Influence Of Polymer Molecular Weight Research Articles

Molecular size of surfactants affects their degree of enrichment in the sea spray aerosol formation

Sea spray aerosol (SSA), the largest source of natural primary aerosol, plays an important role in atmospheric chemical processes and the earth radiation balance. Its formation process is controlled by many factors. In this study, ethylene glycol (EG) and polyethylene glycol (PEG) with three different molecular weights (200, 400, 600) were used to investigate the influence of molecular size on the properties of submicron SSA produced by plunging jet from an adjustable home-built SSA generator. Different parameters were tested to obtain the optimum experimental conditions. The addition of EG and PEG inhibited the production of SSA and increased the geometric mean diameter (GMD) between 10 and 35 nm. However, PEG with a molecular weight of 600 could promote the production of SSA at higher concentrations, which means that the molecular weight and concentration of the polymer would affect the production efficiency of SSA. Combining with the measurement of surface tension, we found no clear relationship between surface tension and the yield of SSA, due to the properties of the substances themselves. Transmission electron microscopy images show that the addition of EG and PEG could significantly change the structure of salt nuclei in SSA. PEG was significantly enriched in SSA (with enrichment factors within the range 92.9–133.4), and the enrichment was independent of the sampling time, while increasing with the increase of molecular weight. Our results highlight the influence of polymer molecular weight on the properties of SSA, and their importance to improve the accuracy of aerosol emission model parameters.

Influence of Polymer Molecular Weight on Chain Conformation at the Polystyrene/Silver Interface.

The dependence between the conformation of polystyrene (PS) and its molecular weight (Mw) in the vicinity of a metal interface was investigated by sum frequency generation (SFG) spectroscopy. Tilt angles θ ≥ 50° (the angle between the C2 axis of the pendant phenyl ring and the surface normal) were observed for all samples because of the interaction between the aromatic rings and the metal surface. Furthermore, it was found that θ decreases with increasing Mw for PS samples ranging from 20 × 103 g/mol to 400 × 103 g/mol. The intensity of the backbone SFG signal was higher for high Mw PS, compared to low Mw PS, indicating a greater number of backbone interactions with the silver substrate surface for the high Mw sample. These structural differences are driven by different entropic and enthalpic contributions to the free energy of adsorption for different polymer molecular weights. Differences in the polymer free volume and in the relative amount of chain ends with higher mobility may also influence the chain conformation. These results suggest that important interfacial properties of polymeric thin films, such as adhesion and wettability, could be tailored by modifying the polymer Mw to achieve the desired interfacial conformation.

Tailoring Different Molecular Weight Phenylene-Polybenzimidazole Membranes with Remarkable Oxidative Stability and Conductive Properties for High-Temperature Polymer Electrolyte Fuel Cells.

Polybenzimidazole (ph-PBI) polymer was synthesized with different molecular weights (MWs) and casted into conductive films for use in high-temperature fuel cells (FCs). A comprehensive study on the influence of polymer MW on membrane cast efficiency, chemical stability, thermal behavior, tensile strength, conductivity, FC performance, and durability was reported. The synthesized materials were characterized by different techniques, including, nuclear magnetic resonance spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, impedance microscopy, and scanning electron microscopy. The results showed the importance of manufacturing ph-PBI membranes with controlled properties to achieve high efficiency FCs. High MW ph-PBI membrane (119 kDa) showed a slower rate of chemical degradation, remarkable mechanical properties, and an improved FC performance compared to low MW ph-PBI membrane (39 kDa), thanks to the architecture of high MW ph-PBI. A gain of 91% in proton conductivity with a 47% in FC power density was obtained for the ph-PBI membrane with MW 119 kDa.

Influence of polymer molecular weight on the properties of in situ synthesized silver–methylcellulose nanocomposite films with a CO2 laser

We investigate the influence of polymer molecular weight on the properties of silver–methylcellulose (Ag–MC) nanocomposite films synthesized by the irradiation of a CO2 laser. Although the reduction power of MC with a smaller molecular weight turns out to be stronger than that with a larger molecular weight in the solution phase, we do not see such a clear difference when MC is in the matrix phase. For the 30 s irradiation at the laser power of 0.8 W, the size of Ag nanoparticles (NPs) in the two types of MC matrix is similar, and it is about 30 nm. However, for the longer irradiation time at the same laser power, aggregation of Ag NPs set in, and it is more serious for the Ag–MC film with MC of larger molecular weight. We also carry out the antibacterial test with the Ag–MC films, and find that the Ag–MC film synthesized at the lower laser power and shorter irradiation time generally exhibits a stronger antibacterial effect.

