Journal articles: 'Viscoelasticity. Polymers. Polymerization'

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Pan, Xiao-Dong, Yuan-Yong Yan, Zengquan Qin, Dennis R. Brumbaugh, and Pat Sadhukhan. "MUSSEL-MIMETIC ELASTOMERS OF VARIED FUNCTIONALITY DESIGN FOR ELASTOMERIC COMPOSITES." Rubber Chemistry and Technology 85, no. 4 (December 1, 2012): 526–46. http://dx.doi.org/10.5254/rct.12.88927.

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ABSTRACT Bulk viscoelasticity and tensile behavior are examined for cross-linked compounds made of mussel-mimetic elastomers of varied functionality design. During polymerization, the mussel-mimetic functionalities containing the 3,4-dihydroxyphenyl (or catechol) group can be incorporated at the molecule chain head, along the backbone, and/or at the molecule chain tail. The compounds are either unfilled or filled to the same filler volume fraction with a single filler chosen among carbon black (hydrophobic), precipitated silica (hydrophilic), and titanium oxide (hydrophilic). For polymers bearing multiple mussel-mimetic functional groups, the polymer cold flow resistance becomes significantly enhanced, arising from the strong intermolecular hydrogen bonding interactions. Such strong intermolecular hydrogen-bonding interactions also affect the bulk viscoelasticity and tensile behavior for the cross-linked gum compounds. Because the mussel-mimetic functional groups exhibit obvious affinity to all three types of filler particles, the extent of modification to bulk viscoelasticity and reinforcement for the filled compounds is observed to vary with the distribution of such functionalities along a polymer molecule, the chemical groups immediately next to the catechol group, and the specific type of filler. As expected, microscale filler dispersion is improved from the strong polymer–filler interactions.

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Privalko, V. P., V. B. Dolgoshey, E. G. Privalko, V. F. Shumsky, A. Lisovskii, M. Rodensky, and M. S. Eisen. "Melt viscoelasticity of polypropylenes prepared under different polymerization regimes." Journal of Macromolecular Science, Part B 41, no. 3 (June 26, 2002): 539–57. http://dx.doi.org/10.1081/mb-120004352.

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Rodríguez, Fátima Pérez, and Enrique J. Jiménez-Regalado. "Micellar polymerization, characterization, and viscoelasticity of combined thermally insensitive terpolyacrylamides." Polymer Engineering & Science 51, no. 12 (May 31, 2011): 2473–82. http://dx.doi.org/10.1002/pen.22015.

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Xu, Tao, Jincheng Mao, Yang Zhang, Xiaojiang Yang, Chong Lin, Anqi Du, Heng Zhang, Quan Zhang, and Jinhua Mao. "Experimental Study on High-Performers Quaternary Copolymer Based on Host–Guest Effect." Polymers 13, no. 17 (September 1, 2021): 2972. http://dx.doi.org/10.3390/polym13172972.

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A quaternary polymer (HGP) was prepared by the free-radical polymerization of acrylamide, acrylic acid, maleic anhydride functionalized β-cyclodextrin (MAH-β-CD), and N-(3-methacrylamidopropyl)-N, N-dimethylnaphthalen-1-aminium chloride (NAP). It was found that host–guest behavior occurred most effectively at a molar rate of NAP and CD with 1:1, which exhibited better solubility than hydrophobically associative polymer. Moreover, the as-prepared polymer has superior salt tolerance, shear resistance, and viscoelasticity due to host–guest strategy. More importantly, the HGP solution simulates the distribution of formation water in the Bohai SZ1-1 oilfield has good rheological properties at 120 °C. All results show that the proposed polymer could be a competitive candidate in oilfield applications such as fracturing fluids, displacement fluids, and drilling fluids.

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Liu, Rui, WanFen Pu, Hu Jia, XiaoPei Shang, Yue Pan, and ZhaoPeng Yan. "Rheological Properties of Hydrophobically Associative Copolymers Prepared in a Mixed Micellar Method Based on Methacryloxyethyl-dimethyl Cetyl Ammonium Chloride as Surfmer." International Journal of Polymer Science 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/875637.

