Equivalent Molecular Weight Research Articles

Enhancing the Energy Density and Cycle Life of Li/Sulfurized Polyacrylonitrile (SPAN) Batteries

Li/sulfurized polyacrylonitrile (Li/SPAN) batteries are garnering attention for their potential in sustainable energy storage with notable advantages such as a high theoretical energy density exceeding 1000 Wh kg-1, surpassing the 750 Wh kg-1 of Li/NMC811, and being free of transition metals. The absence of transition metals addresses concerns related to their cost, scarcity, uneven distribution, and potential toxicity. However, current Li/SPAN batteries have yet to realize their full potential in terms of energy density and cycle life. This shortfall can be attributed to a lack of comprehensive understanding across various system levels, resulting in a dearth of well-directed research efforts.In this work, we conduct a thorough study of the energy density and cycle life of practical Li/SPAN cells using internally developed models. Our analysis revealed refreshed perspectives from the common consensus among the Li/SPAN battery community. Concerning energy density, we find that this output is notably influenced by SPAN voltage, electrolyte weight, and inactive weights. In addition to the conventional method of enhancing SPAN specific capacity, these parameters present fresh opportunities to boost the energy density of Li/SPAN batteries. Details about potential executive strategies and practical viability regarding each parameter are also discussed.Regarding cycle life, while the Coulombic efficiency of Li plating/stripping (Li CE) is widely recognized as a critical factor, our analysis reveals that its impact primarily lies in regulating the consumption of the electrolyte rather than that of Li metal. Therefore, controlling the chemistry of side reactions, represented by the average equivalent molecular weight (i.e., molecular weight over number of exchanged electron) and electrolyte density, emerges as a complementary approach to improve cycle life. Overall, our findings suggest that transitioning from heavy hydrofluoroether-based localized high-concentration electrolytes (LHCEs) to lightweight alkyl ether-based weakly-solvating electrolytes is beneficial for advancing Li/SPAN batteries, both in terms of energy density and cycle life.

Unfractionated Heparin Resourced from Bovine, Ovine, and Porcine Origin Is Bioequivalent

Introduction: Unfractionated heparin (UFH) in the United States is sourced from porcine mucosa and is mainly supplied from China. This sole dependence on one source can potentially lead to a serious health crisis for this essential medicine if there is a shortage of UFH due to any supply chain disruption. A realistic solution would be to develop bovine and ovine mucosa as alternate sources to porcine mucosa to produce UFH. In this study, the pharmacologic profile of single-sourced bovine, ovine, and porcine heparins were evaluated to demonstrate and validate their bio-equivalence. The immunological effect of these heparins in terms of heparin-induced thrombocytopenia (HIT) was also assessed. Materials: Multiple batches of UFH active pharmaceutical ingredient (API) from KinMaster (Brazil), Ronnsi (China), and Medefil (USA) were included in this study. USP compliant anti-Xa and anti-IIa assays (Aniara Diagnostics, USA) were used. HIT antibody was a pool of sera from clinically diagnosed HIT patients. Methods: Molecular weight profile of each heparin type was determined by HPLC. The anticoagulant effects of gravimetric amounts (µg/mL) of each heparin were evaluated by the anti-Xa, anti-IIa, and aPTT (HemosIL, Werfen) assays, then assessed for neutralization by protamine sulfate (PS) in each assay. The HIT profile was evaluated by the platelet aggregation assay. Results: The heparins, irrespective of their source, demonstrated comparable molecular weight profiles (15,020 Daltons bovine, 14,100 Daltons ovine, 14,500 Daltons porcine). While the anti-Xa and anti-IIa showed similar potency for ovine (191 anti-Xa, 188 U/mL anti-IIa) and porcine UFH (205 U/mL anti-Xa, 195 U/mL anti-IIa), the bovine UFH consistently showed lower potency for both activities (108 U/mL anti-Xa, 110 U/mL anti-IIa). Complete neutralization by PS was observed with all UFHs at all concentrations. The HIT profile, irrespective of heparin origin, exhibited a similar, expected, parabolic curve profile at equivalent heparin concentrations with no enhanced effect observed for either bovine or ovine UFH compared to porcine UFH. Conclusion: These studies support the hypothesis that heparin from bovine and ovine origin exhibit comparable in vitro anticoagulant, neutralization, and immunologic profiles, with an equivalent molecular weight profile, and can be considered for use as an alternative source to porcine heparin. This study suggests that heparin derived from bovine and ovine sources produced under current manufacturing practices are effective and safe alternatives to porcine heparin.

