Types Of Monomers Research Articles

Development of molecularly imprinted polymer for the selective recognition of the weakly interacting fenamiphos molecule

The possible manufacture of Molecularly Imprinted Polymers (MIPs) under the conditions of weak interaction between the functional monomer and template molecule is addressed with the help of the case of the Fenamiphos organophosphorus insecticide. The choice of the functional monomer is addressed by investigating MIPs prepared by the surface imprinting technique using three very different types of monomers (methacrylic acid, 4-vinylpyridine and 2–(methacryloyloxyethyl)trimethylammonium chloride), a solid silica support grafted with 3-mercaptopropyltrimethoxysilane on its surface; ethylene glycol dimethacrylate as the cross-linker and acetonitrile as solvent. The prepared materials were characterized by IR, solid state 13C NMR, TGA, DLS, BET and TEM. Their performance as adsorbents were evaluated by modeling their experimental adsorption isotherms using the Langmuir–Volmer model. All MIPs show similar adsorbent performance although the functional monomers were quite different and the interactions with fenamiphos were weak. The latter were assessed by 1H and 31P NMR experiments in DMSO‑d6 solution. The adsorption process presented weakly exothermic and endothermic behavior onto molecular imprints and non-specific sites respectively. The selectivity for adsorption of fenamiphos with respect to its sulfone and sulfoxide metabolites was quite high.

Effect of Substituents on the Homopolymerization Activity of Methyl Alkyl Diallyl Ammonium Chloride.

Among nitrogen-containing cationic electrolytes, diallyl quaternary ammonium salt is a typical monomer with the highest positive charge density, which has attracted the most attention, especially in the research on homopolymers and copolymers of dimethyl diallyl ammonium chloride (DMDAAC), which occupy a very unique and important position. In order to improve the lipophilicity of substituted diallyl ammonium chloride monomers under the premise of high cationic charge density, the simplest, most direct, and most efficient structure design strategy was selected in this paper. Only one of the substituents on DMDAAC quaternary ammonium nitrogen was modified by alkyl; the substituents were propyl and amyl groups, and their corresponding monomers were methyl propyl diallyl ammonium chloride (MPDAAC) and methyl amyl diallyl ammonium chloride (MADAAC), respectively. The effect of substituent structure on the homopolymerization activity of methyl alkyl diallyl ammonium chloride was illustrated by quantum chemical calculation and homopolymerization rate determination experiments via ammonium persulfate (APS) as the initiator system. The results of quantum chemistry simulation showed that, with the finite increase in substituted alkyl chain length, the numerical values of the bond length and the charge distribution of methyl alkyl diallyl ammonium chloride monomer changed little, with the activation energy of the reactions in the following order: DMDAAC < MPDAAC < MADAAC. The polymerization activities measured by the dilatometer method were in the order DMDAAC > MPDAAC > MADAAC. The activation energies Ea of homopolymerization were 96.70 kJ/mol, 97.25 kJ/mol, and 100.23 kJ/mol, and the rate equation of homopolymerization of each monomer was obtained. After analyzing and comparing these results, it could be easily found that the electronic effect of substituent was not obvious, whereas the effect of the steric hindrance was dominant. The above studies have laid a good foundation for an understanding of the polymerization activity of methyl alkyl diallyl ammonium chloride monomers and the possibility of preparation and application of these polymers with high molecular weight.

Effect of different monomers on the electro-optical properties of reverse-mode polymer stabilized liquid crystal

Reverse-mode polymer-stabilized liquid crystal (RPSLC) plays an important role in optical display field and becomes one of the research hotspots because of its normal transparent state without driving voltage. The concentration and type of polymer monomer has a great influence on the electro-optical properties of the RPSLC, so the optimization of the polymer monomer can reduce the driving voltage and hysteresis, and improve the contrast ratio of the RPSLC. In this paper, two kinds of V-type and two kinds of linear type monomers with bi-functional group, and a mesogenic monomer were used, the effect of the concentration and type of non-mesogenic monomers on electro-optical properties of RPSLC were studied with the fixed concentration of mesogenic monomer in experiment. The results show that the electro-optical properties of the RPSLC can be improved more when the suitable ratio of a V-type monomer is added. The maximum and minimum transmittances are 85.9% and 3.1%, the contrast ratio is 27.6, the threshold and saturation voltages are 6.4 V and 11.6 V, and the hysteresis is less than 1 V. Combined with the scanning electron microscopy morphology of polymer network, the mechanism of the influence of non-mesogenic monomer on the electro-optical properties of RPSLC is revealed. These experimental results will be of great significance for the research of RPSLC.

