Free Polymer Research Articles

LPG2 Gene Duplication in Leishmania infantum: A Case for CRISPR-Cas9 Gene Editing.

On the surface of the Leishmania promastigote, phosphoglycans (PG) such as lipophosphoglycan (LPG), proteophosphoglycan (PPG), free phosphoglycan polymers (PGs), and acid phosphatases (sAP), are dominant and contribute to the invasion and survival of Leishmania within the host cell by modulating macrophage signaling and intracellular trafficking. Phosphoglycan synthesis depends on the Golgi GDP-mannose transporter encoded by the LPG2 gene. Aiming to investigate the role of PG-containing molecules in Leishmania infantum infection process, herein we describe the generation and characterization of L. infantum LPG2-deficient parasites. This gene was unexpectedly identified as duplicated in the L. infantum genome, which impaired gene targeting using the conventional homologous recombination approach. This limitation was circumvented by the use of CRISPR/Cas9 technology. Knockout parasites were selected by agglutination assays using CA7AE antibodies followed by a lectin (RCA 120). Five clones were isolated and molecularly characterized, all revealing the expected edited genome, as well as the complete absence of LPG and PG-containing molecule expression. Finally, the deletion of LPG2 was found to impair the outcome of infection in human neutrophils, as demonstrated by a pronounced reduction (~83%) in intracellular load compared to wild-type parasite infection. The results obtained herein reinforce the importance of LPG and other PGs as virulence factors in host-parasite interactions.

Differentiation of Chemisorption and Physisorption of Carbon Dioxide on Imidazolium-type Poly(ionic liquid) Brushes

Amine-functionalized imidazolium-based poly(ionic liquid) brushes on mesoporous silica were synthesized via “grafting through” technique and were applied as model sorbents to understand physisorption and chemisorption of carbon dioxide molecules. The experimental results reveal that the total adsorption capacity of model sorbents derived from temperature programmed desorption (TPD) approach reaches 1.72 mmol·g−1 that is much higher than the sum of adsorption capacity of bare mesoporous silica and free polymers at 25 °C under carbon dioxide partial pressure of 0.2 bar. The proposed physical adsorption and chemical adsorption of carbon dioxide molecules in TPD response curves were validated by volumetric desorption measurement. It is also observed that physical adsorption is completely reversible and chemical adsorption is irreversible. The results demonstrate that the temperature programmed desorption technique is an effective approach to differentiate chemisorption and physisorption of gaseous species on solid sorbents, which is beneficial for understanding of adsorption mechanism and materials design.

Tuning Composition of Polymer and Porous Silicon Composite Nanoparticles for Early Endosome Escape of Anti-microRNA Peptide Nucleic Acids.

Porous silicon nanoparticles (PSNPs) offer tunable pore structure and easily modified surface chemistry, enabling high loading capacity for drugs with diverse chemicophysical properties. While PSNPs are also cytocompatible and degradable, PSNP integration into composite structures can be a useful approach to enhance carrier colloidal stability, drug-cargo loading stability, and endosome escape. Here, we explored PSNP polymer composites formed by coating of oxidized PSNPs with a series of poly[ethylene glycol-block-(dimethylaminoethyl methacrylate-co-butyl methacrylate)] (PEG-DB) diblock copolymers with varied molar ratios of dimethylaminoethyl methacrylate (D) and butyl methacrylate (B) in the random copolymer block. We screened and developed PSNP composites specifically toward intracellular delivery of microRNA inhibitory peptide nucleic acids (PNA). While a copolymer with 50 mol % B (50B) is optimal for early endosome escape in free polymer form, its pH switch was suppressed when it was formed into 50B polymer-coated PSNP composites (50BCs). We demonstrate that a lower mol % B (30BC) is the ideal PEG-DB composition for PSNP/PEG-DB nanocomposites based on having both the highest endosome disruption potential and miR-122 inhibitory activity. At a 1 mM PNA dose, 30BCs facilitated more potent inhibition of miR-122 in comparison to 40BC (p = 0.0095), 50BC (p < 0.0001), or an anti-miR-122 oligonucleotide delivered with the commercial transfection reagent Fugene 6. Using a live cell galectin 8-based endosome disruption reporter, 30BCs had greater endosomal escape than 40BCs and 50BCs within 2 h after treatment, suggesting that rapid endosome escape correlates with higher intracellular bioactivity. This study provides new insight on the polymer structure-dependent effects on stability, endosome escape, and cargo intracellular bioavailability for endosomolytic polymer-coated PSNPs.