Tuning dielectric-semiconductor interfacial properties in organic phototransistors for ultralow light detection

The quality of the dielectric-semiconductor interface plays a very crucial role in determining the photosensory performances of the organic field effect transistors. Herein, we have investigated the influence of polymer molecular weight on the photosensing behaviour of the organic transistors. In this study, we find high molecular weight PMMA to be more effective as gate dielectric in phototransistor applications compared to the low molecular weight PMMA due to the better morphological arrangements of the active semiconducting layer on top of its surface. The maximum values of photosensitivity and responsivity improved substantially from 3.5 × 10 4 and 8.3 × 10 3 A/W in the low molecular weight PMMA devices to 10 5 and 6.9 × 10 4 A/W in the high molecular weight PMMA devices, respectively, under same intensity light irradiation. Moreover, we have also proposed a simple, yet highly efficient interface modification technique to enhance the photosensitivity of the transistors under low light illumination through the plasma treatment of the dielectric layer. After the interface modification of the high molecular weight PMMA devices, the photosensitivity value enhanced significantly from 3.67 × 10 2 to 7.08 × 10 3 under an ultralow optical power of 5 μW/cm 2 . Post interface modification improvements in the device photosensitivity values were attributed to the plasma induced generation of polar surface functionalities which effectively enhance the number of free holes in the channel region by trapping the photo-generated electrons at the interface. This report, thus, represents a step forward towards improving the performance of the phototransistors for their applications in high performance organic optoelectronic devices. • Polymer molecular weight influenced transistor photoresponse has been explored. • Semiconductor grain structure strongly correlates with the device photoresponse. • Strategy of dielectric air plasma treatment has been demonstrated. • Optimum plasma treatment time has been reached to achieve ultralow light sensitivity.

Cell Separation in Aqueous Two-Phase Systems - Influence of Polymer Molecular Weight and Tie-Line Length on the Resolution of Five Model Cell Lines.

The availability of clinical-scale downstream processing strategies for cell-based products presents a critical juncture between basic research and clinical development. Aqueous two-phase systems (ATPS) facilitate the label-free, scalable, and cost-effective separation of cells, and are a versatile tool for downstream processing of cell-based therapeutics. Here, we report the application of a previously developed robotic screening platform, here extended to enable a multiplexed high-throughput cell partitioning analysis in ATPS. We investigated the influence of polymer molecular weight and tie-line length on the resolution of five model cell lines in "charge-sensitive" polyethylene-glycol (PEG)-dextran ATPS. We show, how these factors influence cell partitioning, and that the combination of low molecular weight PEGs and high molecular weight dextrans enable the highest resolution of the five cell lines. Furthermore, we demonstrate that the separability of each cell line from the mixture is highly dependent on the polymer molecular weight composition and tie-line length. Using a countercurrent distribution model we demonstrate that our screenings yielded conditions that theoretically enable the isolation of four of the five cell lines with high purity (>99.9%) and yield.

Antimicrobial Peptide-Polymer Conjugates with High Activity: Influence of Polymer Molecular Weight and Peptide Sequence on Antimicrobial Activity, Proteolysis, and Biocompatibility.

