High Molecular Weight Samples Research Articles

Insights on influence of polymer molecular weight on gas sorption, transport and plasticization in glassy 6FDA-DAM polyimide membranes

It is well-known that spinning of defect-free asymmetric polyimide hollow fibers is promoted by using high polymer molecular weight. On the other hand, effects of polymer molecular weight on microstructure and separation performance of dense film 6FDA-based polyimide membranes relevant to sheath layers of composite membranes are less well-explored. In this work, gas sorption, diffusion and permeation of CO2, N2 and CH4 for 6FDA-DAM dense films are considered for 45 kDa and 176 kDa weight average molecular weights. Such molecular weights are relevant for practical hollow fiber spinning of membranes. Earlier results for polystyrene samples show similar trends in dual mode sorption model results like those noted here for the 6FDA-DAM polyimide case; however, effects on permeation like those considered here were not addressed for the polystyrene case. Here we also address actual pure and mixed gas CO2 and CH4 permeation and show higher free volumes, higher gas permeability but lower 50:50 CO2/CH4 selectivity associated with the higher molecular weight sample. Analysis using the self-consistent dual-mode sorption and transport models help understand the observed trends. Our results suggest denser packing of polymer segments exists in the Henry's law environment of the low molecular weight sample. Moreover, the higher polymer segmental packing in the Henry's law environment suppresses CO2 plasticization with a dual-mode microstructure controlling separation performance and plasticization behavior for this important member of the 6FDA polyimide family. We show evidence of effects of charge transfer complexes as possible main features in these trends. These dense film results help guide future work on dense sheath layers on composite hollow fiber membranes.

Investigation of the Effectiveness of Photo Deprotection of Polypeptides in Solution and within the Core of Miniemulsion-Derived Nanoparticles.

Homopolymerization of ortho-nitrobenzyl (oNB)-protected l-cysteine and l-glutamic acid was systematically studied in different solvents and at different monomer to initiator ratios, revealing the best reaction control in dimethylformamide (DMF) across a range of degrees of polymerization. In the subsequent ultraviolet (UV)-cleavage studies, it was found that quantitative deprotection upon UV exposure at 365 nm was not achievable for either of the homopolypeptides as confirmed by 1H NMR and UV/visible (UV/vis) analyses. While the poly(oNB-l-cysteine) deprotected more readily with no effect of the polypeptide molecular weight, lower molecular weight poly(oNB-l-glutamate) reached maximum deprotection faster than high molecular weight samples. This was further confirmed by the pH changes of the solution. When incorporated into the core of miniemulsion-derived nanoparticles, both oNB-protected copolypeptides were successfully deprotected as evident from a color change and a pH change in the case of poly(oNB-l-glutamate). However, the removal of the deprotection byproduct nitrosobenzaldehyde proved unsuccessful, which indicates a diffusion barrier caused by the nanoparticle's surfactant. The study provides insights and guidelines for the UV deprotection of polypeptides and demonstrates the ability to selectively UV-deprotect polypeptides in the confined space of a nanoparticle dispersion.

Single-Ion Mass Spectrometry for Heterogeneous and High Molecular Weight Samples.

In charge detection mass spectrometry (CD-MS) the mass of each individual ion is determined from the measurement of its mass to charge ratio (m/z) and charge. Performing this measurement for thousands of ions allows mass distributions to be measured for heterogeneous and high mass samples that cannot be analyzed by conventional mass spectrometry (MS). CD-MS opens the door to accurate mass measurements for samples into the giga-Dalton regime, vastly expanding the reach of MS and allowing mass distributions to be determined for viruses, gene therapies, and vaccines. Following the success of CD-MS, single-ion mass measurements have recently been performed on an Orbitrap. CD-MS and Orbitrap individual ion mass spectrometry (I2MS) are described. Illustrative examples are provided, and the prospects for higher resolution measurements discussed. In the case of CD-MS, computer simulations indicate that much higher resolving powers are within reach. The ability to perform high-resolution CD-MS analysis of heterogeneous samples will be enabling and disruptive in top-down MS as high-resolution m/z and accurate charge measurements will allow very complex m/z spectra to be unraveled.

