Flexible Linkage Research Articles

Urea-Linked Covalent Organic Frameworks.

2D covalent organic frameworks (COFs) with flexible urea linkages have been synthesized by condensation of 1,3,5-triformylphloroglucinol (TFP) with 1,4-phenylenediurea (BDU) or 1,1'-(3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diyl)diurea (DMBDU). The resulting COF-117 and COF-118 undergo reversible structural dynamics within their layers, in response to inclusion and removal of guest molecules, emanating from urea C-N bond rotation and interlayer hydrogen-bonding interactions. These compounds are the first urea-linked COFs, serving to expand the scope of reticular chemistry.

Self‐assembly of amphiphilic ABA random triblock copolymers in water

ABSTRACTSelf‐assembly of amphiphilic ABA random triblock copolymers in water serves as a novel approach to create unique structure micelles connected with flexible linkages. The ABA triblock copolymers consist of amphiphilic random copolymers bearing hydrophilic poly(ethylene glycol) and hydrophobic dodecyl pendants as the A segments and a hydrophilic poly(ethylene oxide) (PEO) as the middle B segment. The A block is varied in dodecyl methacrylate content of 20%–50% and degree of polymerization (DP) of 100‐200. By controlling the composition and DP of the A block, various architectures can be tailor‐made as micelles in water: PEO‐linked double core unimer micelles, PEO‐looped unimer or dimer micelles, and multichain micelles. Those PEO‐linked or looped micelles further exhibit thermoresponsive solubility in water. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 313–321

Dynamic modeling and error analysis of planar flexible multilink mechanism with clearance and spindle-bearing structure

To predict the dynamic precision of multilink high-speed precision presses (MLHSPPs), it is essential to develop a dynamic model of the multilink mechanism (MLM). Previous models only considered the effect of the clearance, flexible linkages and crank shaft, and often neglected the effect of supporting bearings’ stiffness on the crank shaft system, which lowers the dynamic analysis accuracy of the MLM for MLHSPPs. In this work, based on both absolute nodal coordinate formulation (ANCF) and finite element method (FEM), an improved computational methodology for the modeling and simulation of a planar flexible MLM with clearance and spindle-bearing structure is presented considering the effect of clearance, flexibility of crankshaft and linkage, and bearing stiffness together, and its corresponding dynamic dimension chain between the slider and crank shaft is constructed. The elastic foundation model (EFM) and stick–slip friction model are used to describe the normal contact and tangential friction force between bushing and pin, respectively. It is demonstrated that the dynamic responses from the flexible model with clearance and spindle-bearing structure under no-load and blanking conditions agree better with the experimental data than those from traditional ones, and the effectiveness of the proposed methodology is proven. The existence of crankshaft-bearing structure aggravates the displacement deviation of slider and the motion of the pin center for revolute joint between lower slider and linkage was characterized by only one permanent contact state. Furthermore, the effect of the clearance size, the blanking force and the contact angle of the bearing on the dynamic responses and the corresponding deviation errors are also investigated.

Flexible Ketone-bridged organic porous nanospheres: Promoting porosity utilizing intramolecular hydrogen-bonding effects for effective gas separation

Two series of flexible ketone-bridged nanoporous organic polymers (NOPs) are readily prepared through one-pot Friedel-Crafts acylation polymerization using pyromellitic dianhydride (PMDA) and terephthaloyl chloride (TC) as acylation reagents, respectively. The carboxyl-appended samples (termed NOP-52@COOH and NOP-53@COOH), derived from PMDA, feature a stable spherical morphology. Unexpectedly, our NOP-52@COOH and NOP-53@COOH deliver much higher surface areas (eg. 738 m2 g−1 for NOP-52@COOH) and pore volumes (eg. 0.53 cm3 g−1 for NOP-52@COOH) than the carboxyl-free samples (i.e. NOP-52 and NOP-53). This is significantly different from the reported trend that the introduction of appended group always leads to inferior surface area and pore volume. The enhancement in porosity originates from the hydrogen-bonding effect between carboxyl and the ketone linkage that effectively prevents the networks from collapsing. More importantly, the as-made carboxyl group-containing networks exhibit stronger affinity towards guest CO2 molecules after comparing to those carboxyl-free ones, and have a competitive CO2 capture capacity under ambient conditions (159 mg g−1, 273 K/1 bar). This provides a feasible pathway for both developing high-surface-area organic polymers with flexible linkages and engineering pore surface properties.

