Effect Of Polymer Chain Length Research Articles

Polymer modification of SARS-CoV-2 spike protein impacts its ability to bind key receptor

The global spread of SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) has caused the loss of many human lives and severe economic losses. SARS-CoV-2 mediates its infection in humans via the spike glycoprotein. The receptor binding domain of the SARS-CoV-2 spike protein binds to its cognate receptor, angiotensin converting enzyme-2 (ACE2) to initiate viral entry. In this study, we examine how polymer modification of the spike protein receptor binding domain impacts binding to ACE2. The horseradish peroxidase conjugated receptor binding domain was modified with a range of polymers including hydrophilic N,N-dimethylacrylamide, hydrophobic N-isopropylacrylamide, cationic 3-(N,N-dimethylamino)propylacrylamide, and anionic 2-acrylamido-2-methylpropane sulfonic acid polymers. The effect of polymer chain length was observed using N,N-dimethylacrylamide polymers with degrees of polymerization of 5, 10 and 25. Polymer conjugation of the receptor binding domain significantly reduced the interaction with ACE2 protein, as determined by an enzyme-linked immunosorbent assay. Stability analysis showed that these conjugates remained highly stable even after seven days incubation at physiological temperature. Hence, this study provides a detailed view of the effect specific type of modification using a library of polymers with different functionalities in interrupting RBD-ACE2 interaction.

Dynamic Assembly of Polymer-Tethered Gold Nanoparticles into a 2D Superlattice at the Air–Liquid Interface: Influence of the Polymer Structure and Solvent Vapor

The two-dimensional (2D) superlattice obtained by self-assembly of gold nanoparticle (NPs) at the air–liquid interface shows a wide range of potential applications in catalysis, sensing, electronic storage, and molecular recognition. However, the dynamic assembly process of the gold NPs at the air–liquid interface is still unclear. In this study, gold NPs grafted with thiol-terminated polystyrene homopolymers (AuNPs@PS) were used as the assembly unit, and the 2D superlattice of AuNPs@PS was prepared by spreading and evaporating the AuNPs@PS toluene suspension at the air/diethylene glycol interface. The effects of polymer chain length, grafting density, and toluene vapor atmosphere on the microstructure of the superlattice were investigated as well. The microstructural evolution process of the AuNPs@PS superlattice at the air/diethylene glycol interface was monitored by the in situ grazing incident small-angle X-ray scattering (GISAXS) technique. The results demonstrate that the transition of long-chain polymer-tethered NPs from random packing to face-centered-cubic packed superlattice followed by two-dimensional hexagonal packing can be observed under a toluene vapor atmosphere. Additionally, by varying the polymer chain length and solvent vapor atmosphere, the spreading rate and superlattice interparticle spacing can be well mediated. This work provides a useful guide to prepare an ordered 2D superlattice with polymer-tethered inorganic NPs.

Insight into poly(1,3-dioxolane)-based polymer electrolytes and their interfaces with lithium Metal: Effect of electrolyte compositions

The transport properties and electrochemical stability of advanced lithiummetal batteries are severely constrained by the actual electrolyte compositions. Herein, for comprehensive atomistic insights and the development of electrolyte scientific theory, molecular dynamics technology is employed to investigate the electrochemical properties of recently attractive poly(1,3-dioxolane)-based electrolytes and their interfaces with lithium metal. This work elaborates on the characteristics of Li+ solvation environments and the effects of polymer chain length or plasticizer content on the experiment-concerned properties of bulk electrolytes, including solvation sheath structures, ionic diffusions, conductivities, transport numbers, etc. Meanwhile, to clarify the influence of polymer or salt concentration on the electrolyte/lithium metal interface, three distinctive interface models were proposed and analyzed based on different electrolyte compositions in this work: liquid-based, polymer-based, and highly-concentrated systems. Compared with the unfavorable liquid interface layer in the liquid-based system, the latter two systems have more electrochemically stable interfacial construction due to the appearance of polymer on the lithium metal surface. Besides, the Li+ solvation structure, which is related to the lithium electrodeposition, exhibits orientation, e.g., small organic liquid molecules in the liquid-based system are more likely to appear on the side that is accessible to the lithium metal surface. These small molecules are essentially excluded from the Li+ solvation structures in the polymer-based electrolyte, which is another important factor for stabilizing the interface. Furthermore, compared with the bulk electrolytes, it is found that ionic conductions at the interfaces are not attenuated in all systems. This work presents a comprehensive, profound view from bulk to interfacial properties, thus providing a theoretical cornerstone for the composition design and performance optimization of polymer electrolytes for lithium metal batteries.

