Low Monomer Content Research Articles

Preparation of sodium alginate grafted polyelectrolyte by adiabatic polymerization and study on its solution properties

In order to improve the salt resistance and shear resistance of partially hydrolyzed polyacrylamide-based oil displacement agents (they are all anionic polyelectrolytes), this paper proposes the preparation of branched low hydrophobic monomer content sodium alginate grafted hydrophobically modified partially hydrolyzed polyacrylamide P(AM-SA-MO8) using acrylamide (AM), sodium alginate (SA), and non-ionic hydrophobic monomer (MO8) as main raw materials through the method of adiabatic polymerization followed by hydrolysis. The polymerization conditions of P(AM-SA-MO8) were optimized, and the solution properties and oil displacement performance of P(AM-SA-MO8) and P(AM-MO8) (copolymer of AM and MO8) were compared. It was found that the viscosity, resistance to Ca2+/Mg2+, shear resistance, resistance factor (RF), residual resistance factor (RRF), and enhanced oil recovery performance of P(AM-SA-MO8) solution were better than those of P(AM-MO8). Especially in seawater, at 75 ℃, the viscosity of 1500 mg/L P(AM-SA-MO8) solution was 6.5 mpa.s, RF was 6.08, RRF was 2.28, and the enhanced oil recovery was 26.28 % with a injection rate of 4.9 ft/day.

Tenecteplase: biochemical and clot lysis activity comparisons.

In the last decades, the recombinant tissue plasminogen activator alteplase has been the standard fibrinolytic treatment of acute myocardial infarction, pulmonary embolism, and acute ischemic stroke. An optimized version of alteplase, tenecteplase, has been developed by exchanging six amino acids to increase half-life, achieve higher fibrin selectivity and increase resistance to plasminogen activator inhibitor-1. Meanwhile, several products containing tenecteplase exist. The aim of this study was to compare the fibrinolytic activity and overall product quality of the 25mg/vial presentation of tenecteplase originator Metalyse® (Boehringer Ingelheim Pharma GmbH and Co., KG, Ingelheim, Germany) to the 16mg/vial formulation of the tenecteplase copy Mingfule® (CSPC Recomgen Pharmaceutical, Guangzhou, Co., Ltd.). We have systematically analyzed and evaluated the biochemical and fibrinolytic differences between Metalyse® and Mingfule® using a wide range of routine quality testing assays, supplemented by mass spectrometry analysis and surface plasmon resonance assays. Additional host cell protein quantification and clot lysis testing following plasmin incubation over time were performed. Several key differences in biochemical composition and clot lysis activity were observed between the two tenecteplase variants. Versus Metalyse®, Mingfule® exhibited lower clot lysis activity and contained less of the two-chain form of tenecteplase. In addition, there were differences in sialic acid content, galactosylation, and fucosylation patterns, with Mingfule® exhibiting more bi- and less tri- and tetra-antennary glycosylation, leading to a different charge and size heterogeneity profile. Furthermore, Mingfule® displayed highly dissimilar binding to the three clearance receptors (LRP-1, ASGR, and mannose receptor) compared with Metalyse®. Purity analysis showed that Mingfule® contained a lower monomer content and, in contrast to Metalyse®, substantial amounts of host cell protein. Taken together, these data demonstrate that the tenecteplase copy Mingfule® has several meaningful fibrinolytic and biochemical differences compared with Metalyse®. This raises the question of whether data from clinical studies with one of the products can be generalized for all tenecteplase variants.

Controllable micro cross-linking towards multifunctional flame-retardant aliphatic polyamide

Constructing micro cross-linking structures into molecular chains has demonstrated the ability to improve basic properties, such as mechanical strength and thermal stability, of thermoplastic polymers. However, this method has limitations when it comes to improving the functionality of polymers. Herein, we reported a multifunctional micro cross-linking network that improves not just mechanical strength but also flame retardancy, dielectric properties, battery performance, antistatic properties, etc. A novel phosphinamide-containing monomer was designed, synthesized, and copolymerized into the polymer chain of polyamide 6, a typical thermoplastic polymer. On the one hand, the micro cross-linking structure was successfully obtained through the amide interchange reaction between the side-chain phosphinamide groups and the main-chain amide groups, leading to a 23.7% improvement of tensile strength and largely maintained tensile toughness. On the other hand, the functional phosphorus groups showed an efficient free-radical-capturing effect during fire, endowing the copolymer with excellent flame retardancy at a low monomer content of 2 mol%. Additionally, the copolymer also possessed great spinnability, melt-crystallization performance, as well as dielectric property, antistatic property, and battery performance, enabling its potential in a wide variety of applications.

