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Materials Chemistry, Inorganic Chemistry, Polymers and Plastics, Organic Chemistry, Methacrylate, Size-exclusion chromatography, Functional polymers, Electrolysis, law.invention, law, Polymer, chemistry.chemical_classification, chemistry, Atom-transfer radical-polymerization, Azide, chemistry.chemical_compound, Inorganic chemistry, Alkyne, and Polymer chemistry

We introduce a novel electrochemical method for the purification of complex water-soluble functional polymers contaminated with copper salts originating from copper-catalyzed azide/alkyne ligation chemistry, for which no standard purification protocol is suitable. A triethylene glycol methyl ether methacrylate (TEGMA) star polymer with 2-ureido-4H-pyrimidone (UPy) end groups was prepared via an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) and copper-catalyzed azide/alkyne cycloaddition (CuAAc) and selected as a model system for electrolysis of an aqueous polymer solution. We systematically investigate the influence of sample concentration, voltage, and time of electrolysis on the quality of the purification. Atom emission spectroscopy (AES) reveals almost quantitative removal of copper, and size exclusion chromatography (SEC) as well as proton nuclear magnetic resonance spectroscopy (1H NMR) ensure the full integrity of the polymer under all selected conditions.

General Chemistry, Biochemistry, Organic Chemistry, Circular dichroism, Chemistry, Hydrogen bond, Polymer, chemistry.chemical_classification, Copolymer, Polymer chemistry, Polymer architecture, Atom-transfer radical-polymerization, Self-assembly, and Supramolecular chemistry

ABA- and BAB-type triblock copolymers possessing pendant, self-assembling motifs in the A and B blocks were synthesized, with 2-ureidopyrimidinone (UPy) and benzene-1,3,5-tricarboxamide (BTA) for the A and B block, respectively. They were investigated to assess if and how the polymer's microstructure influences the self-assembly behavior of the supramolecular motifs and, as a result, the single-chain folding process. BAB-type triblock copolymers were synthesized via atom transfer radical polymerization (ATRP) with molecular weights ranging from 30 to 120kgmol-1; the BTA and UPy motifs were attached using a post-functionalization approach. The ABA-type triblock copolymers were available from previous work. In highly dilute solutions, both types of triblock copolymers fold into single-chain polymeric nanoparticles (SCPNs) via thermally induced BTA self-assembly and photo-triggered UPy dimerization. Chain collapse induced by intramolecular UPy dimerization was evaluated using size-exclusion chromatography (SEC). The BTA self-assembly was monitored by circular dichroism (CD) spectroscopy. The microstructures of SCPNs were visualized by atomic force microscopy (AFM). SEC analysis indicated a more loose packing for the BAB-type folded nanoparticles than for the ABA-type ones, which implies that topological differences in the polymer architecture do affect the folding behavior, although only slightly. The facile synthetic protocol developed here provides topologically different triblock architectures and opens up the area for single-chain folding technology that is applicable in artificial enzymatic systems with compartmentalized domains. ABA- and BAB-type triblock copolymers carrying distinct self-assembling motifs in each block were designed and synthesized. These polymers fold into single-chain polymeric nanoparticles via thermal and photoirradiation treatments. An influence of block sequence on the folded structure is found, which affects the packing size of the resulting folded nanoparticles (see figure). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

General Chemistry, Macromolecule, Chemistry, Substituent, chemistry.chemical_compound, Supramolecular polymers, chemistry.chemical_classification, Chirality (chemistry), Stereochemistry, Supramolecular chemistry, Stereocenter, Crystal structure, and Amide

Mixing experiments were conducted on dilute solutions of asymmetrically substituted benzene-1,3,5-tricarboxamides (BTAs) with stereogenic methyl groups ranging from the α- to the δ-position with respect to the amide in one of the three side groups. While normally the majority compound determines the helical sense preference of the formed supramolecular polymers, we find here that several combinations show a helical preference governed by the minority compound. BTAs with the methyl substituent at the α- and γ-position overrule the helical preference of BTAs with the methyl substituent at the β- and δ-position. This new effect is referred to as a ‘minority-rules’ system.