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A novel cationic surfmer, methacryloxyethyl-dimethyl cetyl ammonium chloride (DMDCC), is synthesized. The micellar properties, including critical micelle concentration and aggregation number, of DMDCC-SDS mixed micelle system are studied using conductivity measurement and a steady-state fluorescence technique. A series of water-soluble associative copolymers with acrylamide and DMDCC are prepared using the mixed micellar polymerization. Compared to conventional micellar polymerization, this new method could not only reasonably adjust the length of the hydrophobic microblock, that is,NH, but also sharply reduce the amount of surfactant. Their rheological properties related to hydrophobic microblock and stickers are studied by the combination of steady flow and linear viscoelasticity experiments. The results indicate that both the hydrophobic content and, especially the length of the hydrophobic microblock are the dominating factors effecting the intermolecular hydrophobic association. The presence of salt influences the dynamics of copolymers, resulting in the variation of solution characters. Viscosity measurement indicates that mixed micelles between the copolymer chain and SDS molecules serving as junction bridges for transitional network remarkably enhance the viscosity. Moreover, the microscopic structures of copolymers at different experimental conditions are conducted by ESEM. This method gives us an insight into the preparation of hydrophobically associative water-soluble copolymers by cationic surfmer-anionic surfactant mixed micellar polymerization with good performance.

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Dmitrenko, A. V., V. A. Demidova, S. S. Ivanchev, L. L. Sul'zhenko, G. G. Teteris, and �. �. Yakobson. "Effect of polymerization modification of filler on viscosity and viscoelasticity of polystyrene melts." Mechanics of Composite Materials 21, no. 3 (1985): 341–48. http://dx.doi.org/10.1007/bf00611621.

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WAGNER, Oliver, Herwig SCHÜLER, Peter HOFMANN, David LANGER, Peter DANCKER, and Juergen BEREITER-HAHN. "Sound attenuation of polymerizing actin reflects supramolecular structures: viscoelastic properties of actin gels modified by cytochalasin D, profilin and α-actinin." Biochemical Journal 355, no. 3 (April 24, 2001): 771–78. http://dx.doi.org/10.1042/bj3550771.

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Polymerization and depolymerization of cytoskeletal elements maintaining cytoplasmic stiffness are key factors in the control of cell crawling. Rheometry is a significant tool in determining the mechanical properties of the single elements in vitro. Viscoelasticity of gels formed by these polymers strongly depends on both the length and the associations of the filaments (e.g. entanglements, annealings and side-by-side associations). Ultrasound attenuation is related to viscosity, sound velocity and supramolecular structures in the sample. In combination with a small glass fibre (2mm×50µm), serving as a viscosity sensor, an acoustic microscope was used to measure the elasticity and acoustic attenuation of actin solutions. Changes in acoustic attenuation of polymerizing actin by far exceed the values expected from calculations based on changes in viscosity and sound velocity. During the lag-phase of actin polymerization, attenuation slightly decreases, depending on actin concentration. After the half-maximum viscosity is accomplished and elasticity turns into steady state, attenuation distinctly rises. Changes in ultrasound attenuation depend on actin concentration, and they are modulated by the addition of α-actinin, cytochalasin D and profilin. Thus absorption and scattering of sound on the polymerization of actin is related to the packing density of the actin net, entanglements and the length of the actin filaments. Shortening of actin filaments by cytochalasin D was also confirmed by electron micrographs and falling-ball viscosimetry. In addition to viscosity and elasticity, the attenuation of sound proved to be a valuable parameter in characterizing actin polymerization and the supramolecular associations of F-actin.

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Kashani Rahimi, Shahab, and Joshua U. Otaigbe. "Polyamide 6 nanocomposites incorporating cellulose nanocrystals prepared byIn situring-opening polymerization: Viscoelasticity, creep behavior, and melt rheological properties." Polymer Engineering & Science 56, no. 9 (April 21, 2016): 1045–60. http://dx.doi.org/10.1002/pen.24335.

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Grosch, K. A. "The Rolling Resistance, Wear and Traction Properties of Tread Compounds." Rubber Chemistry and Technology 69, no. 3 (July 1, 1996): 495–568. http://dx.doi.org/10.5254/1.3538383.

