Polymer Solvent Research Articles

Poly(curcumin-co-poly(ethylene glycol)) films provide neuroprotection following reactive oxygen species insult in vitro.

Curcumin is an antioxidant and anti-inflammatory molecule that may provide neuroprotection following central nervous system (CNS) injury. However, curcumin is hydrophobic, limiting its ability to be loaded and then released from biomaterials for neural applications. We previously developed polymers containing curcumin, and these polymers may be applied to neuronal devices or to neural injury to promote neuroprotection. Thus, our objective was to evaluate two curcumin polymers as potential neuroprotective materials for neural applications. 
Approach: For each curcumin polymer, we created three polymer solutions by varying the weight percentage of curcumin polymer in solvent. These solutions were subsequently coated onto glass coverslips, and the thickness of the polymer was assessed using profilometry. Polymer degradation and dissolution was assessed using brightfield microscopy, scanning electron microscopy, and gel permeation chromatography. The ability of the polymers to protect cortical neurons from free radical insult was assessed using an in vitro cortical culture model.
Main Results: The P50 curcumin polymer (containing greater poly(ethylene glycol) content than the P75 polymer), eroded readily in solution, with erosion dependent on the weight percentage of polymer in solvent. Unlike the P50 polymer, the P75 polymer did not undergo erosion. Since the P50 polymer underwent erosion, we expected that the P50 polymer would more readily protect cortical neurons from free radical insult. Unexpectedly, even though P75 films did not erode, P75 polymers protected neurons from free radical insult, suggesting that erosion is not necessary for these polymers to enable neuroprotection.
Significance: This study is significant as it provides a framework to evaluate polymers for future neural applications. Additionally, we observed that some curcumin polymers do not require dissolution to enable neuroprotection. Future work will assess the ability of these materials to enable neuroprotection within in vivo models of neural injury.&#xD.

Comparative Study of Polymer Globules and Liquid Droplets in Poor Solvents: Effects of Cosolvents and Solvent Quality.

We compare the structures of polymer globules, composed of flexible polymer chains, with liquid droplets made of nonbonded monomers of the same polymer in poor solvents. This comparison is performed in three different poor solvents, with and without the addition of cosolvents. Molecular dynamics simulations are used to analyze the properties of the polymer globules, while semigrand canonical Monte Carlo simulations are used to form metastable liquid droplets of nonbonded monomers through homogeneous nucleation in the same solvents. Our findings show that both globules and droplets are nearly spherical, although droplets display slightly more anisotropy. In the absence of cosolvents, the surrounding solvent structures are similar for both globules and droplets. However, in the presence of cosolvents, significant differences arise in the liquid structure, with the disparities increasing as the solvent quality worsens. Cosolvents tend to accumulate near the surface of globules due to the restricted movement of bonded monomers, which partially immobilizes the cosolvents. This effect becomes more pronounced as the solvent quality declines. Interfacial free energy calculations reveal that cosolvents act like surfactants, promoting larger interfacial areas for both globules and droplets. This effect is more significant for globules due to the greater accumulation of cosolvents at their surface. Therefore, modeling polymer globules as liquid droplets may underestimate the impact of cosolvents on the stability of the globule state. Additionally, the transition states involved in polymer collapse in the presence of cosolvents differ from those involved in the nucleation of liquid droplets in the same solution.

Chiral Nanostructures from Artificial Helical Polymers: Recent Advances in Synthesis, Regulation, and Functions.

Helical structures such as right-handed double helix for DNA and left-handed α-helix for proteins in biological systems are inherently chiral. Importantly, chirality at the nanoscopic level plays a vital role in their macroscopic chiral functionalities. In order to mimic the structures and functions of natural chiral nanoarchitectures, a variety of chiral nanostructures obtained from artificial helical polymers are prepared, which can be directly observed by atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This review mainly focuses on the formation of chiral nanostructures and the morphology regulation triggered by polymer chain length, concentration, solvent, temperature, photoirradiation, and chemical additives. In addition, the distinct chiral functions including chiral recognition, circularly polarized luminescence, drug release, cell imaging, and antibiosis are also discussed.