Materials Chemistry, Polymers and Plastics, Organic Chemistry, Hydrophobic effect, Substrate (chemistry), Aldol reaction, Catalysis, Cyclohexanone, chemistry.chemical_compound, chemistry, Materials science, Molecular recognition, Organic chemistry, Organocatalysis, Fluorescence, and Combinatorial chemistry

Here, a modular approach is reported to introduce a specific function into single-chain polymeric nanoparticles (SCPNs). Hereto, an amphiphilic polymer with pendant benzene-1,3,5-tricarboxamide (BTA) units is mixed with a "free" BTA that contains a functional group, either a fluorescent naphthalimide or a catalytically active l-proline. Taking advantage of hydrophobic interactions and self-recognition properties of the BTA units, the "free" BTAs are captured into the interior of the SCPN in water as evidenced by fluorescence studies. To illustrate that function can be readily introduced using a modular approach, l-proline-based BTAs are incorporated to procure a catalytically active SCPN in water. The aldol reaction between p-nitrobenzaldehyde and cyclohexanone shows good conversions at low catalyst loadings and substrate concentrations, and high stereoselectivities are obtained (de = 91% and ee = 98%). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopy, Structural Biology, Mass spectrometry, Chemistry, Intermolecular force, Moiety, Hydrogen bond, Molecule, Adduct, Organic chemistry, Matrix-assisted laser desorption/ionization, Analyte, and Photochemistry

Analyte-matrix adducts are normally absent under typical matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) conditions. Interestingly, though, in the analysis of several types of organic compounds synthesized in our laboratory, analyte-matrix adduct ion peaks were always recorded when common MALDI matrices such as 4-hydroxy-alpha-cyanocinnamic acid (CHCA) were used. These compounds are mainly those with a benzene-1,3,5-tricarboxamide (BTA) or urea moiety, which are important building blocks to make new functional supramolecular materials. The possible mechanism of the adduct formation was investigated. A shared feature of the compounds studied is that they can form intermolecular hydrogen bonding with matrices like CHCA. The intermolecular hydrogen bonding will make the association between analyte ions and matrix molecules stronger. As a result, the analyte ions and matrix molecules in MALDI clusters will become more difficult to be separated from each other. Furthermore, it was found that analyte ions were mainly adducted with matrix salts, which is probably due to the much lower volatility of the salts compared with that of their corresponding matrix acids. It seems that the analyte-matrix adduct formation for our compounds are caused by the incomplete evaporation of matrix molecules from the MALDI clusters because of the combined effects of enhanced intermolecular interaction between analyte-matrix and of the low volatility of matrix salts. Based on these findings, strategies to suppress the analyte-matrix adduction are briefly discussed. In return, the positive results of using these strategies support the proposed mechanism of the analyte-matrix adduct formation.

General Chemistry, Catalysis, Symmetry breaking, Crystallography, Circular dichroism, Racemic mixture, Optically active, Molecule, Benzene, chemistry.chemical_compound, chemistry, Self-assembly, Chirality (chemistry), and General Medicine

The interplay of two subsequent aggregation processes results in a symmetry-breaking phenomenon in an achiral self-assembling system. Partially fluorinated benzene-1,3,5-tricarboxamide molecules self-assemble into a racemic mixture of one-dimensional P- and M-helical aggregates, followed by bundling into optically active higher-order aggregates or fibers (see picture).

