High Molecular Weight Polymers Research Articles

Independent assessment of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sample preparation quality: Effect of sample preparation on MALDI-MS of synthetic polymers.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) provides detailed and in-depth information about the molecular characteristics of synthetic polymers. To obtain the most accurate results the sample preparation parameters should be chosen to suit the sample and the aim of the experiment. Because the underlying principles of MALDI are still not fully known, a priori determination of optimal sample preparation protocols is often not possible. Employing an automated sample preparation quality assessment method recently presented by us we quantified the sample preparation quality obtained using various sample preparation protocols. Six conventional matrices with and without added potassium as a cationization agent and six ionic liquid matrices (ILMs) were assessed using poly(ethylene glycol) (PEG), polytetrahydrofuran (PTHF) and poly(methyl methacrylate) (PMMA) as samples. All sample preparation protocols were scored and ranked based on predefined quality parameters and spot-to-spot repeatability. Clearly distinctive preferences were observed in matrix identity and cationization agent for PEG, PTHF and PMMA, as the addition of an excess of potassium cationization agent results in an increased score for PMMA and a contrasting matrix-dependent effect for PTHF and PEG. The addition of excess cationization agent to sample mixtures dissipates any overrepresentation of high molecular weight polymer species. Our results show reduced ionization efficiency and similar sample deposit homogeneity for all tested ILMs, compared with well-performing conventional MALDI matrices. The results published here represent a start in the unsupervised quantification of sample preparation quality for MALDI samples. This method can select the best sample preparation parameters for any synthetic polymer sample and the results can be used to formulate hypotheses on MALDI principles. Copyright © 2016 John Wiley & Sons, Ltd.

Structural, Viscoelastic, and Electrochemical Characteristics of Self-Assembled Amphiphilic Comblike Copolymers in Aqueous Solutions.

Self-assembly in aqueous solutions of an amphiphilic comblike polyelectrolyte (80C12) that consists of a polystyrene (PS) backbone onto which quaternary ammonium pendant moieties have been grafted has been investigated by light scattering and cryo-transmission electron microscopy measurements in the presence of KCl and methylviologen dication (MV2+) under conditions mimicking those for electrochemical measurements. Polymer chains self-assemble within branched cylindrical micelles that display viscoelastic properties, characterized by a relaxation time of 4 s. To tune this time, 80C12 was mixed with a polyoxyethylene nonionic surfactant (Brij C12E10). Relatively increasing the amount of the latter leads to a decrease in the relaxation time of the 80C12 solution. Correlatively, electrochemical experiments with a rotating disk electrode show a transition of the mass transport rate, which deviates from the classical Newtonian behavior in the same velocity domain. This result generalizes what has been already observed with solutions of linear polymers of high molecular weight and wormlike micelles based on surfactants subjected to elongational deformations. Moreover, the critical times derived from rheological and electrochemical experiments display the same trend.

Synthesis and investigation of dual pH‐ and temperature‐responsive behaviour of poly[2‐(dimethylamino)ethyl methacrylate]‐grafted gold nanoparticles

Gold nanoparticles (AuNPs) were synthesized by reduction of chloroauric acid (HAuCl4) aqueous solution with hydrazine monohydrate. The AuNPs were immediately treated with cysteamine to obtain amine‐functionalized nanoparticles (Au‐NH2). The reaction of Au‐NH2 with epichlorohydrin and subsequent treatment with sodium hydroxide gave epoxidized AuNPs (Au‐EP). Then, thiol‐capped AuNPs (Au‐SH) were synthesized by reaction of Au‐EP with cysteamine. A ‘grafting to’ approach was utilized to graft bromine‐terminated poly(N,N′‐dimethylaminoethyl methacrylate), synthesized via aqueous atom transfer radical polymerization, with various molecular weights (6280, 25 800, 64 200 and 87 600 g mol−1) onto Au‐SH to obtain Au‐P1, Au‐P2, Au‐P3 and Au‐P4 samples, respectively. All samples were exposed to temperature and pH variations, and Z‐average diameter was monitored using dynamic light scattering. According to the results, polymer‐grafted nanoparticles collapsed at lower temperatures with increasing solution pH for all molecular weight ranges due to deprotonation of tertiary amine groups. However, higher molecular weight polymers were more sensitive to pH variation especially in alkaline media. Also, a high degree of agglomeration was observed for Au‐P4 nanoparticles in alkaline media on increasing the temperature to 55 and 65 °C.

