C12 Alkyl Research Articles

Synthesis of cationic alkylated chitosans and an investigation of their rheological properties and interaction with anionic surfactant

Two methods were used to alkylate high MW chitosan with glycidyltrimethylammonium chloride (GTAC) in order to produce chitosan derivatives that are water-soluble throughout the pH range. In addition, a novel chitosan derivative was created by alkylating one of the products with the GTAC analogue Quab 342 containing C12 alkyl chains. The phase behaviour and rheological characteristics of the chitosan derivatives were studied in the presence of anionic surfactant. The derivatives were found to form soluble complexes at low and high SDS concentrations and that the Quab 342 derivative was able to form gels.

Oximes short-acting CB1 receptor agonists

New oximes short-acting CB1 agonists were explored by the introduction of an internal oxime and polar groups at the C3 alkyl tail of Δ8-THC. The scope of the research was to drastically alter two important physicochemical properties hydrophobicity (log P) and topological surface area (tPSA) of the compound, which play a critical role in tissue distribution and sequestration (depot effect). Key synthesized analogs demonstrated sub-nanomolar affinity for CB1, marked reduction in hydrophobicity (ClogP∼2.5–3.5 vs 9.09 of Δ8-THC-DMH), and found to function as either agonists (trans-oximes) or neutral antagonists (cis-oximes) in a cAMP functional assay. All oxime analogs showed comparable affinity at the CB2 receptor, but surprisingly they were found to function as inverse agonists for CB2. In behavioral studies (i.e. analgesia, hypothermia) trans-oxime 8a exhibited a predictable fast onset (∼20 min) and short duration of pharmacological action (∼180 min), in contrast to the very prolonged duration of Δ8-THC-DMH (>24 h), thus limiting the potential for severe psychotropic side-effects associated with persistent activation of the CB1 receptor. We have conducted 100 ns molecular dynamic (MD) simulations of CB1 complexes with AM11542 (CB1 agonist) and both trans-8a and cis-8b isomeric oximes. These studies revealed that the C3 alkyl tail of cis-8b orientated within the CB1 binding pocket in a manner that triggered a conformational change that stabilized the CB1 receptor at its inactive-state (antagonistic functional effect). In contrast, the trans-8a isomer’s conformation was coincided with that of the AM11542 CB1 agonist-bound structure, stabilizing the CB1 receptor at the active-state (agonistic functional effect). We have selected oxime trans-8a based on its potency for CB1, and favorable pharmacodynamic profile, such as fast onset and predictable duration of pharmacological action, for evaluation in pre-clinical models of anorexia nervosa.

Modulating receptor-ligand binding in biorecognition by setting surface wettability.

Modulation of support wettability used for microarray format biosensing has led to an improvement of results. Hydrophobicity of glass chips was set by derivatizing with single vinyl organosilanes of different chain length and silane mixtures. Thiol-ene photochemical linking has been used as effective chemistry for covalent anchoring of thiolated probes. Lowest unspecific binding and highest signal intensity and SNR were obtained with large hydrocarbon chain (C22) silanes or a shorter one (C10) containing fluorine atoms. SNR resulting values are improved, reaching levels higher than 1500 in some cases, when using vinyl silanes modified with 1% C10 alkyl fluorinated one, because mild hydrophobicity was achieved (water contact angle ca. 110°) for all silanes, including the short C2 and C3, thus giving rise to smaller and better defined array spots. In addition, unspecific binding of reagents and targets was totally withdrawn. Hence, good-performing surfaces for biosensing applications can be built using appropriate organosilane reagent selection, including fluorinated ones. Graphical abstract ᅟ.

Design, Synthesis, and Evaluation of Homochiral Peptides Containing Arginine and Histidine as Molecular Transporters.

