The application of copper‐catalyzed azide/alkyne cycloaddition to monomers containing a ferrocene unit leads to polyferrocenes with ferrocene in the backbone. Catalyst performance and kinetic studies of a model system comprising 1,1'‐bis(azidoethyl)ferrocene and propargyl ether revealed the usage of CuI and DBU as the catalyst in DMF at 50 °C as efficient reaction conditions for the synthesis. The resulting polymers display molecular weight‐averages up to $\overline {M} _{{\rm n}} $ = 10 000 and $\overline {M} _{{\rm w}} $ = 33 000. The polyaddition of monomers both containing ferrocene units led to polyferrocenes with $\overline {M} _{{\rm n}} $ between 4 000 and 11 000 ($\overline {M} _{{\rm w}} $ up to 78 000). The present study thus provides a pathway to polyferrocenes based on modular ligation chemistry.
PHA‐based nano‐biocomposites have been prepared by melt intercalation. Two main PHAs, poly(hydroxybutyrate) and poly(hydroxybutyrate‐co‐hydroxyvalerate) have been studied. Structural characterizations were conducted by advanced techniques like SAXS and TEM. A recent method has determined the degree of clay intercalation and dispersion using solid‐state NMR. Well intercalated small tactoids (3–10 layers) homogeneously dispersed into the polymer are obtained when good PHA–clay affinity exists, i.e., with organo‐modified MMT. In the case of non‐modified MMT, microcomposites are evidenced. Crystallization, mechanical, and thermal properties have been correlated to the materials structures.
A compressed exponential function (CEF) is shown to be represented by a distribution of Gaussian functions. The properties and characteristics of the distribution are detailed and discussed, and are illustrated with reference to the change in the NMR spectroscopy proton Hahn echo relaxation response that takes place in a composite material (prepared by melt compounding a mixture of graphite nanoparticles and pyromellitic anhydride modified polypropylene carbonate (PPC)) during aging at 90 °C. The results show that both the width and the average value of the spin‐spin relaxation rate distribution decrease during aging, suggesting that the molecular motion becomes less constrained and less heterogeneous.
We report herein a quantitative end‐capping chemistry for the efficient synthesis of monotelechelic hyperbranched polyethylenes containing various ω‐end functionalities by quenching Pd‐diimine catalyzed ethylene “living” polymerization with styrene derivatives. This chemistry utilizes the unique reaction of styrene derivatives with cationic Pd‐diimine species to form stable π‐benzyl intermediate complexes, which are inactive for ethylene polymerization. In the synthesis, “living” hyperbranched polyethylene chains were grown with a Pd‐diimine catalyst. Subsequent end‐quenching of the “living” chains with three styrene derivatives renders narrowly distributed telechelic hyperbranched polyethylenes containing different functional ω‐terminal groups.
Glucose‐sensitive p(NIPAM‐4‐VP‐PBA) microgels with different 4‐VP content are synthesized by the functionalization of p(NIPAM‐4‐VP‐AA) microgels with 3‐aminophenylboronic acid. The glucose‐, pH‐, and thermosensitive behavior of the microgels are investigated using DLS. The feeding content of the hydrophilic 4‐VP group increases the hydrodynamic radius and volume phase transition temperature of the resultant microgel. The effect of 4‐VP content on hydrodynamic radius and volume phase transition is systematically studied at different pH values. The effect of 4‐VP content on the glucose sensitivity is studied at physiological pH and temperature. The Lewis base moiety 4‐VP adjusts the working pH of the PBA‐based glucose‐responsive microgel to physiological values.
Ethylene slurry polymerizations were performed using supported nickel diimine catalysts. The effects of catalyst structure and polymerization conditions on catalyst activity, polymer particle morphology, and polymer properties were investigated. Covalently attached supported nickel diimine catalysts activated with ethyl aluminum sesquichloride (EASC) have high activities and made polymers with spherical morphology. Compared with the equivalent homogeneous catalysts, the covalently attached supported catalysts produced polyethylene with higher melting temperatures, higher molecular weights, and broader molecular weight distributions. Borates used as internal activator during the synthesis of these supported catalysts successfully activated the nickel diimine complexes.
Two‐dimensional chromatographic methods were developed using LC‐CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS‐b‐PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D‐LC analysis provides information on the purity of the reaction products, the presence of by‐products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D‐LC is discussed.
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 simple approach for the end‐functionalization of hydroxyl‐terminated polymers with nitroxide moieties using oxoammonium salts (OS) is presented. The functionalization is carried out using only one synthetic pathway in which high levels of functionalization (90%) are found. A mechanism for the functionalization with TEMPO moieties using OS is proposed in which the formation of peroxide groups is suggested. The structures of the functionalized polymers are characterized in detail by 1H NMR, 13C NMR, DQF‐COSY, and HETCOR. Bifunctional macroalkoxyamines are used to demonstrate how to extend the polymer chain for the synthesis of amphiphilic triblock copolymers by polymerizing St in a second block mediated by a nitroxide radical which provides the block length control.
Well‐defined sulfonated block copolymers were prepared by direct thermolysis with block copolymers of n‐butyl acrylate (nBA) and neopentyl styrene sulfonated (NSS), which were synthesized by Cu‐based living radical polymerization ( <1.20). A simple thermal process for 10 min at 150 °C completely deprotected the neopentyl groups in the poly(NSS) block segment to give fully sulfonated polystyrene backbone. SAXS profile of the block copolymer with 47 wt.‐% of poly(NSS) showed lamella structure, which appeared more clearly with long ranged order after sulfonation of the block copolymer.