The swelling mechanism of ethylene-vinyl acetate polymer in different solvents via molecular dynamics and experimental studies.

Ethylene-vinyl acetate (EVA) film is the predominant encapsulation material in crystalline silicon photovoltaic modules, the efficient and eco-friendly processing of which is essential for the recycling of the modules. Among the various existing techniques, the chemical approach uses solvents to induce swelling and dissolution on the EVA film to facilitate the separation of distinct layers. This method demonstrates the potential for achieving low-energy consumption and minimal-damage retrieval of the diverse materials within the components. Nonetheless, the mechanism underlying the swelling of the EVA polymer and the consequent delamination of various layers remains elusive, hindering the proper choice of solvents. In this study, the swelling behaviors of the EVA polymer in water, ethanol, and D-limonene solvents were analyzed via molecular dynamics (MD) simulations. The influence of intermolecular interactions on the swelling degree of the EVA polymers had been examined to determine the dominant factors leading to the discrepancies in the diffusion state of EVA in different solvents. The molecular electrostatic potential (MEP) maps were utilized to explain the differences in interactions from a molecular structure perspective. Furthermore, the results of MD simulations were experimentally verified by solvent-immersion experiments and testing methods. Based on the results, the swelling mechanism of the EVA polymer in the selected solvents was proposed and illustrated, providing theoretical support for chemically-driven photovoltaic module recycling processes.

Dynamics of polymers in coarse-grained nematic solvents.

Polymers are a primary building block in many biomaterials, often interacting with anisotropic backgrounds. While previous studies have considered polymer dynamics within nematic solvents, rarely are the effects of anisotropic viscosity and polymer elongation differentiated. Here, we study polymers embedded in nematic liquid crystals with isotropic viscosity via numerical simulations to explicitly investigate the effect of nematicity on macromolecular conformation and how conformation alone can produce anisotropic dynamics. We employ a hybrid multi-particle collision dynamics and molecular dynamics technique that captures nematic orientation, thermal fluctuations and hydrodynamic interactions. The coupling of the polymer segments to the director field of the surrounding nematic elongates the polymer, producing anisotropic diffusion even in nematic solvents with isotropic viscosity. For intermediate coupling, the competition between background anisotropy and macromolecular entropy leads to hairpins - sudden kinks along the backbone of the polymer. Experiments of DNA embedded in a solution of rod-like fd viruses qualitatively support the role of hairpins in establishing characteristic conformational features that govern polymer dynamics. Hairpin diffusion along the backbone exponentially slows as coupling increases. Better understanding two-way coupling between polymers and their surroundings could allow the creation of more biomimetic composite materials.

Solvation-free energy of uncharged and charged water-soluble synthetic polymer using adaptive Poisson-Boltzmann solver: poly(acrylic acid)

ABSTRACT Implicit solvent based on the Poisson-Boltzmann model of electrostatics provides a faster approach to the calculation of solvation and conformations of polymers compared to explicit solvents in molecular dynamics simulations. While PB-based methods have been used extensively for biological macromolecules, here we present the use of the Adaptive Poisson-Boltzmann Solver (APBS) approach for the solvation of synthetic polymer in water. Stereo-specific (isotactic) poly(acrylic acid) of different chain lengths (20–55 for uncharged and 15–50 for charged) are sampled from atomistic molecular dynamic simulations in explicit water followed by APBS in implicit water. The hydration energy of uncharged and charged polymers varies linearly with the number of units (N). The variation of total solvation energy for SASA (Solvent Accessible Surface Area) and SAV (Solvent Accessible Volume) shows a crossover from one scaling to the other. While such a transition is known for small hydrophobic solutes, we report this for a dilute solution of polymer at uncharged and fully charged conditions and in implicit solvent.

Biomimetic Approach for Optimal Designing of the Shape and Controlled Release of Therapeutics from Tricompartmental Microcarriers for Managing Parkinson's Disease.