Experimental study of drag reduction of polymer-polymer mixtures in horizontal dispersed oil-water flow

An experimental investigation of the effect of various mixtures of different polymers on drag reduction was studied in a dispersed horizontal oil-water flow. The study was carried out in a horizontal pipe flow loop system of 30.6-mm ID and 24m length. All the polymers are anionic water-soluble polymers prepared in 1000ppm master solution and injected at different flow rates to achieve polymer concentrations in the range of 5 to 30ppm in the water phase. As expected, the percentage drag reductions of the individual polymers and of the binary polymer mixtures increased with the increase in the mixture velocity but decreased with the increase in the oil fraction. It has been found that the drag reduction of the mixed polymer solution is higher than the drag reduction of the lower molecular weight polymer. In most of the cases, the drag reduction of the binary mixtures shows a positive deviation from the additive straight lines. The positive deviation is more dominant for the mixture of the high and low molecular weight polymers than the mixture of the high and medium molecular weight polymers. Also, the drag reductions of the mixture of the high and low molecular weight polymers are higher than the drag reductions of the mixture of the high and medium molecular weight polymers. Finally, although positive deviation was observed in this study, no synergism was obtained for all the investigated polymer-polymer mixtures conditions.

Flexible all‐aromatic polyesterimide films with high glass transition temperatures

ABSTRACTA series all‐aromatic poly(esterimide)s with different molar ratios of N‐(3′‐hydroxyphenyl)‐trimellitimide (IM) and 4‐hydroxybenzoic acid (HBA) (IM/HBA = 0.3/0.7 and 0.7/0.3) was prepared with the aim to design flexible high Tg films. Melt‐pressed films, either from high molecular weight polymer or cured phenylethynyl precursor oligomers, exhibit Tgs in the range of 200 °C to 242 °C and are brittle. After a thermal stretching procedure, the films became remarkably flexible and very easy to handle. In addition, the thermally stretched 3‐IM/7‐HBA and 7‐IM/3‐HBA films show tensile strengths of 108 MPa and 169 MPa, respectively. Thermal treatment increased the Tg of 3‐IM/7‐HBA from 205 °C to 248 °C, whereas the Tg of 7‐IM/3‐HBA increased from 230 °C to 260 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44774.

HL2][P(1,2-O2C6Cl4)3] (L = THF, DMF): Brønsted acid initiators for the polymerization of n-butyl vinyl ether and p-methoxystyrene.

The development of solid, weighable Brønsted acids featuring the hexacoordinated phosphorous(v) anion [TRISPHAT]- are reported. H(DMF)2[1] and H(THF)2[1] {[1]- = [P(1,2-O2C6Cl4)3]-} were synthesized and fully characterized by 1H, 31P, 13C and 2D-NOESY NMR spectroscopy, X-ray crystallography, mass spectrometry and elemental analysis. Both, H(DMF)2[1] and H(THF)2[1] are found to be suitable initiators for the polymerization of n-butyl vinyl ether and p-methoxystyrene. Optimal polymerization results for these single-component initiators were generally obtained at -50 °C where high molecular weight polymers were isolated in high yield. 1H NMR spectroscopic analysis and dynamic light scattering of solutions of the isolated polymers provide evidence for a branched structure which presumably arises from chain transfer.

