Short Side Chains Research Articles

Injectable Acylhydrazone-Linked RAFT Polymer Hydrogels for Sustained Protein Release and Cell Encapsulation.

A new class of temperature responsive polymer, termed PADO, is synthesized by reversible addition-fragmentation chain-transfer polymerization. Synthesized from copolymerization of diacetone acrylamide (DAAM), di(ethylene glycol) ethyl ether acrylate, and oligo(ethylene glycol) methyl ether acrylate, PADO polymer phase separates at temperature above its lower critical solution temperature (36-42°C) due to enhanced hydrophobic interactions between the short ethylene glycol side chains. Solution of PADO polymers exhibit injectable shear-thinning properties and reach sol-gel transition rapidly (<5min) at 37°C.Whenthe ketone moieties on DAAM are linked by adipic acid dihydrazdie, PADO polymers form crosslinked and injectable acylhydrazone hydrogels, which are hydrolytically degradable at a mild acidic environment owing to the pH sensitive acylhydrazone bonds. The pH-responsive degradation kinetics can be controlled by tuning polymer contents and ketone/hydrazide ratio. Importantly, the injectable PADO hydrogels are highly cytocompatible and can be easily formulated for pH-responsive sustained protein delivery.

Molecular Brushes with a Polyimide Backbone and Poly(ε-Caprolactone) Side Chains by the Combination of ATRP, ROP, and CuAAC.

An approach to the synthesis of the novel molecular brushes with a polyimide (PI) backbone and poly(ε-caprolactone) (PCL) side chains was developed. To obtain such copolymers, a combination of various synthesis methods was used, including polycondensation, atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and Cu (I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC). ATRP of 2-hydroxyethyl methacrylate (HEMA) on PI macroinitiator followed by ROP of ε-caprolactone (CL) provided a “brush on brush” structure PI-g-(PHEMA-g-PCL). For the synthesis of PI-g-PCL two synthetic routes combining ROP and CuAAC were compared: (1) polymer-analogous transformations of a multicenter PI macroinitiator with an initiating hydroxyl group separated from the main chain by a triazole ring followed by ROP of CL, or (2) a separate synthesis of macromonomers with the desirable functional groups (polyimide with azide groups and PCL with terminal alkyne groups), followed by a click reaction. Results showed that the first approach allows to obtain graft copolymers with a PI backbone and relatively short PCL side chains. While the implementation of the second approach leads to a more significant increase in the molecular weight, but unreacted linear PCL remains in the system. Obtained macroinitiators and copolymers were characterized using 1H NMR and IR spectroscopy, their molecular weight characteristics were determined by SEC with triple detection. TGA and DSC were used to determine their thermal properties. X-ray scattering data showed that the introduction of a polyimide block into the polycaprolactone matrix did not change the degree of crystallinity of PCL.

Bifunctional RAFT Agent Directed Preparation of Polymer/Graphene Oxide Composites.

Polymer/graphene oxide (GO) composites, which combine the physical properties of GO and the processability of polymers, are of increasing interest in a variety of applications ranging from conductive foams, sensors, to bioelectronics. However, the preparation of these composites through physical blending demands the polymers with functional groups that interact strongly with the GO. Here the design and synthesis of a new bifunctional reversible addition-fragmentation chain transfer (RAFT) agent are demonstrated, which allows the synthesis of polymers with predetermined molecular weights and low dispersibilities (Ð), while having functionalities at both polymer termini that allow strong binding to GO. To access polymers with diverse thermal and mechanical properties, acrylonitrile-styrene-acrylate (ASA) copolymers with different types of acrylates, both short and long side chains, are synthesized under the control of the bifunctional RAFT agent. Furthermore, the strong binding between GO and the synthesized polymers is verified and explored to prepare polymer/GO composites with diverse tensile strengths and conductivity in the range of semiconductors. Overall, this novel RAFT agent is expected to expand the utility of polymer/GO composites by providing well-defined polymers with tunable properties and strong binding with GO.

Study on the contrast of the MHC-peptide interaction of B2/B21 haplotype and MHC-related virus resistance in chickens.