[CHIM]Chemical Sciences, Materials Chemistry, Organic Chemistry, Polymers and Plastics, Polymer chemistry, Chemistry, Copolymer, Polystyrene, chemistry.chemical_compound, Monomer, Organic chemistry, Differential scanning calorimetry, Nitroxide mediated radical polymerization, Styrene, Hydroxylamine, and Glass transition

Several (protected) amine and alcohol functionalized styrene monomers were synthesized via readily accessible synthetic routes. The controlled radical copolymerization of these functionalized styrene monomers with styrene was performed using two alkoxyamines, namely N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl) hydroxylamine (MAMA-SG1) and N-tert-butyl-N-(2-methyl-1-phenylpropyl)-O-(1-phenylethyl)hydroxylamine. The copolymers obtained showed low polydispersities, controlled molecular weights, and a random topology. The thermal properties of the polymers were determined with differential scanning calorimetry. All polymers were amorphous and showed glass transition temperatures between 40 and 111 °C. Deprotection of the copolymers afforded amine or alcohol pendant polystyrenes which were readily functionalized with isocyanates. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Materials Chemistry, General Chemistry, Side chain, Hydrogen bond, Stacking, Crystallography, Polar, Intramolecular force, Ethylene glycol, chemistry.chemical_compound, chemistry, Intermolecular force, Stereochemistry, Alkane, and chemistry.chemical_classification

Substituted benzene-1,3,5-tricarboxamides (BTAs) 1-4 comprising polar tetraethyleneglycol (tetraEG) and/or apolar (R)-3,7-dimethyloctyl side chains were synthesised and their self-assembly in the solid state and in solution was investigated. While BTA 1 (comprising 3 apolar side chains) shows helical columnar packing via threefold ?-helical type intermolecular hydrogen bonding in the solid state and up to high dilutions in alkane solution (10 -5 M), helical columnar order is only preserved for asymmetric BTA 2 (comprising 1 polar and 2 apolar side chains) in the solid state and in a concentrated alkane solution (10-2 M). The association constant Kass is reduced by a factor of 107 by introducing one polar tetraEG chain into the BTA. A further increase in the number of polar tetraEG chains attached to BTA core results in the complete loss of intermolecular hydrogen bond formation in the solid state and in solution. Moreover, for the polar BTAs 3-4, comprising 2 or 3 polar tetraEG chains, no self-assembly in water occurs because of the lack of hydrophobic shielding. We propose that tetraEG side chains interfere with the intermolecular hydrogen bonds, weakening the stacking behaviour of these asymmetric derivatives and drastically lowering the association constant due to competing intramolecular hydrogen bonding interactions. In contrast, one methoxyethyl unit does not affect the stability of the aggregation of BTAs (Kass = 3 × 107 M-1) showing that more than one EG unit is required to disrupt the self-assembly of BTAs.

General Chemistry, Catalysis, Organic Chemistry, Chemistry, Supramolecular chemistry, Hydrogen bond, Stereochemistry, Mesophase, Molecule, Chirality (chemistry), Crystallography, Phenylene, Self-assembly, Supramolecular polymers, and chemistry.chemical_classification

The design of supramolecular motifs with tuneable stability and adjustable supramolecular polymerisation mechanisms is of crucial importance to precisely control the properties of supramolecular assemblies. This report focuses on constructing π-conjugated oligo(phenylene ethynylene) (OPE)-based one-dimensional helical supramolecular polymers that show a cooperative growth mechanism. Thus, a novel set of discotic molecules comprising a rigid OPE core, three amide groups, and peripheral solubilising wedge groups featuring C(3) and C(2) core symmetry was designed and synthesised. All of the discotic molecules are crystalline compounds and lack a columnar mesophase in the solid state. In dilute methylcyclohexane solution, one-dimensional supramolecular polymers are formed stabilised by threefold intermolecular hydrogen bonding and π-π interactions, as evidenced by (1)H NMR measurements. Small-angle X-ray and light scattering measurements reveal significant size differences between the columnar aggregates of C(3)- and C(2)-symmetrical discotics, that is, the core symmetry strongly influences the nature of the supramolecular polymerisation process. Temperature-dependent CD measurements show a highly cooperative polymerisation process for the C(3)-symmetrical discotics. In contrast, the self-assembly of C(2)-symmetrical discotics shows a smaller enthalpy release upon aggregation and decreased cooperativity. In all cases, the peripheral stereogenic centres induce a preferred handedness in the columnar helical aggregates. Moreover, one stereogenic centre suffices to fully bias the helicity in the C(2)-symmetrical discotics. Finally, chiral amplification studies with the C(3)-symmetrical discotics were performed by mixing chiral and achiral discotics (sergeants-and-soldiers experiment) and discotics of opposite chirality (majority-rules experiment). The results demonstrate a very strong sergeants-and-soldiers effect and a rather weak majority-rules effect.