(Digital Presentation) Synthesis of Conjugated Polymer Alloy Prepared By Electrochemical Polymerization in Chiral Liquid Crystal

In this research, we synthesized polymer alloy by electrochemical polymerization in chiral liquid crystal. Homopolymers and the copolymer can be synthesized when electrochemical polymerization was conducted in the presence of several types of monomers. The polymer alloy thus prepared contains both blend of homopolymers and copolymers. The polymer alloy shows optical activity. The chirality derived from transcription of liquid crystal during the polymerization reaction results to show optical activity. The polymer alloy can show optical activity with no asymmetric centers. The optical activity is due to existence of charge carriers (polarons) in the main chain as a form of conjugated polymers. This is called chiral charge carrier “chiralions”. This research found that the chiral polymer alloy has chiralions.Polymer alloys have been prepared by blending several kinds of polymers in the reaction. Polymer alloys also can be prepared by melt method. Unsubstituted conjugated polymers have poor solubility and fusibility because of the rigid π-bonds in the skeleton, which is drawback for preparation of π-conjugated polymer-based alloys. We have studied on preparation of chiral conjugated polymer alloys with combination of achiral polymers and chiral polymers.In the present study, conjugated polymer alloys were synthesized with the method described in Figure 1a. Cholesteryl acetate (chiral inducer), 2,7-di(2-thienyl)fluorene (mono1), N-methyl-3,6-di(2-thienyl)carbazole (mono2) and TBAP (supporting salt) were dissolved in 4-cyano-4'-pentylbiphenyl (5CB) as a host liquid crystal to prepare a chiral liquid crystal electrolyte. The electrolyte exhibited a fingerprint structure under observation of polarizing optical microscopy. For the electrochemical polymerization reaction, the electrolyte solution is charged in the cell consisted of two indium-tin-oxide (ITO) glass plates as electrodes and a poly(tetrafluoroethylene) spacer (200 μm thickness). Next, dc voltage of 3.0 V was applied to the ITO glass cell for 30 min for electrochemical polymerization. The polymer was deposited on the anode electrode as a thin film form. After polymerization, the remaining electrolyte solution on the ITO glass electrode was carefully washed with a large amount of hexane, yielding dark blue film. This film is abbreviated as Alloy1. The molecular structure was confirmed by infrared spectroscopy with the KBr method. Alloy1 shows a fingerprint structure under POM observations (Figure 1b). The macroscopic structure of cholesteric liquid crystal was transcribed from the liquid crystal electrolyte solution to Alloy1. Synchrotron XRD measurement was carried out. The peak at 10.3 Å is derived from monomer repeat units. The XRD signal at 5.1 Å and 3.4 Å can be derived from π-stacking of Alloy1. Alloy1 shows UV-vis absorption due to the three signals derived from π-π* transition of the main chain, polarons (radical cations) and bipolarons (radical dications). Electrochemical properties of Alloy1 were evaluated by the cyclic voltammetry (CV). Alloy1 film deposited on the ITO glass was used as a working electrode. An Ag/Ag+ electrode and a platinum wire served as the reference and counter electrodes, respectively. A propylene carbonate solution with 0.1 M of TBAP was employed as an electrolyte solution for the CV measurements. Cyclic voltammograms of Alloy1 shows the oxidation peak and reduction trough (Figure 1c). Plots of the oxidation peak current (I pa) and the reduction peak current (I pc) as a function of the square root of the scan rate show a linear shape of the anodic and cathodic peak current values when scan rates from 10 to 100 mV/s with intervals of 10 mV/s. This result indicated that the redox reaction of Alloy1 was reversible and controlled by electron transfer processes. In-situ circular dichromism (CD) and in-situ optical rotatory dispersion (ORD) spectra of Alloy1 with application of voltages were examined in a propylene carbonate solution with 0.1 M of TBAP. The application voltages were between 0-1.2 V (vs. Ag/Ag+) with intervals of 0.1 V. A negative Cotton effect was observed from the in-situ CD, indicating Alloy1 has left-handed helical structure. The ORD shows negative signals, and changes with applied voltage. The ellipticity signal in the CD and optical rotation in the ORD could control in the electrochemical method, accompanied by electrochemical redox process.We synthesized the polymer alloy by electrochemical polymerization in chiral liquid crystal. The conjugated polymer alloy showed chirality with no chiral centers in the main chain. The CD and ORD bands at NIR range are assigned to doping band as a form of polarons (radical cations). This research evaluated electrochemical control of “chiralions”. Figure 1

Bifunctional Phenol-Enabled Sequential Polymerization Strategy for Printable Tough Hydrogels.