IntroductionThree‐dimensional (3D) structures of MHC class I exert some influence by the MHC–peptide interaction over host resistance to the virus. The thesis aims at studying the connection between MHC–peptide interaction of B2/B21 haplotype and MHC‐related resistance to the virus.MethodsThe structure of chicken MHC class I BF2*0201 from B2 haplotype was studied and contrasted with that of BF2*2101 from B21 haplotype by using DNAMAN and PyMol software.ResultsThe amino acid difference resulted in the difference in size and changeability of the binding groove of the two, resulting in different choices on the binding polypeptide. 3bew's (the crystal structure of BF2*2101 bound to peptide RV10) small side chain His111 replaces the short side chain Tyr111 of 4cvx (the crystal structure of BF2*0201 bound to peptide YL9), and the very small amino acid of Ser69 and Ser97 make the middle of the 3bew's binding groove become apparently broad and bound restrictive of amino acid smaller. Moreover, due to the specific amino acids—Arg9, Asp24, and Asp73 of 4cvx and Arg9, Asp24, and His111 of 3bew, the effect of the polypeptide and the binding groove differ between the two, and 3bew tends to bind polypeptides with negatively charged amino acids, but the large space in the middle can also accommodate other amino acids. Contrasted with the binding groove characteristic of 4cvx, it can be said that the selectivity of 3bew is higher than that of 4cvx in the amino acid type of the binding polypeptide, so the B21 haplotype has more host resistance to the virus than that of the B2 haplotype in chicken.ConclusionThere are usually various kinds of peptides presented by the BF2*2101 molecules of B21 haplotypes, resulting in resistance to pathogenic microorganisms, such as Rous sarcoma virus and/or Marek's disease virus. These findings may have an important theoretical foundation for screening of virus antigen, vaccine design, and genetic resistance breeding.

Polymer Pressure‐Sensitive Adhesive with A Temperature‐Insensitive Loss Factor Operating Under Water and Oil

AbstractLoss factor tan δ determines the viscoelasticity of a material. Higher or lower loss factor tanδ (&gt;1 or &lt;1) suggests a viscous or elastic material. Most polymer pressure‐sensitive adhesives (PSAs) possess a limited operational temperature range (near room temperature), above which the PSAs trend to be more viscous (un‐crosslinked) or more elastic (crosslinked), and below which PSAs become more elastic. These properties are unfavorable for PSA operation. Herein, an underwater PSA possessing short hydrophobic side chains and weak hydrogen bond interactions are described. Proper modulus and stable loss factor close to 1 contributes to an efficient adhesion underwater over a temperature range of 0–100 °C. Moreover, by introducing Teflon particles, the adhesion can be operated under silicon oil from room temperature to 150 °C due to the formation of a drainage surface structure and its temperature insensitivity.

Combinatorial Anti-Leukemic Activity Of Liposomal Ceramide and Inhibitors Of Autophagy

BackgroundCeramides are naturally occurring cellular sphingolipids which are increased following various effective cancer therapies. Bioavailable forms of ceramide are under development as therapeutic tools (Anticancer Agents Med Chem. 2011 Nov;11(9):911-9). Short side chain (C6) ceramide has, in pegylated nanoliposomal (NL) formulations, shown excellent cellular uptake and significant anti-tumor activity in a variety of tumor types and models. Cellular autophagy is an active microsomal process implicated in ceramide metabolism and potentially in the detoxification of C6-ceramide. We have previously shown synergistic combination therapy with Lip-C6-ceramide and vinblastine and its association with autophagy dysfunction in hepatocarcinoma and colorectal cancer models (Cancer Lett. 2013 Sep 1;337(2):254-65.). Methods and findingsWe explored the therapeutic activity of nano-liposomally delivered C6-ceramide (Lip-C6) in cell lines and primary human acute myelogenous leukemia (hAML). Lip-C6 cytotoxicity was tested in multiple human and murine AML lines (in short term viability assays) and in multiple cryopreserved primary human AML cases (in clonogenic assays - colony formation in methylcellulose). Lip-C6 demonstrated anti-AML activity in these cells with an EC50 of 2-23uM Lip-C6. In order to enhance this efficacy the interplay between ceramide induced apoptosis and autophagy was explored. The AML line KG1 was found to be relatively resistant to Lip-C6 (EC50 23uM). KGI showed supra-additive sensitivity to the combination of Lip-C6 with either vinblastine (VBL) or vincristine, both microtubule binding agents with the ability to reduce autophageic flux. KG1 sub-clones with knockdown of ATG5 demonstrated increased sensitivity to Lip-C6 relative to control or scrambled knockdown transfectants, consistent with the hypothesis that autophagy “rescues” this line from ceramide cytotoxicity. To further confirm these findings we examined the interaction of Lip-C6 (20uM) with VBL (5uM) or chloroquine (25uM) in a series of 13 fresh, patient derived AML cases (Figure: A-F). After 48 hours of co-culture, cells were examined for apoptosis of whole leukemic(E) and putative leukemia “stem cell” (LSC - F) fractions by flow cytometry. We also studied the in-vivo activity of Ghost (control) NLs, Lip-C6, VBL-NLs and combinatorial Lip-C6+VBL-NLs in NSG xenografts bearing a single poor prognosis (inversion 3) hAML (data are shown in the figure G.) [Display omitted] ConclusionsWe conclude that VBL and chloroquine both yield significant enhancement of Lip-C6 ceramide anti-hAML cytotoxicity. Available evidence suggests that this effect is mediated by inhibition of autophagy in these ceramide stressed cells. These data suggest that the combination of Lip-6 with autophagy inhibitors delivered simultaneously or in combinatorial formulations may prove clinically useful for these disorders. Disclosures:Kester:Keystone Nano Inc.: Membership on an entity's Board of Directors or advisory committees, Penn state research foundation has licensed ceramide nanoliposome technology to keystone nano Inc. For commercialization, MK is co-founder and CMO of Keystone Nano., Penn state research foundation has licensed ceramide nanoliposome technology to keystone nano Inc. For commercialization, MK is co-founder and CMO of Keystone Nano. Patents & Royalties.

