Ultrahigh Molecular Weight Poly Research Articles

Preparation of poly(endo-norbornene derivatives) with ultra-high molecular weight by combining ROMP and acyclic metathesis reaction

Endo-norbornene derivatives are much cheaper and more accessible. However, it is difficult to prepare endo-polynorbornenes with ultra-high molecular weight (UHMW) by ring opening metathesis polymerization (ROMP) owing to the low activity. The molecular weight of poly(endo-NB-2OH)n could only reach to 309.1 kg mol−1 for 24 h via ROMP. While, UHMW poly(endo-NB-2OH)m was prepared by combining ROMP and acyclic metathesis reaction in much shorter time. The effects of residual monomer, amount of H2SO4, concentration, temperature and reaction time were investigated in depth. The UHMW P(endo-NB-2OH)m (Mn =2645.5 kg mol−1, PDI = 1.74) could be obtained at 80 °C for 5 min with H2SO4/G3 as 10/1 and concentration of 0.1 M. Moreover, UHMW P(endo-NBI-OH)m(Mn =1114.2 kg mol−1, PDI = 1.95) was also successfully prepared by this method. However, the H2SO4/G3 should increase to 30/1, and reacted for 45 min owing to the steric resistance of the cyclic dicarboximide. For P(exo-NBI-OH)n with lower activity, reaction time should prolong to 3 h to obtain UHMW P(exo-NBI-OH)m(Mn =1716.7 kg mol−1, PDI = 1.93). Finally, UHMW P(endo-NB-2alkyne)m, P(endo-NBI-alkyne)m, and P(exo-NBI-alkyne)m were successfully prepared via post-modification. Acyclic metathesis reaction is a robust and universal reaction to prepare other functional UHMW polynorbornenes, especially for the UHMW endo-polynorbornenes, which could not be prepared by ROMP efficiently.

Synthesis of Ultrahigh Molecular Weight Poly (Trifluoroethyl Methacrylate) Initiated by the Combination of Palladium Nanoparticles with Organic Halides

Ultrahigh molecular weight polymers display outstanding properties and have great application potential. However, the traditional polymerization methods have inevitable disadvantages that challenge the green synthesis of ultrahigh molecular weight polymers. The paper achieved an ultrahigh molecular weight poly (trifluoroethyl methacrylate) via a novel polymerization and discussed the mechanistic, kinetic, and experimental aspects. The combination of palladium nanoparticles with ethyl 2-bromopropionate has been identified as an exceedingly efficient system for initiating the polymerization of trifluoroethyl methacrylate. An ultrahigh molecular weight poly (trifluoroethyl methacrylate) with a number-average molecular weight up to 3.03 × 106 Da has been synthesized at a feeding molar ratio of [poly (trifluoroethyl methacrylate)]/[ethyl 2-bromopropionate]/[palladium nanoparticles] = 3.95 × 104:756:1 at 70 °C. The reaction orders concerning palladium nanoparticles, ethyl 2-bromopropionate, and poly (trifluoroethyl methacrylate) were determined to be 0.59, 0.34, and 1.38, respectively. By analyzing a series of characterizations, we verified that the polymerization of poly (trifluoroethyl methacrylate) was initiated by the ethyl 2-bromopropionate residue radicals, which were generated from the interaction between palladium nanoparticles and ethyl 2-bromopropionate. The comparatively large size of the palladium nanoparticles provided a barrier to chain-growing radicals, promoting the synthesis of ultrahigh molecular weight polymers.