Hydrogels are promising material candidates in engineering soft robotics, mechanical sensors, biomimetic regenerative medicine, etc. However, developing multinetwork hydrogels with high mechanical properties and excellent printability are still challenging. Here, a bifunctional phenol-enabled sequential polymerization (BPSP) strategy is reported to fabricate high-performance multinetwork hydrogels under the orthogonal catalysis of efficient ruthenium photochemistry. Benefiting from this bifunctional design, phenols can sequentially polymerize with typical monomers and themselves to fabricate various phenol-containing polymers (Ph-Ps) and Ph-Ps-based multinetwork tough hydrogels, respectively. The as-prepared hydrogels have maximum stress of 0.75MPa and toughness of 2.2MJ m- 3 under the critical strain of 800%. These property parameters are a maximum of 16 times higher than those of the phenol-postmodified and phenol-free hydrogels. Moreover, the rapid coupling polymerization of phenols can shorten the gelation times of hydrogels to as low as ≈4 s, which enables its printable property for customizable applications. As a proof of concept, a 3D scaffold-like structure is optimized as highly sensitive mechanical sensors for detecting various human motions.

Study of the Preparation and Properties of Chrysin Binary Functional Monomer Molecularly Imprinted Polymers.

Chrysin is a natural bioactive molecule with various groups, and it has been a challenge to separate and enrich chrysin from natural products. Molecularly imprinted polymers have been widely used in the extraction of natural products, but the number and type of functional monomers limits the separation effect. The synergistic action of multiple functional monomers can improve the separation effect. In this paper, molecularly imprinted polymers (Bi-MIPs) were prepared using methacrylic acid and acrylamide as binary functional monomers for the separation and enrichment of chrysin. The Bi-MIPs were characterized using thermogravimetric analyzer (TGA), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). The performances of Bi-MIPs were assessed, which included adsorption isotherms, selective recognition and adsorption kinetics. The experimental results show that Bi-MIPs are shaped as a uniform sphere with an abundant pocket structure on its surface. The adsorption of chrysin on the Bi-MIPs followed a pseudo-second-order and adapted Langmuir–Freundlich isotherm models. The adsorption performance of the Bi-MIPs was determined at different temperatures, and the Bi-MIPs showed excellent adsorption performance at 30 °C. The initial decomposition temperature of the Bi-MIPs was 220 °C. After five times of adsorption and desorption, the adsorption performance of the Bi-MIPs decreased by only 7%. In contrast with single functional monomer molecularly imprinted polymers (Si-MIPs), the Bi-MIPs showed excellent specificity, with an imprinting factor of 1.54. The Bi-MIPs are promising materials in the separation and enrichment of chrysin for their high adsorption capacity, low cost and being environmentally friendly.

Preparation of a novel zwitterion flocculant with the characteristics of quaternary ammonium salt cation and dithiocarbamate anion and its application in produced water treatment

In this paper, a novel flocculant with the characteristics of both quaternary ammonium salt cation and dithiocarbamate anion was synthesized. Firstly, a cationic polymer having secondary amine side groups was synthesized by using cationic monomer and diallyl amine (DAA) as monomers via aqueous solution polymerization, and then the secondary amine was modified by carbon disulfide (CS2) to prepare the zwitterion flocculant. By using the oil removal as index, the effects of cationic monomer type, monomer concentration, mass ratio of cationic monomer to DAA, initiator concentration, polymerization temperature and time on the copolymerization results were investigated. The recommended rational condition was as follows: cationic monomer was methacryloxyethyltrimethyl ammonium chloride (DMC), monomer concentration was 50 wt%, mass ratio of DMC:DAA = 4:1, initiator was ammonium persulfate (APS) and its concentration was 0.4 wt%, and polymerization temperature was 60 °C for 8 h. The zwitterion flocculant obtained at the recommended condition had a removal of 99.5% at the dosage of 300 mg/L for produced water obtained from an offshore oilfield. In addition, the flocculation mechanism of the zwitterion flocculant was studied. According to the results of zeta potential measurement and floc morphology, it can be found that the quaternary ammonium salt unit in the zwitterion flocculant can bridge and flocculate oil droplets by destroying the stability of oil droplets in produced water through electrostatic neutralization, while the dithiocarbamate unit can interact with Fe2+ in produced water to form a network structure to catch flocculated oil droplets, and the synergistic effect of quaternary ammonium salt unit and dithiocarbamate unit is helpful for achieving the good flocculation result. The results provide a new selection for produced water treatment.