A novel low colored and transparent shape memory copolyimide and its durability in space thermal cycling environments

Recently, shape memory polymers (SMPs) with high optical transmittance have been paid great attentions to endow the flexible optoelectronics with shape memory functions. Herein, a low colored and transparent shape memory copolyimide (SMcoPI) is obtained by suppressing the charge transfer complex interactions. The optical transmittance of the synthesized SMcoPI film could reach at ∼86% at the wavelength of 450 nm, far higher than the nearly zero optical transmittance of yellow and brown Kapton H. The better optical transparency could be attributed to the loose molecular chain arrangements induced by the meta-substituted groups and flexible ether linkages. The glass transition temperature (Tg) range of the synthesized SMcoPI films is from 179 °C to 220 °C, which is higher than that of reported optically transparent SMPs. The effective decomposition temperature at the weight loss of 5 wt% is 517 °C, showing excellent thermal stability. The SMcoPI also demonstrated good shape memory behaviors with high shape recovery ratio (Rr, >96%) and shape fixity ratio (Rf, >97%). In addition, the SMcoPI could maintain high optical transmittance, good thermostability and excellent shape memory behaviors after the ground-stimulated space thermal cycling test for 250 h. The synthesized SMcoPI has application potentials in high temperature areas or optoelectronic devices.

Synthesis and optical properties of novel soluble and optically transparent semifluorinated poly (ether imide)s

A fluorinated diamine monomer containing flexible ether linkage and bulky trifluoromethyl substituents, namely, bis(4‐amino‐2‐trifluoromethylphenyl) ether (a), is employed to react with nonfluorinated 1,4‐bis(3,4‐dicarboxyphenoxy) benzene dianhydride (3) and CF3‐free 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl] propane dianhydride (4), respectively, to prepare 2 novel soluble and optically transparent semi‐fluorinated poly (ether imide)s (PEIs; 3a and 4a). Compared with the corresponding PEIs based on nonfluorinated 4,4′‐diaminodiphenyl ether (b) and CF3‐free pyromellitic dianhydride (5), the novel semifluorinated PEIs 3a and 4a not only display better solubility in some organic solvents and higher optical transparency with cutoff absorption wavelength (λ0) below 370 nm but also maintain outstanding mechanical properties and thermal stability. 3a and 4a have tensile strength beyond 80 MPa and possess glass‐transition temperatures (Tg) beyond 210°C, coupled with the temperatures of 5% weight loss (T5%) exceeding 500°C. It is also found that 3a and 4a exhibit contact angles against water beyond 110° and water absorptions below 0.8% together with dielectric constants less than 3.2.

Induced-fit adsorption of diol-based porous organic polymers for tetracycline removal

Adsorption is recognized as one of the most efficient approaches for antibiotics removal from water. Inspired by the enzyme-substrate interaction model, we proposed induced-fit adsorption (IFA) model, and rationally designed and fabricated diol-based porous organic polymers (POPs) as adsorbents for tetracycline (TC) removal. For 2,3-naphthalenediol-based POP (NTdiol-POP), the preferable geometry of diol-groups contributed to the high binding energy with TC species and flexible methylene linkages between neighboring rigid naphthalene rings gave rise to precisely matching between TC species and adsorbents, that is, the induced-fit conformation change. As a result, NTdiol-POP exhibited a high saturated adsorption capacity of 155.8 mg g−1. More importantly, NTdiol-POP exhibited excellent TC removal efficiencies in both concentrated solution (96% for 4 p.p.m) and trace level solution (97% for 250 p.p.b).

Synthesis and binary/ternary write-once read-many-times electrical memory behaviors of carbazole-based polyimides bearing flexible linkage segment

An efficient and readily available novel carbazole-based aromatic diamine was synthesized and characterized. Two polyimides (PI-a and PI-b) were prepared via a two-step procedure using the new synthesized diamine reacting with low-cost and the commercialized pyromellitic dianhydride (PMDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), respectively. PIs were characterized and exhibited highly organo-solubility and thermal stability. The Al/PI-a/ITO device showed binary write-once read-many-times (WORM) behavior with an ON/OFF current ratio up to 109 and the threshold voltage as low as −0.21 V, whereas the Al/PI-b/ITO device presented ternary WORM behavior with an ON2/ON1/OFF current ratio up to 105:104:1 and the switching voltage below −3 V. The memory switching mechanisms were further elucidated through molecular simulation based on the density functional theory (DFT) method. This provides an effective strategy to achieve a ternary memory device.