A Genetically Encoded Fluorosulfonyloxybenzoyl-l-lysine for Expansive Covalent Bonding of Proteins via SuFEx Chemistry.

Genetically introducing novel chemical bonds into proteins provides innovative avenues for biochemical research, protein engineering, and biotherapeutic applications. Recently, latent bioreactive unnatural amino acids (Uaas) have been incorporated into proteins to covalently target natural residues through proximity-enabled reactivity. Aryl fluorosulfate is particularly attractive due to its exceptional biocompatibility and multitargeting capability via sulfur(VI) fluoride exchange (SuFEx) reaction. Thus far, fluorosulfate-l-tyrosine (FSY) is the only aryl fluorosulfate-containing Uaa that has been genetically encoded. FSY has a relatively rigid and short side chain, which restricts the diversity of proteins targetable and the scope of applications. Here we designed and genetically encoded a new latent bioreactive Uaa, fluorosulfonyloxybenzoyl-l-lysine (FSK), in E. coli and mammalian cells. Due to its long and flexible aryl fluorosulfate-containing side chain, FSK was particularly useful in covalently linking protein sites that are unreachable with FSY, both intra- and intermolecularly, in vitro and in live cells. In addition, we created covalent nanobodies that irreversibly bound to epidermal growth factor receptors (EGFR) on cells, with FSK and FSY targeting distinct positions on EGFR to counter potential mutational resistance. Moreover, we established the use of FSK and FSY for genetically encoded chemical cross-linking to capture elusive enzyme-substrate interactions in live cells, allowing us to target residues aside from Cys and to cross-link at the binding periphery. FSK complements FSY to expand target diversity and versatility. Together, they provide a powerful, genetically encoded, latent bioreactive SuFEx system for creating covalent bonds in diverse proteins in vitro and in vivo, which will be widely useful for biological research and applications.

Modulating the Stability of Collagen Triple Helices by Terminal Charged Residues.

Cationic or anionic residues are frequently located at the termini of proteins because their charged side chain can form electrostatic interactions with a terminal carboxylate or ammonium group to stabilize the structure under physiological conditions. Here, we used collagen-mimetic peptides (CMPs) to examine how the terminal charge-charge interactions affect the collagen triple helix stability. We designed a series of CMPs with either a Lys or Glu incorporated into the terminus and measured their pH-dependent stability. The results showed that the terminal electrostatic attractions stabilized the triple helix, while the terminal electrostatic repulsions destabilized the trimer. The data also revealed that the repulsions imposed a greater effect than did the attractions on the triple helix. An amino acid with a shorter side chain, such as aspartate and ornithine, was also installed to investigate the length effect on electrostatic interactions, which was found to be insignificant. Meanwhile, simultaneously incorporating cationic and anionic residues into the termini showed slight additive stabilization effects but pronounced additive destabilization consequences. We have demonstrated that the collagen triple helix stability can be modulated by introducing a cationic or anionic residue into the terminus of a peptide, giving useful information for the design of collagen-associated materials.