We report the synthesis, characterization, activity, and biocompatibility of a novel series of antimicrobial peptide-polymer conjugates. Using parent peptide aurein 2.2, we designed a peptide array (∼100 peptides) with single and multiple W and R mutations and identified antimicrobial peptides (AMPs) with potent activity against Staphylococcus aureus (S. aureus). These novel AMPs were conjugated to hyperbranched polyglycerols (HPGs) of different molecular weights and number of peptides to improve their antimicrobial activity and toxicity. The cell and blood compatibility studies of these conjugates demonstrated better properties than those of the AMP alone. However, conjugates showed lower antimicrobial activity in comparison to that of peptides, as determined from minimal inhibition concentrations (MICs) against S. aureus, but considerably better than that of the available polymer-AMP conjugates in the literature. In addition to measuring MICs and characterizing the biocompatibility, circular dichroism spectroscopy was used to investigate the interaction of the novel conjugates with model bacterial biomembranes. Moreover, the novel conjugates were exposed to trypsin to evaluate their stability. It was found that the conjugates resist proteolysis in comparison with unprotected peptides. The peptide conjugates were active in serum and whole blood. Overall, the results show that combining a highly active AMP and low-molecular-weight HPG yields bioconjugates with excellent biocompatibility, MICs below 100 μg/mL, and proteolytic stability, which could potentially improve its utility for in vivo applications.

Crystallinity of Electrospun and Centrifugal Spun Polycaprolactone Fibers: A Comparative Study

Crystalline properties of semicrystalline polymers are very important parameters that can influence the application area. The internal structure, like the mentioned crystalline properties, of polymers can be influenced by the production technology itself and by changing technology parameters. The present work is devoted to testing of electrospun and centrifugal spun fibrous and nanofibrous materials and compare them to foils and granules made from the same raw polymer. The test setup reveals the structural differences caused by the production technology. Effects of average molecular weight are also exhibited. The applied biodegradable and biocompatible polymer is polycaprolactone (PCL) as it is a widespread material for medical purposes. The crystallinity of PCL has significant effect on rate of degradation that is an important parameter for a biodegradable material and determines the applicability. The results of differential scanning calorimetry (DSC) showed that, at the degree of crystallinity, there is a minor difference between the electrospun and centrifugal spun fibrous materials. However, the significant influence of polymer molecular weight was exhibited. The morphology of the fibrous materials, represented by fiber diameter, also did not demonstrate any connection to final measured crystallinity degree of the tested materials.

Influence of polymer molecular weight on in vitro dissolution behavior and in vivo performance of celecoxib:PVP amorphous solid dispersions

In this study, the influence of the molecular weight of polyvinylpyrrolidone (PVP) on the non-sink in vitro dissolution and in vivo performance of celecoxib (CCX):PVP amorphous solid dispersions were investigated. The dissolution rate of CCX from the amorphous solid dispersions increased with decreasing PVP molecular weight and crystallization inhibition was increased with increasing molecular weight of PVP, but reached a maximum for PVP K30. This suggested that the crystallization inhibition was not proportional with molecular weight of the polymer, but rather there was an optimal molecular weight where the crystallization inhibition was strongest.Consistent with the findings from the non-sink in vitro dissolution tests, the amorphous solid dispersions with the highest molecular weight PVPs (K30 and K60) resulted in significantly higher in vivo bioavailability (AUC0–24h) compared with pure amorphous and crystalline CCX.A linear relationship between the in vitro and in vivo parameter AUC0–24h indicated that the simple non-sink in vitro dissolution method used in this study could be used to predict the in vivo performance of amorphous solid dispersion with good precision, which enabled a ranking between the different formulations. In conclusion, the findings of this study demonstrated that the in vitro and in vivo performance of CCX:PVP amorphous solid dispersions were significantly controlled by the molecular weight of the polymer.

Influence of molecular weight on kinetics release of metronidazole from proline-based polymers prepared by RAFT polymerization

In the current study, the influence of polymer molecular weight on the release of metronidazole (MTZ) as a drug model from synthesized proline-based polymers was studied.

Influence of Polymer Molecular Weight on Drug–polymer Solubility: A Comparison between Experimentally Determined Solubility in PVP and Prediction Derived from Solubility in Monomer

In this study, the influence of polymer molecular weight on drug-polymer solubility was investigated using binary systems containing indomethacin (IMC) and polyvinylpyrrolidone (PVP) of different molecular weights. The experimental solubility in PVP, measured using a differential scanning calorimetry annealing method, was compared with the solubility calculated from the solubility of the drug in the liquid analogue N-vinylpyrrolidone (NVP). The experimental solubility of IMC in the low-molecular-weight PVP K12 was not significantly different from that in the higher molecular weight PVPs (K25, K30, and K90). The calculated solubilities derived from the solubility in NVP (0.31-0.32 g/g) were found to be lower than those experimentally determined in PVP (0.38-0.40 g/g). Nevertheless, the similarity between the values indicates that the analogue solubility can provide valuable indications on the solubility in the polymer. Hence, if a drug is soluble in an analogue of the polymer, it is most likely also soluble in the polymer. In conclusion, the solubility of a given drug-polymer system is determined by the strength of the drug-polymer interactions rather than the molecular weight of the polymer. Therefore, during the first screenings for drug solubility in polymers, only one representative molecular weight per polymer is needed.