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Abstract The paper gives a brief survey of the state of friction and abrasion research with a view of the possibility to use laboratory methods for the development of new compounds with optimal traction and abrasion properties. It shows that viscoelasticity plays a decisive role in friction and in this way measurements of the dynamic properties give a good indication of the possibilities for good traction properties. However, friction is still a good deal more complex than the modulus or loss factor curves. It takes in different frequency ranges and temperatures in the contact area so that a direct laboratory measurement of these properties is still very desirable. If the speed and temperature correspond to the log aTv values experienced in practice and the laboratory track structure and texture is not too far removed from that of road surfaces, the correlation with road tests is high. To simulate the structure and texture of road surfaces with durable laboratory surfaces, a combination of two surfaces may be necessary. Abrasion is not only influenced by the strength properties of the rubber but also by oxidation and thermal degradation. To give these processes the correct weight in the laboratory, the testing conditions have to be mild and a combination of several conditions is necessary in order to demonstrate the complexity of interactions, which can lead to ranking reversals. Energy dissipation, speed, and abrasive surface structure and texture are identified as prime variables to achieve a high correlation with road wear. Since viscoelasticity, encompassing not only polymer but also filler, oil-extension, curing and other compound additives, plays a major role in both friction and wear, the rolling resistance of the compound is always effected and has to be taken into account. Modern polymerization methods and new filler concepts make it possible to change the viscoelastic properties in such detail that high friction and—to the degree to which strength contributes to wear—high wear resistance can be combined with low rolling resistance. This development has certainly not reached its climax yet. Exciting times lie ahead for tire compounders, polymer- and filler chemists alike.

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Bai, Jingjing, Weijie Ren, Yulong Wang, Xiaoxia Li, Cheng Zhang, Zhenzhong Li, and Zhongyuan Xie. "High-performance thermoplastic polyurethane elastomer/carbon dots bulk nanocomposites with strong luminescence." High Performance Polymers 32, no. 7 (February 27, 2020): 857–67. http://dx.doi.org/10.1177/0954008320907123.

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In this work, high-performance thermoplastic polyurethane elastomer/carbon dots (TPU/CDs) bulk nanocomposites with strong luminescence were fabricated via in situ polymerization. The CDs were synthesized from citric acid and 2-aminothiophenol. Transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and systematic characterization indicated the formation of the CDs and the covalent conjugation of the CDs with TPU. The optical properties of the TPU/CDs nanocomposites were characterized by ultraviolet–visible and fluorescence spectroscopy. Compared to the initial solid-state CDs (the absolute photoluminescence quantum yields (QY): 20%), all the composites exhibited stronger luminescence behavior. When the CDs content was 0.5 wt%, the QY was as high as 68%. Furthermore, the rheological, mechanical, and thermal properties of the nanocomposites were investigated. The rheological properties established the structure–property relationships of the composites. The incorporation of the CDs enhanced the elastic response in viscoelasticity of the nanocomposites. The tensile strength of 1.0 wt% CDs loaded TPU increased from 18.2 MPa to 28.6 MPa, nearly 57% higher than that of the neat TPU. Given the excellent Ag+ detection performance of the CDs, the high QY and the processability of the nanocomposites, Ag+ detection experiments for the composite film were performed. The study will facilitate the applications of luminescent nanocomposites in potential fields.

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Zhang, Yang, Jincheng Mao, Jinzhou Zhao, Xiaojiang Yang, Tao Xu, Chong Lin, Jinhua Mao, et al. "Preparation of a Hydrophobic-Associating Polymer with Ultra-High Salt Resistance Using Synergistic Effect." Polymers 11, no. 4 (April 4, 2019): 626. http://dx.doi.org/10.3390/polym11040626.