Low viscosity versus high viscosity PMMA bone cement for total joint arthroplasty: Influence of glass transition temperature, residual monomer content, transmittance of chemical functional groups, and crystallinity index on quasi-static flexural strength

The commercially available low viscosity (LV) PMMA bone cement has higher mechanical properties than high viscosity (HV) PMMA bone cement. However, the influence of glass transition temperature, residual monomer content, transmittance of chemical functional groups and crystallinity index on flexural strength is yet to be unveiled. The present study is aimed to investigate the influence of glass transition temperature, residual monomer content, transmittance of chemical functional groups and crystallinity index that contributed to the higher flexural strength of LV bone cement compared to HV bone cement. The thermal behavior analysis indicated higher glass transition temperature and residual content for LV bone cement (87.5 ± 1.80 °C and 15.56±0.62%, respectively) as compared to HV bone cement (81±2.64 °C and 13.69±0.38%, respectively). Moreover, the chemical parameters such as relatively low residual monomer content computed using Raman spectroscopy and low transmittance of chemical functional groups found in FTIR spectra for LV bone cement imply better flexural strength compared to that of HV bone cement. Results indicated the crystallinity index was higher for LV (42.78 ± 0.54%) bone cement than HV bone cement (36.41 ± 0.18%). The difference in flexural strength between LV and HV bone cements governed by glass transition temperature, crystallinity index, residual monomer content and transmittance of chemical functional groups assists in the improvement and applications of PMMA bone cement.

Development of a Promising Method for Producing Oligomeric Mixture of Branched Alkylene Guanidines to Improve Substance Quality and Evaluate Their Antiviral Activity against SARS-CoV-2.

This paper reports the synthesis of branched alkylene guanidines using microfluidic technologies. We describe the preparation of guanidine derivatives at lower temperatures, and with significantly less time than that required in the previously applicable method. Furthermore, the use of microfluidics allows the attainment of high-purity products with a low residual monomer content, which can expand the range of applications of this class of compounds. For all the samples obtained, the molecular-weight characteristics are calculated, based on which the optimal condensation conditions are established. Additionally, in this work, the antiviral activity of the alkylene guanidine salt against the SARS-CoV-2 virus is confirmed.

3D structuring of dense alumina ceramics using fiber-based stereolithography with interparticle photo-cross-linkable slurry

In this paper, we demonstrated optical fiber-based stereolithography of alumina ceramics using concentrated slurry with low monomer content for enabling rapid firing of the printed green objects. Photo-cross-linkable alumina slurries were designed using a partial complex of polyethyleneimine and oleic acid (PEI-OA) as reactive polymer dispersants and multifunctional acrylates (MA) as monomers. The effects of the processing parameters, such as oleic acid contents, MA contents, particle contents, and particle sizes, on photocuring properties were systematically investigated. We found that the reactive amine sites of PEI-OA attached to particles and MA volume concentrations in the liquid phase were the most dominant factors to improve the photocuring properties. Therefore, a slurry composed of larger alumina particles with higher solid contents and PEI-OA with lower OA contents was more favorable for achieving photocuring under reduced MA content. The designed photocurable slurry was then applied to ceramic stereolithography using optical fiber. 3D alumina green parts were drawn by passing blue laser beam through an optical fiber in a droplet of photocuring slurry and dense sintered alumina were successfully fabricated by rapid drying (<10 min) and debinding (<1 h) without any structural collapse.