Linear (HR)n and cyclic [HR]n peptides (n = 4,5) containing alternate arginine and histidine residues were synthesized. The peptides showed 0–15% cytotoxicity at 5–100 µM in human ovarian adenocarcinoma (SK-OV-3) cells while they exhibited 0–12% toxicity in human leukemia cancer cell line (CCRF-CEM). Among all peptides, cyclic [HR]4 peptide was able to improve the delivery of a cell impermeable fluorescence-labeled phosphopeptide by two-fold. Fatty acids of different alkyl chain length were attached at the N-terminal of the linear peptide (HR)4 to improve the molecular transporter property. Addition of fatty acyl chains was expected to help with the permeation of the peptides through the cell membrane. Thus, we synthesized seven fatty acyl derivatives of the linear (HR)4 peptide. The peptides were synthesized using Fmoc/tBu solid phase peptide chemistry, purified by reverse-phase high-performance liquid chromatography (RP-HPLC) and characterized by matrix-assisted laser desorption/ionization (MALDI) spectrometry. The fatty acyl peptides containing C8, C12, C14, and C18 alkyl chain did not show cytotoxicity on SK-OV-3 or CCRF-CEM cell lines up to 50 µM concentration; however, at higher concentration (100 µM), they showed mild cytotoxicity. For example, C16-(HR)4 was also found to reduce the proliferation of SK-OV-3 cells by 11% at 50 µM and C20-(HR)4 showed mild toxicity at 10 µM, reducing the proliferation of SK-OV-3 cells by 21%. Increase in the length of alkyl chain showed cytotoxicity to the cell lines. C20-(HR)4 peptide showed better efficiency in translocation of F′-GpYEEI to SK-OV-3 than the phosphopeptide alone. Further investigation of C20-(HR)4 peptide efficacy showed that the peptide could deliver doxorubicin and epirubicin into SK-OV-3 and also improved the drug antiproliferative ability. These studies provided insights into understanding the structural requirements for optimal cellular delivery of the fatty acyl-(HR)4 peptide conjugates.

Assessment the ecotoxicity and inhibition of imidazolium ionic liquids by respiration inhibition assays

The ecotoxicity and inhibition of 12 imidazolium ionic liquids (ILs) with alkyl chain from C4 to C10 and chloride (Cl-), tetrafluoroborate (BF4-) and bis(trifluoromethanesulfonyl)imide (NTf2-) anions have been studied by means of respiration inhibition assays using activated sludge collected from a wastewater treatment plant. This test represents an alternative easy, economic and quick way to evaluate the true impact of ILs on activated sludge-based wastewater treatment. For comparison purposes, the EC50 values were also determined by the Microtox test (Vibrio fischeri). It was observed that this widely used microbial test overestimates the effect of the ILs on biological wastewater treatment facilities, especially in the case of ILs with lower ecotoxicity. The results of the biological tests showed that the alkyl chain length plays a crucial role in the ecotoxicity of ILs. A significant increase of the toxicity with the length of the n-alkyl chain was found. Regarding to the impact of the anion, the ecotoxicity measured by respiration inhibition assays follows the order NTf2- > Cl- > BF4-, being the anion effect higher as decreasing the length of cation alkyl chain. According to the hazard substances ranking for aquatic organisms (Passino and Smith, 1987), imidazolium ILs with C4 alkyl chain can be classified as “practically harmless” compounds whereas those with alkyl chains C8 or C10 correspond to “highly toxic” species.

High Density Alkyl Diamondoid Fuels Synthesized by Catalytic Cracking of Alkanes in the Presence of Adamantane

Alkyl diamondoid fuel mixtures have been prepared under moderate conditions by AlBr3 catalyzed cracking of nonane and heptane in the presence of adamantane. The fuel mixture prepared with heptane as the alkyl source (HA) contains primarily 1-ethyl-3-methyl adamantane and 1-propyladamantane, while the mixture prepared from nonane (NA) contains primarily C13–C15 alkyl diamondoids. Both fuel mixtures exhibit densities greater than 0.9 g/mL and volumetric net heats of combustion approximately 10 and 6% higher than conventional jet and diesel fuels, respectively. The structural diversity of the fuel blends and presence of multiple branch sites lead to lower viscosities compared to pure alkyl diamondoid fuels. The lower molecular weight blend, HA, exhibits a 40 °C kinematic viscosity of 3.22 mm2 s–1, well within the specification for diesel fuel, and both blends have derived cetane numbers of >42, suggesting that they can be used directly in conventional diesel engines.