Cluster-Induced Desorption/Ionization of Polystyrene: Desorption Mechanism and Effect of Polymer Chain Length on Desorption Probability.

Soft cluster-induced desorption/ionization of polystyrene oligomers was investigated with respect to application in mass spectrometry. Clear peak progressions corresponding to intact polystyrene molecules were observed in the mass spectra, and no fragmentation was detected; efficient desorption was deduced from quartz crystal microbalance measurements. Molecular dynamics (MD) simulations of the process revealed that even in the case of the nonpolar polystyrene molecules cluster-induced desorption proceeds via dissolvation in the polar clusters. Experimentally, a significantly lower desorption efficiency was observed for polystyrene molecules with larger chain length. Taking into account MD simulations and further experiments with mixed samples consisting of long- and short-chain polystyrene oligomers, the reduced desorption efficiency for longer chain polystyrene molecules was attributed to a stronger entanglement of the larger polystyrene molecules.

Cellulose Acetate-g-Polycaprolactone Copolymerization Using Diisocyanate Intermediates and the Effect of Polymer Chain Length on Surface, Thermal, and Antibacterial Properties.

The need for biodegradable and biocompatible polymers is growing quickly, particularly in the biomedical and environmental industries. Cellulose acetate, a natural polysaccharide, can be taken from plants and modified with polycaprolactone to improve its characteristics for a number of uses, including biomedical applications and food packaging. Cellulose acetate-g-polycaprolactone was prepared by a three-step reaction: First, polymerization of ε-caprolactone via ring-opening polymerization (ROP) reaction using 2-hydroxyethyl methacrylate (HEMA) and functionalization of polycaprolactone(PCL) by introducing NCO on the hydroxyl end of the HEMA-PCL using hexamethyl lenediisocyanate(HDI) were carried out. Then, the NCO–HEMA-PCL was grafted onto cellulose acetate (using the “grafting to” method). The polycaprolactone grafted cellulose acetate was confirmed by FTIR, the thermal characteristics of the copolymers were investigated by DSC and TGA, and the hydrophobicity was analyzed via water CA measurement. Introducing NCO-PCL to cellulose acetate increased the thermal stability. The contact angle of the unreacted PCL was higher than that of cellulose acetate-g-PCL, and it increased when the chain length increased. The CA-g-PCL50, CA-g-PCL100, and CA-g-PCL200 showed very high inhibition zones for all three bacteria tested (E. coli, S. aureus, and P. aeruginosa).

Influence of lactide vs glycolide composition of poly (lactic-co-glycolic acid) polymers on encapsulation of hydrophobic molecules: molecular dynamics and formulation studies