Architecture dependent water uptake in model polyelectrolyte membranes

The effect of polymeric architecture on the water uptake in ionomer membranes is modelled by Dissipative Particle Dynamics. We consider four polymers (a-d) of similar ion exchange capacity that contain hydrophobic A and hydrophilic C beads. For architecture a (A[A]C[A][A2])5 and b (A[A]C[A3])5 the C beads are located along the backbone that contain respectively 3 (a) and 2 (b) hydrophobic side chains per repeat unit. For architectures c ((A[C]A4])5) and d ((A[C]A[A3])5) each C bead represents a short hydrophilic side chain. Water is modelled by W beads. For ~20 nm thick membranes the water uptake is followed. The equilibrium water volume fraction varies between ~0.075 (architecture a) and ~0.4 (architecture d), and increases with (1) decreasing amount of C-A bonds per repeat unit and (2) the average number of bonds between hydrophobic beads and the nearest C bead, <Nbondphob-phil>. The potential energy per bead at equilibrium decreases as function of <Nbondphob-phil>. Water uptake is anticipated to show an increasing trend with increase of <Nbondphob-phil> for various architecture families. Some supporting evidence from experiments in literature is discussed. These results are of relevance for the optimization of proton and hydroxide ion conducting pores in electrochemical devices.

Combining ‘grafting to’ and ‘grafting from’ to synthesize comb-like NCC-g-PLA as a macromolecular modifying agent of PLA

The surface modification of nano particles is very important in nanotechnology. Grafting from (GF) and grafting to (GT) are two main methods to prepare surface modified nanoparticles like nanocellulose crystalline (NCC) grafted with polylactic acid (PLA) chains. In the GF method, the NCC can get high grafting degree but short side chains to improve its compatibility with the polymer matrix. The GT method can help obtain long side chains to increase the chain entanglements but owns low grafting density. To take the advantage of both methods, a mixed modification method combining GT and GF methods was put forward to synthesize comb-like NCC-g-PLA (NP) as a macromolecular modifying agent of PLA. Firstly, GT Method was used to obtain long side-chain NP to improve chain entanglement. Secondly, the GF method was applied to obtain NP-g-PLA (NPL) and NP-g-PDLA (NPD) with additional short side chains to improve its dispersion and compatibility in the PLA matrix. The products showed an enhanced nucleation effect, the degree of crystallinity (Xc ) of PLA composites increased almost four times with only 1 wt% NPD or NPL. What’s more, the storage modulus and loss modulus of the composite melts also increased with 1 wt% NPL or NPD. The NPD/PLA shows a higher effect than NPL/PLA owning to stronger interaction originated from the stereocomplex (SC) network of PLA matrix with PDLA short chains in NPD.

Structural Characterization of EnpA D,L-Endopeptidase from Enterococcus faecalis Prophage Provides Insights into Substrate Specificity of M23 Peptidases.

The best-characterized members of the M23 family are glycyl-glycine hydrolases, such as lysostaphin (Lss) from Staphylococcus simulans or LytM from Staphylococcus aureus. Recently, enzymes with broad specificities were reported, such as EnpACD from Enterococcus faecalis, that cleaves D,L peptide bond between the stem peptide and a cross-bridge. Previously, the activity of EnpACD was demonstrated only on isolated peptidoglycan fragments. Herein we report conditions in which EnpACD lyses bacterial cells live with very high efficiency demonstrating great bacteriolytic potential, though limited to a low ionic strength environment. We have solved the structure of the EnpACD H109A inactive variant and analyzed it in the context of related peptidoglycan hydrolases structures to reveal the bases for the specificity determination. All M23 structures share a very conserved β-sheet core which constitutes the rigid bottom of the substrate-binding groove and active site, while variable loops create the walls of the deep and narrow binding cleft. A detailed analysis of the binding groove architecture, specificity of M23 enzymes and D,L peptidases demonstrates that the substrate groove, which is particularly deep and narrow, is accessible preferably for peptides composed of amino acids with short side chains or subsequent L and D-isomers. As a result, the bottom of the groove is involved in interactions with the main chain of the substrate while the side chains are protruding in one plane towards the groove opening. We concluded that the selectivity of the substrates is based on their conformations allowed only for polyglycine chains and alternating chirality of the amino acids.