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Polymer, SRP-2-1, was synthesized by micellar polymerization and characterized by 1H NMR. Salt tolerance and viscoelasticity tests verified that the salt resistance of SRP-2-1 was promoted by the synergistic effects of oxyethylene groups, sulfonate, and hydrophobic chains. It is suggested that the structure of SRP-2-1 became more compact with increasing salinity. Furthermore, a mechanism is proposed as to why SRP-2-1 solution has excellent salt-resistance properties. The experimental results indicate that, because of the good shear resistance properties, the polymer SRP-2-1 could be used as an alternative in many fields, for instance in fracturing fluids, enhanced oil recovery, and sewage treatment.

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Zhang, Yang, Jincheng Mao, Jinzhou Zhao, Tao Xu, Anqi Du, Zhaoyang Zhang, Wenlong Zhang, and Shaoyun Ma. "Preparation of a Novel Fracturing Fluid System with Excellent Elasticity and Low Friction." Polymers 11, no. 10 (September 20, 2019): 1539. http://dx.doi.org/10.3390/polym11101539.

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The quaternary polymer was synthesized by radical polymerization and characterized by 1H NMR. The tests of critical associating concentration and SEM suggest that there is a multilayered and robust network structure in the polymer solution. An excellent elasticity in the polymer solution by the first normal stress difference, viscoelasticity, and thixotropy was observed. The critical crosslinker concentration of polymer with sodium dodecyl sulfate and its interaction mechanism were investigated. According to the reaction kinetics, the supramolecular structure had the lowest activation energy, stable network structure, and greater thermal stability. Then the polymer was employed in the fracturing fluid due to its excellent elasticity using the intermolecular forces, which showed superior sand suspension capacity by dynamic sand suspension measurement. Meanwhile, a theoretical analysis was proposed as to why polymer solution has excellent suspension and drag reduction properties. Therefore, this polymer could be an alternative in many fields, especially in fracking, which is significant for the development of oil and gas resources in deep wells.

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Chen, Qingyuan, Zhongbin Ye, Lei Tang, Tao Wu, Qian Jiang, and Nanjun Lai. "Synthesis and Solution Properties of a Novel Hyperbranched Polymer Based on Chitosan for Enhanced Oil Recovery." Polymers 12, no. 9 (September 18, 2020): 2130. http://dx.doi.org/10.3390/polym12092130.

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A new type of chitosan-modified hyperbranched polymer (named HPDACS) was synthesized through the free-radical polymerization of surface-modified chitosan with acrylic acid (AA) and acrylamide (AM) to achieve an enhanced oil recovery. The optimal polymerization conditions of HPDACS were explored and its structure was characterized by Fourier-transform infrared spectroscopy, hydrogen nuclear magnetic resonance, and environmental scanning electron microscopy. The solution properties of HPDACS in ultrapure water and simulated brine were deeply studied and then compared with those of partially hydrolyzed polyacrylamide (HPAM) and a dendritic polymer named HPDA. The experimental results showed that HPDACS has a good thickening ability, temperature resistance, and salt resistance. Its viscosity retention rate exceeded 79.49% after 90 days of aging, thus meeting the performance requirements of polymer flooding. After mechanical shearing, the viscosity retention rates of HPDACS in ultrapure water and simulated brine were higher than those of HPAM and HPDA, indicating its excellent shear resistance and good viscoelasticity. Following a 95% water cut after preliminary water flooding, 0.3 pore volume (PV) and 1500 mg/L HPDACS solution flooding and extended water flooding could further increase the oil recovery by 19.20%, which was higher than that by HPAM at 10.65% and HPDA at 13.72%. This finding indicates that HPDACS has great potential for oil displacement.

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Mao, Jincheng, Hongzhong Tan, Bo Yang, Wenlong Zhang, Xiaojiang Yang, Yang Zhang, and Heng Zhang. "Novel Hydrophobic Associating Polymer with Good Salt Tolerance." Polymers 10, no. 8 (August 1, 2018): 849. http://dx.doi.org/10.3390/polym10080849.