The work demonstrates the preparation of PLGA (PLGA 50:50, PLGA 75:25) nanoparticles, to encapsulate a hydrophobic molecule (coumarin-6), using the microreactor-based continuous process. The formulations were characterized using dynamic light scattering and transmission electron microscopy to determine their size, homogeneity, zeta potential, and surface morphology. The resulting nanoparticles were safe to the CHO cells (≈80% cell survival), at the concentration of ≤600 µg/mL and were successfully taken up by the cells, as demonstrated using confocal microscopy. Moreover, imaging flow cytometry confirmed that the nanoparticles were internalized in 73.96% of the cells. Furthermore, molecular dynamics simulation and docking studies were carried out to explore the effect of polymer chain length of PLGA and lactide vs glycolide (LA:GA) ratio on their compatibility with the coumarin-6 molecules and to study the coiling and flexibility of PLGA in the presence of coumarin-6 molecules. Flory–Huggins interaction parameter (χ) was calculated for polymer chains of varying lengths and LA:GA ratio, with respect to coumarin-6. χ parameter increased with increase in polymer chain length, which indicated superior interaction of coumarin-6 with the smaller chains. Amongst all the polymeric systems, PLGA55 exhibited the strongest interaction with coumarin-6, for all the chain lengths, possibly because of their homogeneous spatial arrangements and superior binding energy. PLGA27 showed better compatibility compared to PLGA72 and PGA, whereas PLA-based polymers exhibited the least compatibility. Analysis of the radius of gyration of the polymer chains in the polymer–coumarin-6 complexes, at the end of molecular dynamics run, exhibited that the polymer chains displayed varying coiling behavior and flexibility, depending upon the relative concentrations of the polymer and coumarin-6. Factors like intra-chain interactions, spatial arrangement, inter-chain binding energies, and polymer–coumarin-6 compatibility also influenced the coiling and flexibility of polymer chains.

Effect of Polymer Chain Length on the Superlattice Assembly of Functionalized Gold Nanoparticles.

We report on the assembly of gold nanoparticle (AuNPs) superlattices at the liquid/vapor interface and in the bulk of their suspensions. Interparticle distances in the assemblies are achieved on multiple length scales by varying chain lengths of surface grafted AuNPs by polyethylene glycol (PEG) with molecular weights in the range 2000-40,000 Da. Crystal structures and lattice constants in both 2D and 3D assemblies are determined by synchrotron-based surface-sensitive and small-angle X-ray scattering. Assuming knowledge of grafting density, we show that experimentally determined interparticle distances are adequately modeled by spherical brushes close to the θ point (Flory-Huggins parameter, ) for 2D superlattices at a liquid interface and a nonsolvent (χ = ∞) for the 3D dry superlattices.

Molecular dynamics simulation of amorphous polyethylene (PE) under cyclic tensile-compressive loading below the glass transition temperature

The intensive applications of polymer in many engineering composites have imposed an urgent need on the understanding of the mechanical behavior and deformation mechanism of the polymer under cyclic loading. This paper presents the results of a numerical study on the behavior of amorphous polyethylene (PE) subjected to cyclic tensile and compressive loads using molecular dynamics (MD) simulations, based on a united-atom approach. The effects of polymer chain length, the number of chains and strain rates are studied at first. Hysteresis loops, as well as visco-elastoplastic of PE under cyclic loading predicted by MD simulations are qualitatively in agreement with previous experiments. Three distinct hysteresis loops observed in successive loading-unloading reveal the contribution of elasticity, viscosity and plasticity under different loading strains, respectively. The rubber-like recovery behavior of PE at low temperature is attributed to that the mobility of molecular chains is constrained at low temperature. Energy analysis shows that the van der Waals energy and dihedral angle energy are considered to be the primary factors that affects the cyclic behavior of PE.

Separation of antipyretic analgesics by open tubular capillary electrochromatography with homopolymer coatings.

This study developed an open-tubular capillary electrochromatography protocol for the analysis of antipyretic analgesic drugs, which used a multifunctional homopolymer as coating. A controlled/living radical polymerization strategy was adopted to obtain poly(N-acryloxysuccinimide) with a tunable chain-length. The homopolymer coating enhanced the separation performance by contributing to the hydrophobic and hydrogen-bonding interactions between the analytes and the homopolymer. The effect of polymer chain-length and buffer pH and concentration on the separation efficiency was evaluated. In this approach, baseline separation of the three test drugs was achieved within 15 min. The repeatability of the prepared homopolymer coating was investigated, with the relative standard deviations< 2.88% observed in intra- and interday runs. Good linearity in the 5-800 µM range (R2 ≥ 0.998) demonstrates that accurate quantitative analysis of real samples was achieved. Moreover, the proposed assay was used to quantify the three drugs (aminopyrine, 4-aminoantipyrine, and phenacetin) in urine samples, achieving recovery rates between 92.1 and 108.7%. This promising methodology may be used for the analysis of drugs in real bio-samples and for the development of unique homopolymer coatings for open-tubular capillary electrochromatography systems.