Investigation of density, viscosity and derived thermodynamic properties of CO2-free and CO2-loaded poly(ethylene imine) aqueous systems at different temperatures and 0.1 MPa

In this work, the density and viscosity for poly(ethylene imine) (PEI1800/10000) aqueous systems with and without CO2 over PEI concentrations (wt% = 5, 10, 15, 20, 30) are measured at temperatures from (293.15 to 333.15) K and 0.1 MPa. Based on the experimental data, the thermal expansion coefficient (αp), viscosity activation energy (Eη) and CO2 diffusion coefficient (DCO2) are calculated. The results show that the density and viscosity increase as the PEI concentration and CO2 loading increase. The higher molecular weight samples also give higher density and viscosity. The high viscosity further results in the large activation energy and low CO2 diffusion coefficient. All the experimental results are discussed from the perspective of intermolecular interactions which are further verified by the reaction mechanism and FT-IR spectra.

Abstract 42: High-throughput next-generation sequencing research solutions for detection of oncology variants, gene fusion events, and key oncology endpoints

Abstract Introduction: The Ion Torrent Genexus System has redefined the genomic profiling paradigm as the first fully-integrated, next-generation sequencing (NGS) research platform to provide an automated sample-to-report workflow with results in a single day. With a purification instrument, an enhanced chip architecture, and downstream reporting, the Genexus System provides a convenient solution to enable oncology research. Here we highlight the oncology research applications and high-throughput NGS capabilities of the Genexus System with Oncomine Comprehensive Assay Plus (OCA Plus), an oncology research panel that can detect variants, fusions, and evaluate key oncology research endpoints. We demonstrate the ability of OCA Plus on Genexus to evaluate tumor mutational burden (TMB), microsatellite instability (MSI), loss of heterozygosity (LOH), and homologous recombination repair deficiency (HRD). Methods: The high-throughput capabilities of the Genexus System enable it to support large oncology research panels such as OCA Plus, which comprises over 13,000 amplicons. The extensive per sample coverage allows for comprehensive DNA and RNA genomic profiling of relevant cancer biomarkers in over 500 genes including detection of over 1,300 fusion isoforms. We utilized high-molecular weight and FFPE samples, reference controls, and orthogonally tested research samples to evaluate DNA variant calling, RNA fusion calling, and key oncology research endpoints, including MSI, LOH, TMB, and HRD. Results: Commercially sourced reference control and research samples were sequenced using OCA Plus on the Genexus System. Sequencing data metrics showed ≥24 million reads per sample, with four samples supported per run. The high-throughput capacity of the Genexus chip architecture results in >95% of amplicons achieving a minimum of 500X coverage with an average coverage uniformity of ≥95% when evaluated across all >13,000 amplicons. Variant calling was assessed using the AcroMetrix Oncology Hotspot Control which has 328 hotspot variants covered by OCA Plus. Variant calling performance showed a hotspot and de novo variant sensitivity and PPV >95%. MSI score and status were assessed using known MSI-High and microsatellite stable (MSS) research samples and FFPE samples of interest. Results show high concordance with data from OCA Plus on GeneStudio. Conclusions: The increased throughput of the Genexus System combined with minimal touchpoints and a rapid turnaround time enables comprehensive genomic profiling for research assays such as OCA Plus where an increased number of sequencing reads leads to greater sensitivity for detecting rare variants and low-level fusion transcripts. Further, accurate characterization of key oncology research endpoints, such as TMB, MSI, LOH, and HRD, allow the Genexus System to accelerate research in the field of oncology. Citation Format: Kayla Zochowski, Dinesh Cyanam, Geoffrey Lowman, Jennifer Kilzer, Sameh El-Difrawy, Yan Zhu, Tanaya Puranik, Alex Phan, Derek Wong, Edith Kwong, Coleen Nemes, Iris Casuga, Frances Chan, Eun Ji Kim, Jianjun Guo, Vinay Mittal, Emily Norris, Shrutii Sarda, Mohit Gupta, Fan Shen, Steven Roman, Gabriel Vargas, Ying Jin, Annie Kraltcheva, Paul Williams, Amneet Gulati, Justin Rigby, Christopher Hoff, Richard Meade, Elaine Wong-Ho, Andrew Wong, Jamsheed Ghadiri, David Garcia-Viramontes, Scott Myrand, Seth Sadis. High-throughput next-generation sequencing research solutions for detection of oncology variants, gene fusion events, and key oncology endpoints [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 42.