Inspired by the intricate cellular morphology and the discoid shape of red blood cells (RBCs), biomimetic tricompartmental microcarriers (TCM) with controlled release profiles were engineered using an electrohydrodynamic-co-jetting technique for efficient management of Parkinson's disease (PD). While jetting, Levodopa (LD), CD (Carbidopa), and ENT (Entacapone) (3 PD drugs) were directly encapsulated in the three individual compartments of the TCM used for oral administration. The optimal shape and controlled release profiles were obtained by employing the Taguchi orthogonal L9 design-of-experiment approach by systematically varying the processing parameters, i.e., solvent ratio, polymer concentration, and flow rate. The "smaller-the-better" norm for the S/N ratio demonstrated the solvent ratio (DMF content) and polymer concentration as the most influential parameters in ensuring the RBC shape and controlling the release of drugs. Analysis of variance and response surface methodology approach provided insights into the optimal influence of control factors on the response variables. Confirmation experiments further validated the optimized microparticles (Poptimized), demonstrating an error of only ∼0.13% in aspect ratio deviation (ARDEV) and ∼19% (within the tolerance limit) in release factor (RF) from the predicted experiment. Moreover, Poptimized exhibits ∼100% encapsulation efficiency of all three PD drugs, with the cumulative release of ∼100% LD, ∼97% CD, and ∼65% ENT within 5 h of the in vitro study. In addition, in vivo studies such as pharmacokinetics (using healthy rats) and pharmacodynamics [using the MPTP (methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-injected PD-induced mice model] showed that the TCM can effectively control the release of LD (primary drug) for a prolonged period, thereby promising sustained drug delivery and improved therapeutics outcomes.

Removal of Trace Benzene from Cyclohexane Using a MOF Molecular Sieve.

Cyclohexane (Cy), commonly produced by the catalytic hydrogenation of benzene (Bz), is used in large quantities as a solvent or feedstock for nylon polymers. Removing trace unreacted Bz from the Cy product is technically difficult due to their similar molecular structures and physical properties. Herein, we report that a metal-organic framework (MOF) adsorbent shows a molecular sieving effect for Bz and Cy with record-high Bz/Cy adsorption selectivities (216, 723, and 1027) in their liquid mixtures (v/v = 1:1, 1:10, and 1:20), and traps Bz molecules effectively even at low partial pressure in the vapor phase (e.g., 2.49 mmol/g at 8.2 Pa) or at low content in liquid-phase Cy (e.g., 128 mg/g at 20 ppm). Over 99% removal of trace Bz (1000 ppm) from liquid Cy could be achieved in one simple stripping step at room temperature using this sorbent, producing a Cy with >99.999% purity. Single-crystal structure analyses for guest-free and Bz-loaded phases of the MOF disclosed that a narrow slit-like pore aperture and the strong uniting of multiple weak host-guest and guest-guest interactions are the co-origin of its distinct adsorption property for Bz and Cy.

Low-cost high performance piezoelectric fabrics based on Nylon-6 nanofibers.

To fully harness the potential of smart textiles, it is cruical to develop energy harvesters which can function both as fabric and energy generator. In this work, we present a high performance low-cost piezoelectric nano-fabric using even-number Nylon (i.e., Nylon-6). Nylon-6 was chosen for optimal mechanical properties such as mechanical strength and stiffness. To maximize the voltage output, Nylon six nanofibers with varying diameter and crystallinity were synthesized by adjusting the polymer precursor and solvent, along with electrospinning parameters, followed by post thermal treatment. The average diameter of electrospun nanofibers was finely tuned (down to 36nm) by adjusting solution polymer precursor content and electrospinning parameters. The content of desired piezoelectric-active γ crystal phase enhanced upto 76.4% by controlling solvent types and post thermal annealing. The highest peak to peak voltage (V33) of 1.96V were achieved from γ-phase dominant (>60%) Nylon-6 nanofiber fabric which has an average nanofiber diameter of 36nm with high fiber fraction (i.e., > 98%). Unlike its thin film counterpart, piezoelectric electrospun nanofiber fabric demonstrated durability against wear and washing. This work paves a new way to utilize Nylon-6 nanofibers in next-generation electronic textiles.

