Side Chain Length Research Articles

Porous thin films with hierarchical structures formed by self-assembly of zwitterionic comb copolymers

Zwitterions exhibit high dipole moments and strong intra- and inter-molecular interactions. As a result, amphiphilic copolymers with zwitterionic repeat units easily self-assemble. Here, we explore the wide range of self-assembled morphologies formed by zwitterionic comb-shaped copolymers (ZCCs) comprising a hydrophobic backbone and zwitterionic side-chains. We study the effect of polymer structure, architecture, and film preparation method on self-assembled morphology. We synthesized ZCCs with varying zwitterionic side chain density and length, and applied each ZCC as a thin film on glass substrates using different methods. We compared the morphology of these films with ZCCs films coated on a porous substrate by non-solvent induced phase separation, creating mechanically supported thin films (MSTFs) and comparing them with films on non-porous substrates. The porous support led to distinct changes in film morphology, creating hierarchical features including ∼17 nm spherical micelles along with larger nanopores (∼85 nm). This feature size could be tuned using a zwitterionic homopolymer additive. MSTFs exhibited significant changes in water permeance and morphology upon exposure to saline solutions, known to stimulate expansion of the zwitterionic side-chains. These results demonstrate the wide range of morphologies accessible by this comb copolymer family and document the significant effect of a porous support on the film formation process.

Effect of poly[oligo(ethylene glycol) methyl ether methacrylate] side chain length on the brush swelling behavior in A/B/A-B ternary blends with polystyrene.

The phase behavior of ternary blends composed of two homopolymers (A, B) and their corresponding diblock copolymer (A-B) has been widely studied, with emphasis on the volumetrically symmetric isopleth and the formation of bicontinuous microemulsions. However, almost all the previous studies employed linear polymers, and little is known about the impact of polymer architecture on the phase behavior of such ternary blends. Here, we report the self-assembly of three sets of ternary blends of polystyrene (PS) and poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMAn), with different lengths of oligo(ethylene glycol) side chains n. Small-angle X-ray scattering was used to probe the phase behavior at different compositions and temperatures. The order-to-disorder transition temperature was found to be impacted by the side chain length. It was also observed that longer side chains lead to poorer miscibility of homopolymers in the corresponding block, resulting in a more "dry-brush" like swelling behavior.

Divergent synthesis and antitumour activity of novel conformationally constrained (−)-muricatacin analogues

Four novel conformationally restricted (?)-muricatacin analogues, bearing a methoxy group at the C-5 position and with an alkoxymethyl group ?s the C-7 side chain, have been synthesised and their in vitro antiproliferative activity was evaluated against a panel of seven human tumour cell lines, as well as a single normal cell line. All analogues (9?12) showed diverse antiproliferative effects against all tested human malignant cell lines, but were devoid of any significant cytotoxicity towards the normal foetal lung fibroblasts (MRC-5). A structure?activity relationship study reveals that the introduction of tetrahydrofuran ring, the replacement of C-8 methylene group in the side chain of muricatacin analogues with the O-8 ether functionality, as well as the length of side chain may be beneficial for the antiproliferative effects of these lactones. All novel analogues were more potent than lead compound, (?)-muricatacin, against HL-60 cell line.

Biocompatible cationic polypeptoids with antibacterial selectivity depending on hydrophobic carbon chain length.

The overuse of antibiotics has triggered a new infection crisis and natural antimicrobial peptides (AMPs) have been extensively studied as an alternative to fight microorganisms. Polypeptoids, or polypeptide-biomimetics, offer similar properties to polypeptides and a highly tunable structure that has been synthesized by various methods such as ring opening polymerization (ROP) using N-carboxyanhydride monomers. Simultaneous high antibacterial activity and biocompatibility of a structure by efficient synthesis is desired in the application of those materials. Herein, a series of cationic polypeptoids (PNBs) with variable side chain lengths was obtained by introducing positive charges to the main chain in one step and preserving the backbone structure, namely polypeptoids (PNBM, PNBE, PNBB) with different end groups (methyl (M), ethyl (E), butyl (B)). To address the issue of infection in interventional biomedical implants, we report cost-effective modified polyurethane (PU) films (PU-PNBM, PU-PNBE, PU-PNBB) as physical-biological synergistic antibacterial surfaces that overcome problems such as steric hindrance and the solubility of the materials. Antibacterial selectivity was achieved by regulating the different side chain lengths. When methyl and ethyl were used as hydrophobic side chains, they can only selectively kill Gram-positive Staphylococcus aureus. PNBB, the most hydrophobic and with a butyl side chain can kill both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and inhibit the growth of bacterial biofilms. Effective in both solution and modified substrate, its biocompatibility is not compromised while the antibacterial properties are substantially improved. Furthermore, PU-PNBB films demonstrated their potential in vivo antimicrobial efficiency in a model of S. aureus infection established on mouse skin. The synthesis route and the surface modification strategies are convenient, providing a solution to the problem of poor biocompatibility in antimicrobial surface applications and a strategy for the use of peptide polymers for targeted therapy after specific infections in the biomedical field.