Diesel and gasoline like fuel production with minimum styrene content from catalytic pyrolysis of polystyrene

AbstractPyrolysis of waste polystyrene to generate fuel was carried out to yield pyrolysis oil. For the first time, NiO deposited over ZrO2 carrier as catalyst, was deployed and evaluated in the catalytic pyrolysis. Catalysts based on different loading (2, 5, 10, and 15%) of NiO deposited over ZrO2 carrier were prepared by solution combustion synthesis and tested toward screening of catalytic pyrolysis of PS in semi batch reactor. Based on conversion, yield of oil and low styrene monomer content, the catalytic performance with different loadings was evaluated and optimized. Furthermore, the oil obtained from the best catalysts were analyzed using GC–MS for carbon number distribution, depolymerization reactions, and diesel fuel generation. These catalysts were also characterized using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), pyridine FTIR, and scanning electron microscopy (SEM) techniques. As compared to thermal pyrolysis, the catalytic pyrolysis process was found to be highly selective toward diesel like fuel generation with minimum styrene monomer formation. Also, 2 and 10% NiO catalyst showed the best catalytic performance in pyrolysis process that could be ascribed to the presence of Lewis and Brönsted acid sites resulting in selectivity for C16 carbon number, diesel fuel generation, and depolymerization reactions.

Biocompatible polymers via aqueous electrochemically mediated atom transfer radical polymerization

ABSTRACTThe preparation of well‐defined polymers via aqueous atom transfer radical polymerization (ATRP) is challenging due to the high activity and limited stability of ATRP catalysts in water. Optimized conditions previously reported for the ATRP of some water‐soluble monomers cannot be regarded as universal conditions. Indeed, well‐controlled electrochemically mediated ATRP (eATRP) of oligo(ethylene oxide)methyl ether acrylate (OEOA) and 2‐hydroxyethyl methacrylate (HEMA) were achieved by adjusting the conditions in relation to the solubility and reactivity of these monomers and corresponding polymers. Importantly, PEOA with low dispersity and predetermined molecular weight was obtained even with low catalyst loading and high monomer content (up to 50 vol %). Moreover, &gt;90% conversion of HEMA was obtained within 6–7 h, giving PHEMA with dispersity 1.2–1.3. This work confirms eATRP as a versatile, clean technique applicable to a range of water‐soluble, biocompatible monomers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 114–123

Characterization of Aerosol Release during Spraying of Isocyanate Products.

The aerosol release during the professional application of two different isocyanate based two component spray systems was identified and the physicochemical properties of the released airborne aerosols were characterized. For this purpose, aerosol release fractions were measured using a mass balance method described by Schwarz and Koch. Besides the release of total aerosol mass special emphasis was directed to the content of free monomeric MDI (4,4'- and 2,4'-diphenylmethane diisocyanate) in three particle size fractions relevant for inhalation uptake: inhalable, thoracic, and respirable size fraction. Two products were investigated: a two component PUR (polyurethane) spray foam (Elastopor) and a polyurea spray coating (Elastocoat). The mass fraction of the applied products released with the overspray as inhalable aerosol is 6.3 × 10-4 (Elastopor) and 4.0 × 10-4 (Elastocoat). Of the released total overspray aerosol 75 or 80% were in the thoracic size range, and 26 or 47% in the respirable regime for the PUR spray foam or the polyurea spray coating, respectively. At the time point of release the content of monomeric MDI in the aerosol corresponds to the composition of the bulk product. However, analysis of air samples indicates that <1% of the spray foam aerosol mass release fraction is attributed to free monomeric 4,4'- and 2,4'-MDI. For the Spray Coating the monomeric MDI fraction is <0.1%. Higher oligomers of MDI and prereacted oligomeric reaction products make up a few percent of the aerosol. This results in a total fraction of 0.0023% (spray foam) and 0.00015% (spray coating), respectively, of the sprayed monomeric MDI that is transferred into an inhalable aged aerosol. This data demonstrates, that during professional spraying only a small fraction of the total applied mass is released as airborne aerosol. The potential distribution of the theoretically inhalable aerosol in the respiratory tract and a low residual monomer content is described, significantly contributing to a refined safety assessment of the spray applications at the workplaces.