Efficient Synthesis of Ultrahigh Molecular Weight Poly(methyl methacrylate) via Visible Light-Induced RAFT Polymerization in Deep Eutectic Solvent

Efficient Synthesis of Ultrahigh Molecular Weight Poly(methyl methacrylate) via Visible Light-Induced RAFT Polymerization in Deep Eutectic Solvent

Extensional rheology of elastoviscous aqueous PEO/PEG or DMS Boger fluids and weakly elastic alternatives for investigating viscoelastic flows and instabilities

Boger fluids that exhibit a rate-independent shear viscosity (typically ∼ 1 Pa∙s = 1000x water viscosity) and elasticity measurable using torsional rheometers (modulus, relaxation time, or first normal stress difference) are considered as the realization of viscoelastic fluids described by the Oldroyd-B model. However, Boger fluids, conventionally formulated as dilute solutions of high molecular weight (Mw) polymers in relatively high viscosity solvents (or solutions of oligomers or lower Mw polymer), are unsuitable for emulating polymeric fluids used in coating formulations that are lower in viscosity, appear inelastic in torsional shear rheometry, and yet appear prone to viscoelastic instabilities. Therefore, Dontula, Macosko, and Scriven (DMS) (AIChE J, 1998) chose to create an alternative model of elastic fluids by dissolving ultrahigh molecular weight (UHMw) poly(ethylene oxide) (PEO) in an aqueous solution of its lower Mw analog, often referred to as poly(ethylene glycol) or PEG. Even though numerous studies of printing and coating flow instabilities use this aqueous PEO/PEG or DMS Boger fluids as model viscoelastic fluids, only a few explicitly measured elastic properties, especially using relaxation time, and hardly any characterized extensional rheology. In this contribution, we recreate the DMS Boger fluids to examine their elasticity and extensional rheology response using dripping-onto-substrate (DoS) rheometry that relies on an analysis of capillarity-driven pinching dynamics. Though the aqueous PEG solution is often treated as a viscous and Newtonian solvent, we discover that in DoS rheometry, both the PEG solution and the DMS Boger fluid display power law response followed by elastocapillary, in contradiction with the assumptions and the response expected of the Oldroyd-B model. Furthermore, the solution of entangled PEG chains influences specific viscosity, pinching dynamics, and measured extensional rheology response in striking contrast with Newtonian solvents of the same viscosity. Lastly, we describe the possibility of using dilute, aqueous solutions of UHMw PEO as model viscoelastic fluids for coating flows, for both elasticity and extensional viscosity can be determined using DoS rheometry. Due to their water-like viscosity, the aqueous PEO solutions appeal as model fluids that have elasticity, emulate Newtonian fluids in the early stages of pinching, and have a relaxation time tunable by changing polymer Mw or concentration.

Single Crystals of Ultrahigh Molecular Weight Poly(ethylene-alt-CO)s for Solvent-Free Processing and Enhanced Thermal Stability

Single Crystals of Ultrahigh Molecular Weight Poly(ethylene-<i>alt</i>-CO)s for Solvent-Free Processing and Enhanced Thermal Stability

Accessing Functionalized Ultra-High Molecular Weight Poly(α-olefin)s via Hafnium-Mediated Highly Isospecific Copolymerization.

Inspired by the favorable impact of heteroatom-containing groups in phenoxy-imine titanium and late transition metal catalysts, a series of novel pyridylamido hafnium catalysts bearing ─OMe (Cat-OMe), ─CF3 (Cat-CF3), and ─C6F5 (Cat-C6F5) substituents are designed and synthesized. Together with the established hafnium catalysts Cat-H and Cat-iPr by Dow/Symyx, these catalysts are applied in the polymerization of α-olefins, including 1-hexene, 1-octene, and 4M1P, as well as in the copolymerization of these α-olefins with a specifically designed polar monomer. The enhancement of polymer molecular weight derived from catalyst modification and the incorporation of polar monomers is discussed in detail. Notably, the new catalysts are all highly active for α-olefins polymerization, with catalyst Cat-CF3 producing isotactic polymers with the highest molecular weight (Mw = 1649kg mol-1); in copolymerization with polar monomers, catalyst Cat-OMe yields isotactic copolymer with the highest molecular weight (Mw = 2990kg mol-1). Interestingly, catalyst Cat-C6F5 bearing a ─C6F5 group in the N-aryl moiety gives rise to poly(α-olefin) with reduced stereoselectivity. The findings of this study underscore the potential of heteroatom-containing groups in the development of early transition metal catalysts and the synthesis of polymer with novel structures.