Influence of Polymer Molecular Weight on in-vitro Characteristics and Cytotoxicity of Fulvestrant Loaded Nanoparticles

The objective of this research was to fabricate a novel polymeric nanoparticulate system of Fulvestrant (FLV) and investigate the effect of polymer molecular weight variation on in vitro properties and also anti-proliferative potency of the carriers. Two different forms of polymerspoly( lactic-co-glycolic acid) (PLGA) were employed for the fabrication of polymeric nanoparticles (PNPs) by using a combination of diffusion-emulsification-salting out preparation procedure. In vitro evaluation of the PNPs was performed in terms of entrapment efficiency, particle size, surface charge, thermal behavior redispersibility ability, in vitro drug release profile, release mechanisms, stability and anti-proliferative activity. PNPs were obtained in the size range between 191.80 to 211.80 nm with a lower polydesipersity index. FLV release from the developed PNP formulations was more than a 45 days period. Zero order release was obtained with low molecular weight form of PLGA PNPs, while relatively high weights of PLGA PNPs followed square root of time (the Higuchi's pattern) dependent release. Additionally, stability studies showed that PNPs were stable at 4°C for a six months period. In the experimental work, it was also observed that FLV, which was entrapped into the PNPs, displayed strong in vitro antiproliferative activity on MCF-7 human breast cancer cells for a 48 h period, when compared to free the form of FLV. As a conclusion, the PNPs developed in this research may have the potential to deal with the major handicaps of the available IM form of FLV, and may be a new promising delivery preparation approach. Keywords: Fulvestrant, in vitro cytotoxicity, MCF-7, PLGA nanoparticles, polymer molecular weight.

Modeling aqueous two-phase systems: III. Polymers and organic salts as ATPS former

In this work the electrolyte perturbed chain statistical associating fluid theory (ePC-SAFT) is applied to model aqueous two-phase systems (ATPS) containing one of 6 different polymers and one of 8 different organic salts at temperatures between 278.15K and 313.15K. To accurately model the thermodynamic properties of organic-salt solutions, a novel modeling approach was applied, which accounts for the non-spherical shape of the anions. Applying this approach, 14 organic salt solutions have been modeled with an overall average relative deviation of 0.23% for solution densities and 1.51% for osmotic coefficients. The modeling of the polymers (PEG, PEGDME, PPG, and poly(ethylene glycol-co-propylene glycol)) has been carried out using a copolymer approach accounting for different molecular interactions of the polymer segments. Applying this approach, ATPS containing polymers and organic salts were modeled accurately. The overall absolute average deviation of the modeling with respect to the concentrations of the phase-forming components was 2.10wt%. The influence of polymer molecular weight, polymer composition, kind of salt, pH, and temperature on the equilibrium composition and densities of the two phases was modeled correctly with ePC-SAFT. Moreover, it is shown that by applying ion-specific model parameters, ePC-SAFT is even capable of predicting ATPS containing salts which were not used for the parameter estimation.