Specific molecular design of polycarboxylate polymers exhibiting optimal compatibility with clay contaminants in concrete

It is widely recognized that the dispersing ability of polycarboxylate superplasticizers (PCEs) could be hindered due to the presence of clay contaminants in concrete. In this study, a series of allyl ether-based polycarboxylate superplasticizers possessing short polyethylene glycol side chains was successfully synthesized and probed for their clay tolerance. The resulting PCE polymers were characterized via Size Exclusion Chromatography (SEC) to obtain their molecular properties. Thereafter, their dispersing ability was probed in the absence and presence of sodium bentonite. Allyl ether-based polycarboxylate (APEG) polymers possessing short side chains were found to exhibit enhanced clay resistance as compared to that of conventional MPEG PCEs holding long pendant chains. The mode of interaction between APEG PCEs and bentonite was investigated via sorption and XRD measurements. The data revealed that APEG PCEs possessing a lower side chain density intercalate less into the interlayer space of bentonite than those exhibiting higher side chain density.

Structure-Property Relation of Trimethyl Ammonium Ionic Liquids for Battery Applications

Ionic liquids are attractive and safe electrolytes for diverse electrochemical applications such as advanced rechargeable batteries with high energy densities. Their properties that are beneficial for energy storage and conversion include negligible vapor-pressure, intrinsic conductivity as well as high stability. To explore the suitability of a series of ionic liquids with small ammonium cations for potential battery applications, we investigated their thermal and transport properties. We studied the influence of the symmetrical imide-type anions bis(trifluoromethanesulfonyl)imide ([TFSI]−) and bis(fluorosulfonyl)imide ([FSI]−), side chain length and functionalization, as well as lithium salt content on the properties of the electrolytes. Many of the samples are liquid at ambient temperature, but their solidification temperatures show disparate behavior. The transport properties showed clear trends: the dynamics are accelerated for samples with the [FSI]− anion, shorter side chains, ether functionalization and lower amounts of lithium salts. Detailed insight was obtained from the diffusion coefficients of the different ions in the electrolytes, which revealed the formation of aggregates of lithium cations coordinated by anions. The ionic liquid electrolytes exhibit sufficient stability in NMC/Li half-cells at elevated temperatures with small current rates without the need of additional liquid electrolytes, although Li-plating was observed. Electrolytes containing [TFSI]− anions showed superior stability compared to those with [FSI]− anions in battery tests.

Length Effects of Short Alkyl Side Chains on Phase-Separated Structure and Dynamics of Hydrophobic Association Hydrogels

Length Effects of Short Alkyl Side Chains on Phase-Separated Structure and Dynamics of Hydrophobic Association Hydrogels

Importance of Cholesterol Side Chain in the Membrane Stability of Human Erythrocytes.

Cholesterol suppresses the hemolysis and the detachment of cytoskeletal proteins from bilayer in the human erythrocyte membrane under stress conditions. However, there is little information on how cholesterol functions. So, examining the role of a short side chain of cholesterol, we used the plant sterols such as β-sitosterol and stigmasterol. Incorporation of sterols into the membrane using a sterol/methyl-β-cyclodextrin complex was confirmed by the mass spectrometry. Hemolysis of human erythrocytes under high hydrostatic pressure (200 MPa) or hypotonic conditions was suppressed by cholesterol, but not by β-sitosterol and stigmasterol. Moreover, the bilayer-cytoskeleton interaction was also strengthened by cholesterol, but not by β-sitosterol and stigmasterol. Taken together, we suggest that the short side chain of cholesterol plays an important role in the membrane stability of human erythrocytes.

Shape-Changing Bottlebrush Polymers.

Bottlebrush polymers (BBPs), composed of relatively short polymeric side chains densely grafted on a polymer backbone, exhibit many unique characteristics and hold promise for a variety of applications. This Perspective focuses on environmentally induced shape-changing behavior of BBPs at interface and in solution, particularly worm/star-globule shape transitions. While BBPs with a single type of homopolymer or random copolymer side chains have been shown to undergo pronounced worm-to-globule shape changes in response to external stimuli, the collapsed brushes are unstable and prone to aggregation. By introducing a second, solvophilic polymer into the side chains, either as a distinct type of side chain or as the outer block of block copolymer side chains, the collapsed brushes not only are stabilized but also create unimolecular micellar nanostructures, which can be used for, e.g., encapsulation and delivery of substances. The current challenges in the design, synthesis, and characterization of stimuli-responsive shape-changing BBPs are discussed.

Impact of Sulphate Ions Content on Performance of Maleic and Acrylic Superplasticizers in Cement Paste.