Materials Chemistry, Metals and Alloys, Surfaces, Coatings and Films, General Chemistry, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Catalysis, Hydrogen bond, Polymer chemistry, Chemistry, Hydrogen, chemistry.chemical_element, Organic chemistry, Supramolecular chemistry, Ethylene glycol, chemistry.chemical_compound, Correlation and dependence, technology, industry, and agriculture, inorganic chemicals, and lipids (amino acids, peptides, and proteins)

Substitution of hydrogen bond directed supramolecular assemblies with ethylene glycol chains leads to a reduction in the association constant in apolar solvents, where the reduction of the association constant is dependent on the length of the aliphatic spacer connecting the hydrogen bonds and the ethylene glycol chain.

SDG 12 - Responsible Consumption and Production, Education, General Chemistry, 1h nmr spectroscopy, Organic reaction, Molecule, Column chromatography, Benzene, chemistry.chemical_compound, chemistry, Spectroscopy, Computational chemistry, Nanotechnology, Organic synthesis, and Ultraviolet visible spectroscopy

Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.

Materials Chemistry, Metals and Alloys, Surfaces, Coatings and Films, General Chemistry, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Catalysis, Non-equilibrium thermodynamics, Nanoparticle, Atomic force microscopy, Materials science, Self-assembly, Polymeric nanoparticles, Dewetting, Nanotechnology, Single chain, and Solvent evaporation

Evaporative self-assembly of dilute solutions containing single-chain polymeric nanoparticles results in characteristic morphologies imaged using atomic force microscopy. Quantitative comparison of experimental data to morphologies obtained by lattice-gas simulations shows that the nonequilibrium patterns emerge from a complex interplay between dewetting, solvent evaporation and nanoparticle diffusion.

Organic Chemistry, Polymers and Plastics, Biochemistry, Bioengineering, Moiety, Chemistry, Polymerization, Supramolecular chemistry, Polystyrene, chemistry.chemical_compound, Polymer, chemistry.chemical_classification, Solvent, Copolymer, Intramolecular force, and Polymer chemistry

A library of copolymers with pendant, protected ureido-pyrimidinone (UPy) groups was prepared applying controlled polymerization techniques. The polymer backbones were based on polyacrylate, polymethacrylate, polystyrene and polynorbornene and differ in stiffness, molecular weight and the linking moiety between the backbone and the UPy group. In all cases, the percentage of protected UPy groups was kept constant. The effect of solvent on the behaviour of the polymers before and after removal of the protecting groups was evaluated in, among others, chloroform and tetrahydrofuran (THF). After deprotection of the UPy protecting group, the UPys dimerize via four-fold H-bonding in THF, inducing a collapse into single-chain polymeric nanoparticles (SCPNs), as evidenced by a combination of 1H-NMR spectroscopy, size-exclusion chromatography and dynamic light scattering. In chloroform, on the other hand, dimerization of the UPy groups is present but interchain interactions occur as well, resulting in less-defined SCPNs. Remarkably, the flexibility of the polymer backbone, the polymer molecular weight and the nature of the linker unit all do not affect SCPN formation. In contrast, the interaction between solvent and the UPy moiety is a critical parameter for SCPN formation. For example, strong intramolecular dimerization of the UPys is observed in THF while interparticle interactions are suppressed. From this investigation we conclude that a wide variety of polymer backbones are suitable for polymer collapse via supramolecular interactions and thus allow for the formation of SCPNs but that the solvent choice is crucial to enhance intramolecular H-bonding and, at the same time, to suppress interparticle interactions.