Effects of chirality and side chain length in Cα,α-dialkylated residues on β-hairpin peptide folded structure and stability.

Strategic incorporation of achiral Cα,α-dialkylated amino acids with bulky substituents into peptides can be used to promote extended strand conformations and inhibit protein-protein interactions associated with amyloid formation. In this work, we evaluate the thermodynamic impact of chiral Cα,α monomers on folding preferences in such systems through introduction of a series of Cα-methylated and Cα-ethylated residues into a β-hairpin host sequence. Depending on stereochemical configuration of the artificial monomer and potential for additional hydrophobic packing, a Cα-ethyl-Cα-propyl glycine residue can provide similar or enhanced folded stability relative to an achiral Cα,α-diethyl analogue.

Bulk depolymerization of graft polymers based on trans-cyclobutane-fused cyclooctene

Graft polymers with various sidechain lengths and grafting densities are prepared using trans-cyclobutane-fused cyclooctene macromonomers; the solvent-free depolymerization of these graft polymers in the presence of a ruthenium catalyst is studied.

Extraction of Metal Ions Using a Calix[4]arene Carboxylic Acid Derivative in Aromatic Ethers

If calixarenes can be dissolved in a relatively safe non-halogen solvent, they can be used in a liquid-liquid extraction process suitable for mass processing. In the present study, extraction behavior of metal ions using a calix[4]arene carboxylic acid derivative (tOct[4]CH2COOH) dissolved in aromatic ethers was investigated. The solubility of tOct[4]CH2COOH in aromatic ethers decreases with increase of the length of aliphatic side chain of the ethers. The solubility of tOct[4]CH2COOH in 1-butoxybenzene (BB) was 28.0 mmol/L, which is smaller than that in chloroform but is higher than those in hexane and toluene. Divalent metal ions Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) were extracted using tOct[4]CH2COOH in BB through proton exchange reaction at similar pH range in toluene, which is higher than that in chloroform. The extraction reaction of Cu(II) using tOct[4]CH2COOH in BB was determined by slope analysis and loading test. The stoichiometry between tOct[4]CH2COOH and Cu(II) was 2:1.

PEGMAs with short and long side chains: what is the effect in the formation of stars and brushes by RAFT polymerization?

PEGMA RAFT polymerization presents diverse kinetic characteristics, such as initiation rate (acceleration or inhibition), retardation effect, and dispersity, according to the length of the PEG side chain.

A trick of the tail: computing the entropic contribution to the energetics of quinone-protein unbindung.

We estimate the entropic contributions to the free energy of quinone unbinding in bacterial and mitochondrial respiratory chains using molecular dynamics (MD) and Monte Carlo (MC) computer simulations. For a varying length of the isoprenoid side chain, MD simulations in lipid bilayers and in unpolar solvents are used to assess the dihedral angle distributions along the chain. These form the basis of a MC estimate of the number of molecular structures that do not exhibit steric self-overlap and that are confined to the bilayer. We obtain an entropy drive of TΔS = 1.4 kcal mol-1 for each isoprene unit, which in sum is comparable to the redox potential differences involved in respiratory chain electron transfer. We postulate an entropy-driven zipper for quinone unbinding and discuss it in the context of the bioenergetics and the structure of complex I, and we indicate possible consequences of our findings for MD-based free energy computations.

Tuning of scleroglucan adsorption on carbonate surfaces via grafting alkyl side chains of different lengths: a theoretical and experimental study.