Kinetics of alkaline delignification of hemp and determination of lignin content by thermogravimetry

Raw hemp (Cannabis sativa L.) was subjected to alkaline delignification with the application of NaOH ranging from [0.125M] to [1M] for times from 5 to 480 min. Lignin contents of the original and delignified samples were determined. The samples were subjected to thermogravimetric analysis (TGA) under a N2 atmosphere with temperatures ramped from 25 to 600 °C at 10 °C min-1. Lignosulfonates samples of low, medium and high molecular weight were subjected to the same TGA and showed that lignin decomposed over the entire temperature range. The contributions of lignin to the mass loss during thermal decomposition of hemp and kinetics of lignin content and the most relevant TGA results were determined. Regression models estimating the lignin content of the fibers based on TGA results were formulated. These models allow for the prediction of mean lignin content within ± 0.1% (based on dry weight of pulp) in the central range of the experimental field.

Archaeal Viruses: Production of Virus Particles and Vesicle-like Viruses and Purification Using Asymmetrical Flow Field-Flow Fractionation.

Asymmetrical flow field-flow fractionation (AF4) is a separation method based on hydrodynamic size of the sample components. It can separate a broad size range of components (~103 to 109Da; particle diameter from ~1nm to ~1μm), but is especially well suited for high molecular weight samples such as virus-sized particles and extracellular vesicles. Separation takes place in an open channel where the flows control sample elution. Separation does not involve stationary phase, allowing gentle separation and good recoveries. The method is compatible with a wide variety of buffers. Coupling to various analytical detectors enables rapid assays on the molecular weight and size and their distribution, degradation, and aggregation of the sample components giving information on the sample quality. In addition to being an advanced analytical method, AF4 can be used in a semipreparative mode for purification. Here, we summarize archaeal virus production methods and virus purification by AF4 and provide examples on the steps that need optimization for obtaining good separation with the focus on halophilic archaeal viruses. Importantly, AF4 method is suitable for a variety of viruses and extracellular vesicles regardless of their host organism.

Lignosulfonates as charge carriers and precursors forthe synthesis of nanoparticles

The conductometry method was used to study the polyelectrolyte behavior of lignosulfonates in an aqueous solution. Electrical conductivity was found to be a complex function of concentration (8.5 ∙ 10–5– 9.0 ∙ 10 –2 mol/dm3), molecular weight of lignosulfonates (Mw 9250, 46,300), cation nature (Na+, Cа2+), as well as association of free counterions with polyion and temperature (288–353 K). It was shown that the molar electrical conductivity in the Kohlrausch coordinates decreases with increasing polymer concentration due to a decrease in the mobility of dissociated counterions under the action of the electrostatic potential of the macroion. In lignosulfonates solutions, an increase in temperature causes an increase in the number of particles capable of charge transfer. An inflection point was found on the temperature dependences of the electrical conductivity of high molecular weight samples, indicating structural changes in macromolecules. The reasons for this behavior of high molecular weight lignosulfonates in an aqueous solution were discussed. The activation energy of electrical conductivity was calculated, the average value of which is 14.24 kJ/mol for low molecular weight samples, and 12.17 kJ/mol for high molecular weight samples up to the inflection point and 16.49 kJ/mol after. It was found that a bimodal distribution of particles, as well as the formation of a double electric layer on their surface, is characteristic of lignosulfonates obtained. Solvent replacement (nanoprecipitation) yielded lignosulfonate nanoparticles ranging in size from 40 to 90 nm. The shape of the obtained particles is determined by the nature of organic solvent and is independent of lignosulfonates molecular weight. When using ethyl alcohol as a co-solvent, spherical nanoparticles were obtained, and pyramidal lignosulfonate nanoparticles were prepared when using acetone.

