Cationic and Anionic Conjugated Polyelectrolytes: Aggregation‐Mediated Fluorescence Energy Transfer to Dye‐Labeled DNA

An electrostatic complex of water‐soluble conjugated polyelectrolytes (CPs) between anionic poly(9,9‐bis(4′‐sulfonatobutyl)fluorene‐co‐alt‐1,4‐phenylene) disodium salt (a‐PFP) and cationic poly(9,9‐bis((6′‐N,N,N,‐trimethylammonium)hexyl)fluorene‐co‐2,1,3‐bezothiadiazole) dibromide (85:15) (c‐PFB₁₅) was tested as a fluorescence resonance energy transfer (FRET) donor to Texas Red (TR)‐labeled single‐stranded DNA (ssDNA‐TR) via two‐step FRET processes. Electrostatic complexation of a‐PFP and c‐PFB₁₅ in water leads to aggregation of polymer chains, a concomitant reduction of intersegment distances, and energy transfer to the benzothiadiazole (BT) segments. The following complexation with ssDNA‐TR leads to energy transfer from BT to TR via two‐step FRET processes. This detection schematic shows an FRET‐induced signal amplification, which can be achieved by adjusting the charge ratio in the cationic/anionic CP complex and controlling the number density of the binding CPs around the acceptor, resulting in enhanced antenna effects and sensitivity in CP‐based FRET DNA detection assays.

     

Lewis Acid‐Induced N‐Methyleneamines as Initiators in the Synthesis of Secondary Amine‐Terminated Polymers

Summary: The cationic polymerization of poly(tert‐butyl vinyl ether) using N‐methyleneamine equivalents derived from a Lewis acid/1,3,5‐trimethylhexahydro‐1,3,5‐triazine (TMTA) co‐initiating system is reported. The resulting polymers possessed secondary amine functionality at the chain terminus, verified by derivatization with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) and subsequent analysis with GPC‐UV (470 nm) and ¹H NMR.

Use of N‐methyleneamine equivalents lacking aryl substituents to afford amine‐terminated poly(tert‐butyl vinyl ether).     

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.

     

Low‐Temperature Growth of Thick Polystyrene Brushes via ATRP

Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator‐functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled.

Formation of polystyrene brushes at T < T_g by ATRP of styrene from α‐bromoester initiator‐functionalized poly(glycidyl methacrylate) layers.     

Nickel(II) α‐Diimine Catalyst for Grignard Metathesis (GRIM) Polymerization

A nickel α‐diimine catalyst was used for Grignard metathesis (GRIM) polymerization of 2,5‐dibromo 3‐hexylthiophene and 2‐bromo‐5‐iodo‐3‐hexylthiophene monomers. GRIM polymerization of 2‐bromo‐5‐iodo‐3‐hexylthiophene generated regioregular polymers with molecular weights ranging from 3 000 to 12 000 g · mol⁻¹. The nickel α‐diimine catalyst was also successfully used for the GRIM polymerization of a bulky benzodithiophene monomer.

     

Novel Water‐Soluble Shape‐Regulatable Luminescent Nanoparticles by Non‐Covalently Bonded Self‐Assembly

Summary: Novel non‐covalently connected water‐soluble nanoparticles that contain poly(fluorene‐co‐phenylene) with hydroxy‐capped alkoxy side chains (PF3BOH) and poly(acrylic acid) (PAA) have been obtained and characterized. With different proportions of PF3BOH and PAA, the shape and size of the nanoparticles can be regulated. The nanoparticles are quite stable in water with no precipitate being observed after weeks. Transmission electron microscopy and dynamic laser light scattering are used to confirm the morphology of the PF3BOH/PAA nanoparticles. Their optical properties have been investigated and show similar optoelectronic properties to a PF3BOH solid film although they do not undergo aggregation.

TEM images of the nanoparticles obtained upon varying the PAA/PF3BOH content.     

Heterogenization of a Modified Grubbs–Hoveyda Catalyst on a ROMP‐Derived Monolithic Support

A ring‐opening metathesis polymerization‐ (ROMP‐) based monolith was synthesized using a Grubbs' first generation catalyst. The living termini were used for surface grafting of norborn‐5‐ene‐2‐ylmethyl hexafluoroglutarate. The free carboxylic acid groups of the graft polymer were converted into the corresponding silver salt and reacted with the Grubbs–Hoveyda catalyst [RuCl₂(CH (2‐iPrO )C₆H₄)(IMesH₂)] (IMesH₂ = 1,3‐bis(2,4,6‐trimethylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene) to yield a stable heterogeneous version of this catalyst for use in ring‐closing metathesis (RCM) under continuous flow conditions.

The monolith‐supported Grubbs–Hoveyda catalyst.     

