High Molecular Weight Linear Polymers Research Articles

Soft glassy materials with tunable extensibility.

Extensibility is beyond the paradigm of classical soft glassy materials, and more broadly, yield-stress fluids. Recently, model yield-stress fluids with significant extensibility have been designed by adding polymeric phases to classically viscoplastic dispersions [Nelson et al., J. Rheol., 2018, 62, 357; Nelson et al., Curr. Opin. Solid State Mater. Sci., 2019, 23, 100758; Dekker et al., J. Non-Newtonian Fluid Mech., 2022, 310, 104938]. However, fundamental questions remain about the design of and coupling between the shear and extensional rheology of such systems. In this work, we propose a model material, a mixture of soft glassy microgels and solutions of high molecular weight linear polymers. We establish systematic criteria for the design and thorough rheological characterization of such systems, in both shear and extension. Using our material, we show that it is possible to dramatically change the behavior in extension with minimal change in the shear yield stress and elastic modulus, thus enabling applications that exploit orthogonal modulation of shear and extensional material properties.

High-molecular-weight linear polymers improve microvascular perfusion after extracorporeal circulation.

High-molecular-weight linear polymers (HMWLPs) have earned the name "drag-reducing polymers" because of their ability to reduce drag in turbulent flows. Recently, these polymers have become popular in bioengineering applications. This study investigated whether the addition of HMWLP in a venoarterial extracorporeal circulation (ECC) model could improve microvascular perfusion and oxygenation. Golden Syrian hamsters were instrumented with a dorsal skinfold window chamber and subjected to ECC using a circuit comprised of a peristaltic pump and a bubble trap. The circuit was primed with lactated Ringer solution (LR) containing either 5 ppm of polyethylene glycol (PEG) with a low molecular weight of 500 kDa (PEG500k) or 5 ppm of PEG with a high molecular weight of 3,500 kDa (PEG3500k). After 90 min of ECC at 15% of the animal's cardiac output, the results showed that the addition of PEG3500k to LR improved microvascular blood flow in arterioles and venules acutely (2 h after ECC), whereas functional capillary density showed improvement up to 24 h after ECC. Similarly, PEG3500k improved venular hemoglobin O2 saturation on the following day after ECC. The serum and various excised organs all displayed reduced inflammation with the addition of PEG3500k, and several of these organs also had a reduction in markers of damage with the HMWLPs compared to LR alone. These promising results suggest that the addition of small amounts of PEG3500k can help mitigate the loss of microcirculatory function and reduce the inflammatory response from ECC procedures.NEW & NOTEWORTHY High-molecular-weight linear polymers have gained traction in bioengineering applications. The addition of PEG3500k to lactated Ringer solution (LR) improved microvascular blood flow in arterioles and venules acutely after extracorporeal circulation (ECC) in a hamster model and improved functional capillary density up to 24 h after ECC. PEG3500k improved venular hemoglobin O2 saturation and oxygen delivery acutely after ECC and reduced inflammation in various organs compared to LR alone.

BIO9: The Addition of High Molecular Weight Linear Polymers Improves Microvascular Perfusion in an Animal Model of Veno-arterial Extracorporeal Circulation.