Fully biobased, elastomeric and compostable random copolyesters of poly(butylene succinate) containing Pripol 1009 moieties: Structure-property relationship

Fully biobased random copolymers of poly(butylene succinate) (PBS) containing different amount of Pripol 1009 moieties were synthesized by melt polycondensation. Molecular characterization confirmed the chemical structure and the random distribution of counts (NMR) and indicated that high molecular weight samples were obtained (GPC). All the polymers under study were semicrystalline, developing the typical α-PBS crystalline phase, the melting temperature and the crystallinity degree regularly decreasing with the increase of Pripol content. Pripol moieties determined also an improvement of polymer chain flexibility, as proved by the glass transition temperature decreasing, and of thermal stability. Polymer mechanical response was nicely tuned by changing copolymer composition, the copolymer with the highest Pripol content showing the typical behavior of thermoplastic elastomers despite its random nature. Lastly, biodegradation rate in compost also increased with the content of Pripol due to the parallel decrease of sample crystallinity degree. Surprisingly, microorganisms present in the compost preferentially attack BS comonomeric units despite their semicrystalline nature.

The effect of molecular weight on thermal properties and degradation behavior of copolymers based on TMC and DTC

A series of copolymers [P (TMC-co-DTC)] with different molecular weights based on trimethylene carbonate (TMC) and 2, 2-dimethyltrimethylene carbonate (DTC) were synthesized via ring-opening copolymerization, by adjusting the amount of Sn(Oct)2. The thermal performance showed that the Tg and Td of the obtained amorphous copolymer rose with the increase of molecular weight from 118 to 213 kDa. Then the in vitro enzymatic experiment was carried out in lipase solutions, it could be concluded that the higher the molecular weight, the faster the degradation rate of the P (TMC-co-DTC), which may be related to the stronger hydrophobicity of the high molecular weight sample. Furthermore, the degradation mechanism of P (TMC-co-DTC) was determined to be the surface erosion, due to the result of the unchanged molecular weight during the degradation period. The fact that polycarbonate copolymer produces no acidic compounds in the process of enzymatic degradation had also been confirmed. This study provides confirmation for adjusting the degradation behavior performance of polycarbonate materials by molecular weight to meet the needs of more abundant clinical applications.

Dynamics of polystyrene probed by muon spin spectroscopy

Muon spin spectroscopic measurements were made on atactic low-molecular-weight (LMW) (1.3 kg mol−1) and high-molecular-weight (HMW) (202 kg mol−1) polystyrene. Muoniated cyclohexadienyl radicals, which are formed by muonium addition to the phenyl side groups, are used as local probes of bulk dynamics. Muon spin relaxation is caused by the secondary γ-relaxation process, which involves motion of the phenyl rings, and is sensitive to the glass transition. The activation energy of the γ-relaxation process in the rubbery state is 0.60(2) eV in the HMW sample and 0.37(3) eV in the LMW sample.

Asymmetrical Flow Field-Flow Fractionation on Virus and Virus-Like Particle Applications.

Asymmetrical flow field-flow fractionation (AF4) separates sample components based on their sizes in the absence of a stationary phase. It is well suited for high molecular weight samples such as virus-sized particles. The AF4 experiment can potentially separate molecules within a broad size range (~103−109 Da; particle diameter from 2 nm to 0.5−1 μm). When coupled to light scattering detectors, it enables rapid assays on the size, size distribution, degradation, and aggregation of the studied particle populations. Thus, it can be used to study the quality of purified viruses and virus-like particles. In addition to being an advanced analytical characterization technique, AF4 can be used in a semi-preparative mode. Here, we summarize and provide examples on the steps that need optimization for obtaining good separation with the focus on virus-sized particles.

Dimethylacetamide-promoted Direct Arylation Polycondensation of 6,6′-Dibromo-7,7′-diazaisoindigo and (E)-1,2-bis(3,4-difluorothien-2-yl)ethene toward High Molecular Weight n-Type Conjugated Polymers

A highly efficient and eco-friendly protocol for the synthesis of an alternating copolymer poly(7,7′-diazaisoindigo-alt-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene) (PAIID-4FTVT) via direct arylation polycondensation (DArP) is presented. Through detailed study, we found that the inhibitory effect of 7,7′-diazaisoindigo on DArP stemmed from the coordination of N atom with catalyst can be overcome by using dimethylacetamide (DMAc) as the co-solvent. Thus, PAIID-4FTVT with number-average molecular weight (Mn) > 100 kDa was synthesized via DArP by optimizing the content of DMAc. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy revealed that PAIID-4FTVT was defect-free. Top gate and bottom contact (TG/BC) organic thin-film transistors (OTFTs) were fabricated to characterize the semiconducting properties of the polymers. PAIID-4FTVT displayed unipolar n-type characteristics with the electron mobility (µe) strongly dependent on Mn. The highest µe up to 0.25 cm2·V−1·s−1 was achieved with the high molecular weight sample.