Effect of surface wettability on the antibacterial activity of nanocellulose-based material with quaternary ammonium groups

Cellulose nanocrystals (CNCs) is a kind of natural, renewable, and biocompatible materials that can be functional via the surface modification. A covalently bonded CNCs-g-PDMAEMA was prepared by grafting 2-(dimethyl-amino) ethyl methacrylate (DMAEMA) on the CNCs’ surface via atom transfer radical polymerization (ATRP). Subsequently, the tertiary amino groups of the CNCs-g-PDMAEMA were transferred to quaternary ammonium groups by adding alkyl bromides with different carbon chain lengths (C10-C18). It was found that the antibacterial activity of the prepared materials is related to the quaternary group structure. The material containing C10 alkyl in quaternary group exhibited the best antibacterial efficiency, which was closely associated with the wettability of the quaternary CNCs-based polymers. The lower wettability of materials with higher hydrophobicity may impose a restriction on the polymeric antibacterial groups’ accessibility to the cytoplasmic membrane of bacteria. The antimicrobial CNCs-based composites may be potential to apply as coating agents for aseptic packaging.

Electrostatically Driven Guest Binding in a Self-Assembled Porous Network at the Liquid/Solid Interface.

We present here the construction of a self-assembled two-dimensional (2D) porous monolayer bearing a highly polar 2D space to study guest co-adsorption through electrostatic interactions at the liquid/solid interface. For this purpose, a dehydrobenzo[12]annulene (DBA) derivative, DBA-TeEG, having tetraethylene glycol (TeEG) groups at the end of the three alternating alkoxy chains connected by p-phenylene linkers was synthesized. As a reference host molecule, DBA-C10, having nonpolar C10 alkyl chains at three alternating terminals, was employed. As guest molecules, hexagonal phenylene-ethynylene macrocycles (PEMs) attached by triethylene glycol (TEG) ester and hexyl ester groups, PEM-TEG and PEM-C6, respectively, at each vertex of the macrocyclic periphery were used. Scanning tunneling microscopy observations at the 1,2,4-trichlorobenzene/highly oriented pyrolytic graphite interface revealed that PEM-TEG was immobilized in the pores formed by DBA-TeEG at higher probability because of electrostatic interactions such as dipole-dipole and hydrogen bonding interactions between oligoether units of the host and guest, in comparison to PEM-C6 with nonpolar groups. These observations are discussed based on molecular mechanics simulations to investigate the role of the polar functional groups. When a nonpolar host matrix formed by DBA-C10 was used, however, only phase separation and preferential adsorption were observed; virtually no host-guest complexation was discernible. This is ascribed to the strong affinity between the guest molecules which form by themselves densely packed van der Waals networks on the surface.

Crystallizability of substituted poly(lactic acid)s: Effects of alkyl side-chain structure

The side-chain-substituted poly(lactic acid)s (SPLAs) having C3–C4 alkyl side chains (Pr, iPr, n-Bu, iBu, and s-Bu for propyl, isopropyl, n-butyl, isobutyl, and sec-butyl groups, respectively) were synthesized from l-amino acids, and their crystallizability was systematically investigated (unknown for Pr, n-Bu, and s-Bu but already known for iPr and iBu). s-Bu was found to be a crystalline polymer like iPr, whereas Pr and n-Bu had no or very little crystallizability like iBu. The crystal structure, melting behavior, and crystallization rate of s-Bu were examined in detail. The crystal structure and crystallinity (ca. 60%) of s-Bu were not affected at all by the crystallization temperature and casting solvent. The melting temperature and spherulite growth rate of s-Bu were compared with those of iPr and referenced data of SPLA with methyl side chains (Me) [i.e., poly(l-lactic acid)] and that with ethyl side chains (Et) [i.e., poly(l-2-hydroxybutanoic acid)]. The magnitude relation among melting temperatures of SPLAs would be iPr > s-Bu > Me > Et, and that among spherulite growth rates iPr > Me ≈ s-Bu > Et.