Controllable Synthesis of Chain Center Dye-Labeled Star Polymers for Quantitative Examination of Interchain Conformation by Time-Resolved Fluorescence Resonance Energy Transfer.

Using a "core-first" approach with atom transfer radical polymerization, fluorescent center-functional star polymers of equivalent molecular weight but with varying numbers of arms (di-, tri-, and tetra-arm) were prepared. The sensitivity of fluorescence, combined with a dye-labeling technique introducing a fluorescent donor (carbazole) and an acceptor (anthracene) at the center of poly(methyl methacrylate) (PMMA) chains, enabled the application of time-resolved fluorescence resonance energy transfer to obtain quantitative insights into the conformation of the star polymer chains in the film state. When the results of star-branched polymers were compared with those of linear polymers of identical type and molecular weight, the impact of branching on polymer behavior was isolated for examination. Although the star topology does not alter the average intercoil distance, it affects the distance dispersity. Star polymers with higher arm numbers display decreased dispersity from distance due to reduced intermolecular aggregation at their geometric centers. This study presents the first spectroscopic evidence regarding the distribution of geometric centers in star polymers, offering a physical understanding of chain interpenetration and entanglement within star polymers.

Effects of Defatting Pretreatment on Polysaccharide Extraction from Rambutan Seeds Using Subcritical Water: Optimization Using the Desirability Approach.

Rambutan seeds are by-products generated from fruit-processing factories; the leftover seeds are buried in landfills, generating methane emissions. This work aimed to extract polysaccharides (POLS) from rambutan seeds by using subcritical water extraction (SWE). The effects of defatting pretreatment and operating parameters in SWE were investigated using a Box-Behnken design. The results show that defatting pretreatment significantly enriched the POLS yield, while it had no significant effect on the total sugar content. Using the desirability approach, the suitable feedstock for SWE was defatted rambutan seeds. The maximum desirability of 0.86 was found at a temperature range of 145-150 °C, an extraction time of 15 min, and a liquid-solid ratio of 10:1. The POLS yield and total sugar content were in the range of 52.33-55.63 g/100 g feedstock and 83.37-87.45 g/100 g POLS, respectively. The extracted POLS had an equivalent molecular weight of 413.70 kDa that could be used as an extender in plant-based products. In conclusion, the defatting pretreatment of rambutan seeds not only improved the POLS yield obtained via SWE but also generated additional lipids that could be utilized as an unconventional source of specialty fat.

Experimental evidence for immiscibility of enantiomeric polymers: Phase separation of high-molecular-weight poly(ʟ-lactide)/poly(ᴅ-lactide) blends and its impact on hindering stereocomplex crystallization

Although polymers tend not to mix, it remains challenging to characterize the immiscibility of enantiomeric poly(ʟ-lactide) (PLLA) and poly(ᴅ-lactide) (PDLA), particularly with equivalent and high molecular weight (high MW), which frustratingly disfavors the exclusive stereocomplexation. By introducing a random copolymer (PLC) of ʟ-lactide and caprolactone to form binary blends with PLLA and PDLA, the phase behavior of high-MW PLLA/PDLA blends was investigated mainly by using differential scanning calorimetry (DSC) and atomic force microscopy (AFM). DSC results showed that PLLA/PLC blends exhibited a single glass transition temperature (Tg), which depended on the blending ratio and precisely corresponded with the theoretical values calculated from the Fox equation. In comparison, PDLA/PLC blends showed composition-dependent heat-capacity increment at two unchanged Tg values of pure PLC and PDLA. AFM observation revealed that PLC is completely miscible with PLLA at high MW but is immiscible with PDLA, logically suggesting immiscibility of high-MW PLLA and PDLA. Moreover, AFM results demonstrated that high-MW PLLA/PDLA blends exhibited spherical droplets in asymmetric blends and bicontinuous interpenetrating worm-like patterns in symmetric counterparts, showing distinct and well-defined interfaces, confirming the microphase separation. Additionally, different MWs fundamentally led to significant differences in miscibility, which consequently affected the crystallization behaviors of PLLA/PDLA blends. This work provides evidence for (im)miscibility and its crucial impact on the crystallization of PLLA/PDLA blends and has important implications for understanding the stereocomplexation of polymers.

