Effect Of Spacer Length Research Articles

Structure-Property Relationships in Auxetic Liquid Crystal Elastomers-The Effect of Spacer Length.

Auxetics are materials displaying a negative Poisson's ratio, i.e., getting thicker in one or both transverse axes when subject to strain. In 2018, liquid crystal elastomers (LCEs) displaying auxetic behaviour, achieved via a biaxial reorientation, were first reported. Studies have since focused on determining the physics underpinning the auxetic response, with investigations into structure-property relationships within these systems so far overlooked. Herein, we report the first structure-property relationships in auxetic LCEs, examining the effect of changes to the length of the spacer chain. We demonstrate that for LCEs with between six and four carbons in the spacer, an auxetic response is observed, with the threshold strain required to achieve this response varying from 56% (six carbon spacers) to 81% (four carbon spacers). We also demonstrate that Poisson's ratios as low as -1.3 can be achieved. Further, we report that the LCEs display smectic phases with spacers of seven or more carbons; the resulting internal constraints cause low strains at failure, preventing an auxetic response. We also investigate the dependence of the auxetic threshold on the dynamics of the samples, finding that when accounting for the glass transition temperature of the LCEs, the auxetic thresholds converge around 56%, regardless of spacer length.

Design and analysis of gate all around stacked nanosheet-DRAM for future technology node

This paper reports a stacked Dynamic random-access transistor (DRAM) memory structure that is based on gate all-around nanosheet access transistor. A TCAD study is done to compare nanosheet DRAM and conventional saddle fin recessed channel access transistor (SRCAT) in terms of DRAM electrical characteristics and its row hammer-induced leakage. The nanosheet DRAM shows superior characteristics in terms of current driving capability, speed, and refresh than SRCAT. The nanosheet DRAM also shows significantly lower hammer-induced failure as compared to SRCAT because the original leakage path from the cell to the neighboring cell gets blocked due to the nanosheet device structure. We also investigate the effect of spacer length on nanosheet DRAM characteristics and show that extended spacer length is favorable for having better DRAM characteristics due to the floating body effect. Our study demonstrates the potential, and advantages of nanosheet DRAM architecture compared to the conventional SRCAT DRAM.

Effect of spacer length between N atoms of linear alkyl triamines on adsorption of anionic platinum(IV) ions

In this study, the effect of carbon chain length between N atoms in linear alkyl triamines on the adsorption of anionic platinum ions was studied. For this purpose, bis(3-aminopropyl)amine (BAPA-SG) and diethylenetriamine (DETA-SG) groups were covalently bonded to the silica gel surface. The modified silica gels were characterized through C, H, N elemental analyses and FTIR spectroscopy before being utilized for adsorption and preconcentration Pt(IV) ions from aqueous solutions. Various factors influencing the batch adsorption of Pt(IV) ions with BAPA-SG and DETA-SG, such as nitric acid, chloride, initial Pt(IV) concentration, and contact time, were investigated. The adsorption of Pt(IV) ions was most efficient in the solutions containing 0.1 M hydronium and 0.1 M chloride ions. The adsorbed amount of Pt(IV) increased with an increase in the initial concentration of Pt(IV). The adsorption of Pt(IV) ions with BAPA-SG and DETA-SG reached equilibrium in 2 and 4 h, respectively. The kinetics of Pt(IV) adsorption on both modified silica gels were found to be compatible with the Pseudo-second-order kinetic model. Langmuir isotherm accurately described the adsorption Pt(IV) ions with BAPA-SG and DETA-SG, with maximum monolayer adsorption capacities of 158.7 and 227.3 mg/g, respectively. In the column solid phase extraction studies, Pt(IV) ions could be quantitatively recovered from 500 mL sample solutions using both modified silica gels by eluting with acidic thiourea solutions. The recovery of Pt(IV) by DETA-SG from chloride-containing solutions was more effective than with BAPA-SG. As a result, it was concluded that diethylenetriamine-bonded silica gel could adsorb Pt(IV) ions more effectively than bis(3-aminopropyl)amine bonded silica gel.