Effect of powder properties on the physicochemical and rheological characteristics of gelation inulin–water systems

This study investigates the influence of physical properties of powder on the potential functionality of inulin as a polymeric gelator. Inulin powder was characterized using high-performance anion exchange chromatography, wide-angle X-ray, and particle size. Moreover, the inulin–water system was described using rheological properties, optical microscopy, and textural analysis. Four commercial inulins (LC, Instant, Fib97, and HP) were characterized and dissolved in distilled water at three different concentrations (15, 20, and 25%, w/w) at 25 °C. Inulin LC (degree of polymerization, 18.80; semi-crystalline state) and HP (degree of polymerization, 23.74; amorphous state) formed a gel from a concentration of 15% (w/w) and 20%, respectively. Inulin Fib97 (degree of polymerization, 6; amorphous state) and Instant (degree of polymerization, 8; amorphous state) were not able to develop a gel structure. This indicates the significant effect of polymer chain length to form a gel. Textural properties as well as wide-angle X-ray scattering and optical microscopy ascertained a difference in inulin HP– and LC–water system properties. This dissimilarity is related to the different physical properties of powders such as crystallinity and particle size. Indeed, new inulin powders were produced, having the same chemical composition but different physical states (amorphous or crystalline) or particle sizes. The results showed that an amorphous powder with a bigger particle size gave a greater gelation of inulin–water systems. However, beyond a certain size of particles, the systems lose their gelation properties.

Contact angle dynamics on pseudo-brushes: Effects of polymer chain length and wetting liquid

In this study we investigate the exceptional wetting properties of thin polymer layers. Here the polymer is deposited in the form of a polydimethylsiloxane (PDMS) pseudo-brush and contact line dynamics are measured for both varying polymerization index and nature of the partially-wetting liquid. We use a custom-built experimental apparatus to explore wetting dynamics over 7 decades of velocity, with a precision of 0.01° in variations of the contact angle. We show that the presence of a pseudo-brush can result in a remarkably small contact angle hysteresis as well as the appearance of an additional source of dissipation and that these two phenomena depend on the chain length and the wetting liquid. Qualitatively, we interpret these findings as the ability of the layer to behave as a liquid-like interface, and quantitatively by using a simple model of viscoelastic dissipation in soft thin films.

Effect of Polymer Chain Length on the Physical Stability of Amorphous Drug-Polymer Blends at Ambient Pressure.

Rational selection of polymers for amorphous drug stabilization is necessary for further successful development of solid dispersion technology. In this paper, we investigate the effect of polymer chain length on the inhibition of amorphous drug recrystallization. To consider this problem, we prepared a drug-polymer blend (in 10:1 drug to polymer ratio) containing bicalutamide (BIC) and polyvinylpyrrolidone (PVP) with different chain lengths K10, K30, and K90. We applied broadband dielectric spectroscopy to compare the molecular dynamics of investigated samples and thoroughly recognize their crystallization tendencies from supercooled liquid state. Despite the lack of differences in molecular dynamics, we noticed significant changes in their crystallization rates. To rationalize such behavior, we performed positron annihilation lifetime spectroscopy measurements. The results showed that the value of free volume was the highest for blend with PVP K90, which at the same time was characterized by the greatest tendency to crystallize. We postulate that the polymer chain, depending on its length, can have different configurations in the space, leading to better or worse sample stabilization. Our results highlight how important is detailed understanding of physical properties of polymers for judicious selection of the best stabilization approach.