ADMET Polymerization: Greener Method for Synthesis of End-Functionalized Poly(Arylene Vinylene)s

Recent results for synthesis of conjugated polymers, poly(arylene vinylene)s exemplified as poly(fluorene vinylene)s and poly(phenylene vinylene)s, by acyclic diene metathesis (ADMET) polymerization have been introduced. The methods using molybdenum and ruthenium catalysts afforded defect-free, high molecular weight polymers with all trans olefinic double bonds, and significant reduction of by-products (halogen, sulfur etc.) in addition of decrease of structurally defects have been attained. The methods also demonstrated precise synthesis of end-functionalized polymers that showed unique optical properties combined with the end groups. Catalytic one-pot syntheses of end-functionalized poly(9,9-dialkylfluorene-2,7-vinylene)s have been attained by both ruthenium (by chain-transfer) and molybdenum catalysts and the method should provide more green route for synthesis of conjugated materials with better device performance.

Production, Characterization and Valuable Applications of Exopolysaccharides from Marine Bacillus subtilis SH1.

Exopolysaccharides (EPSs) are high molecular weight polymers consisting of different sugar residues they are preferable for replacing synthetic polymers as they are degradable and nontoxic. Many microorganisms possess the ability to synthesize and excrete exopolysaccharides with novel chemical compositions, properties and structures to have potential applications in different fields. The present study attempt to optimize the production of EPS by marine Bacillus subtilis SH1 in addition to characterization and investigation of different valuable applications. Effect of medium type, incubation period and pH were studied using the one factor at a time experiments. It was shown that the highest productivity (24 gl-1) of exopolysaccharides was recorded by using yeast malt glucose medium with pH 9 at the fourth day of incubation. Experimental design using Response Surface Methodology (RSM) was applied to optimize various nutrients at different concentrations. The finalized optimized medium contained (gl-1) glucose (5), peptone (2.5), yeast extract (4.5) and malt extract (4.5) increased the production of EPS to 33.8 gl-1 with1.4 fold increase compared to the basal medium. Chemical characterization of the extracted EPS showed that, FTIR spectra exhibited bands at various regions. Moreover, HPLC chromatogram indicated that the EPS was a heteropolysaccharide consisting of maltose and rhamnose. The study was extended to evaluate the potentiality of the extracted polysaccharides in different medical applications. Results concluded that, EPS exhibited antibacterial activity against Aeromonas hydrophila, Pseudomonas aeruginosa and Streptococcus faecalis and the highest antibacterial activity (7.8, 9 and 10.4 AU/ml) was against S. faecalis at 50, 100 and 200 mg/ml respectively. The EPS exhibited various degree of antitumor effect toward the tested cell lines (MCF-7, HCT-116 and HepG2). In addition, EPS exhibited antiviral activity at 500 μg/ml. The antioxidant capacity increased with increasing the concentration of the sample. Scanning electron microscopic analysis showed that EPS had compact film-like structure, which could make it a useful in the future applications as in preparing plasticized film.

Structural characterization and physicochemical properties of Descurainia sophia seed gum

In this research, compositional, structural and rheological properties of a water-soluble gum from Descurainia sophia seed (DSSG) were evaluated. The gum contained, on average, 78.23 ± 3.09% carbohydrate, 14.12 ± 1.73% uronic acid, 5.14 ± 0.83% moisture, 2.12 ± 0.11% protein, 3.01 ± 0.21% ash, and 0.77 ± 0.09% fat. This gum is a high molecular weight polymer, composed of galactose (44.17%), mannose (49.91%), as well as a trace amount of rhamnose (2.10%) and arabinose (3.82%). 13C and 1H NMR spectra of DSSG demonstrated this gum had a galactomannan structure with a mannose/galactose ratio (M/G) of 1.09. Furthermore, the presence of carboxyl groups, which may act as binding sites for calcium ions, was demonstrated by FTIR analysis. The intrinsic viscosity of DSSG was 8.82 dl/g based on Tanglerpaibul and Rao model. Rheological investigation of DSSG solutions in different concentration levels revealed a shear thinning behavior.