Easy Access to Ultrahigh-Molecular Weight Poly(1,3-dioxolane) by Rare Earth Triflates

Easy Access to Ultrahigh-Molecular Weight Poly(1,3-dioxolane) by Rare Earth Triflates

Soluble ultra-high molecular weight poly(4,4′-diphenylether-5,5′-bibenzimidazole) based membranes with remarkable mechanical strength and specific proton conductivity for high temperature proton exchange membrane fuel cells

Reducing the thickness of membrane electrolyte is one important direction to improve Ohmic polarization and the according performance of high-temperature proton exchange membrane fuel cells for its widespread applications. Herein, we report that robust thin membranes can be formed using a soluble ether-contained poly(4,4′-diphenylether-5,5′-bibenzimidazole) with an ultra-high molecular weight of 170 kDa. Due to the enhanced chain entanglement of high molecular weight polymers, the formed thin membrane exhibits promising mechanical strength, thermal and oxidation stability. The optimized membrane with thickness of 61 μm and phosphoric acid uptake of 606 wt% has the high specific proton conductivity of 25.9 S cm−2 at 160 °C under anhydrous conditions and mechanical strength of 11.2 MPa. The accordingly fabricated membrane electrode assembly delivers a peak power density of 0.544 W cm−2 with the open circuit voltage of 0.915 V at 160 °C using air as oxidant, outperforming the value of 0.522 W cm−2 for the commercial membrane electrode assembly with thickness of 250 μm and phosphoric acid uptake of 1018 wt%.

Synthesis of ultrahigh molecular weight poly(butyl acrylate) in the presence of palladium nanoparticles

Synthesis of ultrahigh molecular weight poly(butyl acrylate) in the presence of palladium nanoparticles

Synthesis of Ultrahigh Molecular Weight Poly(methyl Methacrylate) via the Polymerization of MMA Initiated by the Combination of Palladium Carboxylates with Thiols.

A novel synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) using organosulfur compounds combined with a catalytical amount of transition metal carboxylates as an initiator has been developed. The combination of 1-octanethiol with palladium trifluoroacetate (Pd(CF3COO)2) was found to be a very efficient initiator for the polymerization of methyl methacrylate (MMA). An ultrahigh molecular weight PMMA with a number-average molecular weight of 1.68 × 106 Da and a weight-average molecular weight of 5.38 × 106 Da has been synthesized at the optimal formulation of [MMA]:[Pd(CF3COO)2]:[1-octanethiol] = 94,300:8:23 at 70 °C. A kinetic study showed that the reaction orders with respect to Pd(CF3COO)2, 1-octanethiol, and MMA are 0.64, 1.26, and 1.46, respectively. A variety of techniques such as proton nuclear magnetic resonance spectroscopy (1H NMR), electrospray ionization mass spectroscopy (ESI-MS), size exclusion chromatography (SEC), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron paramagnetic resonance spectroscopy (EPR) were employed to characterize the produced PMMA and palladium nanoparticles (Pd NPs). The results revealed that Pd(CF3COO)2 was firstly reduced by the excess of 1-octanethiol to form Pd NPs at the early stage of the polymerization, followed by the adsorption of 1-octanethiol on the surface of nanoparticles and subsequent generation of corresponding thiyl radicals to initiate the polymerization of MMA.

Synthesis of ultra-high molecular weight poly(methyl methacrylate) with hydrosilane as initiator

Hydrosilanes, including diethylsilane (DES), triethylsilane (TES), phenylsilane (PSH), and diphenylsilane (DPS), have in the present study been used as initiators for the preparation of poly(methyl methacrylate) (PMMA) in the presence of Pd nanoparticles (Pd NPs). DPS initiated the polymerization of MMA in the production of PMMA, with a number average molecular weight ( M n ) of 2.00×10 6 Da and a dispersity (PDI) of 1.81 in the presence of 18.9 ppm of Pd NPs. The kinetic of the polymerization was investigated and the reaction orders, with regard to the MMA, DPS, and Pd NPs, were calculated as 0.85, 0.58, and 0.80, respectively. The molecular weight of the PMMA was measured using gel permeation chromatography (GPC) and the structure was characterized using proton nuclear magnetic resonance ( 1 H NMR). The transmission electron microscopy (TEM) and electron spin resonance (ESR) results revealed that the polymerization took place at the surface of the Pd NPs through a radical mechanism. • A novel route for preparing ultra-high molecular weight poly(methyl methacrylate) with hydrosilane as initiator had been proposed. • An ultrahigh molecular weight poly(methyl methacrylate) with number-average molecular weight of 2.00×10 6 Da was synthesized at mild conditions. • Kinetic of the polymerization of MMA initiated by DPS was investigated. • The mechanism study reveals that the polymerization was conducted via a radical mechanism.

