The forced assembly of two immiscible polymers, produced by layer‐multiplying co‐extrusion, is analyzed by means of USAXS. Comparison of scattering and AFM results sheds light on many details of the nanolayered structure in PET/PC films. The role played by the volume concentration and cold crystallization of PET on the experimental scattering is discussed. The appearance of at least two scattering maxima in all cases, corresponding to higher orders of the same repeating distance, accounts for the high regularity of the developed nanostructure. It is finally shown that long spacing values, derived from a localized area in AFM, are in a good agreement with the USAXS values averaged over much larger areas.
Nowadays, microwave‐assisted polymer chemistry is a rapidly growing field of research. In the last few years, various examples of reaction accelerations, selectivities, and higher yields have been reported. In this contribution, the current state of the art is summarized and an overview on microwave‐assisted polymerizations is presented, whereby special attention is given to advantages and promising future trends in this intriguing field of research.
Segmented block copolymers comprised of flexible PEO segments and monodisperse crystallizable bisestertetraamide segments have been synthesized. The influence of the terephthalic units in the soft phase on the transitions and the thermal mechanical and elastic properties are studied. The presence of terephthalic units in the copolymer increases the glass transition temperature of the soft phase by ≈5 °C. The low‐temperature flexibility of the copolymers is improved because of the lower crystallinity and melting temperature of PEO. With the use of terephthalic‐extended PEO segments, segmented block copolymers with low moduli (G' < 15 MPa) and good elastic properties could be obtained.
Nanoprecipitation of poly(methyl methacrylate) (PMMA) in the presence of water‐soluble core cross‐linked star (CCS) polymers is investigated. Slowly dropping water into DMF solutions containing PMMA and CCS polymers of varying compositions produces colloidally stable particles with CCS polymers being effectively incorporated. During the solvent‐shifting process, CCS polymers migrate to and concentrate at the particle surface to stabilize the formed particles, which is confirmed by X‐ray photoelectron spectroscopy, transmission electron microscopy, and contact angle measurements. This stabilizing effect is realized via the steric effect of the CCS polymers adsorbed at the particle surface.
A straightforward synthesis of a conjugated rod/spacer/rod‐type block copolymer containing PCz electron‐donor and PDI electron‐acceptor blocks is described. Two chromophores are covalently connected through sebacate units as saturated spacer. The resulting donor/spacer/acceptor‐type block copolymer (PCz‐S‐PDI) can be applied to limit charge recombination between donor/acceptor interfaces and to control the scale length of nanostructure formation. PCz‐S‐PDI was used to produce a solar cell with the power conversion efficiency of 0.004%.
Two kinds of amino‐functionized, triphenylamine and fluorene based copolymers, PFT‐N and PTFF‐N, were synthesized by palladium‐catalyzed Suzuki coupling reaction. The corresponding quaternized polyelectrolytes PFT‐NBr and PTFF‐NBr were obtained through post‐polymerization. The quenching behaviors of PFT‐NBr and PTFF‐NBr in methanol were investigated by the titration of Fe(CN). All of these polymers were investigated as emitting layer in multilayer PLEDs. Devices' performance together with electrochemical properties of these polymers indicate that both of the hole and the electron injection capabilities of them were improved due to the simultaneous introduction of the triphenylamine segment and the aminoalkyl (ammonium) group.
The synthesis of two new monomers based on 4‐hydroxythiazoles, with a non‐classical chromophore structure similar to the luciferin dye of glowworms, is presented. These dyes are functionalized with methacrylates and copolymerized with methyl methacrylate using a RAFT polymerization process. The obtained polymers reveal PDI values below 1.2 and are characterized by NMR spectroscopy, SEC including a diode‐array detector, UV‐vis and fluorescence spectroscopy. In addition, thin films of the polymers are prepared by spin‐coating and investigated regarding their optical properties.
Amphiphilic hyperbranched polymers carrying two types of β‐cyclodextrin groups including ionic and covalent bonding were synthesized via atom transfer radical polymerization and immobilization reaction. Their inclusion capabilities for single or double‐guest molecules were investigated by UV‐visible spectroscopy. Using Chlorambucil and Lonidamine as the double model drugs, their encapsulation efficiencies indicate that these polymers possess the capabilities of high drug‐loading. Furthermore, the release behaviors of these polymers were studied via UV‐visible spectroscopy. The results indicate that they can slow the release rate of double model drugs. Varying the pH values of environment or regulating their shell layer structures can control the release behaviors of double model drugs.
A comparative study of nano‐SiO2/PP composites prepared by reactive compatibilization was conducted. Nano‐SiO2 was first grafted with three polymers bearing specific reactive groups. The grafted particles were then melt‐compounded with functionalized and matrix PP. Due to the reaction between the grafted polymers and functionalized PP, nano‐SiO2 was covalently connected to the matrix and the mechanical properties of the nanocomposites were significantly improved. It was found that chain flexibility of the graft polymers is critical for inducing plastic deformation of the matrix, provided that interfacial chemical bonding has been built up.
Organic field‐effect transistors (OFETs) are a promising cost‐effective alternative to silicon‐based field‐effect transistors, and possess low‐cost, light‐weight, and flexibility advantages. Conjugated polymers based on fused‐thiophene building blocks have received considerable attention in the emerging field of organic electronics. In this review the most recent developments in conjugated polymers based on fused‐thiophene rings for high‐performance OFETs are summarized. The focus is on correlations of polymer chemical structures with properties, such as energy levels, film‐forming property, film morphology, and OFET performance. This structure–property relationship analysis may guide rational structural design and evaluation of organic semiconductors.