Stereoregular pendant electroactive polymers with extended pendants via post‐polymerization copper catalyzed azide‐alkyne cycloaddition

AbstractRecent work on non‐conjugated pendant electroactive polymers (NCPEPs) has demonstrated significant impacts of structural parameters such as backbone stereoregularity and the spacer connecting the pendant to the backbone on properties, most notably on charge carrier mobilities. Tuning of the pendant group however has not been reported for stereoregular NCPEPs. Here we present a family of novel isotactic poly((carbazolyl‐alkyl‐triazolyl)methyl methacrylates) (PCzATMMAs) for which the effects of increasing the pendant group from carbazole to 3,6‐bis(4‐(2‐ethylhexyl)thiophen‐2‐yl)‐carbazole were investigated. Based on unsuccessful post‐polymerization functionalization with this extended group via previously reported transesterification and thiol‐ene methodologies, we report functionalization via copper‐catalyzed azide‐alkyne cycloaddition which was demonstrated to be highly effective. The effect of spacer length was also investigated for comparison with previously established effects with alkyl spacers. Within the family of PCzATMMAs, hole mobilities were found to increase with longer spacer length and with thermal annealing. The incorporation of an extended pendant with alkyl solubilizing chains was found to result in a lower hole mobility than the equivalent polymer with an unfunctionalized pendant group. Importantly, the copper catalyzed azide‐alkyne cycloaddition proved to be an effective method of post‐polymerization functionalization for stereoregular NCPEPs when extending beyond a simple carbazole pendant.

Enhancing the Elasticity of Conjugated Polymers through Precise Control of the Spacing between the Backbone and Siloxane Side-Chains.

Intrinsically stretchable conjugated polymers (CPs) have extensively been studied for the development of novel flexible electronic devices. In this work, a method to control the elastic properties of CPs has been proposed via regulation of spacer length between the siloxane side-chain and the backbone. The target polymers were CP films with the structure P(mC-Si) for four different numbers of the spacer methylene groups, namely, m = 5, 6, 7, and 8. The effect of spacer length on the aggregation state as well as on electrical and elastic properties of the prepared films was then investigated. An adjustable lamellar spacing (dL-L), in addition to improved elastic properties, was achieved as the spacer length was changed in the prepared polymer films. Moreover, P(7C-Si) has a sufficient dL-L value of 35.77 Å, which provides enough space for inter-chain sliding to dissipate stress. This facilitated the dissipation of stress during the straining process. At a strain value of 100% in the vertical direction, the mobility of the P(7C-Si) film was 0.79 cm2 V-1 s-1 and reduced to 84.0% of the initial value without any applied strain. The study provides clear evidence that tuning the spacer length between the silicone endgroup and backbone is an effective way to improve the intrinsic stretchability of CPs with siloxane side chains.

Spacer length effect of tributylsilyl-terminated side chains on the properties of poly(diketopyrrolopyrrole-alt-terthiophene)s

The spacer length effect of seven poly(DPP-alt-terthiophene)s with tributylsilylalkyl side chains was systematically studied, and the polymer SiC6 exhibited the best device performance with a reliable hole mobility up to 2.69 cm2 V−1 s−1 from o-xylene.

Effect of spacer length on the micellization of cationic trisiloxane surfactants

Siloxane surfactants, hydrophobic (poly)siloxane chain and hydrophilic polar headgroup linking with spacer ((CH2)3 or (CH2)3S(CH2)3), exhibit peculiarly chemical and physical properties. The aggregation behavior and surface properties of siloxane surfactant can be influenced by the hydrophobicity of spacer. Cationic trisiloxane surfactants ([Si3-C3-Min]Br, [Si3-C4-Min]Br, and [Si3-C5-Min]Br) with the same imidazolium group, hydrophobic heptamethyltrisiloxane, and spacer (different number of methylene) were synthesized. The effect of the spacer on micellization in aqueous solution was investigated. Compared with 1-methyl-3- trisiloxaneimidazolium chloride ([Si3Min]Cl), critical micelle concentration (CMC), effectiveness (πCMC), and minimum area occupied by a surfactant molecule (Αmin) values of the investigated surfactants decrease with increase the number of methylene in spacer, while, γCMC value increases as the length of spacer increase. The micellization process was enthalpy driven. The ΔHm0 value becomes more exothermic for [Si3-C5-Min]Br attributed to the increasing hydrophobicity of spacer. The ΔHm0 of [Si3-C3-Min]Br is less exothermic than that of [Si3-C4-Min]Br and [Si3-C5-Min]Br. Spherical aggregates with the range of 20–500 nm were formed in aqueous solution at 2 times CMC.