Thermo‐oxidative degradation of ultrahigh molecular weight poly(ethylene oxide) in volatile organic solvents

AbstractThe degradation of ultrahigh molecular weight poly(ethylene oxide) (UHMWPEO) was investigated in three volatile organic solvents, methanol, chloroform, and tetrahydrofuran. Particularly, degradation rate was determined by means of Ubbelohde viscometry and degradation products were characterized by using electron spin resonance spectroscopy (ESR) and Fourier transform infrared spectroscopy (FTIR). The highest degradation rate was observed for UHMWPEO in tetrahydrofuran, with the lowest one in methanol. The ESR results showed that PEO‐C• and •OH radicals were produced during the degradation process. Among these selected solvents, tetrahydrofuran was found to generate free radicals through an autoxidation mechanism. This would accelerate the degradation of UHMWPEO, resulting in the observed highest degradation rate in the UHMWPEO/tetrahydrofuran solution. Esters were also detected in the degradation products of these UHMWPEO solutions, while formates and formate ions were generated in the solutions of UHMWPEO/tetrahydrofuran and UHMWPEO/cloroform except for PEO/methanol. Furthermore, the degradation mechanism of UHMWPEO was deduced. This work enabled an in‐depth understanding on the thermo‐oxidative degradation mechanism of UHMWPEO in representative organic solvents, which would be instructive for developing optimal solution‐based processing technique of UHMWPEO.

Two-Dimensional Zeolitic Imidazolate Framework ZIF-L: A Promising Catalyst for Polymerization

Here, for the first time, a 2D and leaf-like zeolitic imidazolate framework (ZIF-L) is reported for the synthesis of ultrahigh molecular weight (UHMW) poly(methyl methacrylate) (PMMA) with Mn up to 1390 kg mol−1. This synthesis method is a one-step process without any co-catalyst in a solvent-free medium. SEM, PXRD, FT-IR, TGA, and nitrogen sorption measurements confirmed the 2D and leaf-like structure of ZIF-L. The results of PXRD, SEM, TGA demonstrate that the catalyst ZIF-L is remarkably stable even after a long-time polymerization reaction. Zwitterionic Lewis pair polymerization (LPP) has been proposed for the catalytic performance of ZIF-L on methyl methacrylate (MMA) polymerization. This MMA polymerization is consistent with a living system, where ZIF-L could reinitiate the polymerization and propagates the process by gradually growing the polymer chains.

Design and Analysis of an Extruder for Bio-Composite Filament Fabrication

Fused Deposition Modelling (FDM) or Fused Filament Fabrication (FFF) is an additive manufacturing technique in which layers of materials are fused together in a pattern to form an item. Acrylonitrile Butadiene Styrene (ABS), Poly Lactic Acid (PLA), Poly Ethylene Terephthalate (PET), Poly Vinyl Alcohol (PVA), Sandstone, and other materials are utilised in this FDM 3D printer. However, the rapid changes of Global needs and advances in Engineering domain, are in need of the combination of new materials to cater to fulfil the society and technical demands. Therefore, this work attempts to develop a new bio-composite filament for making components, which are associated with medical application. The commercially available extruders are not so cost effective and custom based for the biomaterials chosen for this work. The selected materials for making the bio-composite are Poly Lactic Acid (PLA), Ultra High Molecular Weight Poly Ethylene (UHMWPE) along with Cissus quadrangularis (Adamant creeper) powder. So, it is essential to design and develop an extruder indigenously to make the Bio-composite filament. For this first phase, the basic components of the customized designed extruder are modelled using Solidworks 2018 and assembled. Subsequently the usage viability analysis is done by using ANSYS 18.1 at Manufacturing Engineering CAD laboratory. The thermal and dynamic analysis are successfully carried out. The results reveal that the heat sink of extruder could withstand up to 〖300〗^0 C and the heat transfer rates are reported.