Controlled Self-Assembly of Multiple-Responsive Superamphiphilc Polymers Based on Host-Guest Inclusions of a Modified PEG with β-Cyclodextrin.

Superamphiphilic polymers (SAPs) constructed by host-guest inclusion can self-assemble into various nanostructures in solution, which can find applications in many fields such as nanodevices, drug delivery, and template synthesis. Herein, we report the controlled self-assembly of multiple-responsive SAP based on a selective host-guest inclusion of β-cyclodextrin (β-CD) with a modified poly(ethylene glycol) (PEG) (FcC11AzoPEG) consisting of a ferrocene (Fc) end group, a C11 alkyl chain, an azobenzene (Azo) block, and a poly(ethylene glycol)methyl ether (PEG) chain. These SAPs can self-assemble into interesting nanostructures in water upon exposure to different stimuli because β-CD can be selectively included with different guests, such as Fc, Azo, and C11 alkyl chain, under different stimuli. The inclusion complex of Fc with β-CD (Fc@β-CD SAP) can form nanowire micelles in aqueous solution. The nanowire micelles can be transformed into spindle micelles with the addition of oxidant because the majority of β-CDs dissociated from the complex Fc@β-CD SAP due to a conversion of Fc to Fc+ and will preferentially include with Azo group to form another dominant inclusion complex (Azo@β-CD SAP). After UV irradiation, the spindle micelles can be further transformed into spherical micelles because most of β-CDs are excluded from the complex Azo@β-CD SAP due to a trans- to cis-Azo conversion and then form a dominant inclusion complex with C11 alkyl chains (C11@β-CD SAP). This work not only demonstrates the selective host-guest inclusion of stimuli-responsive groups modified PEG with β-CD but also provides a useful approach for construction of diverse morphologies.

Carbon dioxide-in-oil emulsions stabilized with silicone-alkyl surfactants for waterless hydraulic fracturing

The design of surfactants for CO2/oil emulsions has been elusive given the low CO2-oil interfacial tension, and consequently, low driving force for surfactant adsorption. Our hypothesis is that waterless, high pressure CO2/oil emulsions can be stabilized by hydrophobic comb polymer surfactants that adsorb at the interface and sterically stabilize the CO2 droplets. The emulsions were formed by mixing with an impeller or by co-injecting CO2 and oil through a beadpack (CO2 volume fractions (ϕ) of 0.50–0.90). Emulsions were generated with comb polymer surfactants with a polydimethylsiloxane (PDMS) backbone and pendant linear alkyl chains. The C30 alkyl chains are CO2-insoluble but oil soluble (oleophilic), whereas PDMS with more than 50 repeat units is CO2-philic but only partially oleophilic. The adsorbed surfactants sterically stabilized CO2 droplets against Ostwald ripening and coalescence. The optimum surfactant adsorption was obtained with a PDMS degree of polymerization of ∼88 and seven C30 side chains. The emulsion apparent viscosity reached 18 cP at a ϕ of 0.70, several orders of magnitude higher than the viscosity of pure CO2, with CO2 droplets in the 10–150 µm range. These environmentally benign waterless emulsions are of interest for hydraulic fracturing, especially in water-sensitive formations.

Atomic Force Microscopy and Angular-Dependent X-ray Photoelectron Spectroscopy Studies of Anchored Quaternary Ammonium Salt Biocides on Quartz Surfaces.