Alkaline stability of ether bond free fluorene-based anion exchange polymer containing cycloaliphatic quaternary ammonium groups

Quaternary piperidinium cation was incorporated into aryl-ether-bond-free fluorene-based polymer by flexible alkyl side chains to synthesize a highly conductive and chemically stable anion exchange membrane (AEM). The membrane of the OH− form shows good solubility in dimethyl sulfoxide and methanol but not soluble in water. In a fully hydrated state, the OH− conductivity reached 58 mS cm−1 at 80 °C. The results of 1H NMR spectra revealed that the alkyl-substituted N-methylpiperidinium cationic group was excellent alkaline stable as only 13% cationic group was degraded after 168 h storage in 1 M NaOH solution at 80 °C.

Rational design of phosphonate/quaternary amine block polymer as an high-efficiency antibacterial coating for metallic substrates

Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices. Here, we report a novel phosphonate/quaternary amine block polymer as the high-efficiency antibacterial coating for metallic substrates. Three pDEMMP-b-pTMAEMA block polymers that bearing identical phosphonate segments (repeat units of 15) but varied cationic segments (repeat units of 8, 45, and 70) were precisely prepared. Stable cationic polymer coatings were constructed on TC4 substrates based on the strong covalent binding between phosphonate group and metallic substrate. Robust relationship between the segment chain length of the polymer coating and the antibacterial property endowed to the substrates have been established based on quantitative and qualitative evaluations. Results showed that the antibacterial rate of the modified TC4 surface were 95.8 % of S. aureus and 92.9 % of E. coli cells attached. Interestingly, unlike the cationic free polymer or cationic hydrogels, the surface anchored cationic polymers do compromise the viability of the attached C2C12 cells but without significant cytotoxicity. In addition, the phosphonate/quaternary amine block polymers can be easily constructed on titanium, stainless steel, and Ni/Cr alloy with significantly improved antibacterial property, indicating the generality of the block polymer for surface antibacterial modification of bio-metals.

Greatly Enhanced Gas Selectivity in Mixed-Matrix Membranes through Size-Controlled Hyper-cross-linked Polymer Additives

Membrane technology without a phase-change process has demonstrated its low-cost, high-energy-efficiency advantages. High fractional free volume polymers of intrinsic microporosity (PIMs), such as ...

Control of Physical Aging in Super-Glassy Polymer Mixed Matrix Membranes.

ConspectusSince the discovery of polymers of intrinsic microporosity (PIMs) in 2004, the fast size-selective interconnected pore cavities of the polymers have caused the upper bound of membrane performance to be revised, twice. Simultaneously, porous materials have meant that mixed matrix membranes (MMMs) are now a relatively simple method of enhancing transport properties. While there are now reliable routes with mixed matrices to improve the fundamental transport properties of membrane materials, many of the other properties crucial for separation applications remain largely unaddressed. Physical aging severely affects membrane performance over time, especially for those prepared from high fractional free volume polymers. Gradual densification of the glassy polymer chains causes the connected pore channels present in these materials to constrict. Studies now suggest that aging of superglassy polymer materials is a two-step process; a rapid densification occurs within the first few days, followed by a gradual rearrangement of packed chains over longer time frames toward a theoretical equilibrium state. Although advantageous in terms of size selectivity, the considerable drop in permeation over the days and weeks after manufacture greatly impacts material applicability. While often still permeating faster than traditional membrane materials, the continuous gradual collapse of cavities in these polymers are a significant challenge in the application of high free volume polymer membranes. In 2014, we discovered that the porous aromatic framework PAF-1 not only greatly improved the membrane's void space and speed of gas transport but also seemingly froze several glassy polymers in a low-density state, holding the polymer's pore channels open, a process termed as Porosity Induced Side chain Adsorption (PISA).This discovery of PISA fundamentally challenged the conventional wisdom at the time that the aging rate could only be addressed by densification of the polymer. Unlike other high-performance glassy polymers, membranes containing PAF-1 can retain their high permeability for more than a year. Several other examples of antiaging behavior have been subsequently reported by the team, where control of aging rate as a function of gas penetrant, selectivity increases, and stability at higher pressures was reported. These works also demonstrate that these mixed matrix systems had applicability for several other separations, including pervaporation, solvent nanofiltration, and as separators for energy applications. In our subsequent studies, the antiaging mechanism has been elucidated as an effect of the interaction between the polymer's accessible pendant methyl group and the aromatic pore surface of PAF-1 or other antiaging additives. In otherwise identical MMMs, where this hypothesized methyl-π interaction is either absent or interrupted, we find that the antiaging behavior expected by the fixation of the polymer chains to the pore surface and PAF-1 does not occur. As a design approach for mixed matrix membranes, targeted interfacial interactions are a promising pathway for developing other stable membranes, enabling the exciting class of PIM materials to improve industrial separation efficiency.