Effect of spacer length between two weak NH hydrogen atoms of secondary diamido reagents on anionic platinum extraction

We have prepared three secondary diamides with 2-ethylhexyl branches and different spacer lengths as extraction reagents to investigate the extraction behavior of Pt(IV) in acid chloride media. Protonation of the carbonyl oxygen atoms of three diamides was investigated by peak observation of NH hydrogen atoms in 1H NMR spectra at varying HCl concentrations. The pKa values of the three diamides were determined, and the extraction was carried out at a lower HCl concentration using only NH hydrogen atoms for Pt(IV) extraction, not protonated carbonyl oxygen atom. The short time to reach equilibrium of Pt(IV) extraction indicated that the extraction occurred via outer-sphere coordination. Various spectroscopic data supported the extraction by the NH hydrogen atoms, and the extracted species were [PtCl6]2−. Slope analysis helped elucidate the stoichiometry but not the extraction mechanism, because of the high affinity of diamides and coexisting anions. Extraction reactions with the three diamides were also proposed. For selective extraction of [PtCl6]2−, extraction behavior of various metal ions were also carried out. For practical purpose, kerosene/2-ethylhexanol (80 vol%/20 vol%) was used as diluent, and selective extraction of [PtCl6]2− was compared using commercially available reagents, TOA, TBP, 2-ethylhexylacetoamide, and three diamido reagents. Furthermore, stripping of [PtCl6]2− loaded on three diamido reagents was investigated with stripping reagents. The spacer length of the three diamides significantly affected the extraction efficiency of [PtCl6]2−.

Extraction of Platinum Hexachloride Anion Using Two Amido Hydrogen Atoms of Secondary Diamides with Different Spacer Length

Abstract Three secondary diamides having different space lengths were prepared and their extraction behavior toward Pt(IV) was investigated in acid chloride media. Given 1H NMR investigation, the carbonyl oxygen atoms were not protonated and only NH protons were applied to the solvation extraction of [PtCl6]2−. The effect of spacer length between two NH hydrogen atoms is discussed for s size-discriminating effect of a chlorometalate through the results of the extraction.

Effect of Spacer Length between Two Weak Nh Hydrogen Atoms of Secondary Diamido Reagents on Anionic Platinum Extraction

Effect of Spacer Length between Two Weak Nh Hydrogen Atoms of Secondary Diamido Reagents on Anionic Platinum Extraction

Augmentation of laminar flow heat transfer in annular flat tubes by means of helical screw-tape inserts in the inner tube.(Dept.M)

The heat transfer characteristics and friction factor in horizontal double pipes of flat tubes with full length helical screw element of different twist ratio and helical screw inserts with different spacer length are investigated. Cold and hot water are used as working fluid in tube side and shell side respectively. The experiments covered a range of Reynolds numbers 5.7*102 ≤ Re ≤ 1.31*103. The effect of spacer length and twist ratio on the heat transfer augmentation and friction factor on heat transfer have been presented separately. The study shows that, Nusslet number (Nu) and friction factor (f) decrease with the increase of spacer length (S) and twist ratio (Y) for flat tube. The comparison between the data of present plain circular tube with that of previous plain circular tubes showed good agreement but the data of present plain flat tube showed a higher in heat transfer and pressure drop than that of plain circular tube. The correlations of average Nusselt number and friction factor with Re, S and Y are presented.

Effect of Spacer Length in Pyrene-Modified-Phenylboronic Acid Probe/CyD Complexes on Fluorescence-based Recognition of Monosaccharides in Aqueous Solution.

The chemical sensing of saccharides is of importance for the diagnosis of diabetes. Various enzymatic sensors have been developed, but their heat and pH instability issues need to be resolved. In this regard, the development of artificial saccharide sensors with high stability is attracting attention. We have designed a heat- and pH-stable supramolecular inclusion complex system composed of cyclodextrin (CyD) as a host and a phenylboronic acid (PB) probe possessing pyrene as a fluorescent guest. Several probes possessing alkyl spacers having various lengths between the PB and the pyrene moiety, Cn-APB (n = 1 - 4), were newly synthesized and evaluated with respect to their monosaccharide recognition ability on the basis of the fluorescence response through the cyclic esterification of monosaccharide and PB. These Cn-APB/CyD supramolecular inclusion complexes have exhibited a selective fluorescence response towards fructose in aqueous solution based on the photo-induced electron transfer mechanism. The spacer length of the alkyl group in Cn-APB significantly affects the affinity for saccharides. With respect to the complex between C4-APB and PB-modified CyD (3-PB-γ-CyD), it was found that the supramolecular inclusion complexes had high selectivity for glucose with significant fluorescence enhancement. These results indicate that the lengths of the alkyl spacers in the probe molecules are important to control the recognition of saccharides in aqueous solution.