Synthesis and Properties of Adhesive Polymer-Methylmethacrylate Materials

Kinetics of emulsion polymerization of hydrophilic vinyl monomers in the presence of polyvinylpyrrolidone and technological principles of their synthesis are determined. Reasonable technological parameters in the synthesis of copolymers are determined. Physicochemical properties of the synthesized copolymers (surface tension, the size of latex particles, and pH) are determined. Synthesized graft copolymers were used to create high-adhesion polymer-monomer compositions. These compositions have high reactivity at room temperature. It can be regulated by the nature of the polymer matrix and the introduction of comonomers and fillers due to the influence of physicochemical factors on the process of polymer formation. The rate of polymerization and the degree of monomer conversion largely depend on the nature of the polymer matrix. The highest polymerization rate and the maximum degree of conversion are observed when using a copolymer of polyvinylpyrrolidone and polymethylmethacrylate. Materials based on the developed compositions are characterized by a low residual monomer content and high operational properties, such as surface hardness, Vicat softening temperature, and adhesive bond strength to supports of different nature.

Fabrication of ZrB2-SiC ceramic composites by optimized gel-casting method

The ZrB2-SiC ceramics with homogenous microstructures were successfully fabricated by the optimized gel-casting method and pressureless sintering. The effects of the processing parameters, including the monomer content, cross-linker/monomer ratios, initiator addition, catalyst concentration and polymerization temperature, on the final gel properties were systematically investigated. The rheological behavior and stability of ZrB2-SiC suspensions were evaluated, and the microstructures and mechanical properties of sintered ceramics were also analyzed. The homogenous gel networks containing low monomer content (4wt%) and without catalysts had been successfully obtained, which could be mainly attributed to the homogeneous distribution of crosslinking points and temperature-induced gelation. The crack-free and complex-shaped ZrB2-SiC ceramic composites were achieved by the optimized gel-casting, which could reach the highest relative density of 97.2% and the flexural strength of 402 ± 57MPa, respectively. This study provides an optimized gel-casting process for fabricating ZrB2-SiC ceramics with excellent properties by low colloidal additives and without catalysts.

Thermoforming of Polylactic Acid Foam Sheets: Crystallization Behaviors and Thermal Stability

Biobased polylactic acid (PLA) foam packaging has been commercialized as an alternative to conventional polystyrene (PS) foam. However, PLA’s low glass transition temperature results in its inherently poor heat resistance and in turn limits the application to cold-fill packaging. In this study, low-density PLA foam sheet was extruded using an industry-scale tandem extrusion line and subsequently laminated with a PLA film casted from a high heat deflection temperature (HDT) PLA resin with a very low d-lactide monomer content (i.e., ∼0.4 mol %). Experimental results reveal that the crystallization behaviors of PLA foam sheets were sensitive to both thermoforming temperature and process-induced strain. Furthermore, this work has demonstrated that heat-resistant biodegradable PLA foam sheets could be realized by laminating them with solid films made of high-HDT PLA to serve as environmentally sustainable alternatives to PS foams in hot-fill packaging applications.

Hybrid silica with bimodal mesopore system: Synthesis and catalytic evaluation

As-synthesized CTA–MCM-41 silica possesses basic siloxy (SiO-) catalytic sites, enabling it to be used in reactions such as transesterification and Knoevenagel condensation. Its application in basic catalysis has shown promising results, but attempts to reuse it in more than one cycle has revealed rapid loss of activity due to the removal of cetyltrimethylammonium (CTA) cations from the interior of the channels. The present work describes the encapsulation of nanoparticulate methacrylic polymers during the conventional synthesis of MCM-41, resulting in hybrid silicas containing polymers in the interior of the inorganic and organic matrix. Aqueous dispersions containing surfactant and monomers were characterized by small-angle X-ray scattering (SAXS), which confirmed the expansion of the micelles due to the presence of the encapsulated monomers. Transmission electron microscopy (TEM) was used to observe the formation of polymer nanoparticles stabilized by the surfactant (cetyltrimethy lammonium bromide). Infrared absorption spectroscopy and chemical analysis showed that these particles were present in the material after the synthesis. Analysis of the silicas using SAXS and nitrogen physisorption showed the expansion of the channels of the CTA–MCM-41 and the formation of two mesopore systems in the silica. Catalytic evaluation demonstrated that the silicas synthesized in the presence of the emulsified polymers possessed better catalytic stability when low monomer contents and monomers with larger alkyl chains were used. The encapsulation of nanoparticles of methacrylic polymer in the interior of the CTA–MCM-41 channels helped to avoid leaching of the CTA cations during the reaction.