STRUCTURE-ACTIVITY RELATIONSHIPS AND SURFACE IMMOBILIZATION OF POLYCATIONIC ANTIMICROBIALS

Antimicrobial agents have been the subject of scientific interest for the last few decades. However, the emergence of a novel coronavirus and pandemic that ensued has brought a new sense of urgency to the field of antibacterial research. The most urgent needs to mitigate the pandemic are self-disinfecting health equipment and antimicrobial protective equipment such as gowns for healthcare workers and face masks for the general public. At a time of high demand for antimicrobial products, understanding the mechanisms involved in antimicrobial polymers will be a benefit. In this review, the definition of antimicrobials and their classification according to the mode of action, as well as their chemical structure, were explained and used to build the fundamental understanding about antimicrobials and the working principles behind their action. The discussion continued with factors that affect the antimicrobial activity, which is the focus of the review. The first part of the review deals with free antimicrobial polymers in solution. The effect of molecular weight, counterions, spacer length and alkyl chain to the efficacy of antimicrobial polymers are highlighted and discussed at length. Focus in the second part shifts towards surface-immobilized antimicrobial polymers and their methods of immobilization.

Controlled Radical Polymerization toward Ultra-High Molecular Weight by Rationally Designed Borane Radical Initiators

Summary Ultra-high-molecular-weight (UHMW) polymers can display outstanding properties; however, it is challenging to synthesize UHMW polymers by using external free radical initiators. To address this, here, we report the ration design and adoption of B-alkylcatecholborane (RBCat) as a radical initiator in controlled radical polymerization in the presence of a chain-transfer agent. The autoxidation of RBCat with one alkyl substituent generates only one alkyl radical. The oxygen is incorporated and stored in the oxidized form (ROOB-Cat) that slowly releases the alkyl radical. The rationally designed alkyl radical is proposed to preferentially activate the chain-transfer agent (CTA) and grow the polymer chain from CTA, so limited free polymer chains are formed from the initiating alkyl radicals. Polymerizations of (meth)acrylates are achieved with narrow molecular weight distribution (Ð = 1.10) and predetermined molecular weights even in a UHMW range (up to 3 million). The successful chain extension of UHMW indicates the high degree of control of the polymerization.

Surface Nanostructures Based on Assemblies of Polymer Brushes.

Studies on the fabrication of hierarchical surface nanostructures have significantly promoted the development of materials with new surface properties and functionalities. In this Minireview, progress on the fabrication of surface nanostructures based on surface organization of polymer brushes are outlined. In the past decades, self-assemblies of polymer brushes, including homopolymer, block-copolymer and mixed-polymer brushes, have aroused great interest in the fields of chemistry and materials science. Recent studies demonstrate that surface co-assemblies of polymer brushes and free polymer chains on solid surfaces are considered as an efficient approach to the preparation of hierarchical nanostructures. Some typical surface nanostructures and properties achieved through surface co-assembly approach are reviewed in this article. Meanwhile, the fundamental problems in the co-assembly approach are discussed and the potential applications of the hierarchical surface nanostructures are presented.

Modification of cellulose nanocrystal with dual temperature- and CO2-responsive block copolymers for ion adsorption applications

