaneously forms supramolecular thermoresponsive hyperbranched polymers via molecular recognition between AD and β‐CD moieties. To the best of our knowledge, this work represents the first report of the construction of supramolecular thermoresponsive hyperbranched polymers from well‐defined polymeric AB₂ building units.

     

Solvent Vapor‐Induced Nanowire Formation in Poly(3‐hexylthiophene) Thin Films

Summary: Nanowire lengths and length‐to‐width aspect ratios in regioregular poly(3‐hexylthiophene) (P3HT) were simply controlled through changes in the solvent vapor pressure during solidification. It is demonstrated that the nanowires grew by rod‐to‐rod association, in which the molecular long axis of the P3HT chains appeared to be well‐oriented parallel to the silicon substrate (Si/SiO_x). The formation of the nanowires took place by one dimensional self‐assembly, governed by π‐π stacking of the P3HT units.

TEM high contrast images showing P3HT nanowires fabricated by spin‐coating under a solvent vapor pressure.     

Anisotropic Electronic Conductivity in Layer‐By‐Layer Composite Film Composed of Water‐Soluble Conjugated Polymers and SWNTs

This paper reports the anisotropic electrical properties of a layer‐by‐layer (LBL) film composed of water‐soluble conjugated polymers and single‐walled carbon nanotubes (SWNTs). The water‐soluble poly (p‐phenylene ethynylene)s (PPEs) are capable of a strong π‐π interaction with the sidewall of SWNTs and results in a very stable PPE‐SO₃/SWNTs composite in aqueous solution. Aligned LBL films were prepared by self‐assembly using the anionic PPE/SWNTs and cationic PPE on various substrates. The polarized Raman spectra exhibited the cos²α polarization dependence of the G‐band intensity between the polarization direction and the SWNTs alignment direction. The electric conductivity within the LBL films can be controlled by the deposition direction in the LBL formation.

     

Copolymerization of Hepta‐1,6‐diene with Ethylene Catalyzed by Cobalt Complexes

Copolymerization of hepta‐1,6‐diene with ethylene using a cobalt–bis(imino)pyridine complex affords a polymer that contains trans‐1,2‐five‐membered rings in the repeating unit from hepta‐1,6‐diene. The ratio of the repeating units of diene to those of ethylene is controlled from 3: 97 to 50:50, depending on the reaction conditions. Isotope‐labeling reactions reveal that the major chain transfer pathway involves β‐hydrogen elimination of the polymer end formed after ethylene insertion.

     

Effect of Drawing Induced Dispersion of Nano‐Silica on Performance Improvement of Poly(propylene)‐Based Nanocomposites

Summary: A new route that combines graft pre‐treatment and drawing techniques with melt mixing to prepare nanoparticle‐filled thermoplastic polymer composites is reported. Nano‐SiO₂ particles are first modified by graft polymerization and then the grafted nanoparticles are melt‐compounded with poly(propylene) (PP) to produce composite filaments via drawing. Finally, the filaments are injection molded into bulk materials. Because the proposed manufacturing method is able to induce separation of the nanoparticles and the formation of beta‐crystals in the PP matrix, the resultant PP‐based nanocomposites are much tougher than the unfilled polymers, as characterized by either static or dynamic tests, in addition to showing a simultaneous increase in strength and stiffness.

Force–time curves of PP and its nanocomposites recorded during notch impact tests.     

Enzyme‐Catalyzed Ring‐Opening Polymerization of Unsubstituted β‐Lactam

The synthesis of poly(β‐alanine) by Candida antarctica lipase B immobilized as novozyme 435 catalyzed ring‐opening of 2‐azetidinone is reported. After removal of cyclic side products and low molecular weight species pure linear poly(β‐alanine) is obtained. The formation of the polymer is confirmed with ¹H NMR spectroscopy and MALDI‐TOF mass spectrometry. The average degree of polymerization of the obtained polymer is limited to = 8 by its solubility in the reaction medium. Control experiments with β‐alanine as a substrate confirmed that the ring structure of the 2‐azetidinone is necessary to obtain the polymer.