Parylene-MEMS technique-based flexible electronics

This paper reports a novel fabrication strategy for flexible electronics based on the parylene-MEMS (micro-electromechanical system) technique. A set of parylene-filled trenches is used to mechanically connect silicon-based functional units and realize a flexible 4$\times$6 temperature controlling array as a preliminary demonstration. The trench-filling performance of the parylene deposition is carefully studied, and an optimized process is established to minimize the keyhole inside the parylene-filled trench. The effect of trench width on the flexibility and bendability of the prepared flexible electronics devices is analyzed by finite element modeling. Performances of the thermal/electrical isolation and the mechanical connection of the prepared parylene-filled trenches have been tested. The experimental results indicate that the highest thermal isolation efficiency is approximately 72.5% with the 10 paralleled, 7 $\mu$m wide and 50 $\mu$m deep parylene-filled trenches. The leakage current of the 10 paralleled, 5 $\mu$m wide and 100 $\mu$m deep parylene-filled trenches is less than 2 pA under a voltage of 100 V. Besides, these parylene-filled trenches acting as the flexible linkage of connected silicon-based functional units exhibit high connection performance without rupture when the loading pressure is under 200 kPa. Due to the powerful silicon microfabrication capability and excellent compatibility of the parylene-MEMS technique, the present flexible electronics strategy holds a promising potential for applications in various areas.

Magnetic and Heat Resistant Poly(imide-ether) Nanocomposites Derived from Methyl Rich 9H-xanthene: Synthesis and Characterization

In this study a new series of magnetic and heat resistant nanocomposites were prepared based on a highly soluble poly(imide-ether) (PIE) reinforced with two different types of magnetic nanoparticles via a solution intercalation technique. New PIE with good solubility and desired molar mass containing bulky xanthene rings and amide groups in the side chains was synthesized via thermal cyclization of the poly(amic acid) precursor, obtained from the reaction of a new diamine derived from 9H-xanthene and 4,4′-oxydiphthalic dianhydride (ODPA). Improved solubility was attributed to the presence of xanthene group and flexible ether linkage in the polyimide backbones that reduce the chain-chain interaction and enhance solubility by penetrating solvent molecules into the polyimide chains. Fe3O4 nanoparticles (MNPs) which synthesized from chemical co-precipitation route were coated with silica (SiO2), sequentially with (3-aminopropyl)triethoxysilane and poly-melamine-terephthaldehyde (MNPs-PMT), and then separately dispersed in the poly(amic acid) solutions and thermally imidized to form PIE/Fe3O4 and PIE/MNPs-PMT nanocomposites. The nanostructures and properties of the resultant materials were investigated using FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The properties of the nanocomposites were strongly related to the dispersion and interaction between the nanoparticles and PIE matrix. The thermogravimetric analysis (TGA) results showed that the addition of MNPs-PMT nanoparticles resulted in a substantial increase in the thermal stability of the corresponding PIEN. The temperature at 10% weight loss (T10) was increased from 416 °C to 428 °C for PIEN containing 3 wt% MNPs-PMT as compared to neat PIE, as well the char yield enhanced. Furthermore, the MNPs-PMT nanoparticles had better dispersion in the polymer matrix due to the strong intermolecular hydrogen bond interactions between the NH and C=N groups of surface-modified nanoparticles and the PIE matrix than the uncoated Fe3O4 nanoparticles, and exhibited a better intercalated morphology and improved thermal properties. Also, the PIEN nanocomposites under applied magnetic field exhibited the hysteretic loops of the superparamagnetic nature.

Novel heat-resistant and soluble poly(amide–ether)/zinc oxide nanocomposites: synthesis, characterization and computational study