Effect of molecular weight on vitrification kinetics and molecular mobility of a polymer glass confined at the microscale

We employ fast scanning calorimetry (FSC) to investigate how varying the molecular weight interferes in the vitrification kinetics and molecular mobility of micrometric poly(4-tert-butyl styrene) (PtBS). In line with recent results, we find marked negative deviations of the fictive temperature Tf, that is, the metric employed to characterize vitrification kinetics, with the sample size and for all molecular weights. In contrast, the molecular mobility remains size independent and bulk-like. This implies that vitrification kinetics and molecular mobility are decoupled. Furthermore, quantifying the magnitude of such decoupling through the Frenkel–Kobeko–Reiner approach, indicates that this is more pronounced in the high molecular weight samples than in the low molecular weight PtBS employed in the present work.

Facile method based on 19F-NMR for the determination of hydroxyl value and molecular weight of hydroxyl terminated polymers.

A new, facile and low-sample consuming technique for the determination of hydroxyl values (OHVs) in poly(hydroxyalkanoate)s (PHAs) is herein presented. After a fast, uncatalyzed and non-destructive trifluoroacetylation of all PHA hydroxyl groups, OHVs are calculated through 19F-NMR measurements, comparing integral values of the only two signals in the spectra: the fluorinated hydroxyl groups and the internal standard (trifluorotoluene) signals. Furthermore, the combined ex situ functionalization with a simple workup of the fluorinated polymer allowed to obtain spectra with an improved signal/noise ratio and short acquisition time if compared to 1H-NMR-based methods. The results obtained by 19F-NMR measurements are then validated by the established standard method based on acid/base titration and the 1H-NMR-based method. The proposed approach shows to be valuable not only for low molecular weight PHAs, but also for high molecular weight samples, which typically cannot be analysed by conventional 1H-NMR-based methods due to the very low concentration of hydroxyl terminal groups. Thanks to the observed high reliability, the method was also successfully applied to evaluate the OHVs of various commercial hydroxyl terminated polymers with different molecular weights in order to further show its wide applicability.

Crystallization Behavior and Mechanical Properties of Microinjection Molded High Density Polyethylene Parts

Ultra-thin high density polyethylene (HDPE) parts with two different molecular weights were prepared by microinjection molding (MIM). The dependence of crystalline morphology and orientation, as well as the resulting mechanical properties of the samples, on molecular weight is described. The toughness of the high-molecular-weight (HMW) sample was over 2 times that of the low-molecular-weight (LMW) one, in parallel with a significant increase of tensile strength. Microstructure characterizations, including differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS), were performed to investigate the variations of the microstructure. It is suggested that the increased crystallinity and higher degree of both molecular and lamellar orientation were beneficial to the enhancement of strength of the HMW sample. SAXS results showed that a highly oriented crystalline structure, i.e. shish-kebabs, were formed in parts of both of the two HDPE. Furthermore, a larger number of shish and kebab structure or lamellae was formed in the HMW sample due to the fact that the crystallinity was increased and the lamellar thickness and lateral crystallite size was reduced. Therefore, a stronger physical cross-linking network was formed in the HMW sample because of the increased connection points, which was in favor of the notable improvement of toughness. We suggest this issue is of great significance for achieving materials with high performance by tailoring the microstructure.