Tolman Length for Binary Polymer–Polymer and Polymer–Solvent Systems

Tolman Length for Binary Polymer–Polymer and Polymer–Solvent Systems

CHEMICAL RESISTANCE OF NHBR AND NBR IN PROPYLENE

ABSTRACT The chemical resistance of HNBR and NBR in propylene is considered as no resistance by many chemical compatibility handbooks and industry chemical resistance tables and charts. This situation drives the change of the elastomer compounds from cheap HNBR/NBR to expensive fluoroelastomer for applications involving propylene. However, in the literature, NBR and HNBR are rated as having good or excellent chemical resistance to all other hydrocarbons, such as ethylene, ethane, propane, butane, and butylene. It seems that there are some special or unknown characteristics of propylene that make it very harsh to both NBR and HNBR; therefore, it is important to investigate the chemical resistance of NBR and HNBR in propylene. In this study, the chemical resistance of HNBR and NBR in propylene is investigated according to ISO 23936-2 and ASTM Standard D 471. The test results are crucial for the applications of HNBR/NBR in contact with propylene. Based on the tests, we investigated tensile property changes, volume changes, and glass transition temperatures and chemical structures of HNBR/NBR after aging in high-pressure propylene at an elevated temperature. The Hansen solubility parameters (HSPs) of HNBR and NBR and many hydrocarbons such as ethylene, ethane, propylene, propane, butane, and butylene were estimated. Based on the HSP, the polymer–solvent interaction parameters between HNBR/NBR and hydrocarbons were also estimated to explain the chemical resistance of HNBR/NBR in propylene. An aging mechanism was proposed to explain the changes of HNBR and NBR in propylene aging. This study enhanced guidance on chemical resistance of HNBR/NBR in propylene to the elastomer industry.

Molecular dynamics simulation of CO2 in organic solvent and polymer–solvent solutions

Molecular dynamics simulation of CO2 in organic solvent and polymer–solvent solutions

Unveiling the apparent density of swollen PDMS in hydrocarbons – A distinction between dimensional-based and volume-additivity methods

This article reports the swelling-induced effect on the density, mass, area, and thickness of the polydimethylsiloxane (PDMS) membrane in C6–C12 linear alkanes. Their time dependence (up to 500 min) was determined at 20 °C and atmospheric pressure. From the combination of areal and thickness data, the experimental PDMS volumes of the swollen polymer were calculated, and the time dependence of the apparent density of the swollen membrane (i.e. its mass divided by its real volume) was revealed. The equilibrium apparent density of the swollen PDMS increased with the increasing number of C-atoms of liquid alkanes and liquid density. For higher alkanes (C number > 10), the calculated equilibrium apparent density of the swollen polymer was thus higher than that of the dry polymer. The dimensional-based PDMS volumes of the swollen polymer were compared with those calculated by the volume-additivity rules. For each C6–C12 linear alkane, the volume-additivity method overestimated the swollen polymer volumes compared to the experimentally determined ones. Such a finding indicates the non-ideal PDMS swelling character, which is not solely additive due to the force interactions between the polymer chains and solvent molecules and moving of polymer chains apart (free volume increases).

Solvent and additive-controlled supramolecular isomerism in zinc coordination polymers

A new series of Zn(II) supramolecular isomers containing ditopic 1,3-di(pyridin-4-yl)urea (4bpu) ligand were synthesized and characterized by infrared analysis, elemental analysis and TGA as well as single-crystal X-ray diffraction analysis. Four solvent-induced pseudopolymorphic zinc (II) coordination polymers (CPs), namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1), {[Zn(4bpu)(OAc)2](C2H5OH)}n (2), {[Zn(4bpu)(OAc)2](HOCH2CH2OH)}n (3), and {[Zn(4bpu)(OAc)2](0.5H2O)}n (4), were prepared by the reaction of Zn(OAc)2.2H2O and 4bpu via self-assembly under varying solvent systems. Also, a pair of polymorphic coordination polymers namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1α) and {[Zn3(4bpu)3(OAc)6](CH3OH)2}n(1β), was prepared in the presence of different organic additives. Single-crystal X-ray diffraction confirmed that 1−4 and 1α display 1D polymeric zig-zag chains and 1β exhibits 1D triple-stranded ladders that were self-assembled through various supramolecular interactions. In addition, a series of dissolution-recrystallization structural transformations (DRST) were performed on these supramolecular isomers.