High molecular weight linear polymers have been used in turbulent flow applications such as crude oil transfer to reduce drag. These polymers have branched into bioengineering applications to improve pressure changes within the macrocirculation and improve RBC distribution within the microcirculation. The current study aims to determine whether the addition of these polymers to priming fluids used for veno-arterial extracorporeal circulation (VA-ECC) procedures improve microvascular flow and tissue oxygenation. To assess the microcirculation, male Golden Syrian hamsters were instrumented with a dorsal skinfold window chamber, and an exteriorized carotid artery catheter was implanted for arterial blood and blood pressure access. After baseline (BL) measurements were taken, the hamster underwent surgery under isoflurane to insert a drainage catheter into the jugular vein. A heparin bolus (0.05 IU/g) was then provided, and the animal was connected to the VA-ECC circuit. The circuit, consisting of a peristaltic pump and bubble trap, was primed with lactated ringers (LR, control), LR with 5 ppm of 500 kDa polyethylene glycol (PEG500k) or LR with 5 ppm of 3500kDa polyethylene glycol (PEG3500k). Blood flow was ramped up over 15 minutes, maintained at 15% of the animal’s cardiac output for 60 minutes, then ramped down over 15 minutes. The animal was then surgically closed and placed on a heating pad and allowed at least 30 minutes to wake up from the anesthetic plane before taking measurements at 1, 2, and 24 hours after VA-ECC. Capillary perfusion (Figure 1) within the skinfold preparation showed a significant decrease immediately post-ECC for all three groups. However, the PEG3500k group consistently showed significant increase in functional capillary density (FCD) as compared to both other groups after ECC. 24 hrs after ECC, FCD was recovered close to BL levels for both PEG groups, while the LR control did not. Arteriole and venule velocity (Figure 2) was significantly elevated at both 1 and 2 hrs post-ECC for the PEG3500k group when compared to the other two groups. Arteriole flow for the PEG3500k was significantly improved over the LR control at 24 hrs post-ECC, and was significantly higher than BL levels. Hemoglobin saturation within arterioles and venules (Figure 3) revealed that PEG3500k had higher venule saturation at 1 and 2 hrs post-ECC compared to both other groups. The results indicate that the use of PEG3500k improved microvascular perfusion acutely post-ECC, and continued to up to 24 hrs afterwards. The most important changes were in arteriole perfusion and FCD, since that directly impacts oxygen delivery and metabolic washout respectively. Ultimately, this aids in maintaining organ function and preventing the development of ischemic injury and inflammatory cascades. Future studies could optimize the molecular weight, concentration, and type of polymer, along with testing in a clinical ECC circuit to determine hemodynamic changes.Figure 1. Functional capillary density (FCD), normalized to baseline (BL, represented by the dotted line). † P < 0.05 as compared to BL, within each group. * P < 0.05; ** P < 0.01; *** P < 0.001 between groups, at each timepoint.Figure 2. Perfusion within the microcirculation. From top to bottom: diameter, velocity, blood flow. Arterioles are on the left, while venules are on the right. Note that all values were normalized to baseline (BL, represented by the dashed line) and that blood flow was calculated from the diameter and velocity measurements of each vessel. Bar plots represent mean and standard deviation. † P < 0.05 as compared to BL, within each group. * P < 0.05; ** P < 0.01; *** P < 0.001; **** P < 0.0001 between groups, at each timepoint.Figure 3. Hemoglobin oxygen saturation within the microcirculation. Top = arterioles, bottom = venules. Bar plots show mean and standard deviation. † P < 0.05 as compared to BL, within each group. * P < 0.05; ** P < 0.01; *** P < 0.001; **** P < 0.0001 between groups, at each timepoint.

FOLLICULAR FLUID HYALURONIC ACID POLYDISPERSITY IS ASSOCIATED WITH AGE AND IN VITRO FERTILIZATION CYCLE OUTCOME: A PILOT STUDY

Human follicular fluid is rich with Hyaluronic acid (HA). HA is synthesized as a high-molecular weight (HMW) linear disaccharide polymer. It is fragmented into low-molecular weight (LMW) HA by the activity of hyaluronidases and reactive oxygen species. HA size determines its biological function: HMW HA (>1000kDa) displays anti-inflammatory and immunosuppressive properties, and LMW HA (generally <500kDa) can induce the release of pro-inflammatory cytokines. Our group has previously demonstrated that LMW HA fragments compromise estradiol production and gamete quality of mouse follicles, in vitro.