INFLUENCE OF POLYMER MOLECULAR WEIGHT ON LIGHT HARVESTING AND PERFORMANCE PARAMETERS OF THE ORGANIC SOLAR CELL

In the present article, we try to illustrate the behavior of the most common organic solar cell under the influence of polymermolecular weight (in the range of 21,100-128,800 g/mol) on light harvesting and device performance parameters. The presentwork demonstrates that, the molecular weight of donor polymer plays an important role in the light harvesting and performanceof a common-bulk heterojunction organic solar cell based on poly(3-hexylthiophene) (P3HT), as a donor polymer, and[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as an acceptor. Through this study it is found that, the optical absorptionof P3HT:PCBM solar cell active layer is increased by increasing P3HT molecular weight. This may be as a result of increasingactive layer thickness and/or increasing backbone chain length of the polymer. In the same time, the absorption wavelengthrange is narrowed and the absorption peak position is shifted towards lower wavelengths due to the entanglement in polymerchains and reduction in polymer crystallinity at higher P3HT molecular weights. The external quantum efficiency (EQE) of theinvestigated solar cells is increased by increasing P3HT molecular weight until the molecular weight that entangles the P3HTchins and, therefore, restricts the charge carrier transfer and, then, reduces the EQE of the P3HT:PCBM solar cell. The performanceparameters of the P3HT:PCBM solar cell are improved by increasing P3HT molecular weights around 25,300 g/moland, after that, deteriorated at higher P3HT molecular weights up to 128,800 g/mol as a result of polymer chain entanglementand reduction of the P3HT crystallinity. The present study shows that the best P3HT molecular weight is 25,300 g/mol, whichproduces power conversion efficiency around 2.5 %.

Novel pentablock copolymer-based nanoparticulate systems for sustained protein delivery.

The design, synthesis, and application of novel biodegradable and biocompatible pentablock (PB) copolymers, i.e., polyglycolic acid-polycaprolactone-polyethylene glycol-polycaprolactone-polyglycolic acid (PGA-PCL-PEG-PCL-PGA) and polylactic acid-polycaprolactone-polyethylene glycol-polycaprolactone-polylactic acid (PLA-PCL-PEG-PCL-PLA) for sustained protein delivery, are reported. The PB copolymers can be engineered to generate sustained delivery of protein therapeutics to the posterior segment of the eye. PB copolymers with different block arrangements and molecular weights were synthesized by ring-opening polymerization and characterized by proton nuclear magnetic resonance ((1)H-NMR), gel permeation chromatography (GPC), and X-ray diffraction (XRD) spectroscopy. Immunoglobulin G (IgG) was selected as a model protein due to its structural similarity to bevacizumab. The influence of polymer molecular weight, composition, and isomerism on formulation parameters such as entrapment efficiency, drug loading, and in vitro release profile was delineated. Crystallinity and molecular weight of copolymers exhibited a substantial effect on formulation parameters. A secondary structure of released IgG was confirmed by circular dichroism (CD) spectroscopy. In vitro cytotoxicity, cell viability, and biocompatibility studies performed on human retinal pigment epithelial cells (ARPE-19) and/or macrophage cell line (RAW 264.7) demonstrated PB copolymers to be excellent biomaterials. Novel PB polymers may be the answer to the unmet need of a sustained release protein formulation.

Influence of polymer molecular weight in osteoinductive composites for bone tissue regeneration

In bone tissue regeneration, certain polymer and calcium-phosphate-based composites have been reported to enhance some biological surface phenomena, facilitating osteoinduction. Although the crucial role of inorganic fillers in heterotopic bone formation by such materials has been shown, no reports have been published on the potential effects the polymer phase may have. The present work starts from the assumption that the polymer molecular weight regulates the fluid uptake, which determines the hydrolysis rate and the occurrence of biological surface processes. Here, two composites were prepared by extruding two different molecular weight l/d,l-lactide copolymers with calcium phosphate apatite. The lower molecular weight copolymer allowed larger fluid uptake in the composite thereof, which was correlated with a higher capacity to adsorb proteins in vitro. Further, the large fluid absorption led to a quicker composite degradation that generated rougher surfaces and enhanced ion release. Following intramuscular implantation in sheep, only the composite with the lower molecular weight polymer could induce heterotopic bone formation. Besides influencing the biological potential of composites, the molecular weight also regulated their viscoelastic behaviour under cyclic stresses. The results lead to the conclusion that designing biomaterials with appropriate physico-chemical characteristics is crucial for bone tissue regeneration in mechanical load-bearing sites.