The semi-flexible polysaccharide scleroglucan (Sclg) is a well-known viscosity modifier and its highly hydrophilic nature limits its utilization as a polymeric surfactant of high efficiency. Grafting hydrophobic alkyl moieties onto the chain backbone provides a convenient means to reduce the hydrophilicity of Sclg. Herein, by using a self-consistent field theory (SCFT) that considers both the semi-flexibility of the Sclg main chain and the presence of grafted alkyl chains, we study the influences of the grafted alkyl moieties with different lengths (C6, C10 or C18) on the adsorption behaviors of the resultant polymeric surfactants on a carbonate surface. The extended SCFT well predicts the experimentally observed side alkyl-length-, salt- and temperature-enhanced surface excess of the modified Sclgs. The accumulation profiles of the main chains of different modified Sclgs are nearly superimposable under each solution condition. However, increasing the alkyl-length enhances the accumulation of the adsorbed side-chain segments on the surfaces. Polymer/surface entropic repulsion forces and side-chain/surface interactions govern the adsorption behaviors in regions near the surface, while the adsorption behaviors far away from the surface are controlled by the side chain/side chain interactions. On the basis of conformation profiles of the directly adsorbed chains, a model depicting the effects of the alkyl-length on the adsorbed chain conformations is proposed. These combined theoretical/experimental results enable production of advanced bio-polymeric surfactants with wide tunability and high performance.

Dynamic geometry design of cyclic peptide architectures for RNA structure.

Designing inhibitors for RNA is still challenging due to the bottleneck of maintaining the binding interaction of inhibitor-RNA accompanied by subtle RNA flexibility. Thus, the current approach usually needs to screen thousands of candidate inhibitors for binding. Here, we propose a dynamic geometry design approach to enrich the hits with only a tiny pool of designed geometrically compatible scaffold candidates. First, our method uses graph-based tree decomposition to explore the complementarity rigid binding cyclic peptide and design the amino acid side chain length and charge to fit the RNA pocket. Then, we perform an energy-based dynamical network algorithm to optimize the inhibitor-RNA hydrogen bonds. Dynamic geometry-guided design yields successful inhibitors with low micromolar binding affinity scaffolds and experimentally competes with the natural RNA chaperone. The results indicate that the dynamic geometry method yields higher efficiency and accuracy than traditional methods. The strategy could be further optimized to design the length and chirality by adopting nonstandard amino acids and facilitating RNA engineering for biological or medical applications.

Optimized charge transport in N-substituted isatin-based acceptor–donor–acceptor small molecules by regulating the side chain length for solution-processable organic thin-film transistors

A series of acceptor–donor–acceptor small molecules based on fused-ring as donor and N-substituted isatin with different side-chains (from methyl to n-decyl) as acceptors were synthesized for solution-processable organic thin-film transistors.

Adhesion and mechanical properties of poly(dimethylsiloxane) bottlebrush elastomers.

Poly(dimethylsiloxane) (PDMS) bottlebrush elastomers (BBEs) are attractive soft materials with well-controlled bulk mechanical properties. However, their surface and interfacial properties have not been studied in depth. We report a detailed study of the adhesion of PDMS BBEs to glass using a contact adhesion test to determine the critical energy release rates, Gc, as a function of interfacial separation velocity. For BBEs, Gc for initiating separation, G0, was found to be independent of the crosslink density. We hypothesize that the monomer chemistry of side chains plays a primary role in defining surface properties for this materials system. After crack initiation, BBEs showed a significantly lower Gc and less velocity dependence than linear chain networks. Scaling analysis attributes these properties to the faster dissipative relaxation mechanisms within the BBEs. These findings demonstrate that the adhesion properties of BBEs can be finely tuned through the monomer chemistry and side chain length for potential applications.

Controlling the mechanical properties of hydrogels via modulating the side-chain length.

Even though the toughness of hydrogels is usually adjusted by changing the cross-linking density and structure, or the polymer concentration, we have discovered a new strategy to control the toughness via modulating the side-chain length. In this study, this strategy was applied to biocompatible poly(oligo(ethylene glycol) methyl ether methacrylate) with long ethylene-oxide side chains.