Ultra-High-Molecular-Weight, Narrow-Polydispersity Polyacrylamides Synthesized Using Photoiniferter Polymerization to Generate High-Performance Flocculants.

Ultra-high-molecular-weight, water-soluble polyelectrolytes are commonly employed as flocculants for solid-liquid separation via colloidal destabilization, enabling the rapid and efficient removal of particulate matter from wastewater streams. A drive toward more sustainable and less polluting industrial practices, coupled with the desire to reduce freshwater usage and improve closed-loop systems, demands the development of flocculants with ever-higher dewatering dose performance. Herein, the use of trithiocarbonate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization under either blue LED (λmax = 470 nm) or UV (λmax = 365 nm) irradiation, known as photoiniferter polymerization, was successfully utilized to generate ultra-high-molecular-weight (Mn > 1,000,000 g mol-1) polyelectrolyte copolymer flocculants with narrow molecular weight distributions (Mw/Mn < 1.2). Cationic and anionic polyelectrolyte flocculants were synthesized containing various monomer compositions of acrylamide (AM), dimethylacrylamide (DMA), 3-(acryloyloxyethyll)trimethylammonium chloride (DMAEAq), 3-(acrylamidopropyl)trimethylammonium chloride (APTAC), sodium acrylate (NaAA), and sodium 2-(acrylamido)-2-methylpropylsulfonate (NaATBS) with high monomer conversion using simple experimental apparatus. The narrow molecular weight distribution cationic polyelectrolytes showed improved flocculation efficiency in the clarification of kaolin suspensions of up to 50% in comparison to a broad polydispersity (Mw/Mn > 5.0) commercial benchmark with an equivalent number average molecular weight. The improved performance of the narrow-polydispersity copolymers is attributed to the reduction in the content of the lower-molecular-weight polymer chains, which impart lower flocculation performance.

Enhanced nucleation of bimodal molecular weight distribution polymers: A molecular dynamics study

We perform coarse-grained molecular dynamics (CGMD) simulations to study the homogeneous nucleation of bimodal and unimodal molecular weight distribution polymers with equivalent average molecular weight. First, a statistical method is proposed to determine the critical nuclei and thus calculate the free energy barrier of nucleation. From the temperature dependence of diffusion coefficient, we also determine the activation energy of diffusion. Then we calculate the nucleation rate and find that it is consistent with the classical nucleation theory for homogeneous nucleation in semi-crystalline polymers. Compared with unimodal system, the bimodal system exhibits lower interfacial free energy and consequently lower free energy barrier for nucleation, while the two systems have similar activation energy for diffusion. This suggests that the promoted nucleation rate of bimodal molecular weight distribution polymer is a result of the reduction of interfacial free energy, which is eventually a consequence of chain-folding nucleation of long chain component.

Placental drug transport and fetal exposure during pregnancy is determined by drug molecular size, chemistry, and conformation