Reaction Mechanisms of N-isopropylacrylamide Soap-Free Emulsion Polymerization Based on Two Different Initiators

Poly(N-isopropylacrylamide) (PNIPAM) microgels were prepared through soap-free emulsion polymerization using 2,2′-azobisobutyronitrile (AIBN) or potassium persulfate (KPS) as initiator. UV-Vis spectrophometer was used to monitor the polymerization kinetics at very low monomer contents (≤0.2 wt% based on water). The absorbance at 220 nm was investigated, being proportional to the NIPAM concentration, but not PNIPAM, and thus was chosen to characterize the residual monomer concentration. The results showed the effect of the initiator was particularly noticeable in the initial polymerization period. The KPS-initiated polymerization started with a shorter induction time, while the AIBN initiated one started more slowly but had a higher rate in the later stage of polymerization. The change of particle mean Dh (hydrodynamic diameter) and Dh distribution and molecular weight during the polymerization processes were examined by dynamic light scattering (DLS) and gel permeation chromatography (GPC), respectively, to investigate the reaction mechanisms of the NIPAM soap-free emulsion polymerization based on the two different initiators. The reaction mechanisms based on AIBN and KPS are discussed in detail in the article. The results indicated that the mechanisms of forming PNIPAM microgels based on AIBN and KPS are different. When AIBN was used as initiator, the reaction mainly took place in the monomer droplets which were stabilized by the formation of PNIPAM, and with high reaction rate. But when KPS was used as initiator, the nucleation and the PNIPAM microgels forming field both were in the aqueous phase.

A Novel Embed Fluorescence Method for Monitoring the Change from Emulsion Polymeriztion to Microemulsion Polymerization

In this paper, we present a novel embed fluorescence method that allows one to monitor the change from emulsion polymerization to microemulsion polymerization with low monomer contents. The microemulsion polymerization of methyl methacrylate (MMA) was investigated using N-(2-anthracene) methacrylamide (AnMA) as the probe whose fluorescence emission intensity was proportional to the conversion of MMA into the polymer.In this research, the trace amount of AnMA unit looked like embed in the MMA chain. In a solution containing 3wt% of MMA with respect to water, with the anionic surfactant of sodium dodecyl sulphate (SDS) and water-soluble initiator of potassium persulfate (KPS), the process of changing from emulsion to microemulsion has been monitored. By contrast, with the non-ionic surfactant of polyoxyethylene (20) oleyl ether (Brij98) or water-insoluble initiator of 2,2′-azobis(isobutyronitrile) (AIBN), the process of changing from emulsion to microemulsion also have been monitored.

Features of the Emulsion Polymerisation of Styrene with a Low Monomer Content in the Reaction System

Features of the Emulsion Polymerisation of Styrene with a Low Monomer Content in the Reaction System

The Kinetics of Methyl Methacrylate Miniemulsion Polymerization Characterized through a Fluorescence Method

In this paper, we followed the kinetics of methyl methacrylate (MMA) through a novel fluorescence method. The real-time measurement results show that in the regime of very low monomer contents, such as a solution containing 0.1 wt% of MMA with respect to water and with the anionic surfactant of sodium dodecyl sulphate (SDS), the kinetic of the miniemulsion could be followed by this embed fluorescence method. The processes of changing from emulsion to miniemulsion with different amount of surfactant and cosurfactant also have been monitored.

A sensitive fluorescence method for monitoring the kinetics of microemulsion polymerization

We present a fluorescence method that allows one to monitor the kinetics of microemulsion polymerization of very low monomer contents (water-to-monomer ratio can readily be superior to 1000). The microemulsion polymerization of methyl methacrylate (MMA) was investigated using N-(2-anthracene)methacrylamide (AnMA) as the probe whose fluorescence emission intensity was proportional to the conversion of MMA into the polymer. The real-time-measurement results show that in the regime of very low monomer contents, the surfactant exerted a profound effect on the kinetic process. In a microemulsion containing 0.1 wt% of MMA with respect to water, with the anionic surfactant of sodium dodecyl sulfate (SDS), the fast polymerization was preceded by an induction period whose length increased with reducing the concentration of the water-soluble initiator of potassium persulfate (KPS). By contrast, with the non-ionic surfactant of polyoxyethylene (20) oleyl ether (Brij98), the induction period was short and the decrease in the KPS concentration mainly resulted in a decrease of the reaction rate. The unprecedented sensitivity of this fluorescence method made it possible to access kinetic data of microemulsion polymerization with very low monomer contents for the first time, providing new insight into the effects of surfactant and initiator on this heterophase polymerization process.

