Effect Of Side Chain Structure Research Articles

On the Stability of Non‐fullerene Acceptors and Their Corresponding Organic Solar Cells: Influence of Side Chains

AbstractSide chain engineering is a widely explored strategy in the molecular design for non‐fullerene acceptors (NFAs). Although the relationship between side chain structures and optoelectronic properties of NFAs is well clarified, the effect of side chain structures on the stability of NFAs and their corresponding organic solar cells (OSCs) is rarely reported. Herein, a series of Y‐family NFAs with varying side‐chains are studied to investigate their degradation upon multiple stresses including water, oxygen from ambient, chemical environment from ZnO electron transport layer, temperature, and ultraviolet light. The results show that all of these Y‐family NFAs are highly stable against water and oxygen in ambient dark condition, while their photochemical and thermal stabilities decrease with the increasing side chain length. NFAs with shorter side chains are not only more resistant to photo‐oxidation and photocatalytic reactions, but also can hamper the formation of large phase‐separated NFA domains upon storage in both glovebox and ambient conditions. As such, the PM6:NFA OSC with short side‐chain NFA also exhibits superior operational stability, associating with a higher T80 lifetime. This study demonstrates that the side chains must be considered to obtain stable OSCs.

A comprehensive study on the effect of backbone stereochemistry of a cyclic hexapeptide on membrane permeability and microsomal stability.

Backbone stereochemistry of cyclic peptides has been reported to have a great influence on microsomal stability and membrane permeability, two important factors that determine oral bioavailability. Here, we comprehensively investigated the correlation between the backbone stereochemistry of cyclic hexapeptide stereoisomers and their stability in liver microsomes, as well as passive membrane permeability.

Effect of side chain on conformational properties of comb-like polycarboxylate in salt solutions

To investigate the effect of side-chain structure of comb-like polycarboxylates (PCE) on conformational properties in salt solutions, PCE with polyethyleneoxide (PEO) of different lengths were synthesized using methallyl polyethylene glycol (MPEG, Mw = 1200, 2400, 4000). Adding counter-ions (i.e., Na+, Ca2+) to dilute PCE solutions was found to induce a more complicated conformational changes, since the screening of the electrostatic intramolecular repulsion and the different complexation behaviors of Ca2+ with carboxylic groups. Laser light scattering (LLS) and conductivity measurements were used to investigate the conformations of PCE at various pH values. PCE of a long side chain polymer and the sparse grafting studied herein possesses a more coiled polymer backbone due to the intramolecular steric hindrance, which resulted in a more exposed extent of carboxylic groups on the backbone at the same pH values. Obviously, the solution conformation of PCE strongly impacts the accessible carboxylic groups contribution to complexation of the carboxylic oxygen atoms of PCE with Ca2+. In this way it may provide a new insight to design the polymer dispersants.

Effect of Side Chain Structure and Number of Hydroxyl Groups of Primary, Secondary and Tertiary Amines on their Post-Combustion CO2 Capture Performance

The effect of the side chain structure and the number of hydroxyl groups in primary, secondary and tertiary amines on kinetics of CO2 absorption (40oC, 15% CO2 feed gas) and desorption (at 90oC), equilibrium loading, heat duty, cyclic capacity, heat of absorption and pKa were investigated. The results showed that, compared with their straight-chain analogues, steric hindrance in branched-chain alkanolamines resulted in much higher solubilities and lower initial absorption rates. Steric hindrance in tertiary amines increased the desorption rate but lowered the heat duty. More hydroxyl groups attached to nitrogen group resulted in a lower absorption rate and amine basicity.

Effect of side-chain structure on hydrothermolysis of lignin model compounds

Hydrothermal-controlled selective cleavage of CβO and CαCβ bonds was well realized via modification the side-chain structure of lignin. To elucidate the reaction pathway and the origin of selectivity, the sites of the benzylic alcohol (Cα–OH) and benzylic ketone (CαO) on the cleavage mechanisms of βO4 lignin dimers were investigated. Results clearly demonstrated the hydrothermolysis process could be divided into three stages: (1) intramolecular elimination reactions, (2) the cleavage of CαCβ or CβO bonds and (3) secondary reactions of intermediates. Reaction pathways were highly susceptible to the side-chain structure. The CαCβ and CβO bonds of 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-ethanone tended to directly cleave and form aromatic monomers. However, many different species dimers were produced via the intramolecular elimination reactions when the hydroxyl group was introduced at the Cα or Cγ position, which participated in a variety of reaction mechanisms, resulting in more complex products distribution. In addition, the results also indicated that dehydration of Cα-OH group significantly facilitated the cleavage of CβO bonds, but oxidation of the Cα-OH into Cα=O group weakened the CαCβ bond. Based on the compositions and structures of products, several cleavage pathways of dimers were proposed, explaining well the origin of selectivity.