Pregnant people are unable to take many prescription and over-the-counter medications because of suspected or known risk to the fetus. This undermedication contributes to the high maternal mortality rate in the United States and detracts from the quality of life of pregnant people. As such, there is an urgent need to develop safe pharmaceutical formulations for use during pregnancy. Most drugs are small molecules that easily cross the placenta, which is the biological barrier that separates the maternal and fetal bloodstreams. One potential approach to preventing fetal drug accumulation is to design drug compounds that are excluded by the placenta; however, there is little understanding of how macromolecular drug properties affect transplacental transport. To address this knowledge gap, we examined the transport behavior of fluorescently-labeled polymers with varying size, conformation, and chemistry. We compared these polymers to unconjugated fluorescein, a small molecule model drug that readily crosses biological barriers. We found that molecular size affected transplacental transport in an in vitro model, BeWo b30 monolayers, as well as in pregnant mice, with larger polymers having lower permeability. In addition to size, polymer chemistry altered behavior, with polyethylene glycol (PEG) molecules permeating the placental barrier to a greater extent than dextrans of equivalent molecular weight. PEG molecules were also more readily taken up into placental cells in vivo. These findings will inform the future development of drug conjugates or other macromolecular medicines that can safely be used during pregnancy.

The effect of concentration extender on the making of lignin phenol-formaldehyde from coconut fibre as an environmentally friendly adhesive

This study aims to make adhesives with a variety of concentration extenders. First, the coconut husk was delignified with 25% NaOH and then precipitated with sulfuric acid. The yield of lignin from coconut coir was 38.92%, with a purity of 68%, a phenolic hydroxyl content of 2.47%, and an equivalent molecular weight of 1666.67 g/mol. Lignin was then used to synthesize phenol-formaldehyde (LPF) lignin by adding tapioca flour extender with variations of 10%, 20% and 30% of the mass of phenol through the resol method with 50% NaOH catalyst. Then the characterization was carried out using FTIR Spectrophotometer, XRD and adhesive test. The results showed that the LPF copolymer with a 10% extender was better than the LPF copolymer without an extender for wood adhesives with adhesive resistance of 955.34 N and low formaldehyde emission of 0.44 mg/L.

Intelligent modeling of hydrogen sulfide solubility in various types of single and multicomponent solvents

This study aims to study the solubility of acid gas, i.e., hydrogen sulfide (H2S) in different solvents. Three intelligent approaches, including Multilayer Perceptron (MLP), Gaussian Process Regression (GPR) and Radial Basis Function (RBF) were used to construct reliable models based on an extensive databank comprising 5148 measured samples from 54 published sources. The analyzed data cover 95 single and multicomponent solvents such as amines, ionic liquids, electrolytes, organics, etc., in broad pressure and temperature ranges. The proposed models require just three simple input variables, i.e., pressure, temperature and the equivalent molecular weight of solvent to determine the solubility. A competitive examination of the novel models implied that the GPR-based one gives the most appropriate estimations with excellent AARE, R2 and RRMSE values of 4.73%, 99.75% and 4.83%, respectively for the tested data. The mentioned intelligent model also performed well in describing the physical behaviors of H2S solubility at various operating conditions. Furthermore, analyzing the William's plot for the GPR-based model affirmed the high reliability of the analyzed databank, as the outlying data points comprise just 2.04% of entire data. In contrast to the literature models, the newly presented approaches proved to be applicable for different types of single and multicomponent H2S absorbers with AAREs less than 7%. Eventually, a sensitivity analysis based on the GPR model reflected the fact that the solvent equivalent molecular weight is the most influential factor in controlling H2S solubility.

Techno-economic analysis of non-aqueous hybrid redox flow batteries

Renewable energy has become indispensable to improving human life, but its growth is hampered by a lack of cost-effective energy storage systems to solve the intermittency problem. Non-aqueous hybrid redox flow batteries (NAqHRFBs), based on lithium metal anode and organic redox molecules (redoxmers), have been investigated as an attractive energy storage option because of their high cell voltages and energy densities compared to other redox flow battery candidates. However, little is known about the economic potential of NAqHRFBs, as well as the operational and materials impacts. This work establishes a techno-economic model to analyze the capital costs of NAqHRFBs with selected organic redoxmers, including 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). Sensitivity analyses for current density, area-specific resistance, cell voltage, electrolyte composition, redoxmer price, and equivalent molecular weight indicate the key factors in controlling NAqHRFB capital cost. To make the current NAqHRFB cost-effective, the first priority is to increase the operation current density over 10 times of those used in lab-scale tests, followed by adjusting redoxmer-related characteristics to afford more cost reduction space such as decreasing the unit price by ∼20 fold. The results have shed light on potential material development and system engineering directions to make NAqHRFBs viable for renewable energy storage.