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A hydrophobic associating polymer named DiPHAM (acrylamide/sodium acrylamide-2-methylpropanesulfonic/sodium acrylate/N,N-di-n-dodecylacrylamide) with good salt tolerance was synthesized via photo-initiation polymerization. The critical association concentration (CAC) of DiPHAM was determined by viscosity changes to be 490 mg/L with different DiPHAM concentrations and particle sizes varied under such dynamic conditions. The influences of aqueous metal ions with different charges on its aqueous solution were investigated by measuring apparent viscosity, viscoelasticity, thixotropy, rheology, and particle size, and by SEM observation. The apparent viscosity of the DiPHAM solution was affected by metal ions to some extent, but the viscosity of the polymer can be still maintained at 55 mPa·s under 20 × 104 mg/L NaCl. Divalent metal ions show greater impact on DiPHAM aqueous solutions, but the polymer solutions showed resistance to the changes caused in viscosity, structure, and viscoelasticity by Ca2+ and Mg2+ ions. The salt tolerance of DiPHAM is due to the combination of hydrophobic association, the electrostatic shield, and double layer compression of the hydration shell. Increasing the ion concentration enhances the dehydration and further compresses the hydration shell, making the non-structural viscosity decrease, even “salting out”. Measurements of rheological properties showed that DiPHAM solutions could maintain a relatively high viscosity (0.6%-71 mPa·s/0.3%-50 mPa·s) after 120 min of continuous shearing (170 s−1) at 140 °C. Under high-salinity (5000 mg/L Ca2+/3000 mg/L Mg2+) conditions, the solution with 0.6 wt% DiPHAM still maintained a high viscosity (50 mPa·s/70 mPa·s) after continuously shearing for 120 min at 120 °C and 170 s−1. The good salt tolerance of DiPHAM can lead to a variety of applications, including in fracturing fluids for enhanced oil recovery (EOR) and in sewage treatment.

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Bai, Cancan, Yangchuan Ke, Xu Hu, Liang Xing, Yi Zhao, Shichao Lu, and Yuan Lin. "Preparation and properties of amphiphilic hydrophobically associative polymer/ montmorillonite nanocomposites." Royal Society Open Science 7, no. 5 (May 2020): 200199. http://dx.doi.org/10.1098/rsos.200199.

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In this research, a novel amphiphilic hydrophobically associative polymer nanocomposite (ADOS/OMMT) was prepared using acrylamide (AM), sodium 4-vinylbenzenesulfonate (SSS), N, N′-dimethyl octadeyl allyl ammonium bromide (DOAAB) and organo-modified montmorillonite (OMMT) through in situ polymerization. Both X-ray diffraction patterns and transmission electron microscopy images verified the dispersion morphology of OMMT in the copolymer matrix. Then, the effect of the introduction of OMMT layers on the copolymer properties was studied by comparing with pure copolymer AM/SSS/DOAAB (ADOS). The thermal degradation results demonstrated that the thermal stability of the ADOS/OMMT were better than pure copolymer ADOS. During the solution properties tests, ADOS/OMMT nanocomposite was superior to ADOS in viscosifying ability, temperature resistance, salt tolerance, shear resistance and viscoelasticity, which was because OMMT contributed to enhance the hydrophobic association structure formed between polymer molecules. Additionally, the ADOS/OMMT nanocomposite exhibited more excellent interfacial activity and crude oil emulsifiability in comparison to pure copolymer ADOS. These performances indicated ADOS/OMMT nanocomposite had good application prospects in tertiary recovery.

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Baeza, Guilhem P., Anne-Caroline Genix, Nathalie Paupy-Peyronnet, Christophe Degrandcourt, Marc Couty, and Julian Oberdisse. "Revealing nanocomposite filler structures by swelling and small-angle X-ray scattering." Faraday Discussions 186 (2016): 295–309. http://dx.doi.org/10.1039/c5fd00117j.