Ring‐Opening Polymerization of ε‐Caprolactone by Poly(ethylene glycol) by an Activated Monomer Mechanism

Summary: The polymerization of ε‐caprolactone (CL) in the presence of HCl · Et₂O by an activated monomer mechanism was performed to synthesize diblock or triblock copolymers composed of poly(ethylene glycol) (PEG) and poly(ε‐caprolactone) (PCL). The obtained PCLs had molecular weights close to the theoretical values calculated from the CL to PEG molar ratios and exibited monomodal GPC curves. We successfully prepared PEG and PCL block copolymers by a metal‐free method.

The non‐metal catalyzed living ring‐opening polymerisation of ε‐caprolactone by PEG.     

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.

     

A Template‐Free Route to Polypyrrole Nanofibers

A template‐free method for the production of polypyrrole nanofibers is presented. By adding a small amount of bipyrrole into the oxidative polymerization of pyrrole, a drastic change in the morphology of the observed material is observed from large, granular particles to nanofibrils with an average diameter of 20 nm. This simple procedure allows for the production of polypyrrole nanofibers without the presence of surfactants or other structural directing agents. The polypyrrole nanofibers can form stable water dispersions which can be cast into films of sufficient quality to function as chemical sensors for analytes such as ammonia.

     

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.

     

Fabrication of Biomimetic Superhydrophobic Coating with a Micro‐Nano‐Binary Structure

Summary: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor‐induced phase separation occurred during the solidifying process and a rough surface with a micro‐nano‐binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.

SEM image of a single micro‐flower.     

Square Lamellar Structure Having Phase‐Separated Microdomain in H‐Shaped Block Copolymer Thin Film

The morphology of a H‐shaped block copolymer (poly(ethylene glycol) backbone and polystyrene branches (PS)₂PEG(PS)₂) in a thin film has been investigated. A peculiar square lamella that has a phase‐separated microdomain at its surface is obtained after spin coating. The experimental temperature plays a critical role in the lamellar formation. The copolymer first self‐assembles into square lamellar micelles with an incomplete crystalline core due to the crystallizability of PEG. In the subsequent process of solvent evaporation, phase separation between PS and non‐crystalline PEG attached at the chain‐folded PEG surface takes place, which results in phase‐separated microdomains being formed at the lamellar surface.

     

Thermoreversibly Crosslinked Poly(ε‐caprolactone) as Recyclable Shape‐Memory Polymer Network

A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels–Alder (DA) adducts, star‐shaped poly(ε‐caprolactones) (PCL) end‐functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt‐blending complementary end‐functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability.

     

Micelles‐Encapsulated Microcapsules for Sequential Loading of Hydrophobic and Water‐Soluble Drugs

Layer‐by‐layer (LbL) assembly was conducted on CaCO₃ microparticles pre‐doped with polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA) micelles, and resulted in micelles encapsulation in the microcapsules after core removal. Distribution of the micelles in the templates and capsules was characterized by transmission electron microscopy and confocal laser scanning microscopy. The micelles inside the capsules connected with each other to form a chain and network‐like structure with a higher density near the capsule walls. The hydrophobic PS cores were then able to load small uncharged hydrophobic drugs while the negatively charged PAA corona could induce spontaneous deposition of water‐soluble positively charged drugs such as doxorubicin.

     

A Soluble High Molecular Weight Copolymer of Benzo[1,2‐b:4,5‐b′]dithiophene and Benzoxadiazole for Efficient Organic Photovoltaics

The synthesis and characterization of a soluble high molecular weight copolymer based on 4,8‐bis(1‐pentylhexyloxy)benzo[1,2‐b:4,5‐b′]dithiophene and 2,1,3‐benzoxadiazole is presented. High efficiency organic photovoltaic (OPV) devices comprised of this polymer and phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) were fabricated by additive processing with 1‐chloronapthalene (CN). When the active layer is cast from pristine chlorobenzene (CB), power conversion efficiencies (PCEs) average 1.41%. Our best condition—using 2% chloronapthalene as a solvent additive in CB—results in an average PCE of 5.65%, with a champion efficiency of 6.05%.

     

Synthesis of 2‐alkyl‐4,5‐aryl‐2H‐[1λ6,2,3,6]‐thiatriazine‐1,1‐dioxides

Sulphamoyl chlorides and chlorosulphonyl isocyanate react with monosubstituted hydrazones and alkylhydrazonates to sulphamoyl hydrazones and sulphamoyl hydrazonates respectively. Reaction of benzil monoalkylhydrazones with chlorosulphonyl isocyanate results in formation of 2‐alkyl‐4,5‐aryl‐2H‐ [1λ⁶,2,3,6]‐thiatriazine‐1,1‐dioxides.