Hydrophobically Associating Polymers Dissolved in Seawater for Enhanced Oil Recovery of Bohai Offshore Oilfields.

As compared to China’s overall oil reserves, the reserve share of offshore oilfields is rather significant. However, offshore oilfield circumstances for enhanced oil recovery (EOR) include not just severe temperatures and salinity, but also restricted space on offshore platforms. This harsh oil production environment requires polymers with relatively strong salt resistance, solubility, thickening ability, rapid, superior injection capabilities, and anti-shearing ability. As a result, research into polymers with high viscosity and quick solubility is recognized as critical to meeting the criteria of polymer flooding in offshore oil reservoirs. For the above purposes, a novel hydrophobically associating polymer (HAP) was prepared to be used for polymer flooding of Bohai offshore oilfields. The synthetic procedure was free radical polymerization in aqueous solutions starting at 0 °C, using acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and poly(ethylene glycol) octadecyl methacrylate (POM) as comonomers. It was discovered that under ideal conditions, the molecular weight of HAP exceeds 2.1 × 107 g⋅mol−1. In a simulated reservoir environment, HAP has substantially greater solubility, thickening property, and salt resistance than conventional polyacrylamide (HPAM), with equivalent molecular weight. Finally, the injectivity and propagation of the two polymers in porous media were investigated. Compared with HPAM, which has a similar molecular weight, HAP solution with the concentration of 0.175% had a much better oil displacement effect in the porous medium, which can enhance oil recovery by 8.8%. These discoveries have the potential to pave the way for chemical EOR in offshore oilfields.

Combining Hyperbranched and Linear Structures in Solid Polymer Electrolytes to Enhance Mechanical Properties and Room-Temperature Ion Transport

Polyethylene oxide (PEO)-based polymers are commonly studied for use as a solid polymer electrolyte for rechargeable Li-ion batteries; however, simultaneously achieving sufficient mechanical integrity and ionic conductivity has been a challenge. To address this problem, a customized polymer architecture is demonstrated wherein PEO bottle-brush arms are hyperbranched into a star architecture and then functionalized with end-grafted, linear PEO chains. The hierarchical architecture is designed to minimize crystallinity and therefore enhance ion transport via hyperbranching, while simultaneously addressing the need for mechanical integrity via the grafting of long, PEO chains (M n = 10,000). The polymers are doped with lithium bis(trifluoromethane) sulfonimide (LiTFSI), creating hierarchically hyperbranched (HB) solid polymer electrolytes. Compared to electrolytes prepared with linear PEO of equivalent molecular weight, the HB PEO electrolytes increase the room temperature ionic conductivity from ∼2.5 × 10–6 to 2.5 × 10−5 S/cm. The conductivity increases by an additional 50% by increasing the block length of the linear PEO in the bottle brush arms from M n = 1,000 to 2,000. The mechanical properties are improved by end-grafting linear PEO (M n = 10,000) onto the terminal groups of the HB PEO bottle-brush. Specifically, the Young’s modulus increases by two orders of magnitude to a level comparable to commercial PEO films, while only reducing the conductivity by 50% below the HB electrolyte without grafted PEO. This study addresses the trade-off between ion conductivity and mechanical properties, and shows that while significant improvements can be made to the mechanical properties with hierarchical grafting of long, linear chains, only modest gains are made in the room temperature conductivity.