Cellulose fatty acid esters as sustainable film materials – effect of side chain structure on barrier and mechanical properties

Bio-based films were prepared by acylation of cellulose with saturated, unsaturated and branched fatty acids. The products showed increased thermal stability, low water vapour transmission rates and enhanced tensile and elastic properties.

The Effect of Side-Chain Structure on Copolymer-Based Bulk Heterojunction Solar Cells

This paper describes the synthesis and photovoltaic studies of copolymer based on benzo[1,2-b:4,5-b′]dithiophene and 2,1,3-benzothiadiazole. Bulk-heterojunction solar cells were fabricated by using chlorobenzene, and 2% chloronapthalene as a solvent additive in chlorobenzene. The copolymers as the electron donor were blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as the electron acceptor. The effect of side–chain on BDT was compared between 4,8-bis(1-pentylhexyl)benzo[1,2-b: 4,5-b′]dithiophene (C11BDT) and 4,8-bis(1-butylhexyl)benzo[1,2-b:4,5-b′]dithioph ene (C9BDT). The power conversion efficiency (PCE) was improved with the shorter side–chain. The highest PCE was found in PC9BDTBT with 2.29%.

Effect of Side-Chain Structure of Polycarboxylic Acid Type Water-Reducer on Hydration of C<sub>3</sub>A

Several polycarboxylate superplasticizers (PCs) with different side-chain structure have been synthesized. The effect of side-chain structure of PCs on hydration of C3A has been investigated by XRD, TG-DSC and SEM. The results show that PCs restrain hydration of C3A as a whole, but accelerate formation of Al(OH)3 and C3AH6; with increase molecular weight of long-side-chain, hydration of C3A is slowed, and the formation of Al (OH)3 and C2AH8 also become slowed. With increase proportion of long-side-chain, hydration of C3A and formation of C3AH6 are slowed, but existence of C2AH8 become obvious. The six-party flake hydrated products of C3AH6 are formed with a large number of grafted carboxyl.

Effect of Molecular Weight of Long-Side-Chain of Polycarboxylic Acid Type Water-Reducer on Hydration of C<sub>3</sub>A

Several polycarboxylic acid type water-reducing agents (PCs) with different side-chain structure have been synthesized. The effect of side-chain structure of PCs on hydration of C3A has been investigated by XRD, TG-DSC and SEM. The results show that PCs restrain hydration of C3A as a whole, but accelerate the transformation from C2AH8 to Al (OH) 3 and C3AH6; for structure of the PCs, the bigger molecular weight of long-side-chain of PCs is advantage to restrain hydration of C3A. And it also is better to formation of six-party flake hydrated products. But the little molecular weight of long-side-chain of PCs tends to form the cube-shaped hydrated products.

Poly(β-aminoester)s with Pendant Primary Amines for Efficient Gene Delivery

Three hydrolytically degradable poly(beta-aminoester)s containing ester bonds in the main chain and primary amines in the side chain, synthesized by Michael polyaddition, were applied to deliver foreign DNA into cells in vitro. These linear polycations can condense DNA into small-sized particles with positive surface charge at high N/P ratios. Their high buffer capacity at pH 5-7 facilitated the escape of DNA from the endosome and resulted in efficient gene expression. Under the optimal conditions, poly(beta-aminoester)s with a pendant aminoethyl group showed higher transfection efficiencies than branched poly(ethylenimine) (PEI) 25KDa in 293T cells. The effect of side chain structure of the poly(beta-aminoester) on transfection efficiency has been investigated, which indicated that the poly(beta-aminoester) containing the pendant aminoethyl group was the most efficient carrier for both of 293T cells and COS-7 cells. The combination of hydrolytical degradation, high buffer capacity, relatively low cytotoxicity, and high transfection efficiency suggested that this kind of poly(beta-aminoester)s are novel promising nonviral gene carriers.

Synthesis and biological activities of new 1α,25-dihydroxy-19-norvitamin D 3 analogs with modifications in both the A-ring and the side chain