A siloxane surface-anchored quaternary ammonium salt (AQAS: BIOSAFE HM4100 in this study) has been chemisorbed onto a quartz substrate. The aim of this study is to elucidate, using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), the structure of the chemisorbed AQAS layers. The AQAS biocide includes a C18 alkyl chain previously invoked in lysis potency. The AQAS coverage appears in zones on the surface, which include a first layer (2.6 ± 0.1 nm) and multilayering that were explored using AFM. The XPS data exhibited two N 1s signals at about 402 and 399 eV, with only the former exhibiting angular dependence. This signal at 402 eV was assigned to the first anchored layer with perpendicular orientation determined by the AQAS anchoring to the surface. In preliminary AFM studies of bacteria on these AQAS surfaces, perturbations on the Staphylococcus aureus cells and the degradation of Escherichia coli cells suggest lysis potency.

Assessment of Compost-Derived Humic Acids Structure from Ligno-Cellulose Waste by TMAH-Thermochemolysis

In this study, we used the TMAH-thermochemolysis to characterize more precisely the chemical structure of the humic acids (HAs) extracted from two composts a basically lignocellulosic substrate and to follow up their biotransformation during the composting process. The analysis of the pyrograms obtained for both composts [date palm waste alone (DPW) and date palm waste-couch grass clippings mixture (DPCG)] allowed to distinguish a dominance of aromatic compounds from lignin and from nonspecific origin (92.7 and 85.5% respectively for DPW and DPCG mixture). A few nitrogen-derived and polysaccharides compounds was recorded in our HAs. For both composts, the lignin structures were represented by guaiacyl (G) and syringyl (S) units. The lack of lignin derived from p-coumaric structures could be ascribed to their degradation by influence of the extraction. This support can be confirmed by the absence in our samples of compounds with the C3 alkyl side-chain of ferulic acid. The high level of lignin-derived compounds explains the slow biodegradation and humification observed especially during DPW composting. The lignocellulose nature of date palm substrate limits the microbial proliferation responsible of the degradation and transformation of OM which is partially ameliorated by couch grass addition. This is in correlation with temperature evolution observed for DPW compost. Some variations in the chemical composition of the macromolecular content were recorded for both composting. An increase of the abundance of the nitrogen products from 6.4 and 11.6% to 8.2 and 13.8% respectively for DPW and DPCG mixture was observed. This increase can attributed to the decomposition of certain protein structures and microbial metabolism with a possible incorporation into the new formed HAs. The strong increase of methylpyrrole (isomer 8) and the strong decrease of 1H-indole for DPCG mixture indicate that the degradation phenomena were more extensive for this mixture than for DPW compost. The decrease of the total abundance of aromatic compounds of non specific origin for DPW compost against an increase for DPCG mixture indicate that humification process was more advanced in this latter leading to the incorporation of some structures into the new formed HAs. The decrease of phenol (14) toward the end DPW composting suggests its degradation and transformation into others variety of phenolic derivatives, whereas its increase for DPCG mixture can be related to its incorporation during humic structure formation. This can confirm that the speed of degradation and humification is more important for DPCG mixture than DPW compost. Also a significant decrease of guaiacyl derivatives was observed for DPCG mixture. The results of the calcul of S/G ratios were not in agreement with the literature. The support of the preferential degradation of S or G moieties is not valid here. The decomposition of the lignin structures is connected to the accessibility of the biomass microbial to the S or G lignin. The slight increase by the same value of the acid/aldehyde ratio for both composts indicates a low and equal degree of oxidization of the lignin.

Impact of Headgroup Asymmetry and Protonation State on the Aggregation Behavior of a New Type of Glycerol Diether Bolalipid.