Functionalization of polysulfones by using “Click” chemistry is described for the example of a small fluorescent analyte propargylpyrene. First, PSUs were converted to azido‐functionalized polymers by successive chloromethylation and azidation. Propargylpyrene was prepared independently as a fluorescent click component. Finally, the azido‐functionalized PSUs were coupled with propargylpyrene with high efficiency by copper‐catalyzed azide/alkyne click reactions. The final polymers and intermediates at various stages were characterized by 1H NMR, FT‐IR, GPC, UV‐Vis, and fluorescence spectroscopy techniques.
Novel α,ω‐functionalized amphiphilic lipopolymers are prepared that are composed of a proximal lipid moiety and a hydrophilic poly(2‐oxazoline)‐based (POx) polymer chain. The synthesis begins from bifunctional lipoinitiators, which are asymmetrically protected as tert.butyldiphenylsilyl (TBDPS) ethers, followed by cationic living ring‐opening polymerization of 2‐oxazolines in a one‐pot multistep reaction. This results in polymers with defined terminal end groups and narrow molar mass distributions. All protective groups involved can be readily cleaved in a single step reaction keeping the structure of the polymer intact, giving access to (lipo)polymers with a variety of defined identical or chemical orthogonal α,ω‐functionalities. The synthetic strategy is a versatile tool for the preparation of defined polymer–drug or polymer–protein conjugates or asymmetric functionalized model lipid membranes for the quantitative study of membrane‐associated phenomena such as transmembrane transport and cell adhesion/recognition.
4‐Alkyloxy‐3,5‐bis(hydroxymethyl)phenylacetylenes with eight types of alkyl groups were synthesized and polymerized with a chiral catalytic system. We found that the length of the alkyl groups played a very important role in achieving helix‐sense‐selective polymerization. Five helix‐sense‐selective polymerizations were achieved resulting in polymers with alkyl groups whose chain length was longer than six. We think that the longer ‐ chain alkyl groups prevented the polymers from becoming insoluble by forming intermolecular hydrogen bonds between the hydroxyl groups, and stabilized their one‐handed helical structure by promoting the formation of intramolecular hydrogen bonds.
A new pH sensor, which consists of a fluorophore and gold nanoparticle (AuNP) attached to each chain end of a pH‐sensitive polysulfonamide, respectively, is synthesized, and its pH sensitivity is investigated in terms of the fluorescent quenching efficiency of AuNP. Since the pH‐sensitive polymeric linker exhibits a pH‐induced coil–globule transition that is rapid enough to show a typical two‐state transition, it shows drastic on‐and‐off quenching efficiency with variation of pH due to the change in the distance between fluorophore and AuNP. This AuNP‐based pH sensor exhibits a well‐defined on‐and‐off behavior at a small change in pH, and therefore can be used for an ideal alarm‐type sensor.
Due to their pronounced viscoelastic properties polymer microcapsules are able to undergo mechanical deformations when they are stimulated by external signals. The aim of our work was to prepare new types of electric switchable microcapsules based on the interfacial polycondensation of octadecyltrichlorosilane (OTS) and to investigate their deformation behavior in externally electric fields. In a series of experiments we explored the influence of different additives on the deformation behavior of the capsules in electric fields as well as on the shear rheological properties of the polysiloxane networks at the planar interface. We could show that the additives had a significant influence on the rheological membrane properties, but we observed only small changes in the deformation of the whole capsules.
Star polymers with methacryloyl groups at the chain ends were synthesized by esterification of hydroxyl end‐functional star polymers. First, the linear hetero‐telechelic macroinitiator (MI) was prepared by ATRP using a functional initiator. The obtained MI was chain‐extended and cross‐linked with DVB and then esterified into methacryloyl chain‐end functionality. The degree of esterification was controlled by changing the initial molar ratios of methacryloyl chloride to hydroxyl groups. The methacryloyl‐containing star polymers were cross‐linked either intermolecularly or intramolecularly under heating or UV irradiations, depending on the concentrations of star polymers during the cross‐linking reactions.
We synthesized xanthene‐based oligothiophene‐layered polymers containing bithiophenes, terthiophenes, quaterthiophenes and quinquethiophenes by the Suzuki‐Miyaura coupling reaction. The polymers were characterized by various spectroscopic and electrochemical methods. They were well soluble in common organic solvents and thermally stable. Effective π‐π interactions among the layered oligothiophene units in the polymer backbone were not observed in the ground state as well as in the excited state. A possible application of the polymers in opto‐electronic devices such as hole transporting materials is expected.
A series of optically inactive polythiophene derivatives bearing the azobenzene moiety are synthesized in an isotropic toluene solution. The polymers are then dissolved in a cholesteric liquid crystal (Ch*LC) medium within the liquid crystal (LC) temperature range. The dissolution process in Ch*LC produces intermolecular π‐stacking with structural chirality. Although the polymers thus prepared have no chiral center or axial chirality in the primary structure, they do exhibit consistent chiroptical activity derived from three‐dimensional chiral aggregations. Furthermore, photochemical cis–trans isomerization of the substituents allows light‐driven chiroptic modulation of the polymer.
A novel method for the synthesis of alkoxyamines that are subsequently used as initiator/regulators for NMP is reported. This method can be applied to low‐molecular‐weight olefins as well as to macromolecules containing alkene moieties to form poly(alkoxyamines). The reaction sequence comprises hydroboration of olefins with catecholborane followed by oxidation of alkylborane intermediates using nitroxides in the presence of methyl vinyl ketone to ultimately yield alkoxyamines that serve as suitable initiators for NMP. The first application of these alkoxyamines for the preparation of comb and star polymers is presented.