In a series of studies on structure–activity relationships of 2-substituted 19-norvitamin D analogs, we found that 1α,25-dihydroxy-19-norvitamin D 3 analogs with 2β-hydroxyethoxy or 2 E-hydroxyethylidene moieties show strong binding affinity for the vitamin D receptor (VDR) as well as marked transcriptional activity. To further examine the effects of side chain structure on the activity of 2-substituted 19-norvitamin D analogs, we have synthesized new 19-norvitamin D 3 analogs with modifications in both the A-ring at the C(2) position and the side chain. The side chains of these analogs contained a double bond between C(22) and C(23) or an oxygen atom at C(22). The biological activity of the analogs was evaluated in vitro. All the side chain-modified analogs were less active than 1α,25-dihydroxyvitamin D 3 1e and the parent compounds 3– 6e possessing a natural 20 R-configuration in binding to the VDR, but, except for the (20 R)-22-oxa analogs 3– 6d, were significantly more potent in transcriptional activity. Of the side-chain-modified analogs 4 and 5, the 2β-hydroxyethoxy- and 2 E-hydroxyethylidene-22,24-diene-24a,26a,27a-trihomo analogs showed markedly higher transcriptional activity (25- and 17.5-fold, respectively) compared with 1e. Elongation of the side chain at the C-24, C-26, and C-27 positions and introduction of a 22,24-diene moiety strongly increased transcriptional activity, as seen in the 20- epi analogs 3– 6f.

Effect of side chain structure of polyimides on a pretilt angle of liquid crystal cells

A series of poly(amic acid)s had been synthesized from cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 4,4′-diaminodiphenyl methane (DDM) and functional diamines with various side chain structures. The functional diamines, like 3,5-diamino benzoic acid hexadecane-1-yl ester which had long alkyl or rigid alicyclic side chains with different flexibility had been synthesized. Pretilt angles of liquid crystal cell fabricated with the poly(amic acid)s were measured and investigated factors affecting on the pretilt angles. The pretilt angles of the liquid crystal on the polyimide ( 5a) with rigid side group was 0.6°, on the other hand, the pretilt angle on the polyimide ( 5b) and ( 5c) with flexible side chains were very high above 89.6°. Furthermore, the pretilt angle of liquid crystal on the polyimide ( 5c) film having rigid cylindrical structure with 6-methylheptyl at the chain end was still high above 86.0° even after the rubbing process.

Effect of side chain structure on the liquid crystalline properties of polymers bearing cholesterol, dihydrocholesterol and bile acid pendant groups

Four methacrylate derivatives of steroid molecules, namely cholic acid methyl ester, lithocholic acid methyl ester, cholesterol and dihydrocholesterol, were synthesized. A 10-carbon spacer separates the rigid core and the polymerizable methacrylate group. These monomers and their corresponding polymers were characterized for their liquid crystalline properties by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. It was found that only the compounds bearing the planar cholesterol-based moieties, and not those bearing the esterified bile acid groups, possess liquid crystalline phases. A detailed X-ray study showed that the dihydrocholesterol polymer possesses the same two mesophases as the cholesterol polymer, but with reduced thermal stability.

Effect of side-chain structures on gene transfer efficiency of biodegradable cationic polyphosphoesters

Cationic polyphosphoesters (PPEs) with different side-chain charge groups were designed and synthesized as biodegradable gene carriers. Poly( N-methyl-2-aminoethyl propylene phosphate) (PPE-MEA), with a secondary amino group (CH 2CH 2NHCH 3) side chain released DNA in several hours at N/P (amino group of polymer to phosphate group of DNA) ratios from 0.5 to 5; whereas PPE-HA, bearing CH 2(CH 2) 4CH 2NH 2 groups in the side chain, did not release DNA at the same ratio range for 30 days. Hydrolytic degradation and DNA binding results suggested that side chain cleavage, besides the polymer degradation, was the predominant factor affected the DNA release and transfection efficiencies. The side chain of PPE-MEA was cleaved faster than that of PPE-HA, resulting poor cellular uptake and no transgene expression for PPE-MEA/DNA complexes in COS-7 cells at charge ratios from 4 to 12. In contrast, PPE-HA/DNA complexes were stable enough to be internalized by cells and effected gene transfection (3400 folds higher than background at a charge ratio of 12). Interestingly, gene expression levels mediated by PPE-MEA and PPE-HA in mouse muscle following intramuscular injection of complexes showed a reversed order: PPE-MEA/DNA complexes mediated a 1.5–2-fold higher luciferase expression in mouse muscle as compared with naked DNA injection, while PPE-HA/DNA complexes induced delayed and lowered luciferase expression than naked DNA. These results suggested that the side chain structure is a crucial factor determining the mechanism and kinetics of hydrolytic degradation of PPE carriers, which in turn influenced the kinetics of DNA release from PPE/DNA complexes and their transfection abilities in vitro and in vivo.

Motion of spin-labeled side chains in T4 lysozyme: effect of side chain structure.