تحضير وتشخيص كاسرات أستحلاب جديدة من بوليمرات طبيعية وصناعية

This research included the preparation and characterization of new demulsifies from natural and synthetic polymers of chitosan and polyvinyl alcohol that are environmentally friendly and at the same time have high efficacy comparable to emulsifiers. imported foreign. The prepared compounds were examined using infrared spectroscopy and nuclear magnetic resonance spectroscopy, and all the spectral signals of the polymers were in good agreement with the chemical composition of the polymers. And the melting and decomposition that occur on polymers at high temperatures. The effect of the length and type of side chain in the compositions of polymers on the process of water separation of oil emulsions was studied, and they had an important impact on the levels of water separation. The solubility behavior of polymers was also known, so that there was a solubility difference in Different organic solvents according to the type of the side chain of a hydrocarbon nature, and the best solubility of the prepared polymers was a solvent (dimethyl sulfoxide). The best polymerization time was found (12) h, as well as the best temperature at which polymerization takes place is (70 °C) and the prepared emulsion was compared with The commercial emulsifier was evaluated for its efficiency in separating water from crude oil (crude oil Basra) and compared to the commercial emulsifier, it was more efficient than the commercial one in separating water from oil.

Interrogating Polymorphism in Conjugated Poly(thieno)thiophene Thin Films for Field-Effect Transistors

The ability to modulate the polymorphism of semiconducting conjugated polymers (CPs) renders the scrutiny of the correlation between their molecular structure and charge transport characteristics. Surprisingly, investigation into the control over polymorphism to boost the charge mobility is few and limited in scope. Herein, we report, for the first time, two distinct polymorphisms in conjugated poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) thin films, the transformation between them via thermal and solvent vapor annealing, and the correlation of the respective polymorphism to charge transport properties. Specifically, a series of PBTTTs with different alkyl side chains (i.e., hexyl, octyl, decyl, and dodecyl; denoted PBTTT-6, PBTTT-8, PBTTT-10, and PBTTT-12, respectively) and molecular weights (MWs) are synthesized and their polymorphisms are examined by varying both the intrinsic (i.e., alkyl side-chain lengths and MWs) and extrinsic (i.e., thermal and solvent vapor annealing) parameters. Initially, type II (i.e., possessing a smaller interlayer spacing along the alkyl side-chain direction) exists in all as-cast PBTTT films. Upon thermal annealing at different temperatures (150 and 250 °C), PBTTT-6 and PBTTT-8 with shorter alkyl side chains and low MWs favor the transition from type II to type I (i.e., experiencing a larger interlayer spacing). Intriguingly, the type I PBTTT can be readily reverted to type II via subsequent solvent vapor annealing, and such polymorphism transition is highly reversible. The kinetics of the polymorphism transformation as well as the accompanied change in molecular stacking are elucidated. Finally, the charge transport properties of PBTTT thin films are found to depend sensitively on their crystalline structures, including the polymorphism change. This study provides insights into the control over the PBTTT polymorphisms and their intertransition via synergetic intrinsic molecular engineering and extrinsic post-treatments.

Digyalipopeptide A, an antiparasitic cyclic peptide from the Ghanaian Bacillus sp. strain DE2B.

During the continued isolation of different bacteria from highly diverse, low human activity environments in Ghana and the subsequent characterization and biological activity studies of their secondary metabolites, we found both Gram-positive and Gram-negative Bacillus strains to be ubiquitous and widespread. One of such strains, the Ghanaian novel Bacillus sp. strain DE2B was isolated from rhizosphere soils collected from the Digya National Park in Ghana. Chromatographic purifications of the fermented culture extract of the strain DE2B, led to the isolation of a cyclic lipopeptide, digyalipopeptide A (1). Using 1D and 2D NMR data, mass spectrometry sequence tagging, advanced Marfey's analysis, and the GNPS molecular networking we solved the full structure of digyalipopeptide A (1). We found that compound 1 is a member of a somewhat homologous series of peptides produced as a mixture by the strain containing the same amino acid sequence in the cyclic peptide backbone but differing only by the length of aliphatic fatty acid side chains. When tested against Trypanosoma brucei subsp. brucei strain GUTat 3.1 and Leishmania donovani (Laveran and Mesnil) Ross (D10), digyalipopeptide A (1) gave IC50 values of 12.89 µM (suramin IC50 0.96 µM) and 4.85 µM (amphotericin B IC50 4.87 µM), respectively. Furthermore, digyalipopeptide A (1) produced IC50 values of 10.07 µM (ampicillin IC50 0.18 µM) and 10.01 µM (ampicillin IC50 1.53 µM) for Staphylococcus aureus and Shigella sonnei, respectively. The selectivity and toxicity profile of compound 1 was investigated using normal cell lines, macrophages RAW 264.7. When tested against normal macrophages, compound 1 gave an IC50 value of 71.32 μM. Selectivity indices (SI) were obtained by calculating the ratio of the IC50 in RAW 264.7 to the IC50 in the respective microbe and neglected parasite. In the presence of RAW 264.7 cell lines, compound 1 was particularly selective towards Leishmania donovani (Laveran and Mesnil) Ross (D10) with an SI value of 14.71. The bioactivity studies conducted confirm the role of these cyclic lipopeptides as defense chemicals in their natural environment and their ability to be biologically active across different species.