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Polymer nanocomposites are used widely, mainly for the industrial application of car tyres. The rheological behavior of such nanocomposites depends in a crucial way on the dispersion of the hard filler particles – typically silica nanoparticles embedded in a soft polymer matrix. It is thus important to assess the filler structure, which may be quite difficult for aggregates of nanoparticles of high polydispersity, and with strong interactions at high loading. This has been achieved recently using a coupled TEM/SAXS structural model describing the filler microstructure of simplified industrial nanocomposites with grafted or ungrafted silica of high structural disorder. Here, we present an original method capable of reducing inter-aggregate interactions by swelling of nanocomposites, diluting the filler to low-volume fractions. Note that this is impossible to reach by solid mixing due to the large differences in viscoelasticity between the composite and the pure polymer. By combining matrix crosslinking, swelling in a good monomer solvent, and post-polymerization of these monomers, it is shown that it is possible to separate the filler into small aggregates. The latter have then been characterized by electron microscopy and small-angle X-ray scattering, confirming the conclusions of the above mentioned TEM-SAXS structural model applied directly to the highly loaded cases.

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Skvortsov, Ivan Y., Valery G. Kulichikhin, Igor I. Ponomarev, Lydia A. Varfolomeeva, Mikhail S. Kuzin, Kirill M. Skupov, Yulia A. Volkova, Dmitry Y. Razorenov, and Olga A. Serenko. "Solubility, Rheology, and Coagulation Kinetics of Poly-(O-Aminophenylene)Naphthoylenimide Solutions." Polymers 12, no. 11 (October 23, 2020): 2454. http://dx.doi.org/10.3390/polym12112454.

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The effect of temperature and storage time at a constant temperature on the stability of poly-(o-aminophenylene)naphthoylenimide solutions in N-methylpyrrolidone has been analyzed using rotational rheometry. A temperature–time window beyond which an irreversible change in the viscoelastic properties of solutions due to cumulative reactions of continuous polymerization and possible intramolecular cyclization has been detected. The influence of polymer concentration and its molecular weight on the rheological properties of solutions determining the choice of methods for their processing into fibers and films has been investigated. The effect of non-solvents (water and ethanol) additives on the rheological properties of solutions and the kinetics of their coagulation has been studied. Dosed addition of non-solvent into the solution promotes a significant increase in the viscoelasticity up to gelation and phase separation. Non-solvent presence in the polymer solutions reduces the activity of the solvent, accelerates the movement of the diffusion front at coagulation, and minimizes the number of macro defects. The combination of parameters under investigation renders it possible for the first time to develop new principles modifying dopes for wet spinning into aqueous or ethanol coagulation bath and finally to obtain a heat- and fire-resistant polynaphthoylenebenzimidazole fibers.

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Sarikaya, Rizacan, Linyong Song, Qiang Ye, Anil Misra, Candan Tamerler, and Paulette Spencer. "Evolution of Network Structure and Mechanical Properties in Autonomous-Strengthening Dental Adhesive." Polymers 12, no. 9 (September 12, 2020): 2076. http://dx.doi.org/10.3390/polym12092076.

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The inherent degradation property of most dental resins in the mouth leads to the long-term release of degradation by-products at the adhesive/tooth interface. The by-products increase the virulence of cariogenic bacteria, provoking a degradative positive-feedback loop that leads to physicochemical and mechanical failure. Photoinduced free-radical polymerization and sol‒gel reactions have been coupled to produce a novel autonomous-strengthening adhesive with enhanced hydrolytic stability. This paper investigates the effect of network structure on time-dependent mechanical properties in adhesives with and without autonomous strengthening. Stress relaxation was conducted under 0.2% strain for 8 h followed by 40 h recovery in water. The stress‒time relationship is analyzed by nonlinear least-squares data-fitting. The fitted Prony series predicts the sample’s history under monotonic loading. Results showed that the control failed after the first loading‒unloading‒recovery cycle with permanent deformation. While for the experimental sample, the displacement was almost completely recovered and the Young’s modulus increased significantly after the first test cycle. The experimental polymer exhibited higher degree of conversion, lower leachate, and time-dependent stiffening characteristics. The autonomous-strengthening reaction persists in the aqueous environment leading to a network with enhanced resistance to deformation. The results illustrate a rational approach for tuning the viscoelasticity of durable dental adhesives.

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Kim, Jihye, Changsoo Ryu, Jongkwan Ha, Junmyoung Lee, Donghwi Kim, Minkyoo Ji, Chi Soo Park, Jaeryong Lee, Dae Kyong Kim, and Ha Hyung Kim. "Structural and Quantitative Characterization of Mucin-Type O-Glycans and the Identification of O-Glycosylation Sites in Bovine Submaxillary Mucin." Biomolecules 10, no. 4 (April 20, 2020): 636. http://dx.doi.org/10.3390/biom10040636.