フラーレン高分子の合成とマイクロファイバーの作製

Soluble, high molecular weight linear fullerene polymers were synthesized by the Cu(I)-catalyzed azide-alkyne cycloaddition polymerization between dialkyne-substituted C60 and diazide-substituted 1,3,5-tridodecyloxybenzene monomers. It was found that the alkylene spacer length significantly affects the solubility of the resulting polymers. After the optimization of the monomer structures as well as the purification by reprecipitation, soluble fullerene polymers with the number-average molecular weight (Mn) and polydispersity index (Mw/Mn) of 130,000 and 2.42, respectively, were produced. The fullerene polymers were soluble in common organic solvents, such as THF, CH2Cl2, CHCl3, and toluene. We found that fullerene polymer microfibers could be obtained by electrospinning of a CHCl3 solution at a certain polymer concentration.

Synthesis and Rheological Characterization of Star-Shaped and Linear Poly(hydroxybutyrate)

Indium and zinc complexes, [(NNOtBu)InCl]2(μ-Cl)(μ-OTHMB) (2) and (NNiOtBu)Zn(CH2CH3) (3), were used to produce monodispersed three- and six-armed star-shaped PHBs using tris(hydroxymethyl)benzene (THMB) and dipentaerythritol as the chain transfer agents. Reactions catalyzed by complex 2 were highly controlled, with THMB:catalyst ratios of up to 590:1, resulting in star-shaped PHBs with predictable molecular weights (Mn = 1.25–219 kDa) and narrow dispersities (Đ = 1.02–1.08). The zinc-based catalyst, 3, was less controlled than the indium analogue but nevertheless generated moderately syndiotactic PHBs with maximum Mn values of ∼100 kDa. Importantly, 3 allowed the formation of previously unknown 6-armed star PHBs, allowing us to compare the effects of the different PHB architectures on the rheological behavior of the materials. High molecular weight linear and star polymers were characterized using solution and melt viscoelastic studies. Zero-shear viscosity of linear PHBs exhibited a power law relationsh...

Synthesis and Characterization of Complex Mixtures Consisting of Cyclic and Linear Polyamides from Ethyl Bis-Ketal Galactarates

Bis-ketal-protected diethyl galactarate was condensed with different diamines to prepare sugar-based polyamides. Ketal-protected polyamides, which are soluble in organic solvents, were deprotected with 90% trifluoroacetic acid to yield water insoluble materials. FTIR, NMR, GPC, MALDI-TOF, ESI and TGA techniques were used to characterize the structure and the properties of these biodegradable materials. D-galactaric acid-based polyamides are complex mixtures of cyclic and linear structures. High molecular weight linear polymer formation was limited by competitive cyclization reactions. The percentage of cyclization was highly dependent on the nature of the diamine used. Polycondensation with linear aliphatic diamines favored the formation of macrocycles, identified by MALDI-TOF and ESI.

Synthesis and Properties of Polymers Containing 2H-Benzimidazol-2-one Moieties: Polymerization via N-C Coupling Reactions.

Novel homopolymers and copolymers containing 2H-benzimidazol-2-one units have been synthesized by N-C coupling reactions of 1H-benzo[d]imidazol-2(3H)-one and activated aromatic dihalides under conditions similar to those for the synthesis of poly(aryl ether)s and poly(benzimidazole sulfone)s. 1H-Benzo[d]imidazol-2(3H)-one behaved like a bisphenol in the polymerization reaction to afford, quantitatively, high molecular weight linear polymers with inherent viscosities (ηinh) ranging from 0.57 to 1.31 dL/g. The polymers were soluble in various organic solvents, and transparent, flexible, and creasable films were cast from its dichloromethane-solution. The homopolymer had a remarkably high glass transition temperature (Tg 348 °C) and good thermal stability. Only 30 mol % (8.9 wt %) of the 2H-benzimidazol-2-one unit for the copolymer with 4,4'-biphenol was required to raise the Tg of commercial poly(aryl ether), Radel R-5000 from 220 to 269 °C.