Influence of Polymer Molecular Weight on the Parabolic and Linear Growth Regime of PDADMAC/PSS Multilayers

The buildup of polyelectrolyte multilayers is investigated in solution with multiple angle null-ellipsometry. Polyanion poly(styrenesulfonate) (PSS) and polycation poly(diallyldimethylammonium) (PDADMAC) are adsorbed sequentially from 0.1 M NaCl solution. First the films grow parabolically. After Ntrans deposited PDADMAC/PSS layer pairs a transition from a parabolic to a linear growth occurs. For molecular weights above a threshold (Mw(PSS) > 25 kDa and Mw(PDADMAC) > 80 kDa), Ntrans is 15, the thickness per layer pair in the linear growth regime is 12.3 nm. If either the PDADMAC or the PSS molecular weight is decreased below the threshold value, Ntrans either falls (for PDADMAC, lowest value observed is 8) or rises (for PSS, highest value observed is 33), respectively. Simultaneously, in the linear growth regime, the thickness per layer pair decreases (down to 4.3 nm) or rises (up to 25 nm). Furthermore, for low molecular weight PSS, three growth regimes are observed: exponential, parabolic, and linear. T...

Nanosized colloidal particles from thermosensitive poly(methoxydiethyleneglycol methacrylate)s in aqueous media

The formation of well-defined colloidal particles (mesoglobules) from the thermosensitive polymer poly(methoxydiethyleneglycol methacrylate) was observed in dilute aqueous solutions (0.5–1.0 g/L) by turbidimetry and dynamic light scattering (DLS). DLS measurements were performed at 70 °C and showed a strong influence of polymer molecular weight: the hydrodynamic diameters of the mesoglobules increased from ca. 160 to 330 nm with a relatively small, i.e., from 6,400 to 14,000, increase in molecular weight. The addition of sodium dodecyl sulfate (SDS) at surfactant/polymer ratios (s/p, g/g) ranging from 0.3 to 0.5 practically inhibited the clouding of the solutions as the initial transmittance decreased by only 10–30%. Furthermore, a dramatic shift of the original cloud point values taken as a 10% decrease in transmittance, by approximately 20–60 °C was registered upon the surfactant addition. The presence of SDS resulted in size reduction by 52–90% as indicated by DLS.

Effects of polymer molecular weight on relative oral bioavailability of curcumin

BackgroundPolylactic-co-glycolic acid (PLGA) nanoparticles have been used to increase the relative oral bioavailability of hydrophobic compounds and polyphenols in recent years, but the effects of the molecular weight of PLGA on bioavailability are still unknown. This study investigated the influence of polymer molecular weight on the relative oral bioavailability of curcumin, and explored the possible mechanism accounting for the outcome.MethodsCurcumin encapsulated in low (5000–15,000) and high (40,000–75,000) molecular weight PLGA (LMw-NPC and HMw-NPC, respectively) were prepared using an emulsification-solvent evaporation method. Curcumin alone and in the nanoformulations was administered orally to freely mobile rats, and blood samples were collected to evaluate the bioavailability of curcumin, LMw-NPC, and HMw-NPC. An ex vivo experimental gut absorption model was used to investigate the effects of different molecular weights of PLGA formulation on absorption of curcumin. High-performance liquid chromatography with diode array detection was used for quantification of curcumin in biosamples.ResultsThere were no significant differences in particle properties between LMw-NPC and HMw-NPC, but the relative bioavailability of HMw-NPC was 1.67-fold and 40-fold higher than that of LMw-NPC and conventional curcumin, respectively. In addition, the mean peak concentration (Cmax) of conventional curcumin, LMw-NPC, and HMw-NPC was 0.028, 0.042, and 0.057 μg/mL, respectively. The gut absorption study further revealed that the HMw-PLGA formulation markedly increased the absorption rate of curcumin in the duodenum and resulted in excellent bioavailability compared with conventional curcumin and LMw-NPC.ConclusionOur findings demonstrate that different molecular weights of PLGA have varying bioavailability, contributing to changes in the absorption rate at the duodenum. The results of this study provide the rationale for design of a nanomedicine delivery system to enhance the bioavailability of water-insoluble pharmaceutical compounds and functional foods.

REMOVED: Influence of Polymer Molecular Weight and Purity of Polymers in the Synthesis of SRFN-Membranes Via Phase Inversion

REMOVED: Influence of Polymer Molecular Weight and Purity of Polymers in the Synthesis of SRFN-Membranes Via Phase Inversion