The rheology of ultra-high molecular weight poly(ethylene oxide) dispersed in a low molecular weight carrier.

Gel spinning is the industrial method of choice for combining hydrophilic ultra-high molecular weight (UHMW) polymer resins with a hydrophobic support polymer to produce composite filaments for cytapheresis. Cytapheresis is a medical technique for removal of leukocytes from blood. Gel spinning is used to avoid high melt viscosity and thermal sensitivity of UHMW resins and the high melt temperature of the substrate resin but requires the recovery of toxic solvents. The UHMW resin is used because it forms a stable gel phase in the presence of water; a lower molecular weight resin (LMW) simply dissolves. UHMW and LMW resins were both poly(ethylene oxide) (PEO) and the substrate was polyarylsulfone (PAS). The literature indicated PEO undergoes non-oxidative thermal degradation above 200 °C and PAS is processed up to 350 °C. Dynamic oscillatory shear rheometry was used to study 0, 25, 40, 50, 60, and 75 wt. % UHMW PEO in LMW PEO to take advantage of the sensitivity of viscosity to changes in molecular weight and material configuration, indicating degradation. Samples were exposed to 220 °C, 230 °C, 240 °C, 250 °C, 275 °C, and 300 °C temperatures for 5 min to explore conditions that could result in sample degradation. The viscosity decreased less with increasing UHMW PEO content for samples exposed to the same temperature and the viscosity decreased more with increasing exposure temperature for samples with the same UHMW PEO content. Parameters were regressed from observed data to predict the change in molecular weight via empiricisms relating the viscosity to molecular weight, shear rate, temperature, and time.

Faster and better: A polymeric chaperone binder for microenvironment management in thick battery electrodes

Achieving high-performance thick battery electrodes via cost-efficient way is crucial for next-generation lithium/sodium ion batteries. However, the challenge comes from both a poor understanding of electrode microstructures and the lack of industry-friendly strategies on regulating the microstructures during the electrode fabrication. Here, as inspired by the chaperone in biology, a polymeric chaperone binder is reported to efficiently regulate the electrode microstructures. Firstly, the polymeric chaperone binder is realized by alloying poly(vinylidene fluoride) (PVDF) with ultra-high molecular weight poly(ethylene oxide), which generates unprecedented binder performance as compared with PVDF binder. Consequently, high-quality thick electrodes with a high active material (AM) loading around 60 mg/cm2 (about 2 times of the commercial level) are fabricated with over 80% reduction of energy consumption in slurry drying process. Meanwhile, the microstructures and properties of AM microenvironment are further characterized by micro-probe scanning, electro-rheology and bending testing, for the first time. Finally, thick electrodes with a high areal capacity of 8 mAh/cm2 @0.1C, superior C-rate and cycling performance have been demonstrated. In short, this study not only proposes an industry-friendly binder design strategy, but also uncovers the critical roles of binder solution in controlling the AM microenvironment quality and so the overall electrochemical performance.

Influence of gamma radiation on wear and oxidation properties of cross-linked UHMWPE components used in total knee arthroplasty- a review

This study mainly focuses on the wear and oxidation properties of highly cross linked UHMWPE (Ultra high molecular weight poly ethylene) replacing conventional UHMWPE as bearing material in Total Knee Arthroplasty (TKA) which were subjected to radiation under different sources and doses. Analysis of Vitamin E blended and Gamma radiated UHMWPE for TKA by simulation of artificial extended aging and daily heavy activities of a patient was done and observed no further degradation of the material due to wear and oxidation. It is noticed that improving wear resistance and anti-oxidation of the material depends on the radiation dose and post radiation treatment such as remelting used to remove free radicals in material. Mechanical property losses and wear losses during in vivo performance of a patient in longer period for two to three decades were also studied.