Application of Alkyne‐TCNQ Addition Reaction to Polymerization

The polymerization using a high-yielding addition reaction between electron-rich alkynes and 7,7,8,8-tetracyanoquinodimethane (TCNQ) derivatives is described. The bifunctional monomer containing two TCNQ moieties and the counter comonomer bearing two dialkylaniline (DAA)-substituted alkynes are reacted in 1,2-dichloroethane under mild heating conditions. At the high monomer concentrations, high molecular weight linear polymers are obtained, while the reaction at the low monomer concentrations produces a significant amount of the cyclic compounds. A clear relationship between the monomer concentration and the cyclic compound amount is demonstrated. The obtained polymers feature a sufficient thermal stability with the decomposition temperature exceeding 300 °C as well as strong charge-transfer (CT) bands and redox activities ascribed to the produced donor-acceptor moieties. These features are also used to optimize the polymerization conditions and to estimate the chemical structures.

Improving Local Bentonite Performance for Drilling Fluids Applications

Drilling fluid is a vital element of the drilling process. Any drilling fluid must have common properties that facilitate safe and satisfactory completion of the well.The main component of water base mud is clay (mostly bentonite). The present consumption of bentonite clay in the drilling operations in Saudi Arabia alone can reach over 100,000 tons a year and all of it is imported from USA. This trend is expected to continue as drilling activity increases. The large consumption and the high importation cost of this material lead to an attempt to find a local substitute.Clays in Saudi Arabia are represented by numerous commercial stocks. The use of these local clays in the drilling activities can save a huge amount of hard currency that otherwise would be spent on importing it from abroad.Several attempts were made to investigate shale outcrop precipitates in the kingdom. This work focuses on the possibility of the utilization of local bentonite clay minerals as a basic material for drilling fluids used to drill oil and gas wells. The only known bentonite outcrop in the kingdom is in Khulays area, 70 km north Jeddah adjacent to Makkah-Madinah road.API specifications for acceptable drilling mud was the base for evaluating the local bentonite. The properties of the local mud can be improved economically by adding some cheep materials to the prepared mud to enhance its viscosity and filtration loss (such as CMC, Drispac polymer, and bentonite extenders). Also, shearing speed can be used as an enhancement method to improve the dispersion rate of the clay suspension, and hence increase viscosity and decrease filtration loss. But, the used shearing speed should be limited to a practical and economical speed.The bentonite extender can be either a salt or a polymer, it enhances viscosity buildup by slightly flocculating the bentonite suspension. Sodium carbonate is an example of a salt that can be added as an extender. Soaking raw bentonite with a solution of sodium salt resulted, through ion exchange, in a higher sodium bentonite content. More effective extenders than inorganic salts are the high molecular weight linear polymers.

Vanadium Complexes Possessing N2O2S2-Based Ligands: Highly Active Procatalysts for the Homopolymerization of Ethylene and Copolymerization of Ethylene/1-hexene

The family of ligands containing an N2O2S2 core, namely, 1,2-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)ethane (H2L1), 1,3-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)propane (H2L2), 1,4-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)butane (H2L3), and 1,2-di(3-Me-5-t-Bu-salicylaldamino-o-phenylthio)ethane (H2L4), have been prepared and complexed with a variety of vanadium chlorides and alkoxides to afford complexes of the form [V(X)L1] (X = O (1), Np-tol (2), Cl (3)), [V(O)(L2,3)] (L2 (4), L3 (5)), and [V(L4)] (6). Crystal structure determinations of H2L1 and H2L4 show the molecule to be centrosymmetric about the bridging ethane moiety, with structural determination of 1 and 3 revealing isostructural monomeric complexes in which the ligand chelates in such a way as to afford pseudo-octahedral coordination at the vanadium center. Prolonged reaction of H2L1 with [V(Np-tol)(OEt)3] led, via oxidative cleavage of the C-S bond, to the bimetallic complex [V2L1(3-Me,5-t-Bu-salicylaldimino-o-phenylthiolate)2] [VL'] (7), as characterized by single-crystal X-ray crystallography. 7 was also isolated from the reaction of H2L4 and [VO(On-Pr)3]. The ability of 1-7 to catalyze the homopolymerization of ethylene and the copolymerization of ethylene/1-hexene in the presence of dimethylaluminum chloride (DMAC) has been assessed: screening reveals that for ethylene homopolymerization 1-7 are all highly active (>1000 g/mmol.h.bar), with the highest activity (ca. 11 000 g/mmol.h.bar) observed using catalyst 3; the use of trimethyl aluminum (TMA) or methylaluminoxane (MAO) as the cocatalyst led only to poorly active systems producing negligible polymer. Analysis of the polyethylene produced showed high molecular weight linear polymers with narrow polydispersities. For ethylene/1-hexene copolymerization, activities as high as 1,190 g/mmol.h.bar were achieved (4); analysis of the copolymer indicated an incorporation of 1-hexene in the range of 5-13%.