Novel heat-resistant poly(amide–ether)/zinc oxide nanocomposites containing two different types of ZnO nanoparticles were successfully prepared by a solution intercalation technique. A new poly(amide–ether) (PAE) as a source of polymeric matrix was synthesized by direct polycondensation reaction of new diamine containing 1,3,4-oxadiazole and biphenyl groups with 4,4′-(butane-1,4-diylbis(oxy))dibenzoic acid in a medium consisting of N-methyl-2-pyrrolidone,triphenyl phosphite, calcium chloride, and pyridine. Fourier-transform infrared (FTIR), nuclear magnetic resonance (1H NMR), and UV–Vis technique were used for characterization of as-synthesized PAE. The synthesized PAE revealed good solubility in dipolar aprotic solvents at room temperature and the inherent viscosity of the PAE in DMF at a concentration of 0.01 g dL−1 at 25 °C was 0.34 dL/g. Improved solubility was attributed to the presence of flexible ether linkage in the polyamide backbones that reduce the chain–chain interaction and enhance solubility by penetrating solvent molecules into the polyamide chains. The structural and electronic properties of PAE units were studied by ab initio density functional theory method using the B3LYP/6-31G (d) level of theory. Due to incorporation of biphenyl group as an electron donor on the 1,3,4-oxadiazole ring in the structure of PAE, the highest occupied molecular orbitals (HOMO) are localized mainly on biphenyl group. The calculated absorption spectrum of the studied PAE exhibited the maximum absorption wavelength which corresponds to the electronic transition from the HOMO-1 to LUMO with 92% contribution. Zinc oxide nanoparticles were synthesized by a direct precipitation method from zinc nitrate solution and were modified with 1-methyl-3-(trimethoxysilylpropyl) imidazolium chloride. The PAE/ZnO nanocomposite films were prepared by simple dissolution technique using 3 wt% of ZnO nanoparticles and modified ZnO nanoparticles. The morphology, crystalline phase, and thermal stability of the resultant materials were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), thermal gravimetric analysis (TGA), and FTIR techniques. The FE-SEM analysis showed better dispersion of ZnO@ImCl nanoparticles within the poly(amide–ether) matrix in comparison with ZnO nanoparticles, which arises from high interactions between ZnO@ImCl and the PAE chains. Thermogravimetric analysis results indicated improving on thermal properties of the poly(amide–ether) nanocomposites as compared with the neat poly(amide–ether). The incorporation of functional ZnO@ImCl nanoparticles could further improve the thermal properties of poly(amide–ether). The high interaction between poly(amide–ether) and ZnO@ImCl nanoparticles, the presence of oxadiazole, ether, amide and imidazole content of the ZnO@ImCl nanoparticles seem to be responsible for the improvement of the thermal properties. Furthermore, the presence of oxadiazole, ether, amide and bulky biphenyl groups in the poly(amide–ether) backbone increased the solubility in organic solvents.

P4VP-RuII(bda) polyelectrolyte-metal complex as water oxidation catalyst: on the unique slow-diffusion and multi-charge effects of the polyelectrolyte ligand.

In this work, we analyze the catalytic mechanism of P4VP–RuII(bda) polyelectrolyte–metal complex (PMC) as a water oxidation catalyst and elucidate how the unique slow diffusion and multi-charge properties of the polyelectrolyte ligand dominate the catalytic process. Four poly(4-vinyl pyridine)–Ru(bda) (P4VP–Ru) PMCs with different chain lengths and controlled Ru loading amounts were prepared and used as catalysts for catalytic water oxidation. These catalysts present excellent catalytic performance with turnover numbers (TON) from ∼1200 to ∼1700 because of the good hydration properties. Surprisingly, the combined catalysis kinetics and kinetic isotope effect (KIE) studies for P4VP–Ru PMCs confirm the single-site water nucleophilic attack (WNA) mechanism in catalysis, rather than the interaction between two metal oxide units (I2M). A combination of dynamic light scattering characterization, zeta-potential measurement and molecular dynamics simulation reveals that the slow diffusion and multi-charge properties of the polyelectrolyte ligand are responsible for the observed mechanism difference between the P4VP–Ru PMC system and small-molecule multi-nuclear system, though the two systems actually own a similar structural feature (flexible linkages between Ru centers). Our experimental and simulation results highlight the fact that though the existence of flexible linkages between Ru centers could provide large conformation entropy for the occurrence of Ru-dimerization in small-molecule and neutral polymer systems, the entropy elasticity could not overcome the electrostatic interaction energy in the PMC system. Clearly, this work unambiguously clarified why both intra-chain and inter-chain Ru-dimerization (I2M) are prohibited for the PMC system from a perspective of macromolecular chemistry and physics.

Optimum Design Of Elastic And Flexible Linkages For Motion And Path Generation

This paper presents synthesis of rigid and flexible linkages for the purpose of path generation. Optimization technique with DE algorithm is used to minimize the error. Cam-follower mechanism is considered for the synthesis of rigid linkages. Profile of plate cam with offset follower is designed considering no deformation of cam surface. In course of this design fundamental principle of cam motion function is modified and suitable CMF is introduced. An experimental analysis is conducted to verify the theoretical predictions. For flexible linkages, 4-bar with joint clearances and 4-bar linkage with deformation are considered for path generation. In course of analysis the sensitivity to joint clearances are considered.