Non-Darcian flow of shear-thinning fluids through packed beads: Experiments and predictions using Forchheimer's law and Ergun's equation

The flow of shear-thinning fluids through unconsolidated porous media is present in a number of important industrial applications such as soil depollution, Enhanced Oil Recovery or filtration of polymeric liquids. Therefore, predicting the pressure drop–flow rate relationship in model porous media has been the scope of major research efforts during the last decades. Although the flow of Newtonian fluids through packs of spherical particles is well understood in most cases, much less is known regarding the flow of shear-thinning fluids as high molecular weight polymer aqueous solutions. In particular, the experimental data for the non-Darcian flow of shear-thinning fluids are scarce and so are the current approaches for their prediction. Given the relevance of non-Darcian shear-thinning flow, the scope of this work is to perform an experimental study to systematically evaluate the effects of fluid shear rheology on the flow rate–pressure drop relationships for the non-Darcian flow through different packs of glass spheres. To do so, xanthan gum aqueous solutions with different polymer concentrations are injected through four packs of glass spheres with uniform size under Darcian and inertial flow regimes. A total of 1560 experimental data are then compared with predictions coming from different methods based on the extension of widely used Ergun's equation and Forchheimer's law to the case of shear thinning fluids, determining the accuracy of these predictions. The use of a proper definition for Reynolds number and a realistic model to represent the rheology of the injected fluids results in the porous media are shown to be key aspects to successfully predict pressure drop–flow rate relationships for the inertial shear-thinning flow in packed beads.

Influence of extracellular polymeric substances (EPS) treated by combined ultrasound pretreatment and chemical re-flocculation on water treatment sludge settling performance

Extracellular polymeric substances (EPS) are high molecular weight polymers and play a significant role in floc stability, floc size, bioflocculation and sludge settleability. The destruction and reconstruction of EPS improve the performance of solid-water separation processes. In this study, the influence of combined ultrasound pretreatment and chemical re-flocculation on the spatial distribution and composition of EPS was examined. Settleability efficiency demonstrated that the optimal operating condition was an ultrasound pretreatment time of 15 min at pH 6. Sludge particles were greatly disintegrated and the protein-like substances were converted into smaller molecules after ultrasound treatment, and pH had important effects on solubilization and degradation of protein-like substances. The flocs of sludge water after addition of polyacrylamide were larger in size and denser in structure than those resulting from addition of polyaluminium chloride. However, polyaluminium chloride had a better capacity for degrading EPS, especially at a dosage of 1.2 g/g total suspended solids. The results of this research show that the combination of ultrasonication and chemical re-flocculation is effective in treating sludge water from a drinking water treatment plant.

ChemInform Abstract: SuFEx Click: New Materials from SOxF and Silyl Ethers

AbstractReview: [24 refs.

THE EFFECT OF SURFACTANT AND HIGH MOLECULAR WEIGHT POLYMER ADDITION ON PRESSURE DROP REDUCTION IN PIPE FLOW

Abstract - The main aim of this paper is to present a possibility to enhance the drag reduction effect in straight pipe flow by the simultaneous addition to the transported liquid of a small amount of high molecular weight polymers and surfactants. Qualitative analysis of the polymer-micellar additive influence on the shape and character of flow resistance curves has been performed. Also multicomponent polymer-micellar solution flow resistance curves were compared with appropriate single additive polymer or surfactant solution flow resistance curves. The experimental data shows that, for polymer-micellar solutions, the stable transitional zone between the laminar and the turbulent flow regions is extended toward higher values of the critical Reynolds numbers. Occurrence of the phenomenon can be explained by the flow laminarization caused by polymer-micellar aggregates. Existence of the third extended drag reduction zone in the turbulent range of flow has also been observed for the first time.