Previous studies have shown that the mobility of nitroxide side chains in a protein, inferred from the electron paramagnetic resonance (EPR) spectra, can be used to classify particular sites as helix surface sites, tertiary contact sites, buried sites, or loop sites. In addition, the sequence dependence of mobility can identify regular secondary structure. However, in the most widely used side chain, an apparent interaction of the nitroxide ring with the protein at some helix surface sites gives rise to EPR spectra degenerate with those at tertiary contact sites. In the present study, we use selected sites in T4 lysozyme to evaluate novel nitroxide side chains designed to resolve this degeneracy. The results indicate that the reagent 3-(methanesulfonylthiomethyl)-2,2, 5,5-tetramethylpyrrolidin-1-yloxy reacts with cysteine to give a nitroxide side chain that has a high contrast in mobility between helix surface and tertiary contact sites, effectively resolving the degeneracy. The reagent 3-(iodomercuriomethyl)-2,2,5,5-tetramethyl-2, 5-dihydro-1H-pyrrol-1-yloxy reacts with cysteine to provide a mercury-linked nitroxide that also shows reduced interaction with the protein at most helix surface sites. Thus, these new side chains may be the preferred choices for structure determination using site-directed spin labeling.

Polyamide-Type High Pretilt Surface: Effect of Side-Chain Structure and Type of Liquid Crystals on the Generation of Pretilt Angle

Abstract Highly N-aralkylated poly(p-phenylene terephthalamide) (PPTA) with various substituents having benzyl units in their structures were synthesized in a high yield, and their properties as a liquid crystal alignment film were studied. Good liquid crystal alignment and pretilt angles of 0.5 to 8.1 deg were observed on the spin-coated polymer films after rubbing when a nematic liquid crystal, ZLI-2293 was used. The induced pretilt angle showed no correlation with the surface-free energy of the polymer film, but was strongly dependent on the structure of the side chain. The effects of the structural difference of the side chain and type of liquid crystals are discussed in more detail.

Effect of side chain structure on aggregation state and mechanical properties of synthetic polypeptide monolayers at the air-water interface

Aggregation structure of poly(γ-methyl-L-glutamate)(PMLG) and poly(γ-n-hexyl-L-glutamate)(PnHLG) monolayers at the air-water interface was investigated on the basis of the transmission electron microscopic observation. The bright field image of PMLG and PnHLG monolayers exhibited a homogeneous structure at surface pressure of 18 mN·m−1 and 15 mN·m−1, respectively. The bright field image of PMLG monolayers showed linear humps at high surface pressure, suggesting the collapse of monolayers and the orientation of α-helix axis perpendicular to the compression direction. Surface pressure anisotropy was investigated by means of orthogonal Wilhelmy plate method. The surface pressure anisotropy for PMLG was greater than that for PnHLG. Dynamic viscoelastic properties of polypeptides monolayers at the air-water interface were examined on the basis of transient response of surface pressure. The magnitude of dynamic storage modulus E' of the PnHLG monolayer was lower than that of PMLG monolayer. This is ascribed to the active side chain motion of PnHLG at room temperature. The mechanical properties and aggregation structure of polypeptide monolayers were revealed to depend on their thermal molecular motion of side chain.

Effect of side-chain structure on inhibition of yeast fatty-acid synthase by cerulenin analogues.

Yeast fatty-acid synthase (FAS) inhibition by cerulenin analogs with varying side-chain lengths was compared with that of cerulenin, tetrahydrocerulenin and iodoacetamide. Although inhibition by cerulenin was the highest, the analogs having (E,E)-delta 7,10 double bonds showed high inhibition. This strongly suggests that the (E,E)-delta 7,10 double bonds play an important role in the interaction of the inhibitors with the enzyme. It was suggested that the size of the hydrophobic cavity in the condensing enzyme terminates fatty-acid chain elongation by decreasing inhibition by the C18 analog. Like cerulenin itself, the shortest analog (C6) did not induce malonyl-CoA decarboxylase activity.

Probing protein stability with unnatural amino acids.

Unnatural amino acid mutagenesis, in combination with molecular modeling and simulation techniques, was used to probe the effect of side chain structure on protein stability. Specific replacements at position 133 in T4 lysozyme included (i) leucine (wt), norvaline, ethylglycine, and alanine to measure the cost of stepwise removal of methyl groups from the hydrophobic core, (ii) norvaline and O-methyl serine to evaluate the effects of side chain solvation, and (iii) leucine, S,S-2-amino-4-methylhexanoic acid, and S-2-amino-3-cyclopentylpropanoic acid to measure the influence of packing density and side chain conformational entropy on protein stability. All of these factors (hydrophobicity, packing, conformational entropy, and cavity formation) significantly influence protein stability and must be considered when analyzing any structural change to proteins.

アクリルアミド系高分子水溶液の感熱特性 アルコキシアルキル基の影響

アクリルアミド系高分子水溶液の感熱特性 アルコキシアルキル基の影響