Ідентифікація кластерної будови вуглеводнів за температурами плавлення

The presence of oscillatory changes in the substance properties in homologous series of hydrocarbons, in particular for the melting point, is analyzed. A method for predicting the mass burnout rate of normal structure alcohols and alkanes on the basis of melting point values to account for oscillations is presented. It is proved that the tendency to increase melting temperatures depending on the number of carbon atoms in the molecule for selected homologous series of hydrocarbons (alkanes, alkenes, alkynes, cycloalkanes of normal structure) has a certain oscillation by the principle of "even-odd" molecules or gradation deviation from linearity. It is shown that the similarity of this dependence between homologous series arises if alkenes and alkynes are considered as shorter molecules than the corresponding alkanes, and cycloalkanes – as longer. It is accepted as a working hypothesis that this is due to the presence of the smallest structural unit of matter in the clusters form with a certain coordination number. The oscillation properties of the substance are explained by the fact that clustering can occur both at the final carbon site in the molecule and at other carbons in the chain of the molecule, and this fact depends on the "parity-oddness". Based on the known values of melting temperatures in homologous series, the possible structure of clusters is proposed. It is shown that the obtained values of equivalent lengths for these clusters correlate with the corresponding melting temperatures. This correlation is described by the third degree polynomial, which gives an approximation coefficient of 0.995 and a mean deviation of 7.1 K. An approximation formula for calculating these classes melting point of hydrocarbons based on the values of equivalent molecular weight and cluster length has been developed. This calculation is characterized by an approximation factor of 0.997 and a mean deviation of 4.2 K. Emphasis is placed on the possibility of improving the calculation convergence with the substance properties, provided that the structure of the clusters is clarified.

Guar Gum as Flow Improver in Single-Phase Water and Liquid–Liquid Flows

In this study, the effectiveness of guar gum as a flow improver in single-phase water as well as in oil–water flows was investigated. Guar gum is one of the hydrocolloids mostly used as a flow improver because of its unique rheological behaviour. It forms highly viscous shear thinning solutions at very low concentrations. In the oil industry, pressure drop is experienced in the transportation of fluid due to skin friction in the pipeline which translates to high energy cost. The addition of small amount of heavy molecular weight synthetic polymer has been found to enhance flow in pipes. This phenomenon is called drag reduction (DR). However, very few reports exist on the potentials of natural polymers which are more environmentally friendly and cheaper as a DR agent. The experimental rig consists of a horizontal 12- and 20-mm-ID uPVC pipes with oil (ρ = 832 kg/m3; µ = 3.5 cP at 25 °C) and tap water (ρ = 998 kg/m3; µ = 1.0 cP at 25 °C) as test fluids. The molecular weight of guar gum was determined to be 994,035 ± 1.9% g/mol. Results showed that maximum drag reduction of 45% was achieved by the addition of 200 ppm of guar gum to single-phase water flow at Re of 69,000 in the 12-mm-ID pipe. In oil–water flows, maximum DR of 23% was achieved for 0.25 oil fraction and 200 ppm of guar gum. In addition, drag reduction was found to increase with pipe diameter and decrease with increasing oil fraction. DR with guar gum compares better with synthetic polymers of equivalent molecular weight with promise for wider industrial applications.

Glass transition analysis of model metallosupramolecular polyesters bearing pendant pyridine ligands with a controlled ligand–ligand distance

Supramolecular materials formed via metal-ligand coordination, so-called metallosupramolecular materials, have attracted attention due to their ability to modify a broad range of physical properties depending on the association strength at the coordination bond. Here, we demonstrate the correlation between the glass transition properties and the ligand distance by utilizing amorphous polyesters (denoted as PE-Py) with pendant pyridine ligands arranged homogeneously along the chain. The ligand distance is treated as the pyridine group equivalent molecular weight (MPy) and takes values of 900, 750, 550, and 420. The metal salt ZnCl2 forms coordination bonds with the pyridine ligands, generating a metallosupramolecular network. The fraction of coordinated pyridine is finely tuned by the mole ratio between the pyridine ligand and ZnCl2 ([Zn2+]/[Py]) while adhering to the stoichiometric rule. DSC measurements reveal that the variation in the glass transition temperature (Tg) with increasing [Zn2+]/[Py] is closely correlated with 1/MPy. Temperature-ramp rheological measurements are also performed, revealing that the apparent activation energy (Ea) of segmental motion has a quasi-linear relationship with 1/MPy. Thus, the present study demonstrates that the degree of restriction for segmental motion is very systematically strengthened as the ligand distance decreases, highlighting the importance of ligand distance in physical property control of metallosupramolecular materials. We here demonstrate the importance of ligand–ligand distance on physical property tuning of metallosupramolecular materials by utilizing model-like polyesters bearing pyridine ligands at the side groups with a controlled ligand-distance. The ligand distance is treated as the pyridine group equivalent molecular weight (MPy) and takes values of 900, 750, 550, and 420. The metal salt ZnCl2 forms coordination bonds with the pyridine ligands, generating a metallosupramolecular network. DSC and rheological measurements revealed that the glass transition temperatures and apparent activation energy (Ea) of segmental motion changes in a close correlation with 1/MPy.