The role of nanomesh fibres loaded with fluorescent materials on the electro-optical performance of PDLC devices

ABSTRACT In this paper, polymer-dispersed liquid crystal (PDLC) films were prepared from a mixture of prepolymer, liquid crystal and phosphor-loaded reticular nanofibres films by a polymerisation-induced phase separation (PIPS) process. By comparing the microstructure and electro-optical curves of samples with different ratios of monomer types and liquid crystal contents, it was demonstrated that the cavity size of the polymer network had a significant effect on the electro-optical properties of the PDLC films. Reticular nanofibres films loaded with different phosphor contents were introduced into the liquid crystal mixture samples and the changes in the polymer network, electro-optical and fluorescence properties of these samples were analysed using SEM images, electro-optical curves and fluorescence curves. The electro-optical and fluorescence properties as well as the fluorescence properties of reticulated nanofibres films doped with PDLCs loaded with fluorescent materials were found to be improved and the anti-ageing properties are also greatly increased. Therefore, the development of meshed nanofiber membrane-doped PDLC films with faster response time, better optoelectronic properties, and better fluorescence properties will greatly improve the applications of PDLC-based devices in smart windows, sensors, energy efficiency and Potential technical applications in flexible devices.

New non-symmetric azido-diacetylenic s-triazine monomer for polycycloaddition

An original synthesis of a new non-symmetric energetic ABB' type monomer, 2-azido-4-propargylamino-6- propargyloxy-s-triazine, with a total yield of 40% involves the sequential introduction of propargylamino, propargyloxy and azido groups into s-triazine. DFT investigation of azide- Cl alkyne cycloaddition mechanism at M06-2X/6-311++G(d,p) level of theory for this monomer predicts that the regioselectivity of polycycloaddition reaction should increase with the number of propargylamino groups in the monomer structure due to the stabilization of the transition state, leading to 1,5-triazole regioisomer.

Hot-lithography 3D printing of biobased epoxy resins

The introduction of Hot Lithography has opened new perspective in the field of additive manufacturing especially with regard to high viscous formulations. The access to elevated temperature in the 3D printing process not only reduce the viscosity of resin but it allows to achieve higher curing kinetics and degree of conversion. Therefore, it is possible to process new type of monomers which are not reactive enough at room temperature towards UV-curing expanding the formulation design and selection to the 3D-printing of a broader range of epoxy-based formulations. With regard to climate change and the limitation of fossil resources, new needs arise for the origin of the materials. In this view, we investigated the use of two bio-based epoxy monomers (furandimethanol diglycidyl ether (FDE) and resorcinol diglycidyl ether (RDE)) in Hot Lithography 3D printing. Moreover, we compared the performance of the bio-based resins with a commercial fossil-based one, the 1,4-cyclohexanedimethanol diglycidyl ether (CDE). The photocuring process was fully characterized by means of real-time NIR/photorheology and photo-DSC analysis. The thermo-mechanical properties of the final thermosets were investigated by DMTA and tensile test. Finally, the 3D printing of complex shapes was carried out to demonstrate the possibility to obtain arbitrary self-standing shapes. • Hot-lithography 3D-printing of bio-based epoxy resin. • Photocuring of Furan-dimethanol diglycidyl ether epoxy resin. • Photocuring of 1,4-cyclohexanedimethanol diglycidyl ether.