Novel organosoluble and thermally stable polyetherimides based on a new dianhydride monomer 2,6-bis-(isobenzofuran-1,3-dione-5-yl)pyridine (BIDP)

ABSTRACTA series of organosoluble and thermally stable polyetherimides (PEIs) containing pyridine moieties and flexible ether linkages are synthesized based on a new aromatic dianhydride, 2,6-bis-(isobenzofuran-1,3-dione-5-yl)pyridine (BIDP). The prepared polymers are soluble in common aprotic solvents such as DMF, DMSO, NMP and DMAc at room temperature. Thermal behavior of the PEIs is studied by thermogravimetric analysis/dynamic thermal analysis (TGA-DTA). The inherent viscosities of the PEI solutions are in the range of 0.61–0.70 dL/g (in DMSO with a concentration of 0.25 g/dL at 25±0.5°C). The metal ion uptake capacity of PEI-4 for Co(II) removal from aqueous solutions is shown to be remarkably higher than that of the polyimide (PI) with a similar structure reported earlier.

Novel polyimides based on diamine containing thiazole units with thioether linkage and pyridine as pendent group

Three new organic-soluble polyimides (PIs) bearing flexible thioether linkages, thiazole, and pyridine ring units were synthesized from a novel thioether-bridged diamine monomer and commercially available aromatic dianhydrides (1–3) via chemical imidization method. The resulting polymers were obtained in high yields and possessed inherent viscosities in the range of 0.67–0.89. The PIs are characterized by Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry, and thermogravimetric analysis (TGA). All of the PIs exhibited excellent solubility in polar solvent. The polymers showed good thermal stability with glass transition temperatures ( Tgs) in the range of 194–244°C, and decomposition temperatures ( T5%) exceeding 300°C were observed using TGA in nitrogen atmosphere for the current polymers.

Hierarchical Self-Organization of AB n Dendron-like Molecules into a Supramolecular Lattice Sequence.

To understand the hierarchical self-organization behaviors of soft materials as well as their dependence on molecular geometry, a series of ABn dendron-like molecules based on polyhedral oligomeric silsesquioxane (POSS) nanoparticles were designed and synthesized. The apex of these molecules is a hydrophilic POSS cage with 14 hydroxyl groups (denoted DPOSS). At its periphery, there are different numbers (n = 1–8) of hydrophobic POSS cages with seven isobutyl groups (denoted BPOSS), connected to the apical DPOSS via flexible dendron type linker(s). By varying the BPOSS number from one to seven, a supramolecular lattice formation sequence ranging from lamella (DPOSS-BPOSS), double gyroid (space group of Ia3̅d, DPOSS-BPOSS2), hexagonal cylinder (plane group of P6mm, DPOSS-BPOSS3), Frank–Kasper A15 (space group of Pm3̅n, DPOSS-BPOSS4, DPOSS-BPOSS5, and DPOSS-BPOSS6), to Frank–Kasper sigma (space group of P42/mnm, DPOSS-BPOSS7) phases can be observed. The nanostructure formations in this series of ABn dendron-like molecules are mainly directed by the molecular geometric shapes. Furthermore, within each spherical motif, the spherical core consists hydrophilic DPOSS cages with flexible linkages, while the hydrophobic BPOSS cages form the relative rigid shell, and contact with neighbors to provide decreased interfaces among the spherical motifs for constructing final polyhedral motifs in these Frank–Kasper lattices. This study provides the design principle of molecules with specific geometric shapes and functional groups to achieve anticipated structures and macroscopic properties.

Synthesis, thermal and optical properties of new nanosized polyamides containing N-phenyl- and O-naphthyl-s-triazine rings; part 2