Synthesis of Peptide-Based Polymers by Microwave-Assisted Cycloaddition Backbone Polymerization

The optimized reaction conditions for the Cu(I)-catalyzed N-->C polymerization of azido-phenylalanyl-alanyl-propargyl amide to yield either high molecular weight linear polymers or medium-sized cyclic polymers is described. These reaction conditions will be applied to tailor the synthesis, properties, and structure of biologically relevant peptide-based biopolymers.

Experimental approaches to hyaluronan structure

A review of the literature describing experimental studies on hyaluronan (HA) is presented. Methods sensitive to the hydrodynamic properties of HA, analyzed in neutral aqueous solution containing NaCl at physiological concentration, can be shown to fit the expected behavior of a high molecular weight linear semi-flexible polymer. The significant nonideality of HA solutions can be predicted by a simple treatment for hydrodynamic interactions between polymer chains. Nuclear magnetic resonance and circular dichroism studies of HA are also in agreement with a model incorporating dynamically formed and broken hydrogen bonds, contributing to the semi-flexibility of the polymer chain, and segmental motions on the nanosecond time scale. HA shows the capability for self-association in the formation of a viscoelastic putty state at pH 2.5 in the presence of salt, and a gel state at pH 2.5 in mixed organic/aqueous solution containing salt. Ordered and associated structures have also been observed for HA on the surfaces, especially in the presence of surface-structured water. These phenomena can be understood in terms of counterion-mediated polyelectrolyte interactions. The possibility that hyaluronan exists in vivo in environments that induce ordered structures and assemblies is discussed.

Silole‐containing linear and hyperbranched polymers: synthesis, thermal stability, light emission, nano‐dimensional aggregation, and optical power limiting

AbstractLinear polyacetylenes and hyperbranched polyphenylenes carrying 1,2,3,4,5‐pentaphenylsilolyl (PS) pendants are designed and synthesized. Homo‐polymerization of HC≡CPS, HC≡C(CH2)9OPS, and C6H5C≡C(CH2)9OPS and (co)polycyclotrimerization of (HC≡C)2PS with 1‐octyne are effected by NbCl5‐, WCl6‐, MoCl5‐, and TaCl5‐based catalysts. High molecular weight linear (1‐3) and hyperbranched polymers (6) are obtained in high yields (Mw up to ∼70 × 103 and yield up to 85%). All the polymers are thermally stable, losing little weight when heated to 350°C. Whereas all the polymers emit faint light when molecularly dissolved, polymers 2, 3, and 6 become emissive when aggregated in poor solvents or when cooled to low temperatures. Restricted intramolecular rotations of the phenyl rings upon the axes of the single bonds linked to the silole cores may be responsible for the aggregation‐ or cooling‐induced emission. A multilayer electroluminescent device using 3 as an active layer emits a blue light of 496 nm with maximum brightness, current efficiency, and external quantum yield of 1118 cd/m2, 1.45 cd/A, and 0.55%, respectively. Polymers 6 are non‐linear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that of C60, a best‐known optical limiter.