Activity Improvement and Thermal Stability Enhancement of D-Aminoacylase Using Protein-Polymer Conjugates

In this study, the synthesis of new polymer-protein conjugates using a grafting-from strategy was performed by employing photo-induced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. D-aminoacylase is an industrially significant enzyme for the preparation of chiral amino acids and it is coupled with reversible addition-fragmentation (RAFT) chain transfer agent (CTA) using activated ester chemistry. The effects of polymeric side chain compositions on the activity of D-aminoacylase were studied with two different polymeric side chain lengths. For this reason, two monomers, a hydrophilic N-(2-aminoethyl acrylamide) and a hydrophobic and N- (iso-butoxymethyl) acrylamide were used, respectively. It was found that modification by grafting from strategy increased the thermal stability of D-aminoacylase enzyme. Additionally, the hydrophobic monomer conjugate has been reported to increase the activity of the enzyme more than the hydrophilic monomer.

Understanding the effect of MPEG‐PCE's microstructure on the adsorption and hydration of OPC

AbstractPolycarboxylic ethers or polycarboxylate (PCEs) are one of the most employed superplasticizers in construction. However, the understanding of their microstructure–property relationship is still incomplete. Recently, a theoretical model was proposed that relates the microstructure–conformation of the PCE to its effect on the adsorption onto cement particles and cement hydration time. In this work, the effects of a wide range of PCEs with different side chain lengths (P = 5, Group 1; P = 20, Group 2; and P = 45 and 113, Group 3) having flexible backbone worm conformation except one which has stretch backbone worm conformation (P = 113) were experimentally investigated for their effect on adsorption and cement hydration. It is found that PCEs from Group 1 show electrostatic repulsion as dispersing mechanism, unlike PCEs from Groups 2 and 3. Furthermore, the prediction of the theoretical model is also assessed for all the studied PCEs. Only Group 1 PCEs (shortest side chains) showed deviation from the theoretical predictions, and it was attributed to their different behaviors from the standard PCEs for which the theoretical model was developed.

Effect of Bottlebrush Poloxamer Architecture on Binding to Liposomes

Poloxamers─triblock copolymers consisting of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO)─have demonstrated cell membrane stabilization efficacy against numerous types of stress. However, the mechanism responsible for this stabilizing effect remains elusive, hindering engineering of more effective therapeutics. Bottlebrush polymers have a wide parameter space and known relationships between architectural parameters and polymer properties, enabling their use as a tool for mechanistic investigations of polymer-lipid bilayer interactions. In this work, we utilized a versatile synthetic platform to create novel bottlebrush analogues to poloxamers and then employed pulsed-field-gradient NMR and an in vitro osmotic stress assay to explore the effect of bottlebrush architectural parameters on binding to, and protection of, model phospholipid bilayers. We found that the binding affinity of a bottlebrush poloxamer (BBP) (B-E1043P515, Mn ≈ 26 kDa) is about 3 times higher than a linear poloxamer with a similar composition and number of PPO units (L-E93P54E93, Mn ≈ 11 kDa). Furthermore, BBP binding is sensitive to overall molecular weight, side-chain length, and architecture (statistical versus block). Finally, all tested BBPs exhibit a protective effect on cell membranes under stress at sub-μM concentrations. As the factors controlling membrane affinity and protection efficacy of bottlebrush poloxamers are not understood, these results provide important insight into how they adhere to and stabilize a lipid bilayer surface.