Intrinsic Stresses in Thin Glassy Polymer Films Revealed by Crack Formation

Both spin-coating and thermal annealing of thin supported glassy polymer films generally cause stresses arising from rapid solvent evaporation and from a mismatch in expansivities of film and substrate, respectively. While films on adhesive surfaces are typically stable, on slippery substrates film stability is sensitively determined by the thermal protocol, revealing the presence of these stresses. There, contraction of the film upon cooling causes in-plane tensile stresses that can lead to film fracture. While this is a general effect, the details of the film’s response to thermal cycling allow to disentangle the origin of stresses within the film. For high molecular weight polymers, we found that preparation-induced stresses cause substantially reduced thermal expansivities. This demonstrates that intrinsic out-of-equilibrium states in spin-coated glassy films of long polymers are long-lived and thus difficult to equilibrate.

Solution modification of PEDOT:PSS inks for ultrasonic spray coating

PEDOT:PSS is a high-conductivity hole-transporting polymer that is widely used in polymer and perovskite photovoltaic devices, as well as in a host of other antistatic applications. Here we show that modification of PEDOT:PSS inks using ternary solvents and by the addition of small amounts of a high molecular weight polymer make it possible to deposit highly uniform thin films via ultrasonic spray coating. Such films can be deposited using a single pass in the wet phase without the use of surfactants; a process that greatly simplifies their deposition. Using this technique we create films having thickness and roughness comparable to that of spin coated films, whilst properties such as the conductivity and stability can be improved.

Ring-opening metathesis polymerization of cis-5-norbornene-endo-2,3-dicarboxylic anhydride derivatives using the grubbs third generation catalyst

A series of cis-5-norbornene-endo-2,3-dicarboxylic anhydride (NDCA, M1) derivatives (M2-M4) with different types of nonpolar substituted groups were synthesized and characterized by 1H/13C-NMR and mass spectrometry (MS). Ring-opening metathesis polymerization (ROMP) of these monomers using the Grubbs third generation catalyst (G3) generated high molecular weight polymers with much improved solubility compared with the NDCA's homopolymer. It was found that the solubility of these polymers increased with increased substituent's steric hindrance. The living polymerization of NDCA derivative containing the bulkiest substituent (M4) catalyzed by G3 in tetrahydrofuran was confirmed by the kinetic studies with low polydispersity indices (PDI) (<1.30). By using sequential ROMP, well-defined diblock copolymers containing anhydride groups were synthesized.

In vitro synthesis of nearly ultra high molecular weight (NUHMW) polymers using solvent-water suspension method

An easy method for the synthesis of nearly ultra high molecular weight (NUHMW) polymers has been reported in the present investigation for the first time. The method involves the interaction of some suitable reagents of appropriate concentrations and stoichiometry through solvent-water suspension polymerization in addition to radical polymerization, leading to the formation of polymers with optimal yield and high percentage purity. The molecular weight of these polymers can be tailored by varying the acrylonitrile-water and acrylonitrile-DMF ratios, and it is found that presence/absence of sulfuric acid kept in closed conditions has some significant effect on the molecular weight of these polymers. The initiation has been found very slow under ambient conditions, but once a small amount of the material is formed, it takes only a few hours for the conversion of the bulk reaction mixture into the product and sunlight (visible region of spectrum only) shows a positive effect on the synthesis of such polymers. These polymers are of molecular weight greater than 340,000 Da and are soluble in DMSO and DMF solvents only.