Biodegradable polymeric nanoparticles are employed as templates for the biomimetic mineralization of CaP in the aqueous phase. Particles in the sub‐µm range were prepared by a combination of solvent evaporation and miniemulsion techniques. The synthesized particles were subjected to degradation via random saponification. The anionic functional groups produced as a consequence of degradation due to production (ultrasonication step) and post treatment (hydrolysis) steps are used for the CaP mineralization. The composite particles were studied using HRSEM, TEM, and XRD. These polymer/CaP composite nanoparticles have a great potential to be used as a regenerative filler or as a scaffold for nucleation and growth of new bone material.
The successful use of multitasking polycaprolactone‐based hydrophobins for miniemulsion polymerization of model monomers like styrene and methyl methacrylate is demonstrated. These hydrophobins were synthesized in two steps – the synthesis of polyester diol (i.e., polycaprolactone diol) followed by polycondensation with an equimolar amount of azobis(cyanopentanoic acid dichloride). The hydrophobin, besides acting as a hydrophobe and initiator for the miniemulsion polymerization, also provided functionality; in this case degradability to the miniemulsion. An optimum ratio of hydrophobin to monomer was required for making stable dispersions of a small size (average diameter around 100 nm) with relatively high solid content (around 22%).
Two kinds of the totally alkyl‐substituted ladder π‐conjugated compounds, the totally hexyl‐substituted silicon‐bridged stilbene trimer 1 and the totally propyl‐substituted silicon‐ and carbon‐bridged distyrylbenzene 2 , were synthesized. X‐ray crystallography revealed that both compounds adopt the all‐parallel‐aligned packing structures through the interpenetration of the alkyl chains with those of the neighboring molecules. The effect of this packing structure on the photophysical properties was investigated. The fluorescence quantum yield measurements showed that both compounds maintained their high quantum yields (ΦF) even in the crystalline state (ΦF = 0.64 for 1 ; 0.63 for 2 ), suggesting the potential effect of the all‐parallel alignment for attaining the intense emission in the solid state.
New initiating systems for the thermal cationic polymerization of epoxides and vinyl ether derivatives are proposed. They are based on a silane/silver salt interaction, which ensures a good to excellent polymerization at room temperature. Moreover, the polymerization is much more efficient under air. The effects of the silane, silver salt, and monomer structures are investigated. Interestingly, silver nanoparticles Ag(0) are formed in situ. A coherent picture of the involved chemical mechanisms is presented.
Branched α‐olefin 4‐methyl‐1‐pentene (4MP) is polymerized with a cationic α‐diimine palladium catalyst. The influences of polymerization parameters including reaction temperature and monomer concentration on polymer architecture are evaluated in detail. Increasing temperature and lowering monomer concentration can lead to the formation of more complex branched polyolefin because of chain walking. At 0 °C, complex branched polyolefins are generated from quasi‐living polymerization of 4MP with α‐diimine palladium catalyst.
FTIR spectroscopic imaging is combined with linear dichroism measurements to investigate the structures of spherulites of poly(3‐hydroxybutyrate) and isotactic poly(propylene oxide). It is shown that this technique can be used to easily gain qualitative information about relative orientations of chemical bonds within a solid polymeric sample. Furthermore the imaging technique is shown to have the considerable advantage that the obtained images are easy to understand and easy to interpret even without deep knowledge of FTIR linear dichroism measurements.
The concept of Hansen solubility parameters (HSP) is applied to organic semiconductors in order to determine and predict their solubility behavior, which is essential for the design of functional and environmentally friendly ink formulations for organic photovoltaics. Two different conjugated polymers, one semicrystalline and one dominantly amorphous, and one fullerene derivative are selected as prototype candidates to evaluate the applicability of the HSP concept for organic semiconductors. The method for determining the solubility parameters is described and the quality of the HSP fits as well as their suitability for designing of organic electronic inks are discussed in detail.
The influence of the doping level in the formation of specific interactions between plasmid DNA and PEDOT is investigated using experimental assays and theoretical calculations. Electrochemical methods are used to prepare polymer samples with oxidation degrees ranging from 0.14 to 1.05 positive charges per repeating unit. A combination of experimental and theoretical results are used to propose a mechanism for the formation of DNA/conducting polymer complexes, which consists of the initial stabilization of the adducts through non‐specific interactions followed by small structural re‐arrangements that allow to be established specific hydrogen bonds involving the polar groups of the conducting polymer and selected DNA bases.
We report the large scale preparation of nanostructured polyaniline‐Pd nanoparticles composites (designated as PANI(NS)‐PdNPs) through a “seed” induced bulk polymerization. Initially, a small quantity of PANI(NS)‐PdNPs was formed inside the cavities of MCM‐41 and used as the “seed” for the bulk preparation of PANI(NS)‐PdNPs composite. For a comparative purpose a PANI‐PdNPs composite was also prepared in the absence of the seed. FESEM image of PANI(NS)‐PdNPs composite (bulk) shows nanofibrillar morphology. Further, transmission electron microscopy reveals the presence of spherical Pd nanoparticles. PANI(NS)‐PdNPs composite (bulk) showed a good catalytic activity towards reduction of 4‐nitrophenol.
A liquid crystal (LC) ABA triblock copolymer with poly(styrene) (PS) A blocks and a main‐chain nematic LC polyester B block is synthesized by atom‐transfer radical polymerization of styrene with an LC polyester macro‐initiator. The nematic LC and PS amorphous phases are segregated from each other to form lamellae with a spacing of 27 nm. The 16 nm‐thick nematic LC lamellae are significantly smaller than the contour length of the LC segment (63 nm), and the nematic director is parallel to the lamellae. The central LC segment is primarily more extended in the lamellar direction, but folds so as to meander through the LC lamella and bridges adjacent PS domains. The lamellar microstructure exhibits a reversible spacing increase of up to 31 nm with increasing temperature, suggesting a corresponding increase in the probability of the chain folding.