Spacer length effect on the aggregation behaviours of gemini surfactants in EAN

As the symbol of gemini surfactants, the spacer group connects two surfactant monomers and plays an important role in the self-assembling of gemini surfactants. Recent attention has been paid to the effects of spacer nature and length in aqueous systems. In this study, the aggregation behaviours of quaternary ammonium gemini surfactants 12-s-12 with different spacer length (s = 2, 3, 4, 5, 6, 8, 10, 12) have been investigated in the protic ionic liquid EAN. The micellization behaviour was characterized by surface tension measurement. With the help of small-angle X-ray scattering (SAXS), the size and shape of aggregates were verified. The spacer length effect could be reflected by the changes in the micellization and phase behaviours of 12-s-12/EAN systems. The critical packing parameter of gemini molecules would decrease monotonically with the spacer length, which is supported by SAXS results. Due to the charge screening effect of EAN, the aggregation behaviours of 12-s-12 would be mainly influenced by spacer length. Our results would be the important supplement to the spacer length effect of gemini surfactants in the nonaqueous systems. With the increase of spacer chain length, the reverse hexagonal lyotropic liquid crystal phase would transform into the micellar phase.

α-Tocopherol-anchored gemini lipids with delocalizable cationic head groups: the effect of spacer length on DNA compaction and transfection properties.

Understanding the role of structural units in cationic lipids used for gene delivery is essential in designing efficient gene delivery vehicles. Herein, we report a systematic structure-activity investigation on the influence of the spacer length on the DNA compaction ability and the transfection properties of gemini lipids with delocalizable cationic head groups. We have synthesized a series of dimeric cationic lipids varying in spacer length. The DNA binding interactions of liposomal formulations were characterized by gel electrophoresis and ethidium bromide (EtBr) exclusion assays. Condensation potentials were optimized and the best results were observed with cationic lipids possessing a 6 methylene spacer (TIM 6). We found that the size of the lipid/DNA complex decreased with the increase in spacer chain length up to a 6 methylene spacer TIM 6 and increased further. We have optimized the dimeric lipid/DOPE molar formulation using the β-galactosidase activity assay and found that the molar ratio of 1 : 1.5 (gemini lipid/DOPE) showed the maximum transfection among all molar ratios. The cellular uptake and co-localization of lipoplexes were observed by cell analysis and imaging using confocal microscopy. The results confirm that the lipoplex derived from lipid TIM 6 and pCMV-bgal/DNA internalizes via cellular endocytosis. The cytotoxicity studies using the MTT assay revealed that all formulations show comparable cell viability to the commercial standard even at higher charge ratios. Overall, the data suggest that the DNA compaction ability of these lipid dimers depends on the spacer chain length and the gemini lipid containing a six methylene aliphatic spacer has the maximum potential to deliver genes.

Tuning hydrogen bond and flexibility of N-spirocyclic cationic spacer for high performance anion exchange membranes

Although N-spirocyclic cation exhibits superior alkaline stability, its rigidity leads to low conductivity and mechanical stability in anion exchange membranes (AEMs). Herein, N-spirocyclic cationic side chain with novel -NH-(CH2)x-NH- spacer is proposed to promote hydrogen bond networks and flexible aggregation of ionic clusters in AEMs. Chloromethyl N-spirocyclic cation is synthesized and bonded with diamines of different lengths to achieve benzyl free N-spirocyclic side chain, as well as to tune the length of the side chains. Molecular dynamic simulation suggests that amino groups induce hydrogen bond networks with water to broaden hydrophilic pathways for hydroxide ions conduction. Trade-off between diffusion coefficient and solubility parameter of the side chain is proposed to demonstrate the side chain-backbone interaction and thus the effects of spacer length on the aggregation of ionic clusters. It coincides well with the experimental results that PSF-C6-ASD with -NH-(CH2)6-NH- spacer exhibits the largest ion clusters (about 8.5 nm) and the highest OH− conductivity (107.1 mS cm−1 at 80 °C), as well as excellent elongation at break (38.3%) and alkaline stability (tolerance to 8 M hot KOH). The properties are better than that of the previously reported N-spirocyclic based AEMs.