In the present work, we describe the synthesis and the temperature-dependent aggregation behavior of a new class of asymmetrical glycerol diether bolalipids. These bolalipids are composed of a membrane-spanning alkyl chain with 32 carbon atoms (C32) in the sn-3 position, a methyl-branched C16 alkyl chain in the sn-2 position, and a zwitterionic phosphocholine headgroup in the sn-1 position of a glycerol moiety. The long C32 alkyl chain is terminated either by a second phosphocholine (PC-Gly(2C16Me)C32-PC) or by a phosphodimethylethanolamine headgroup (PC-Gly(2C16Me)C32-Me2PE). The temperature- and pH-dependent aggregation behavior of both lipids was studied using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments. The morphology of the formed aggregates in an aqueous suspension was visualized by transmission electron microscopy (TEM). We show that PC-Gly(2C16Me)C32-PC and PC-Gly(2C16Me)C32-Me2PE at pH 5 self-assemble into large lamellar aggregates and large lipid vesicles. Within these structures, the bolalipid molecules are probably assembled in a monolayer with fully interdigitated chains. The lipid molecules seem to be tilted with respect to the layer normal to ensure a dense packing of the alkyl chains. A temperature increase leads to a transition from a lamellar gel phase to the liquid-crystalline phase at about 28-30 °C for both bolalipids. The lamellar aggregates of PC-Gly(2C16Me)C32-Me2PE started to transform into nanofibers when the pH value of the suspension was increased to above 11. At pH 12, these nanofibers were the dominant aggregates.

Genetically encoded lipid-polypeptide hybrid biomaterials that exhibit temperature-triggered hierarchical self-assembly.

Post-translational modification of proteins is a strategy widely used in biological systems. It expands the diversity of the proteome and allows for tailoring of both the function and localization of proteins within cells as well as the material properties of structural proteins and matrices. Despite their ubiquity in biology, with a few exceptions, the potential of post-translational modifications in biomaterials synthesis has remained largely untapped. As a proof of concept to demonstrate the feasibility of creating a genetically encoded biohybrid material through post-translational modification, we report here the generation of a family of three stimulus-responsive hybrid materials-fatty-acid-modified elastin-like polypeptides-using a one-pot recombinant expression and post-translational lipidation methodology. These hybrid biomaterials contain an amphiphilic domain, composed of a β-sheet-forming peptide that is post-translationally functionalized with a C14 alkyl chain, fused to a thermally responsive elastin-like polypeptide. They exhibit temperature-triggered hierarchical self-assembly across multiple length scales with varied structure and material properties that can be controlled at the sequence level.

Enhanced antibacterial activity of functionalized graphene by azo-pyridinium compounds

For enhancement of antibacterial properties, two azo compounds were grafted on the aminated graphene by using the imine linkage. The azo compounds included pyridinium unit with different alkyl long chains. The new nanohybrids were characterized by Fourier transform infrared spectra, X-ray powder diffraction, ultraviolet–visible, field emission scanning electron microscopy (FE-SEM), atomic force microscopy, zeta potential, and energy-dispersive X-ray spectroscopy. The hybrids were investigated for antibacterial effect against Staphylococcus aureus and Escherichia coli as models of Gram-positive and Gram-negative bacteria. The nanohybrids showed a significant effect on both bacteria. Destruction of the cell wall and discharge of intracellular contents could be detected from FE-SEM images of bacteria after exposed to nanohybrids. The nanohybrid with C10 alkyl chain in the pyridinium unit displayed the highest antibacterial activity. Antibacterial activity of graphene–azo nanocomposite against E. coli and S. aureus was enhanced. Destruction of the cell wall and shrinking of bacteria are observed in FE-SEM image.

Polymer-soluble thermostable phosphate-ester copper complexes for near-infrared absorbing dyes with weak absorbance in the visible region