Cellulose nanocrystal (CNC)-grafted smart polymers have potential applications as adsorbents by providing simple regeneration process. In this study, carbon dioxide (CO2)- and temperature-responsive free block copolymers of N-isopropylacrylamide and (2-dimethylaminoethyl) methacrylate with different block lengths were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. In addition, CNC was modified with the similar block copolymers by surface-initiated RAFT method. The synthesized block copolymers were used in nitrate ion removal from aqueous solutions. The synthesis process was confirmed by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance (1H NMR) analysis, thermal gravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Stimuli-responsivity of the free polymers was studied by pH measurement, turbidity investigation, and dynamic light scattering analysis. CO2-responsivity of the block copolymers in aqueous solution was confirmed by reduction of pH in the presence of CO2 by protonation of the PDMAEMA blocks. The copolymers with higher length of PDMAEMA showed highly intense CO2-responsivity. Deprotonation of the PDMAEMA units by purging N2 represents reversible responsivity of the copolymers. Turbidity analysis showed different critical solution temperatures (CST) for the block copolymers with various block lengths. Two different micellar and vesicular morphologies were observed for the self-assembled copolymers at temperatures above and below CST of the copolymers, which is related to the hydrophobic/hydrophilic block ratio. CO2-switched nitrate ion adsorption from aqueous solution at two temperatures (37 and 60 °C) was studied by UV–vis spectroscopy using the synthesized products as adsorbent. Adsorption of nitrate ions from aqueous solutions was increased by protonation of the PDMAEMA segments upon CO2 purging. Presence of CNC, morphology of the self-assembled copolymers, temperature, and time of CO2 purging affect the nitrite ion adsorption capacity. The maximum adsorption capacity (420 mg/g) is related to the sample with vesicular assemblies in aqueous solution and higher PDMAEMA block length at temperatures below CST of the block copolymer. N2 purging resulted in deprotonation of the PDMAEMA blocks and regeneration of the samples. Finally, the CNC substrate can be used in regeneration of the samples with simple filtration process in addition to the stimuli-regeneration process.

Interaction of Different Charged Polymers with Potassium Ions and Their Effect on the Yield Stress of Highly Concentrated Glass Bead Suspensions.

The interaction of different charged polymers, namely anionic polycarboxylate superplasticizer (PCE) and neutral polyethylene glycol (PEG) with potassium ions, and their effect on the yield stress of highly concentrated glass bead suspension (GBS), were studied under different concentrations of potassium ions ([K+]). It was found that, compared to the neutral PEG, the negatively charged PCE can be adsorbed on glass beads (GB), and then decreases the yield stress of GBS. The increasing concentration of free polymer in the interstitial liquid phase with the increased polymer dosage leads to the higher yield stress of GBS, which may be caused by the higher depletion force. In addition, this effect is also related to the charge density of the polymer and the [K+] in the solution. Along with the increase in [K+], the yield stress of GBS increases significantly with the addition of PCE, but this cannot be observed with PEG, which indicates that potassium ions can interact with negatively charged PCE instead of the neutral PEG. At last, the interparticle forces between two single GB with adsorbed PCE in solutions containing [K+] and PCE were measured by colloidal probe atomic force microscopy to better understand the interaction of the charged polymer with counterions.

Statistical Analysis Investigation on Vegetable Oils Stability during Deep Frying using Selected Quality Parameters

The frying process is complicated because of a large number of parameters involved and the interactions between them. High stability liquid oils are in great demand. The best way to decide on the fats and oils suitability for frying is to study their natural stability to oxidation. In this study, consecutive deep-fat frying was done by using potato chips in palm oil, cottonseed oil and groundnut oil at 170 °C. All oils used were refined, bleached and deodorised from good quality authentic crude oils. The study was used to investigate the influence of frying time on oil quality by measuring the concentration of tocopherol content (TC), iodine value (IV), peroxide value (PV), free fatty acids (FFA) and polymer content (PC). Changes in these parameters were determined on the oil samples taken periodically during frying. A MANOVA statistical model was used for the investigations of oil quality parameters while used continuously in frying potato chips. The analysis which was implemented using XLSTAT is showing that the frying time has a significant impact on the compositions of the frying oil. A significant increase in PV, FFA and PC was observed during frying while a decrease in the concentration of TC and IV values was observed. The result concluded that refined, bleached deodorised palm oil is more stable during deep-fat frying compared to cottonseed oil followed by groundnut oil.

Effect of side chain length change of polycarboxylate-ether based high range water reducing admixture on properties of self-compacting concrete