Disentangling and Lamellar Thickening of Linear Polymers during Crystallization: Simulation of Bimodal and Unimodal Molecular Weight Distribution Systems.

We have performed coarse-grained molecular dynamics simulations to study the isothermal crystallization of bimodal and unimodal molecular weight distribution (MWD) polymers with equivalent average molecular weight (Mw). By using primitive path analysis, we can monitor the entanglement evolution during the process of crystallization. We have discovered a quantitative correlation between the degree of disentanglement and crystallinity, indicating that chain disentanglement permits the process of crystallization. In addition, the crystalline stem length also displays a linear relation with the degree of disentanglement at different temperatures. Based on the observation in our simulations, we can build a scenario of the whole process of chain disentangling and lamellar thickening on the basis of chain sliding diffusion. Furthermore, we have enough evidence to infer that the temperature dependence of crystalline stem length is basically a result of temperature dependence of chain sliding diffusion. Our observations are also in agreement with Hikosaka's sliding diffusion theory. Compared to the unimodal system, the disentanglement degree of the bimodal system is more delayed than its crystallinity due to the slower chain sliding of the long-chain component; the bimodal system reaches a larger crystalline stem length at all temperatures due to the promotion of higher chain sliding mobility of the short-chain component.

Yield and structural composition of pomelo peel pectins extracted under acidic and alkaline conditions

Extraction of pectin from pomelo peel was performed using water, acid and alkaline solutions with a microwave power of 1100 W for 2 min, and yield and structural/chemical characteristics of the extracted pectins were investigated. Extraction of pectin with water gave the lowest yield (6.5%, dry weight basis). The water-extracted pectin contained the highest amount of neutral sugar (29.5%), while equivalent molecular weight (MWeq) and degree of methylation (DM) were 43 kDa and 29.7%, respectively. Extraction of pectin with HCl solutions at concentrations of 25, 50, 100 and 200 mM resulted in a significant increase of pectin yields (12.1–20.5%) and pectins with high amount of galacturonic acid (83.3–85.6%). The MWeq and DM of the acid-extracted pectins ranged from 171 to 368 kDa and 53.9–82.5%, respectively. Compared to the acid, extraction with NaOH solutions at the same concentrations provided higher yields (13.9–24.2%), smaller size (142–187 kDa) and lower DM (<1.7%) pectins, while amount of galacturonic acid was comparable. The highest yield of extraction was found at a concentration of 50 mM for both HCl and NaOH solutions. Extraction of pomelo peel with 50 mM NaOH solution by reduction of the microwave power to 550 W and extending the extraction time to 15 min resulted in an increase of pectin yield (29.2%) and pectin with smaller size (76 kDa).

Ciprofloxacin-based polymer additives interact with degradable polyurethane to alter the hydrolysis kinetics of antibiotic-releasing nanofibres