Determination of naproxen by using differential pulse voltammetry with poly (aniline-2-sulfonic acid) modified boron doped diamond electrode

In this study, an electrochemical sensor based on a boron doped diamond electrode (BDDE) was developed for the determination of naproxen (NAP) using a poly(aniline-2-sulfonic acid)/boron doped diamond electrode, p(A2SA/BDDE). Polymerization of A2SA was conducted in a water/acetonitrile (1:1) mixture containing 0.1 M sodium perchlorate (NaClO4) on bare BDDE and the electrochemical properties studied by cyclic voltammetry in ferricyanide/KNO3 solution. The prepared p(A2SA/BDDE) was used for detection of NAP. Effects of parameters such as monomer type and concentration, the number of cycles, and scan rate were investigated using differential pulse voltammetry (DPV) in phosphate buffer containing 0.75 mM NAP. The effect of electrolyte type and pH on DPV responses to NAP were also studied. The oxidative current peak stem from NAP concentration observed at 1.1 V potential. A linear calibration curve was obtained in the range of 0.05–1.00 mM NAP concentration. Correlation coefficient (R2), detection limit, and quantification limit were calculated as 0.9944, 0.0328 mM, and 0.1093 mM, respectively. In conclusion, it may be claimed that the modified electrode constructed in this work can be used successfully as a naproxen-selective membrane due to its ease of preparation, high R2 value, and good reproducibility.

A novel bioderived AB2‐type monomer from castor oil derivative for the preparation of fully biobased hyperbranched polyesters

AbstractDesigning biobased hyperbranched polyesters from vegetable oil has been attracting considerable interests from academic industrial communities. Herein, a novel fully biobased hyperbranched polyester (HBPE) was prepared by self‐condensation of AB2‐type bioderived monomer based on methyl ricinoleate (MR), a castor oil‐derived renewable chemical. The reaction conditions were optimized to obtain the AB2‐type monomer in a high conversion ratio (up to 87%). The self‐condensation of AB2‐type monomers was carried out in the presence of two kinds of transesterification catalysts (Ti(OBu)4 versus Zn(Ac)2), among which Ti(OBu)4 was found to be more efficient one and yield higher molecular weights in the range of 5800~11,500 g/mol. The resulting HBPEs were characterized in terms of Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. The degree of branching was calculated to be 0.33~0.39. Thermal analysis revealed that the as‐prepared HBPEs were amorphous with tunable glass transition temperatures ranging from −44.8 to −24.6°C. All the prepared HBPEs exhibited good thermal stability with the maximum onset decomposition temperature (Tonset) up to 294.6°C. These structural features and properties of resulting biobased HBPEs enabled them to act as a potential ‘greener’ additive for polymers.

Hydrogen-Bonded Organic Frameworks: Functionalized Construction Strategy by Nitrogen-Containing Functional Group.

The construction of hydrogen-bonded organic framework materials by intermolecular hydrogen bonding forces has been rapidly developed in the last decade, among which, the strong intermolecular hydrogen bonding and functional binding sites exhibited by nitrogen-containing functional groups have made them favorites for designing organic components to customize functionalized porous materials. This review systematically introduces the types of nitrogen-containing monomers used to prepare porous hydrogen-bonded organic backbones and the principles of their construction, summarizes the design advantages of crystalline materials from an elemental perspective, and presents the applications of such HOFs in the fields of gas adsorption/separation, molecular recognition, plasmonic conductivity, biomedical, and luminescent materials, etc. Finally, the prospects for the development of such materials are discussed and potential directions for future work are analyzed.

Characterizing the Asymmetry in Hardness between Synthesis and Destruction of Heteropolymers.

We present a simple model describing the assembly and disassembly of heteropolymers consisting of two types of monomers A and B. We prove that no matter how we manipulate the concentrations of A and B, it takes longer than the exponential function of d to synthesize a fixed amount of the desired heteropolymer, where d is the number of A-B connections. We also prove the decomposition time is linear for chain length n. When d is proportional to n, synthesis and destruction have an exponential asymmetry. Our findings may facilitate research on the more general asymmetry of operational hardness.

Systematic Investigation on the Glass Transition Temperature of Binary and Ternary Sugar Mixtures and the Applicability of Gordon-Taylor and Couchman-Karasz Equation.