ABSTRACTWe report the chemistry and properties of two new series of well-defined nano sized spheres aramides-containing N- and O-naphthyl-s-triazines. The polymers were carefully characterized by different techniques including infrared, ultraviolet, fluorescent emission, elemental, thermal analyses and scanning electron microscopy (SEM). The polymers were readily soluble in polar aprotic solvents while insoluble neither in water nor halogenated solvents. Thermal analyses data up to 900°C showed high thermal behavior and the polymers were classified either as “slow burning polymers” or “self-extinguishing polymers” based on their calculated the limiting oxygen index. Interestingly, the naphthyl / phenyl interchange has dramatic improvement on the thermal properties. Obviously, the pyridine / phenylene interchange has no influence on the thermal properties of the addressed polymers. Thermal stability of the aniline-containing polymers proved to be comparable to their naphthylamine analogues. Polymers containing p-phenylene moieties exhibited better thermal results compared to their analogues containing m-phenylene moieties. Benzidine containing polymers and sulfone containing polymers exhibited better thermal stabilities than their analogues containing either ether or methylene flexible linkages. The kinetic data obtained from the nonisothermal decomposition of the prepared polyamides series were also studied. The polymers exhibited emissions ranging from blue to orange wavelength depending on the nature of the signaling unit. The naphthyl / phenyl interchange led to either appreciable red-shifted absorptions in some cases or blue-shifted absorptions in other cases and this behavior may be attributed to the contorted, twisted structural nature of the naphthalene ring. Such attracting properties make these polymers good candidates for applications such as processable high-temperature materials and also as heat-resistant polymeric materials.

A new methodology to calculate the equivalent stiffness matrix of the suspension structure with flexible linkages

The purpose of this work is to present a methodology for calculating the equivalent stiffness matrix of the wheel center of the vehicle suspension. For a suspension, the stiffness matrix of the wheel center, which is effected by the bushings and flexible linkages, control the suspension’s elasto-kinematic ( e–k) specification. The equivalent stiffness matrix of the wheel center is formulated by using the stiffness of the bushings and linkages. And the models of series and parallel springs are used to calculate this equivalent stiffness matrix based on the number of the bushings and linkages. An example is presented to illustrate how to use the proposed methodology to derive the equivalent stiffness matrix of a suspension system with three bushings and flexible linkages. The results show that the equivalent stiffness of the wheel center will decrease if the linkage stiffness is considered. This methodology can be used in all kinds of suspension structure. It can also be used to optimize and design the suspension system.

One‐Pot Preparation of Macroporous Organic‐Silica Monolith for the Organics‐/Oil‐Water Separation

AbstractThree‐dimensional porous monoliths have been considered as attractive candidates for the organics‐/oil‐water separation due to their high porosity, low density and hydrophobic/oleophilic property. To simplify the preparation process, one‐pot method based on thiol‐methacrylate click polymerization was developed to fabricate macroporous organic‐silica monolith by using octakis(3‐mercaptopropyl)octasilsesquioxane, ethylene glycol dimethacrylate and heptadecafluorodecyl methacrylate as starting monomers. The rapid click polymerization was carried out at room temperature under air atmosphere, which made it possible for preparation of monolith with desired scale and geometry. The hybrid monolith with good thermal stability and compressibility generated through‐pores with diameter ranging from several microns to tens of microns. As a result of the flexible organic linkages and fluorocarbon groups, the hybrid monolith showed hydrophobic feature, and could be fast swollen in organic liquids. Particularly, a cylindrical hybrid monolith (15 mm in diameter × 11 mm in height) supported by a modified syringe, which exhibited excellent recyclability and swelling‐squeezing performance, has been applied to selectively absorb organic liquids located on the upper or under water layer.

Rigid aromatic linking moiety in cationic lipids for enhanced gene transfection efficiency

Although numerous cationic lipids have been developed as non-viral gene vectors, the structure-activity relationship (SAR) of these materials remains unclear and needs further investigation. In this work, a series of lysine-derived cationic lipids containing linkages with different rigidity were designed and synthesized. SAR studies showed that lipids with rigid aromatic linkage could promote the formation of tight liposomes and enhance DNA condensation, which is essential for the gene delivery process. These lipids could give much higher transfection efficiency than those containing more flexible aliphatic linkage in various cell lines. Moreover, the rigid aromatic linkage also affords the material higher serum tolerance ability. Flow cytometry assay revealed that the target lipids have good cellular uptake, while confocal microscopy observation showed weaker endosome escape than Lipofectamine 2000. To solve such problem and further increase the transfection efficiency, some lysosomotropic reagents were used to improve the endosome escape of lipoplex. As expected, higher transfection efficiency than Lipofectamine 2000 could be obtained via this strategy. Cytotoxicity assay showed that these lipids have lower toxicity in various cell lines than Lipofectamine 2000, suggesting their potential for further application. This work demonstrates that a rigid aromatic linkage might distinctly improve the gene transfection abilities of cationic lipids and affords information to construct safe and efficient gene vector towards practical application.