Event Abstract Back to Event Ciprofloxacin-based polymer additives interact with degradable polyurethane to alter the hydrolysis kinetics of antibiotic-releasing nanofibres Meghan Wright1, Andrew T. Wong1, Meilin Yang2 and Paul Santerre1, 2 1 University of Toronto, Institute of Biomaterials and Biomedical Engineering, Canada 2 University of Toronto, Faculty of Dentistry, Canada Introduction: Within the field of drug-loaded nanofibres, there has been little investigation into understanding the effect of added drug on electrospun fibre biodegradation characteristics despite evidence that added drugs have the potential to alter the rate of degradation of bulk polymer[1], microparticles[2] and even nanofibres[3],[4]. The goal of the current work was to determine the effect of adding the antibiotic ciprofloxacin (CF) and a proprietary antimicrobial polymer (AP) containing CF on the biodegradation rate of electrospun polycarbonate urethane (PCNU) nanofibre scaffolds. It was hypothesized that the added drug would affect the PCNU biodegradation rate by influencing the unique hydrogen-bonding (H-bonding) and microstructure character of the PCNU[5]. Materials and Methods: PCNU was synthesized with hexane diisocyanate:polycarbonate diol:butane diol in a molar ratio of 3:2:1[5]. The AP (7 and 15% w/w equivalent CF) or free CF-HCl (15% w/w) were incorporated via blend electrospinning. Scaffold H-bonding and microstructure were investigated via attenuated total reflectance Fourier transform IR spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). Matrix degradation and antimicrobial release studies were carried out in PBS at 37°C for 28 days; drug release was measured by high performance liquid chromatography (HPLC), and PCNU degradation was measured using gel permeation chromatography (GPC). The cell compatibility of release products was assessed using human gingival fibroblasts (HGF), and the minimum inhibitory concentration (MIC) of released CF was measured against P. gingivalis cultures. Results and Discussion: CF from the AP scaffold was released slowly over the duration of the study, while drug aggregation within the 15% w/w CF-HCl scaffolds led to a burst release (Fig.1). The addition of drug caused an increase in the hydrolytic stability of the PCNU scaffolds, proportional to the amount of drug added, regardless of the form it was added (Fig.2). Fig.1. Cumulative release of CF in PBS (pH ~ 7) at 37°C (μM). Data are mean ± SD (n=9). Fig.2. Reduction in polystyrene equivalent weight average molecular weight (Mw), as a percent (%) of original (t=0 days), determined by GPC. Data are the mean ± SD (n=9). At day 28, H-bonding (FTIR) within the hard-segment and phase mixing (DSC) had decreased for the 0% w/w CF scaffolds and increased for the drug-loaded scaffolds (data not shown). Increased H-bonding and phase mixing for the latter may have led to shielding of the hydrolytically susceptible carbonate soft-segment, with the result that the drug-loaded scaffolds had greater stability. Accumulated PCNU biodegradation products (regardless of drug presence) significantly decreased HGF relative metabolic activity (Fig. 3). The MIC of released CF was higher than that of CF-HCl off-the-shelf (~0.5 µg/mL vs. 0.25 µg/mL respectively). Fig.3. Relative metabolic activity as a % of the growth medium control of Day 7 scaffold release products. * Represents significant difference from growth medium control (p < 0.05). Data are the mean ± SE (n=9). Conclusion: The results indicate the ability to use AP to generate electrospun scaffolds with a sustained (>28 days) release of CF. The combination of sustained drug release and delayed scaffold degradation presents a viable treatment modality for medical device applications requiring long term antimicrobial management (e.g. post-surgical oral wounds). National Science and Engineering Research Council (NSERC) Synergy; NSERC CGS D; IBBME; Interface Biologics Inc. for supply of AP

Formation of Nanofibers from Pure and Mixed Waste Streams Using Electrospinning

New methods are needed to reprocess the excess of plastics in the waste stream. In this work, bottle-grade polyethylene terephthalate (PET), Styrofoam, and polycarbonate from compact discs (CDs) were spun into nanofibers as fine as ca. 100 nm in diameter using the electrospinning technique. The mechanical properties of the fibers were evaluated using microtensile testing. The elastic moduli ranged from 15 to 60 MPa, and displayed stiffnesses comparable or greater than fibers made from commercial polymers of equivalent molecular weight. Nanofibers were also prepared from blends of Styrofoam and recycled polycarbonate. Recycled PET fibers were tested for application in water filtration and had greater than 99% filtration efficiency of 1 μm particles. Nanofibers from both pure and mixed waste streams are expected to have applications in myriad areas such as ultra/microfiltration, composites, and tissue engineering.