The paper presents test results of the impact of sulphate ions from calcium sulphates: Hemihydrate, dihydrate and anhydrite, on rheological properties and hydration heat of cement pastes with, and without, superplasticizers, derivatives of maleic (SP-2) and acrylic (SP-1) acids. It is demonstrated that cement pastes fluidity depends on superplasticizer chemical structure, and its effect is expressed by a hydrophilic coefficient. As maleic superplasticizers have flexible comb-like structure composed of a shorter backbone chain containing COO− carboxylate groups and very long side chains, cement pastes showed higher fluidity than with acrylic superplasticizer with ladder-like structure, longer backbone chains with shorter side chains. SP-1 showing lower hydrophilicity coefficient and fewer COO− groups was found to be less sensitive to increased sulphate ion content in pastes. However, with SP-2 with higher hydrophilicity, a gradual fluidity loss (increased paste viscosity) was observed. Plastic viscosity was approximately at the same level in SP-1-containing pastes. Tests showed that sulphates definitely changed polycarboxylate superplasticizers performance. A high concentration of sulphate ions reduced maleic superplasticizer efficiency. Under these conditions, SP-1 is more effective and therefore more suitable for fluidity of pastes containing higher SO42− ions content. Thus, sulphate ions concentration in the paste should be considered when selecting superplasticizer.

Reprocessible, rubbery, printable polymers

3D Printing Three-dimensional (3D) printing is a valuable tool for rapidly prototyping complex parts from a range of materials. A challenge in printing most elastomers (rubber-like, highly stretchable polymers) is that they are mechanically soft and thus require external support during the printing process. Nian et al. developed a series of bottlebrush polymers composed of polydimethylsiloxane and poly(benzyl methacrylate) that have a high overall molecular weight because of their high density of short side chains but form few entanglements in the melt state. The polymers can be 3D printed without a support structure but are 100 times softer than other printed elastomers. At the same time, the printed structures can be stretched up to 600% and are stable up to 180°C but can be reprocessed with the aid of solvents. Chem. Mater. 33 , 2436 (2021).

Improving the performance of quaternized SEBS based anion exchange membranes by adjusting the functional group and side chain structure

Polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) has attracted more and more attention recently for using as the matrix of anion exchange membranes (AEMs) in fuel cells due to its low cost, superior mechanical properties and ether-free total C-C bond backbone. In this work, the short side chain of chloromethyl and long side chain of bromohexanoyl groups are grafted into the SEBS copolymer via the chloromethylation and Friedel-Crafts acylation reactions. After quaternized by different nitrogen heterocyclic compounds including 1-methylimidazole (Im), 1-methylpyrrolidine (Mpy), N-methylpiperidine (Pip) and 2-methyl-1-pyrroline (Mpyl), various SEBSCn-x AEMs are prepared. Combing with small molecule model experiment results, Mpy and Pip cations grafted SEBS membranes are confirmed to possess good alkali resistance, while SEBSC1-x membranes with Im and Mpyl cations are not suitable for AEMs due to their poor alkaline stability. Meanwhile, long side-chain cation grafted SEBSC6-x AEMs with lower ion exchange capacity (IEC) values exhibit higher water uptake, ionic conductivity and mechanical strength simultaneously comparing with short side-chain cation grafted SEBSC1-x AEMs. As an example, the SEBSC6-Pip membrane with an IEC of 0.48 mmol g−1 exhibits a water uptake of 47% at 80 °C, an OH− conductivity of 57.7 mS cm−1 at 80 °C, a tensile strength of 52 MPa at room temperature, and a conductivity retention percent of 75% after 600 h in 1 M KOH at 80 °C, demonstrating a big potential for the AEM fuel cell application.

Impact of polycarboxylate superplasticizers (PCEs) with novel molecular structures on fluidity, rheological behavior and adsorption properties of cement mortar

Polyether macromonomers have shown diversified structures recently. In this work, a series of polycarboxylate superplasticizers (PCEs) were synthesized via copolymerization using a novel macromonomer, ethylene–glycol monovinyl polyethylene glycol (EPEG). The molecular structures were modified by varying the side chain length, carboxylate density and integrating sulfonic group. The synthesis reaction of PCEs with high reaction conversion ratio was achieved through rapid reaction(20–30 min) at low temperature (5-20℃). The fluidity of PCEs, the rheological parameters and the compressive strength of mortar were measured. The adsorption behavior and zeta potential of the cement particles were also measured. Results have shown that PCEs with short side chain and high carboxylate density had high adsorption ability, high dispersion capacity in mortar. In addition, PCEs with sulfonic group had increased adsorption amount on the cement surface. These results could allow further progress in the application of EPEG macromonomer.