Transportation of heavy oils using polymer-stabilized oil-in-water emulsions

The increase in demand for crude oil and the depletion of light crude oil reserves have led to increase in the production of heavy crude oils. This has resulted in an interest in decreasing the pumping costs by techniques such as heating, dilution and/or mixing with water. Among the aforementioned methods, emulsification of heavy crude oil with water is the cheapest, and hence, optimizing its application has found increasing attention. This study uses one of the heavy crude oils in Oman to study the viscosity reduction achieved by emulsification with water at different oil fractions, temperatures, shear rates and salt content. Two chemicals were used to stabilize the emulsions, namely a nonionic surfactant and an anionic, high molecular weight polymer. It was found that viscosity reduction higher than 90% can be obtained through the creation of oil-in-water emulsions with oil content of less than 70%. Generally, it was found that there is no effect on the viscosity reduction obtainable from oil-in-water emulsions produced using the nonionic surfactant at shear rate up to 1620 s−1, temperature up to 80 °C and salt content up to 2.0 wt%. On the other hand, the viscosity reduction using water-in-oil emulsions at a temperature of 30 °C increases with surfactant concentration and shear rate. Also, the increase in salt content adversely affected the viscosity reduction obtained using water-in-oil emulsions. Moreover, it was possible to create oil-in-water emulsions with 60% oil content and viscosity reduction of around 100% in tap water using 100 and 1000 ppm polymer at all temperatures investigated. However, the use of 2.0 wt% salt resulted in lowering the viscosity reduction to 53 and 80% at 30 and 45 °C, respectively. This diverse effect of salt was almost neutralized at 60 and 80 °C resulting in viscosity reduction higher than 90%. The emulsions created using 3 wt% surfactant were generally stable for one week to a temperature of around 23 °C. The stability of oil-in-water emulsions with an oil content higher than 60% was not affected by the presence of salt. The emulsions prepared with an oil content of 60% in 100 ppm polymer were stable only for 1 h. However, the stability in water for these emulsions was greatly enhanced by increasing the viscosity of the continuous water phase by using 1000 ppm polymer, which resulted in stability higher than 70% after 24 h of incubation at 23 °C. The presence of 2.0 wt% salt in 1000 ppm polymer emulsions resulted in rendering these emulsions as instable even after 1 h of incubation. It can be concluded that high molecular weight polymers can find application in drag reduction for heavy crude oils after thoroughly investigating the effect of different polymer molecular parameters such as molecular weight and charge density.

Cadmium acetate as a ring opening polymerization catalyst for the polymerization of rac-lactide, ε-caprolactone and as a precatalyst for the polymerization of ethylene

In the present study, we have discussed the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA) and e-caprolactone (e-CL) using Cd(OAc)2. Cd(OAc)2 appeared to be a good catalyst for the polymerization of rac-LA and e-CL yielding high molecular weight (Mn) polymers with narrow molecular weight distributions (MWDs). The catalytic activity of the system can be increased markedly upon using catalytic amount of BnOH as external alcoholic initiator. There is a first order dependence of the rate constant with respect to monomer concentrations as understood from the kinetic studies. The rate was found to be faster in the presence of BnOH. The polymerization process was controlled. The polymerization proceeded via the coordination-insertion mechanism without BnOH as well as activated monomer mechanism in the presence of BnOH. In the absence of BnOH, the acetyl group initiated the polymerization as understood from the 1H NMR and MALDI-TOF analysis. The benzyloxy group initiated the polymerization in the presence of BnOH. Moderate activity towards the polymerization of ethylene was observed using MAO as alkyl aluminum activator. The polymerization parameters towards the polymerization of ethylene were widely investigated.

Regulation and control of polymer network deformation in reverse-mode polymer-stabilised cholesteric texture

ABSTRACTBy simulating the dynamic response processes of reverse-mode polymer-stabilised cholesteric texture (PSCT) via double exponential rise/decay model, the deformation of polymer networks were quantitatively characterised. The polymer network deformation is shown to be controlled by regulating monomer concentration and the applied electric field. Increased monomer concentration facilitates the production of polymer fibrils of a higher polymer molecular weight while suppressing distortion of the polymer network. Decreased polymer network deformation assists in the decrease of the undesired hysteresis phenomenon while also demonstrating a shorter field-off response time of PSCT; however, the trade-off is increased operation voltage and decreased contrast ratio. The observed results provide useful guidelines for future PSCT material and device optimisations.