Molecular weight dependent structure and charge transport in MAPLE‐deposited poly(3‐hexylthiophene) thin films

ABSTRACTIn this work, poly(3‐hexylthiophene) (P3HT) films prepared using the matrix‐assisted pulsed laser evaporation (MAPLE) technique are shown to possess morphological structures that are dependent on molecular weight (MW). Specifically, the structures of low MW samples of MAPLE‐deposited film are composed of crystallites/aggregates embedded within highly disordered environments, whereas those of high MW samples are composed of aggregated domains connected by long polymer chains. Additionally, the crystallite size along the side‐chain (100) direction decreases, whereas the conjugation length increases with increasing molecular weight. This is qualitatively similar to the structure of spin‐cast films, though the MAPLE‐deposited films are more disordered. In‐plane carrier mobilities in the MAPLE‐deposited samples increase with MW, consistent with the notion that longer chains bridge adjacent aggregated domains thereby facilitating more effective charge transport. The carrier mobilities in the MAPLE‐deposited simples are consistently lower than those in the solvent‐cast samples for all molecular weights, consistent with the shorter conjugation length in samples prepared by this deposition technique. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 652–662

Comparing Two Electrochemical Approaches for Measuring Transference Numbers in Concentrated Electrolytes

We compare two experimental approaches for measuring the cation transference number in mixtures of polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt: the well-established current-interrupt method proposed by Ma et al. [J. Electrochem. Soc., 142, 1859 (1995)], and a more recent method based on measuring the steady-state current proposed by Balsara and Newman [J. Electrochem. Soc., 162, A2720 (2015)]. In electrolytes comprised of high molecular weight PEO, the data from the two techniques agree, highlighting the equivalence of these two approaches. However, in lower molecular weight PEO electrolytes the values of the two approaches diverge at low salt concentrations. We posit this is because the approach of Ma et al. requires measurements that are sensitive to the nature of the interface between the electrolyte and the electrode. The transference numbers measured by the approach of Balsara and Newman for both low and high molecular weight samples vary from 0.7 to −0.8 and are within experimental error throughout the entire salt concentration window.

Intercrystalline Links Determined Kinetics of Form II to I Polymorphic Transition in Polybutene-1

The effect of intercrystalline links containing tie molecules and entangled loops on polymorphic transition from form II to form I in polybutene-1 (PB-1) of different molecular weights has been investigated by differential scanning calorimetry and small-angle X-ray scattering techniques. The PB-1 samples were isothermally crystallized at a range of temperatures to develop metastable form II crystalline modification of different lamellar thickness, long spacing, and number of intercrystalline links in the amorphous phase. Tammann’s two-stage crystal nuclei development method was applied to promote a faster polymorphic transition from form II to I; that is, form I nuclei were developed at the early low temperature stage, and form I crystals were formed at the later high temperature stage. At a given annealing condition, the transition rate in the high molecular weight sample is found to increase with the increase of the prior form II crystallization temperature, while it shows a negative correlation between...

Comparison of Methods for Determining the Mechanical Properties of Semiconducting Polymer Films for Stretchable Electronics.

This paper describes a comparison of two characterization techniques for determining the mechanical properties of thin-film organic semiconductors for applications in soft electronics. In the first method, the film is supported by water (film-on-water, FOW), and a stress-strain curve is obtained using a direct tensile test. In the second method, the film is supported by an elastomer (film-on-elastomer, FOE), and is subjected to three tests to reconstruct the key features of the stress-strain curve: the buckling test (tensile modulus), the onset of buckling (yield point), and the crack-onset strain (strain at fracture). The specimens used for the comparison are four poly(3-hexylthiophene) (P3HT) samples of increasing molecular weight (Mn = 15, 40, 63, and 80 kDa). The methods produced qualitatively similar results for mechanical properties including the tensile modulus, the yield point, and the strain at fracture. The agreement was not quantitative because of differences in mode of loading (tension vs compression), strain rate, and processing between the two methods. Experimental results are corroborated by coarse-grained molecular dynamics simulations, which lead to the conclusion that in low molecular weight samples (Mn = 15 kDa), fracture occurs by chain pullout. Conversely, in high molecular weight samples (Mn > 25 kDa), entanglements concentrate the stress to few chains; this concentration is consistent with chain scission as the dominant mode of fracture. Our results provide a basis for comparing mechanical properties that have been measured by these two techniques, and provide mechanistic insight into fracture modes in this class of materials.