Criticality of inter-yarn friction in high-performance fabrics for the design of soft body armour

Inter-yarn friction plays a pivotal role in determining the impact resistance of woven fabric based soft armour panels (SAPs). This study presents a comparison of ballistic performance of SAPs made from para-aramid, ultra-high molecular weight polyethylene (UHMWPE) and poly para-phenylene-2,6-benzobisoxazole (PBO) woven fabrics and demonstrates the importance of inter-yarn friction. Plain woven fabrics were prepared using para-aramid, UHMWPE and PBO yarns and SAPs of constant areal density were produced using multiple layers of these fabrics. It is found that despite lower tenacity and modulus of para-aramid fibres, in comparison to those of UHMWPE and PBO, para-aramid SAP exhibits the lowest back face signature (BFS) owing to the highest inter-yarn friction. On comparing UHMWPE based SAPs made from fabrics with yarns of different fineness, fine UHMWPE yarn based fabric exhibits higher inter-yarn friction owing to more number of crossovers per unit length, which further translates into lower BFS of respective SAP. Therefore, while selecting fibres for soft body armour applications, inter-yarn friction should be considered along with the tensile properties.

Characterization of ultrahigh molecular weight poly(ethylene oxide) by size-exclusion chromatography with multiangle light scattering detection

This study investigated the experimental conditions needed to obtain molecular weight distribution (MWD) of ultrahigh MW poly(ethylene oxide) (PEO) using size exclusion chromatography (SEC) hyphenated with a multiangle light scattering photometer (MALS) and a differential refractive index detector (RI). Ultrahigh MW components yielded non-linear angular dependency in scattered light intensities. The first-order linear fitting using Zimm formalism resulted in significant differences in MW depending on if the signals from detector 4 to 16 were used in the fitting or only five low-angles from 4 to 8 were used. In contrast, no significant differences in MW were obtained for lower MW PEO samples (equal or less than 1000 KDa) between the two fitting approaches. It was thus proposed to use only the five low-angles to derive MW for a sample with broad polydispersity including both ultrahigh and low MW components. The SEC separation was done using one column designed for ultrahigh MW polymer separation connected with another mixed-bed column. The ultrahigh MW column allowed separation and characterization of polymeric components in the MW range between 10 and 50 million Dalton (MDa) and the size range between 300 and 600 nm in radius of gyration (Rg). Online calibration curves were obtained from the linear fittings of MW as a function of elution volume. MW polydispersity was derived from the online calibration curve showing that the ultrahigh MW PEO had higher polydispersity than the lower MW samples. The double logarithmic plot of radius of gyration versus MW indicated that both ultrahigh MW and low MW PEO would adopt expanded coil conformations in the aqueous solution.

Dynamic Mechanical Behavior of Basalt/aramid Hybrid Fiber Reinforced Uhmwpe Light Weight Composite

ABSTRACT The main focus of this research is to analyze the physical, mechanical, and dynamic-mechanical properties of the high-performance polymer composite. The composites are fabricated by hot compressing basalt and aramid fibers with UHMWPE (Ultra High Molecular Weight Poly Ethylene) at 200°C temperature and 200 bar pressure. Four different weight fractions of composites were fabricated namely UBA 1 having 70% UHMWPE, 10% basalt and 20% aramid; UBA 2 having 70% UHMWPE, 15% basalt and 15% aramid; UBA 3 having 70% UHMWPE, 20% basalt and 10% aramid; UBA 4 having 70% UHMWPE, 30% basalt and no aramid. The tensile strength, impact strength, hardness, and storage modulus of UBA 4 were found to be greater compared to the other composites. The UBA1 shows the highest flexural strength compared to the other samples. From XRD, the average crystalline size was calculated as 3.02 nm. The SEM image of the composites shows good adhesion of fibers and matrix in both UBA 1 and UBA 4. The dynamic mechanical properties of UBA 4 were also found to be better compared to all four samples for structural application.