Choline Chloride-Urea Deep Eutectic Solvent/Cu-Mn Iminodiacetate Coordination Polymer as an Efficient Catalytic System for Synthesis of Morita-Baylis-Hillman Adducts with Antimicrobial Activity.

This work shows the synthesis of a series of Morita-Baylis-Hillman adducts from isatin derivatives via an efficient green approach involving the use of a new catalyst system, a mixture of copper-manganese iminodiacetate 1D coordination polymer (Cu/Mn-IDA) and choline chloride-urea deep eutectic solvent (ChCl/urea 1:2). The adducts 2a-2i were obtained in good to excellent yields (59-97%) with shorter reaction times. The results demonstrate for the first time the synergistic catalytic effect of the combination of deep eutectic solvent and coordination polymer on the Morita-Baylis-Hillman reactions. The catalyst recyclability was investigated, and it was found that Cu/Mn-IDA maintains consistent performance for at least four catalytic cycles. The synthesized compounds were evaluated for their in vitro antimicrobial activity against four bacteria and eight fungi species. Among all, 2a, 2b, 2d, 2e, and 2g showed antifungal and antibacterial activities in 70-83% of the strains tested. The adduct 2e exhibited significant antifungal activity with a minimum inhibitory concentration value of 128 μg mL-1 compared to the standard drug fluconazole (minimum inhibitory concentration, 256 μg mL-1).

Enhancing permeability of CA/MoS2 pervaporation membrane via electric field-induced orientation of MoS2 nanosheets

The formation of a mixed matrix membrane by incorporating nanofillers into a polymer matrix is a potential strategy to improve the separation performance of polymer membranes. However, agglomeration and random arrangement of nanofillers in the mixed matrix membrane result in lower permeation flux increase than expected. In this work, mixed matrix membranes composed of cellulose acetate polymer and varying amounts of Molybdenum disulfide (MoS2) nanosheets as nanofillers were prepared, and an electric field was applied to induce the alignment of MoS2 nanosheets in the membrane thickness direction. The effects of solution parameters including solvent type, MoS2 content, and polymer concentration as well as electric field parameters i.e., frequency, strength, and action time on MoS2 orientation were investigated using a stereoscopic microscope. The pervaporation desalination performance of mixed matrix membranes with randomly arranged MoS2 and orientally arranged MoS2 was assessed. At 2 wt% MoS2 content, the mixed matrix membrane with orientally arranged MoS2 exhibited a flux of 5.44 kg/(m2·h), representing a 25.9 % increase over the mixed matrix membrane with randomly arranged MoS2, while maintaining a salt rejection rate of over 99.9 %. The mixed matrix membrane demonstrated good long-term stability with consistent water flux and salt rejection during 120 h of operation.

Folding behaviors of two-dimensional flexible polymers.

Unlike one-dimensional polymers, the theoretical framework on the behaviors of two-dimensional (2D) polymers is far from completeness. In this study, we model single-layer flexible 2D polymers of different sizes and examine their scaling behaviors in solution, represented by Rg ∼ Lν, where Rg is the radius of gyration and L is the side length of a 2D polymer. We find that the scaling exponent ν is 0.96 for a good solvent and 0.64 for under poor solvent condition. Interestingly, we observe a previously unnoticed phenomenon: under intermediate solvent conditions, the 2D polymer folds to maintain a flat structure, and as L becomes larger, multiple folded structures emerge. We introduce a shape parameter Q to diagram the relationship of folded structures with the polymer size and solvent condition. Theoretically, we explain the folding transitions by the competition between bending and solvophobic free energies.

Methodical evaluation of Boyle temperatures using Mayer sampling Monte Carlo with application to polymers in implicit solvent.