Glass transition temperatures (Tg) of carbohydrate mixtures consisting of only one monomer and glycosidic binding type (aldohexose glucose, α1-4-glycosidic bonded) were studied by differential scanning calorimetry (DSC). The aim of this work was to systematically assess the predictability of Tg of anhydrous binary and ternary sugar mixtures focusing on the components Tg, molecular chain length, and shape. Binary systems were investigated with glucose as a monosaccharide and its linear di-, tri-, tetra-, penta-, hexa-, and heptasaccharides. Additionally, the Tg of ternary carbohydrate systems prepared with different glucose/maltose/maltotriose mass fractions were studied to evaluate the behavior of more complex mixtures. An experimental method to prepare fully amorphized, anhydrous mixtures were developed which allows the analysis of mixtures with strongly different thermodynamic pure-component properties (Tg, melting temperature, and degradation). The mixtures’ Tg is systematically underestimated by means of the Couchman–Karasz model. A systematic, sigmoidal deviation behavior from the Gordon–Taylor model could be found, which we concluded is specific for the investigated glucopolymer mixtures. At low concentrations of small molecules, the model underestimates Tg, meeting the experimental values at about equimolarity, and overestimates Tg at higher concentrations. These deviations become more pronounced with increasing Tg differences and were explained by a polymer mixture-specific, nonlinear plasticizing/thermal volume expansion effect.

The effect of molecular structure on the properties of cationic polyacrylate and its flocculation‐flotation performance of oilfield oily wastewater treatment

AbstractWith the increasing amount of oily wastewater produced in the offshore oilfield, more efficient air flotation agent is needed to be developed. Cationic polyacrylate with amphiphilic structure has been found to be a type of potential efficient air flotation agent. However, the effect of molecular structure on its properties and performance was lack of research. In this paper, copolymers with tertiary amine as side group were synthesized by copolymerization of ethyl acrylate (EA) and tertiary amine monomers, and then a series of cationic polyacrylates were prepared by quaternization of tertiary amine with quaternization reagent. The effects of tertiary amine monomer type (including dimethylaminopropyl methacrylamide (DPM) and dimethylaminoethyl methacrylate (DEM)), quaternization reagent type (including 3‐Chloro‐1,2‐Propanediol and 3‐chloro‐2‐hydroxytrimethylammonium chloride) and quaternization degree on the cationic polyacrylate properties and its flotation performance were investigated. The experimental results showed that the flotation performance increased with the increasing hydrophilicity and cation degree of the hydrophilic unit in the cationic polyacrylate. When the tertiary amine monomer was DPM, quaternization reagent was 3‐chloro‐2‐hydroxytrimethylammonium chloride, and theoretical quaternization degree was 100%, the oil removal of product PE‐M‐1.0 was the highest. When PE‐M‐1.0 dosage was 50 mg/L, gas flow was 1 L/min, flotation time was 10 min, its oil removal rate was higher than 95% in the range of 20‑60°C. The results of zeta potential measurement and microfluidic experiment showed that PE‐M‐1.0 can increase the size of oil droplets by destroying the electric double layer on the surface of oil droplets and maintain the stability of bubbles, which was helpful for the improve of gas bubble‐oil droplet collision probability and adhesion efficiency.

Mechanically strong, thermal-insulated, and ultralow dielectric polyimide aerogels with adjustable crosslinking methods

Polyimide (PI) aerogels can exhibit controllable physical and chemical properties by changing the type of dianhydride and diamine monomers. However, few works aim to reveal the effects of monomer hybridization and crosslinking methods on the properties of polyimide aerogels. In this work, we studied the effects of single and double crosslinking methods on the density, microstructure and properties of PI aerogels. The results showed that different crosslinking methods could cause completely opposite variation trends of shrinkage and density. The single crosslinking PI aerogels possess large shrinkage of 23.8% and high thermal conductivity of 59.9 mW/(m·K). However, with the same formula, the PI aerogels prepared by the double crosslinking method possess smaller shrinkage of 12.3% and lower thermal conductivity of 28.7 mW/(m·K). The dielectric constant of the double crosslinking PI aerogels shows a lower dielectric constant of 1.10 compared to the single crosslinking PI aerogel of 1.34 when containing the same content of 6FDA. The addition of 6FDA can also increase the 5% thermal decomposition temperature of PI aerogels from 445.5 °C to 460 °C. The as-prepared double-crosslinking PI aerogels present superior properties of lightweight, low dielectric constant and dielectric loss, low thermal conductivity and high temperature resistance, which provides a new way for adjusting the performance of PI aerogels. • PI aerogels prepared by the double crosslinking method possess low shrinkage (12.3%) and thermal conductivity (28.7mW/(m·K)). • The dielectric constant of double crosslinking PI aerogels shows low dielectric constant of 1.10. • The addition of 6FDA can also increase the 5% thermal decomposition temperature of PI aerogels from 445.5 °C to 460 °C.