In this study, the effect of side chain length, molecular weights changes and adsorption amount of polycarboxylate ether-based high range water reducing admixtures having constant main chain length, free non-ionic amount and anionic/non-ionic ratio on fresh properties, early and advanced age compressive strength, water absorption capacity and ultrasonic pulse velocity value of self-compacting concretes (SCC) were investigated. FTIR (Fourier transform infrared) and GPC (Gel Permeation Chromatography) analyzes were carried out to characterize admixtures. According to the test results, all SCC mixtures produced within the scope of the study provided EFNARC criteria. If the admixture side chain length is higher or shorter than a certain value, the admixture requirement is increased for providing the desired target slump-flow value in SCC mixtures. This negative effect is thought to be due to the weakness of the steric hindrance effect for admixture with short side chain, the low adsorption amount and interlacing risk of side chains for admixture with the long side chain. On the other hand, the increase in the side chain length of the admixtures had a positive effect on the time-dependent fresh state performance of the mixtures. This positive effect is thought to be due to the low adsorption amount of the admixture, the increase in the side chain length and the increase of the non-adsorbed free polymer content in the mixture. While side chain length change of the water reducing admixture affected the 1 and 2-day compressive strength values of SCC mixtures, the 3, 7 and 28-day compressive strengths and the 28-day water absorption, ultrasound and dynamic elasticity modulus values did not significantly affect.

Synergistic action of doxorubicin and 7-Ethyl-10-hydroxycamptothecin polyphosphorylcholine polymer prodrug

There are opportunities for improvements to the efficiency and toxicity of widely used cancer chemotherapy agents such as doxorubicin (DOX·HCl) and 7-Ethyl-10-hydroxycamptothecin (SN38). We developed a safe and effective combination therapy by encapsulating DOX into micelles of a zwitterionic polymer prodrug, SN38 conjugate of poly (α-azide caprolactone-co-caprolactone)-b-poly (2-methacryloyloxyethyl phosphorylcholine [P(CL/CL-g-SN38)-b-PMPC)] which was described in our previous work. The polymer prodrug micelles displayed a higher loading capacity of DOX due to the π-π stacking effect between DOX and SN38 in comparison with the micelles self-assembled by prodrug's precursor, poly(α-azide caprolactone-co-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine (P(ACL/CL)-b-PMPC). The DOX loaded prodrug micelles decelerated the release of DOX, and also prolonged its circulation. The micelles showed favorable cellular internalization by 4T1 cells. DOX loaded SN38 prodrug micelles displayed good in vitro anticancer effects owing to the synergistic action of doxorubicin and SN38 and were as effective as DOX·HCl, but with lower toxicity than DOX·HCl. Given the synergetic effects of free drug and polymer prodrug, this nanomedicine may offer a safe and effective drug delivery methodology for conventional drug formations.

Fabrication of oriented electrospun cellulose nanocrystals–polystyrene composite fibers on a rotating drum

ABSTRACTNitrobenzene (CNC‐1), trifluoromethyl benzene (CNC‐2) modified and polystyrene‐grafted (CNC‐g) cellulose nanocrystals in polystyrene (PS)‐N,N dimethylformamide (DMF) solutions were electrospun and collected as stretched and aligned fibers on a rotating drum. Scanning electron microscope pictures showed significant alignment in the case of unmodified and nitrobenzene‐modified CNC‐1/PS nanocomposite fibers once the linear speed of rotor reached to 15 m s−1. Fiber diameter decrease was more strong with rotor speed increase in the case of trifluoromethyl benzene modified (CNC‐2) and polystyrene‐grafted (CNC‐g) cellulose nanocrystals/PS systems. Dynamic mechanical analysis including storage and elastic modulus of electrospun‐oriented fibers were performed on surface‐modified and polymer‐grafted CNC/PS samples. According to α transition peak, the increase in the glass‐transition temperature with filler concentration was the highest in polymer‐grafted CNC‐g/PS composite fibers. It was due to the interpenetration of grafted polymer brushes and free polymer chains in continuous phase and resulted in restrictions of motions of polymer chains in the PS matrix. The elastic moduli of nitrobenzene (CNC‐1) and trifluoromethyl benzene (CNC‐2)‐modified CNC‐filled PS composite fibers agreed well with percolation model, which indicates the CNC–CNC interactions and network formation with an increase in concentration. Magnitude of the elastic modulus of polymer grafted CNC‐g at 0.33 vol % in PS was significantly higher than the prediction from percolation theory. It was due the immobilized polymer chains around CNC‐g particles. However, grafted polymer chains, at higher CNC concentrations acted like stickers among CNC particles and caused CNC agglomerates with entrapped free polystyrene from the matrix, thus caused a decrease in the elastic modulus. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48942.