Effect of spacer lengths on the interplay of intrachain and interchain in polynorbornene homopolymers embedded with polyhedral oligomeric silsesquioxane (POSS): A molecular simulation approach

Molecular models of polynorbornene homopolymers, with POSS (polyhedral oligomeric silsesquioxane) group linked to the side chain via various numbers of methylene spacers, were constructed and named as P-m-POSS (where m represents the number of methylene units that connect amide and POSS end group on the side chain, m = 0, 4, and 9), respectively. By molecular mechanics (MM) and molecular dynamics (MD) simulation methods, molecular geometry, chain mobility and packing characteristics were investigated to elucidate the complex interplay of intrachain and interchain in homopolymers dependent on various methylene spacer lengths of the side chain. With short spacer length containing less number of methylene units, the synergetic mobility of the main chain and the side chain can be observed in P-0-POSS by analysis of mean square displacement (MSD), denoting an intrachain coupling restraint within molecule. It is also noticed that the disorganization of twisted side chains surrounding the main chain results in a loose and irregular packing in P-0-POSS, validated by the amorphous morphology in experiment. As the spacer length increased with more methylene units in P-4-POSS, side chains with the highest mobility are partially stretched and independent of the main chain, suggesting the invalidation of intrachain coupling restraint. Furthermore, with the longest spacer length containing 9 methylene units, fully stretched side chains are decoupled from the main chain and have a tendency to be close to each other in P-9-POSS. The interchain correlation between side chains in P-9-POSS facilitates a distinctively regular interdigitation in bulk structure, resulting in the highest crystallinity in experiment.

Effect of Spacer Length in Naphthobispyrazine-Based π-Conjugated Polymers on Properties, Thin Film Structures, and Photovoltaic Performances

Abstract Incorporation of an electron-deficient building unit based on a large π-system into the polymer backbone is a powerful strategy for the development of high-performance π-conjugated polymers. The naphthobispyrazine (NPz) tetracyclic π-electron system is a promising electron-deficient building unit but its use in π-conjugated polymers has seldom been investigated. Here, we synthesized four NPz-based π-conjugated polymers with different donor units, namely thiophene (P1), bithiophene (P2), terthiophene (P3), and quaterthiophene (P4), and systematically studied their structure-property relationships. The absorption range was significantly red-shifted when the spacer length was longer than bithiophene due to the decreased steric hindrance between the NPz moieties. Furthermore, the crystallinity in the polymer thin films was dramatically improved when the spacer length was longer than terthiophene. These results clearly affect the efficiency of polymer/fullerene-based solar cells, with the maximum efficiency of 4.4% obtained using P3. This study may be helpful for the design of NPz-based π-conjugated polymers with improved performance.

Structures and properties of side-chain liquid crystalline polynorbornenes containing an amide group: hydrogen bonding interactions and spacer length effects

Side-chain liquid crystalline polynorbornenes based on benzanilide mesogens exhibit rich self-organization behaviours and enhanced mechanical properties owing to the lateral hydrogen bond interaction that can be tuned by the spacer length.

Target capturing performance of microfluidic channel surface immobilized aptamers: the effects of spacer lengths.

Aptamers have been widely used to recognize and capture their targets in sensitive detection applications, such as in detections of circulating tumor cells. In this study, we investigate the effects of different lengths of oligo-T spacers on surface tethered sgc8 aptamers and their target capturing performances. To achieve this, sgc8 aptamers were immobilized onto microfluidic channel surfaces via oligo-T spacers of different lengths, and the target capturing performances of these immobilized aptamers were studied using CCRF-CEM cells. We demonstrate that the capturing performances of the immobilized aptamers were significantly affected by steric hindrance. Our results also show that aptamers immobilized on surfaces via spacers of ten Ts demonstrated the best cell capturing performances; aptamers with either too short or too long oligo-T spacers showed reduced cell capturing performances. Therefore it can be concluded that spacer optimizations are critically important for surface tethered aptamers that are commonly used in microfluidic devices for sensitive target sensing and detections.

Labeling of Nanofiber-Forming Peptides by Site-Directed Bioconjugation: Effect of Spacer Length on Self-Assembly.

The conjugation of small organic molecules to self-assembling peptides is a versatile tool to decorate nanostructures with original functionalities. Labeling with chromophores or fluorophores, for example, creates optically active fibers with potential interest in photonic devices. In this work, we present a rapid and effective labeling procedure for a self-assembling peptide able to form nanofibers. Rapid periodate oxidation of the N-terminal serine residue of the peptide and subsequent conjugation with dansyl moiety generated fluorophore-decorated peptides. Three dansyl-conjugated self-assembling peptides with variable spacer-length were synthesized and characterized and the role of the size of the linker between fluorophore and peptide in self-assembling was investigated. Our results show that a short linker can alter the self-assembly in nanofibers of the peptide. Herein we report on an alternative strategy for creating functionalized nanofibrils, able to expand the toolkit of chemoselective bioconjugation strategies to be used in site-specific decoration of self-assembling peptides.