Study on the polymerization process and monomer reactivity of EPEG‐type polycarboxylate superplasticizer

AbstractIn this study, the binary aqueous free radical copolymerization process of ethylene‐glycol monovinyl polyethylene glycol (EPEG) and acrylic acid (AA) was studied. The influence of monomer type and molar ratio on the conversion ratio of EPEG and the molar ratio of copolymer were investigated via gel permeation chromatography (GPC) by comparing the macromonomer molecular structures, side chain densities, and carboxyl group concentrations. According to the results, the reactivity of EPEG copolymerized with AA was higher than that of isoprenyl oxypoly (ethylene glycol) ether (IPEG, also referred to as TPEG) with AA. The copolymerization reaction between EPEG and AA could be completed within 30 min at 10–20°C. At the initial stage, the copolymer content quickly attained 60% within 15 min, reflecting the short induction period and high chain propagation rate constant. The fluidity tests in cement mortar revealed that polycarboxylate superplasticizers (PCEs) with short side chains and high conversion ratio exhibited better dispersion capacity than PCEs with long side chains.

Insights into phenol monomers in response to electron transfer capacity of humic acid during corn straw composting process

Quinone is the important redox functional group for electron transfer capacity (ETC) of humic acid (HA). Lignin, as major component in corn straw, can be decomposed into phenol monomers, then oxidation into quinones for synthesis of HA during composting process. However, it is still unclear that the effects of type and variation characteristics of phenol monomers on redox characteristics of HA during straw composting process. In this study, p-hydroxybenzoic acid (P1), vanillic acid (P2), syringic acid (P3), p-hydroxy benzaldehyde (P4), 4-coumaric acid (P5), 4-hydroxyacetophenone (P6), ferulic acid (P7) and 4-hydroxy-3-methylacetophenone (P8) were recognized and clustered into three groups. The concentration of polyphenol presented a significant downward trend during the straw composting process. Based on the relationships among phenol monomers to ETC, electron donating capacity (EDC), electron accepting capacity (EAC) and quinone, we found that P1, P2, P3, P5 and P7 were significantly related to ETC, EDC and EAC of HA (P < 0.05). Furthermore, NH4+-N and NO3−-N were the main micro-environmental factors linking to ETC-related phenol monomers and redox characteristics of HA in straw composts (P < 0.05). Finally, two groups of core microflora that promoting the ETC-related phenol monomers and NH4+-N, and ETC-related phenol monomers and NO3−-N were identified by Mantel test, respectively. This study contributes a new insight for polyphenol way for redox capacity of HA in traditional composting and utilization of straw compost in contaminated environments.

Synthesis of a new polymer from arginine for the preparation of antioxidant, pH-sensitive, and photoluminescence nanocomposite as a cancer drugs carrier

In this study, we aimed to synthesize a new photoluminescent nanocomposite based on hyperbranched polymers derived from arginine through an easy method for drug delivery application. Hence, a new hyperbranched polymer (HBPAC) via co-polymerization of citric acid (as A3 type monomer) and L-arginine (as AB2 type monomer) was synthesized and composited with glucose-derived quantum dot (GluQD) to obtain the HBPAC-GluQD nanocarrier. The HBPAC-GluQD was characterized, and its potential was studied as a nanocarrier. The particles size of the nanocomposite was about 90–200 nm. The antioxidant study of the HBPAC-GluQD revealed its excellent antioxidant properties. Also, the prepared HBPAC-GluQD showed photoluminescence (PL) in the blue range under 322 nm excitation with a QY of 72.8%. In vitro bioimaging investigations determined that HBPAC-GluQD has a potential for bioimaging applications. In-vitro release investigation of the HBPAC-GluQD nanocarrier exhibited that the composite has pH-responsive behavior and showed that the highest release happens at pH 5. Also, the stability, red blood cells compatibility, and MTT assay were evaluated. The obtained results showed that the HBPAC-GluQD as a nanocarrier is stable enough, biodegradable, and hemocompatible in physiological condition. Also, apoptosis, cellular uptake, and MTT analysis showed that the HBPAC-GluQD-DOX/MTX could efficiently induce cellular apoptosis.