Understanding the Cellular Uptake of pH-Responsive Zwitterionic Gold Nanoparticles: A Computer Simulation Study.

Surface functionalization of nanoparticles (NPs) with stealth polymers (e.g., hydrophilic and zwitterionic polymers) has become a common strategy to resist nonspecific protein adsorption recently. Understanding the role of surface decoration on NP-biomembrane interactions is of great significance to promote the application of NPs in biomedical fields. Herein, using coarse-grained molecular dynamics (CGMD) simulations, we investigate the interactions between stealth polymer-coated gold nanoparticles (AuNPs) and lipid membranes. The results show that AuNPs grafted with zwitterionic polymers can more easily approach the membrane surface than those coated with hydrophilic poly(ethylene glycol) (PEG), which can be explained by the weak dipole-dipole interaction between them. For zwitterionic AuNPs which can undergo pH-dependent charge conversion, different interaction modes which depend on the polymer protonation degree are found. When the protonation degree is low, the particles just adsorb on the membrane surface; at moderate protonation degrees, the particles can directly translocate across the lipid membrane through a transient hydrophilic pore formed on the membrane surface; the particles are fully wrapped by the curved lipid membrane at high protonation degrees, which may lead to endocytosis. Finally, the effect of polymer chain length on the cellular uptake of zwitterionic polymer-coated AuNPs is considered. The results demonstrate that longer polymer chain length will block the translocation of AuNPs across the lipid membrane when the protonation degree is not high; however, it can improve the transmembrane efficiency of AuNPs at high protonation degrees. We expect that these findings are of immediate interest to the design and synthesis of pH-responsive nanomaterials based on zwitterionic polymers and can prompt their further applications in the field of biomedicine.

SCC-DFTB Study on Structure, Electronic and Sensing Properties of Polypyrrole

Polypyrrole (PPy) have been considered as one of the most promising conducting polymers for gas sensor application because it can be efficiently operated at room temperature, light weight, thermal stability and ease of preparation. In this work, we have investigated the geometric and electronic structures of PPy based on B3LYP/3-21G*, B3LYP/6-31G* and SCC-DFTB methods. The effects of polymer chain length of PPy on structural and electronic properties including bond length, bond angle, torsion angle, the highest occupied orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and energy gap have been studied from the optimized PPy oligomers (n=1-10). The results show that the bond length, bond angle and torsion angle from SCC-DFTB method are C-N = 1.38 Å, N-H = 1.04 Å, C-C = 1.45 Å, N-C-C = 122 °, C-C-C = 131 °, N-C-C-C = 179 ° and C=C-C=C = 179 °, respectively. The HOMO and LUMO are in range of -5.49 to -4.23 eV and -0.078 to-1.92 eV, respectively. The energy gap decreases with increasing polymer chain length from 5.41 to 2.31 eV. Furthermore, sensing behavior of PPy for detection of toxic gases such as ammonia (NH3), carbon dioxide (CO2) and nitrogen dioxide (NO2) has been studied and discussed in details.

Matrix-Free Polymer Nanocomposite Thermoplastic Elastomers

Thermoplastic elastomer (TPE) grafted nanoparticles were prepared by grafting block copolymer poly(styrene-block-(n-butyl acrylate)) onto silica nanoparticles (NPs) via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The effects of polymer chain length and graft density on the mechanical properties were investigated using films made solely from the grafted NPs. The ultimate tensile stress and elastic modulus increased with increasing PS chain length. The dispersion of the silica NPs and the microphase separation of the block copolymer in the matrix-free polymer nanocomposite were investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The higher polymer graft density TPEs exhibited better microphase separation of the block copolymers and more uniform silica NP dispersion than lower polymer graft density TPEs with similar polymer chain length and composition.