Near-infrared absorbing dyes must be thermally stable above their processing temperatures. Here, polymer-soluble thermostable phosphate-ester copper complexes that meet these requirements are reported for use as near-infrared absorbing dyes with a wide absorption range from 700 to 1200 nm, and a weak absorbance in the visible region. C5–C12 alkyl phosphate-ester copper complexes were synthesized and their thermal stabilities were evaluated by thermogravimetric analysis. The previously reported acetoxy-butyl-phosphate copper complex, which contains an ester group, was also synthesized for comparison. The mass of the alkyl-phosphate-ester copper complexes remained constant up to 170 °C, whereas that of the acetoxy-butyl-phosphate copper complex started to decrease below 100 °C. Some copper complexes showed decomposition temperatures above 250 °C. The thermal-decomposition behavior of the n-pentyl-phosphate copper complex, cyclohexyl-phosphate copper complex and 2-ethylhexyl-phosphate copper complex was investigated by thermal-decomposition gas analysis measured by purge-and-trap gas chromatography/mass spectrometry. Cleavage of the O–C bond was the main decomposition reaction for both complexes. The difference in the thermal stabilities of the cyclohexyl-phosphate copper complex and other alkyl-phosphate-ester copper complexes is presumed to result from their different tendencies towards cleavage of the O–C bond. The absorption spectra of the 2-ethylhexyl-phosphate copper complex and the isodecyl-phosphate copper complex showed a broad absorbance from 700 to 1200 nm and a weak absorbance in the visible region. Therefore, these compounds are suitable for window materials that require heat-shielding properties and transparency. The spectra also indicated that the structures of these copper complexes are similar regardless of the substituent on the ligand.

Antimicrobial sponge prepared by hydrophobically modified chitosan for bacteria removal

Hydrophobically modified chitosan (HMCS) prepared by reacting chitosan with dodecyl aldehyde can generate very stable foam when dissolved in mild acidic condition under vigorous mechanical stirring. A durable and lightweight (density of 32 mg/ml) sponge was obtained by freeze-drying the stably formed HMCS foam. In addition to the cationic nature of chitosan, the grafted C12 alkyl chains were also able to help HMCS sponge for capturing E. coli cells (∼4.0 × 108 cells/mg sponge) by intercalating into the outer membrane of E. coli cells. E. coli cells captured on HMCS sponge were found to be mostly dead and easily released into the bulk solution so that the active surface could be continuously regenerated for capturing and killing the rest of alive cells. In comparison with its counterpart (chitosan sponge), HMCS sponge maintained a higher operational stability for the removal of E. coli cells. After 5 repeated cells removal operation, the removal capacity of HMCS sponge could be regenerated back to >90% by thorough washing with ethanol.

Decoration of Polyfluorene-Wrapped Carbon Nanotubes via Strain-Promoted Azide–Alkyne Cycloaddition

A generalizable method to decorate carbon nanotubes deposited as a thin film without damaging nanotube optoelectronic properties remains elusive. Here, reactive, noncovalently functionalized polymer–nanotube thin films were prepared using a polyfluorene that is decorated with azide groups in its side chains. The azides allow for Strain-Promoted Azide–Alkyne Cycloaddition to occur between the polymer–nanotube complex and strained cyclooctyne derivatives. It was found that quantitative functionalization of the nanotube thin film occurred efficiently at room temperature, without any catalyst or by-product removal required. This interfacial chemistry resulted in no damage to the nanotube structure or properties, as evidenced by absorption, fluorescence, and Raman spectroscopy. The polymer–nanotube thin films were investigated using thermogravimetric analysis, and it was found that the mass losses upon heating under an inert atmosphere were consistent with complete functionalization of the thin films. Using polyethylene glycol or C16 alkyl chains functionalized with a strained cyclooctyne, we modulated the hydrophobicity of the thin film and found that we could prepare Janus nanotube films via stepwise functionalization.

On the Influence of Intersurfactant H-Bonds on Foam Stability: A Study with Technical Grade Surfactants

Abstract From the literature on the foam stability of various surfactants with C12 alkyl chains but different head groups a clear picture emerges: Foams are more stable when hydrogen bonds can form between the head groups, i. e. when the polar head group has a hydrogen bond donor and a proton acceptor. These observations suggest that hydrogen bonds between neighbouring molecules at the surface enhance foam stability. To support this hypothesis, we carried out a systematic foaming study of two types of technical grade surfactants, one of them being capable of forming H-bonds and the other one not. As was the case for the pure surfactants we found again that more stable foams are formed when the head group is capable of forming intersurfactant H-bonds: These results will certainly affect the future design of surfactants.