Elucidating the Role of Ionomer in the Performance of Platinum Group Metal-free Catalyst Layer via in situ Electrochemical Diagnostics

The ionomer content in platinum group metal (PGM)-free polymer electrolyte fuel cell (PEFC) cathode catalyst layer (CCL) plays an important role in the electrode gas transport properties, proton conductivity, and hence, membrane electrode assembly (MEA) performance. In this work, the ionomer content in the CCL is varied, influencing electrode microstructure by altering porosity, tortuosity, as well as ionomer distribution and coverage of the catalyst particles. A novel technique consisting of a H2 pump, combined with a Pt black sensor layer, is used to measure the bulk mass transport resistance of a series of PGM-free CCL prepared with different ionomer contents. The values for bulk electrode mass transport resistance are contrasted with electrode proton transport resistance in the cathode catalyst layer, establishing a clearly defined trade-off between two key performance limiting phenomena and identifying a need for novel PGM-free electrode fabrication strategies.

Monte Carlo simulation on the adsorption of polymer chains on polymer brushes

&lt;sec&gt; The adsorption of polymer on surface is a hot topic in physical, chemical and biological communities, which is influenced by many factors, such as the topological structure and the flexibility of the polymer, the attractive interaction between the polymer and the surface, the detailed structure of the surface, etc. The adsorption of polymers on solid surfaces is extensively studied, while the adsorption behaviors of polymers on soft surfaces are still unclear.&lt;/sec&gt;&lt;sec&gt; In this work, the static and dynamical characters of the adsorption of a free polymer chain on polymer brushes are studied by using Monte Carlo simulation. The brush is formed by grafted polymers with length &lt;i&gt;N&lt;/i&gt;&lt;sub&gt;b&lt;/sub&gt; and distance &lt;i&gt;d&lt;/i&gt;. Results indicate that, with increasing the adsorption energy (&lt;i&gt;ε&lt;/i&gt;) between the free polymer and the brush, the free polymer shows a phase transition from a desorbed state to an adsorbed state. Based on the dependence of the number of the adsorption segment of the free polymer (&lt;i&gt;m&lt;/i&gt;&lt;sub&gt;ad&lt;/sub&gt;) on the adsorption energy &lt;i&gt;ε&lt;/i&gt;, we defined the critical adsorption point (&lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt;) where the phase transition occurs. &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt; is nearly independent of the length of the free polymer, but it increases with decreasing the length of the grafted polymer or increasing the distance between the grafted polymers. When &lt;i&gt;ε&lt;/i&gt; &lt; &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt;, the free polymer is desorbed and its size is the same as that in free space. When &lt;i&gt;ε&lt;/i&gt; ≈ &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt;, the free polymer is sucked into the brush and meanwhile the size is compressed. While when &lt;i&gt;ε&lt;/i&gt; &lt;inline-formula&gt;&lt;tex-math id="Z-20200813163453"&gt;\begin{document}$\gg $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20200411_Z-20200813163453.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20200411_Z-20200813163453.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt;, the free polymer is strongly adsorbed on the surface of the brush and forms a quasi two-dimensional conformation, and meanwhile the whole adsorption process contains two stages: the adsorption process of the free polymer and the diffusion process of the brush. Moreover, with the increase of &lt;i&gt;ε&lt;/i&gt;, the diffusion of the free polymer shows an obvious transition from the normal model to the sub-diffusion model near &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt;. The transition of the diffusion model maybe useful for separation of polymers with different attractive polymer-brush interactions. For example, one may construct a brush surface and use it as a polymer separation device. Under weak driving force parallel to the surface, polymers with polymer-brush interaction &lt;i&gt;ε&lt;/i&gt; &lt; &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt; can move quickly, while polymers with &lt;i&gt;ε&lt;/i&gt; &gt; &lt;i&gt;ε&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt; will move slowly or be trapped on the brush.&lt;/sec&gt;

Printed Organic Complementary Integrated Circuits Using SAM Processing Free Polymer p-type Semiconductor

Printed Organic Complementary Integrated Circuits Using SAM Processing Free Polymer p-type Semiconductor

Drag reduction by linear flexible polymers and its degradation in turbulent flow: A phenomenological explanation from chemical thermodynamics and kinetics

Based on chemical thermodynamics and kinetics analysis, this work provides a phenomenological explanation of drag reduction and its degradation by linear flexible polymers. We propose that drag reduction happens due to the unstable thermodynamic environment created by the elongation of free polymers and aggregates, and degradation of drag reduction happens due to the unstable kinetic environment with the chain scission of the free polymer and aggregate. Experimental results from microscopic and macroscopic scales further validate the proposed theory. Fourier series is employed to explain the molecular weight distribution that happens in the drag reduction.