Optimization of hyaluronan-based eye drop formulations

Hyaluronan (HA) is frequently incorporated in eye drops to extend the pre-corneal residence time, due to its viscosifying and mucoadhesive properties. Hydrodynamic and rheological evaluations of commercial products are first accomplished revealing molecular weights varying from about 360 to about 1200kDa and viscosity values in the range 3.7–24.2mPa s. The latter suggest that most products could be optimized towards resistance to drainage from the ocular surface. Then, a study aiming to maximize the viscosity and mucoadhesiveness of HA-based preparations is performed. The effect of polymer chain length and concentration is investigated. For the whole range of molecular weights encountered in commercial products, the concentration maximizing performance is identified. Such concentration varies from 0.3 (wt%) for a 1100kDa HA up to 1.0 (wt%) for a 250kDa HA, which is 3-fold higher than the highest concentration on the market. The viscosity and mucoadhesion profiles of optimized formulations are superior than commercial products, especially under conditions simulating in vivo blinking. Thus longer retention on the corneal epithelium can be predicted. An enhanced capacity to protect corneal porcine epithelial cells from dehydration is also demonstrated in vitro. Overall, the results predict formulations with improved efficacy.

Thermoresponsive Agarose Based Microparticles for Antibody Separation.

We report the development of thermoresponsive 4-mercaptoethylpyridine (MEP)-based chromatographic microsphere based resins for antibody separation that show switchable release abilities by adsorbing immunoglobulins at 40 °C and releasing the proteins at 5 °C. The thermoswitchable release properties were introduced to the porous resins by the grafting of linear poly(N-isopropylacrylamide) (PNIPAM) chains synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, which were modified to possess MEP end functionalities. Adsorption of γ-globulins as a model antibody on the shortest PNIPAM-MEP (3 kDa) grafted microparticles display binding capacities of up to 20 g L(-1) at 40 °C and a significant decrease in binding capacity to less than 2.5 g L(-1) at 5 °C. By switching the temperature to 5 °C, the release of bound γ-globulins is shown to be as high as 90%. The effects of polymer chain length on the binding capacity are studied in detail and found to be critical as they influence the density of MEP functionalities on the particle surfaces.

Theoretical Study on Structural and Electronic Properties of EDOT:SS Oligomers Complex

In this paper, we have reported a theoretical study of the geometric and electronic structures of EDOT:SS oligomers based on semi-empirical Austin model1 (AM1) method and density functional theory at B3LYP/3-21G* level. The effects of polymer chain length of both EDOT and SS on structural and electronic properties including bond length, bond angle, binding distance, charge, the highest occupied orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and energy gap have been studied from the optimized oligomers which were built by varying repeating unit of monomer as n = 1, 2, 3 and 4. The results show that AM1 is not appropriate for geometry optimization of EDOT:SS system comparing to B3LYP/3-21G* level. The binding distance between H atom on EDOT and O atom on SS tends to close together with the average distance of 2.21 Å. The most positive charges locate at sulfur atoms on EDOT and EDOT:SS. The electrical conductivity of EDOT, SS and EDOT:SS increases when polymer chain is extended.

The effect of polymer chain length on the mechanical properties of triblock copolymer gels

An ABA triblock copolymer in a midblock selective solvent is studied as a function of the chain length, using a novel dissipative particle dynamics (DPD) model which includes a modified segmental repulsive potential (mSRP) that restricts chain crossing. Deformation under uniaxial tension using the DPD method, with and without the mSRP, was used to extract the cross-link and entanglement portions of the modulus. The results exhibit the expected theoretical scaling with chain length for lower strain rates. Structural properties, such as bridge fraction and the extent of entanglements in the polymer matrix, were also quantified.

Photoinduced charge separation in aqueous solution of porphyrin-quinone end-capped poly(methacrylic acid)

Photoinduced charge separation from porphyrin (P) to benzoquinone (Q) moieties covalently attached to the opposite chain ends of poly(methacrylic acid) (PMMA) was studied. The effect of polymer chain length, pH and ionic strength of the aqueous solution on the rate constant of charge separation and efficiency of P+• -Q - radical ion