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Bovine submaxillary mucin (BSM) is a gel-forming glycoprotein polymer, and Ser/Thr-linked glycans (O-glycans) are important in regulating BSM’s viscoelasticity and polymerization. However, details of O-glycosylation have not been reported. This study investigates the structural and quantitative characteristics of O-glycans and identifies O-glycosylation sites in BSM using liquid chromatography–tandem mass spectrometry. The O-glycans (consisting of di- to octa-saccharides) and their quantities (%) relative to total O-glycans (100%; 1.1 pmol per 1 μg of BSM) were identified with 14 major (>1.0%), 12 minor (0.1%–1.0%), and eight trace (<0.1%) O-glycans, which were characterized based on their constituents (sialylation (14 O-glycans; 81.9%, sum of relative quantities of each glycan), non-sialylation (20; 18.1%), fucosylation (20; 17.5%), and terminal-galactosylation (6; 3.6%)) and six core structure types [Gal-GalNAc, Gal-(GlcNAc)GalNAc, GlcNAc-GalNAc, GlcNAc-(GlcNAc)GalNAc, and GalNAc-GalNAc]. O-glycosylation sites were identified using O-glycopeptides (bold underlined; 56SGETRTSVI, 259SHSSSGRSRTI, 272GSPSSVSSAEQI, 307RPSYGAL, 625QTLGPL, 728TMTTRTSVVV, and 1080RPEDNTAVA) obtained from proteolytic BSM; these sites are in the four domains of BSM. The gel-forming mucins share common domain structures and glycosylation patterns; these results could provide useful information on mucin-type O-glycans. This is the first study to characterize O-glycans and identify O-glycosylation sites in BSM.

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Chen, Yuanyuan, Kaiyue Lu, Yuhan Song, Jingquan Han, Yiying Yue, Subir Kumar Biswas, Qinglin Wu, and Huining Xiao. "A Skin-Inspired Stretchable, Self-Healing and Electro-Conductive Hydrogel with a Synergistic Triple Network for Wearable Strain Sensors Applied in Human-Motion Detection." Nanomaterials 9, no. 12 (December 6, 2019): 1737. http://dx.doi.org/10.3390/nano9121737.

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Hydrogel-based strain sensors inspired by nature have attracted tremendous attention for their promising applications in advanced wearable electronics. Nevertheless, achieving a skin-like stretchable conductive hydrogel with synergistic characteristics, such as ideal stretchability, excellent sensing performance and high self-healing efficiency, remains challenging. Herein, a highly stretchable, self-healing and electro-conductive hydrogel with a hierarchically triple-network structure was developed through a facile two-step preparation process. Firstly, 2, 2, 6, 6-tetrametylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils were homogeneously dispersed into polyacrylic acid hydrogel, with the presence of ferric ions as an ionic crosslinker to synthesize TEMPO-oxidized cellulose nanofibrils/polyacrylic acid hydrogel via a one-pot free radical polymerization. A polypyrrole conductive network was then incorporated into the synthetic hydrogel matrix as the third-level gel network by polymerizing pyrrole monomers. The hierarchical 3D network was mutually interlocked through hydrogen bonds, ionic coordination interactions and physical entanglements of polymer chains to achieve the target composite hydrogels with a homogeneous texture, enhanced mechanical stretchability (elongation at break of ~890%), high viscoelasticity (maximum storage modulus of ~27.1 kPa), intrinsic self-healing ability (electrical and mechanical healing efficiencies of ~99.4% and 98.3%) and ideal electro-conductibility (~3.9 S m−1). The strain sensor assembled by the hybrid hydrogel, with a desired gauge factor of ~7.3, exhibits a sensitive, fast and stable current response for monitoring small/large-scale human movements in real-time, demonstrating promising applications in damage-free wearable electronics.

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Journal articles on the topic 'Viscoelasticity. Polymers. Polymerization'

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