The Boyle temperature, TB, for an n-segment polymer in solution is the temperature where the second osmotic virial coefficient, A2, is zero. This characteristic is of interest for its connection to the polymer condensation critical temperature, particularly for n → ∞. TB can be measured experimentally or computed for a given model macromolecule. For the latter, we present and examine two approaches, both based on the Mayer-sampling Monte Carlo (MSMC) method, to calculate Boyle temperatures as a function of model parameters. In one approach, we use MSMC calculations to search for TB, as guided by the evaluation of temperature derivatives of A2. The second approach involves numerical integration of an ordinary differential equation describing how TB varies with a model parameter, starting from a known TB. Unlike general MSMC calculations, these adaptations are appealing because they neither invoke a reference for the calculation nor use special averages needed to avoid bias when computing A2 directly. We demonstrate these methods by computing TB lines for off-lattice linear Lennard-Jones polymers as a function of chain stiffness, considering chains of length n ranging from 2 to 512 monomers. We additionally perform calculations of single-molecule radius of gyration Rg and determine the temperatures Tθ, where linear scaling of Rg2 with n is observed, as if the polymers were long random-walk chains. We find that Tθ and TB seem to differ by 6% in the n → ∞ limit, which is beyond the statistical uncertainties of our computational methodology. However, we cannot rule out systematic error relating to our extrapolation procedure as being the source of this discrepancy.

Mechanical Design Principles of Conductive Gels Applied for Flexible Electronics

AbstractReaping the benefits of the burgeoning investigation of gels in recent decades, flexible electronics based on conductive gels have been extensively explored. Gels consisting of polymer networks and solvents provide ideal platforms for fabricating flexible electronics due to their soft mechanical nature, excellent biocompatibility, water‐like environment, and ease of processing. The majority of investigations of flexible electronics primarily focus on functionalities such as sensing capability, energy density, luminance, fluctuating frequency, and so on, whereas the distinguishing feature of flexible electronics lies in its inherent deformable mechanics in comparison to metal‐ or semiconductor‐based stiff electronics. However, the comprehensive design and investigation of the mechanical properties of deformable conductive gels have not received sufficient attention to improve the overall performance of flexible electronics. A comprehensive summary is provided, listing six crucial mechanical parameters—stretchability, modulus, strength, elasticity, hysteresis, and fatigue—which exert significant influence on the functionalities of flexible electronics. This review aims to direct researchers’ attention toward the mechanical design of deformable conductive gels and presents representative strategies for their mechanical modulation.

Effect of concentration and electrical charge of maltodextrin, and packing factor on electrospinning processing

The power law ηrel ∼ Ca of maltodextrins with higher entanglement concentrations (Ce) of dextrose equivalent (DE) 4, 10, and 18 exhibits an unusually high exponent a, ranging from 10.34 to 14.38 in congested solutions where particles occupy significant space. This contrasts with the dilute exponents (a ∼2) typically observed in polymer–solvent systems. To address this issue, several viscosity factors were evaluated using the Einstein–Roscoe and Mooney equations, which demonstrated viscosity dependence due to volume fraction (ϕ) > 0.35, shape, crowding factor (k) packing factor (1/k∼0.5) and centered cubic cell (CC), particularly for larger chain sizes (>20 glucoses) in DE-4. Chain electrical charges significantly stiffen the chain and increase its length beyond the theoretically predicted Kuhn persistent length (Lp), which seems to be responsible for the exponential increase in viscosity. Normalizing the viscosity/charge data revealed a log–log plot consistent with the exponent a of the general power law theory. In addition to concentration, electrospinning processing is influenced by strong particle–particle charge interactions, (ϕ), packing factor (1/k), CC, and chain sizes. The Maxwell model demonstrated poor interaction for DE-4 (modulus ∼286 Pa at maximum ϕ due to loose packing of CC, in contrast to DE-18, which exhibited a modulus of 994 Pa for a solution with maximum ϕ> 0.5 and a congested solution of 52% w/v, packing factor of 0.68, and high particle–particle interaction of the body-centered cubic (BCC) cell, favoring electrospun fiber formation. The packing factor, ϕ, and cell type, are highly sensitive and have potential applications in food systems, 3D bioprinting, among many other scientific domains.