Influence of Dietary Feeding of Low Monomer Content Grape Seed Extract on Vitellogenin Production and Cholesterol Levels in Goldfish, Carassius auratus

Grape seed extract (GSE) is a source of naturally occurring compounds known as proanthocyanidins and flavan-3-ols, which are recognized to exert a protective effect on human health, so GSE is widely used mainly as a nutritional supplement. However, polyphenols may have, in some cases, estrogenic effects or may interfere with the endocrine system. For that reason, it was considered of interest to investigate the beneficial or detrimental effects induced by low monomer content grape seed extract (LMC-GSE) in a teleost experimental model, the juvenile goldfish (Carassius auratus); therefore, biomarkers of estrogenic exposure together with cholesterol titers were assessed in both plasma and tissue samples taken from fish fed with different doses of LMC-GSE for 4 weeks. Dietary LMC-GSE (71 or 35 mg/g diet) did not affect vitellogenin (VTG) synthesis; on the contrary, VTG production was exclusively induced in fish fed with an estradiol-17beta (E2)-incorporated diet. In addition, it was found that both plasma E2 levels and hepatic total cholesterol were not affected by LMC-GSE dietary regimens.

A novel poly(N‐isopropylacrylamide‐co‐N‐hydroxymethyl acrylamide) gel: preparation in the absence/presence of a pore‐forming agent and characterization

AbstractPoly(N‐isopropylacrylamide) (PNIPAM) homopolymer gel and copolymer gels of N‐isopropylacrylamide (NIPAM) and N‐hydroxymethyl acrylamide (NHMAAM) were prepared in the absence/presence of a pore‐forming agents, poly(ethylene glycol) (PEG) (PEG 400 or PEG 2000) using N,N′‐methylenebisacrylamide (NMBA) as a crosslinker in aqueous solution at 4°C. The chemical structures and microscopic morphologies of PNIPAM and P(NIPAM‐co‐NHMAAM) copolymer gels were investigated by FT‐IR and SEM (scanning electron microscopy), respectively. The effects of initial monomer concentration (0.5 and 1 M), the contents of crosslinker (0.25 and 1%) and comonomer (1–3 mol%), the absence/presence of pore‐forming agent in the feed, and the molecular weight of pore‐forming agent on the compressive elastic moduli and equilibrium swelling values (ESVs) of both polymers were investigated. While the use of a pore‐forming agent during the polymer synthesis favored the formation of porous gels and increased the swelling values, it led to decrease in the compressive elastic moduli of PNIPAM and P(NIPAM‐co‐NHMAAM) gels. The swelling values of gels, which were prepared at high monomer (1 M) and crosslinker (1%) contents, were not dependent on the comonomer NHMAAM incorporation to PNIPAM, the use of pore‐forming agents, and the use of former and latter parameters together. The twice increase in initial monomer concentration at low NMBA (0.25%) content highly enhanced the elastic moduli of PNIPAM. One mol% NHMAAM incorporation into PNIPAM especially at low monomer (0.5 M) and crosslinker (0.25%) contents made the highest increase (4.7 times) in the elastic moduli of gel, and further increase in the NHMAAM content of gel decreased the moduli of gels at all crosslinker and monomer concentrations. It was concluded that the increase in the elastic moduli of copolymer gels with 1 mol% NHMAAM, which were prepared at low crosslinker and monomer concentrations, can be attributed to the increase in crosslinking through the condensation reaction between N‐methylol groups or N‐methylol and NH groups in NHMAAM and NIPAM. Copyright © 2008 John Wiley &amp; Sons, Ltd.