Manganese‐based transition metal complexes as new catalysts for olefin polymerizations

AbstractThree manganese complexes, Mn(acac)3 (acac = acetylacetonate), Cp2Mn (Cp = cyclopentadienyl), and Mn(salen)Cl [salen = 1,2‐cyclohexanediamino‐N,N′‐bis(3,5‐dit‐butyl‐salicylidene)], were used for ethylene and propylene polymerizations. These complexes, in combination with an alkylaluminum cocatalyst such as methylaluminoxane (MAO) or diethyl aluminum chloride (AlEt2Cl), could promote ethylene polymerizations that yielded extremely high molecular weight linear polymers, but were inactive for propylene polymerizations. The counterparts supported on MgCl2 showed activities even for propylene polymerizations and had remarkably enhanced activities for ethylene polymerizations. In the presence of an electron donor such as ethylbenzoate, the MgCl2‐supported manganese‐based catalysts yielded a highly isotactic polypropylene with a high molecular weight. © 2001 John Wiley &amp; Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3733–3738, 2001

An Overview on Chitin and Chitosan Applications with an Emphasis on Controlled Drug Release Formulations

Chitin is a high molecular weight linear polymer of N-acetyl-D-glucosamine (N-acetyl-2-amino-2-deoxy-D-glucopyranose) units linked by β-D (1→4) bonds. It is a highly insoluble material resembling c...

Entropically driven phase separation of highly branched/linear polyolefin blends

Small-angle neutron scattering (SANS) was used to examine the melt phase behavior of a heavily branched comb PEE polymer blended separately with two linear PEE copolymers. In this case, PEE refers to poly(ethylene-r-ethylethylene) with 10% ethylene units; therefore, the molecular architecture was the only difference between the two components of the blends. The molecular weights of the two linear random copolymers were 60 and 220 kg/mol, respectively. The comb polymer contained an average of 54 long branches, with a molecular weight of 13.7 kg/mol, attached to a backbone with a molecular weight of 10 kg/mol. Three different volume compositions (25/75, 50/50, and 75/25) were investigated for both types of blends. SANS results indicate that all the blends containing the lower molecular weight linear polymer formed single-phase mixtures, whereas all the blends containing the high molecular weight linear polymer phase-separated. These results are discussed in the context of current theories for polymer blend miscibility. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2965–2975, 2000

Linear Monodisperse π-Conjugated Oligomers: Model Compounds for Polymers and More

The development of structure-property relationships for monodisperse oligomers has been extremely useful to rationalize the properties of high molecular weight linear π-conjugated polymers. A great variety of spectacular molecular architecture has been generated, culminating in the recent preparation of molecular wires such as 1 with lengths exceeding 10 nm that have potential applications in molecular electronics.

Uncrosslinked epoxide-amine addition polymers, 45. Linear addition polymerization of 2,2-bis[4-(2,3-epoxypropoxy)- phenyl]propane and arylamines in highly concentrated solutions

In highly concentrated solutions (40 to 70 wt.-%) such as in chlorobenzene (CB) or 2-methoxyethanol (ME) the addition polymerization of 2.2-bis[4-(2,3-epoxypropoxy)phenyl]propan (DGEBA) and disecondary diamines leads to high molecular weight linear addition polymers. The broad molecular weight distribution (M w /M n = 4 to 17) is caused by the formation of cyclic oligomers. After precipitation in acetone, M w /M n values of 2.8 to 3.4 were obtained which indicate a regular linear step-growth polymerization. Differential scanning calorimetry (DSC) investigations show that CB retards the addition polymerization, whereas ME exhibits an acceleration of the polymerization. The suggested kinetic model describes the reaction behavior over the whole range of polymerization by one parameter set only. In order to find the optimum parameters, the set of differential equations was solved numerically by multivariate non-linear regression. An excellent agreement between calculated and experimental curves was found.

A neutron reflectometry study of polystyrene network interfaces

We have used neutron reflectometry to measure interfacial widths between two polystyrene films, where either one or both films are crosslinked. The observed interfacial width between two networks is larger than the size expected for “dangling ends”, which suggests motion of heterogeneous regions of the networks. In the case when one of the networks is replaced by a linear polymer, the interfacial profile can be asymmetric with a diffusion “front” of linear polymer penetrating the network to a length scale of up to 200 A. In the case of a more densely crosslinked network and a high molecular weight linear polymer the interface is symmetric implying negligible penetration.