High Molecular Weight Polymers Research Articles

Synthesis of high molecular weight L-Polylactic acid (PLA) by reactive extrusion at a pilot plant scale: Influence of 1,12-dodecanediol and di(trimethylol propane) as initiators

• Technical feasibility of using DDD and DTMP as initiators in the synthesis of PLA by using REX. • High molecular weight polymers with commercial properties are obtained. • FTIR, NMR and SEC methodologies have been applied for yield monitoring and molecular weight estimations. The present work describes the synthesis of polylactic acid (PLA) of isotactic high molecular weights via reactive extrusion ring-opening polymerization of L -lactide in presence of 1,12-dodecanediol (DDD) or di(trimethylol propane) (DTMP) as initiators. Weight-average molecular weights between 183 and 217 kDa were deduced by both diffusion NMR and SEC measurements. The functionality of each initiator allowed the obtention of PLA of linear multiarm branching with superior mechanical and rheological properties than those described in commercial references. PLA_DTMP demonstrated good performance in cast filming and PLA_DDD in injection molding. The reactive extrusion process presented herein has been validated in a relevant industrial environment and represents an interesting alternative to traditional synthesis methods with consequent cost savings.

Controlled Synthesis of Well-Defined Polyaminoboranes on Scale Using a Robust and Efficient Catalyst.

The air tolerant precatalyst, [Rh(L)(NBD)]Cl ([1]Cl) [L = κ3-(iPr2PCH2CH2)2NH, NBD = norbornadiene], mediates the selective synthesis of N-methylpolyaminoborane, (H2BNMeH)n, by dehydropolymerization of H3B·NMeH2. Kinetic, speciation, and DFT studies show an induction period in which the active catalyst, Rh(L)H3 (3), forms, which sits as an outer-sphere adduct 3·H3BNMeH2 as the resting state. At the end of catalysis, dormant Rh(L)H2Cl (2) is formed. Reaction of 2 with H3B·NMeH2 returns 3, alongside the proposed formation of boronium [H2B(NMeH2)2]Cl. Aided by isotopic labeling, Eyring analysis, and DFT calculations, a mechanism is proposed in which the cooperative "PNHP" ligand templates dehydrogenation, releasing H2B═NMeH (ΔG‡calc = 19.6 kcal mol-1). H2B═NMeH is proposed to undergo rapid, low barrier, head-to-tail chain propagation for which 3 is the catalyst/initiator. A high molecular weight polymer is formed that is relatively insensitive to catalyst loading (Mn ∼71 000 g mol-1; Đ, of ∼ 1.6). The molecular weight can be controlled using [H2B(NMe2H)2]Cl as a chain transfer agent, Mn = 37 900-78 100 g mol-1. This polymerization is suggested to arise from an ensemble of processes (catalyst speciation, dehydrogenation, propagation, chain transfer) that are geared around the concentration of H3B·NMeH2. TGA and DSC thermal analysis of polymer produced on scale (10 g, 0.01 mol % [1]Cl) show a processing window that allows for melt extrusion of polyaminoborane strands, as well as hot pressing, drop casting, and electrospray deposition. By variation of conditions in the latter, smooth or porous microstructured films or spherical polyaminoboranes beads (∼100 nm) result.

Soil conditioning tests on sandy soil for earth pressure balance shield tunneling and field applications

When performing earth pressure balance (EPB) shield tunneling in a sandy stratum, spewing and incomplete soil discharge often occur. Soil conditioning agents are needed to modify the excavated soil so that it has flow plasticity. Conditioned sandy soil and conditioning agents from Nanchang Metro Line 4 were evaluated using laboratory and performance tests. The results show that the foam expansion rate (FER) and half-life time (H-T) increase with increasing foam agent concentration (cf) up to a critical concentration of 5%. A high molecular weight polymer inhibits the FER and H-T of the foam. However, when the VR (the volume ratio of the polymer and foam agent) exceeds 0.3, the polymer increases the viscosity of the foam agent solution, which reduces the foam drainage rate and increases the foam stability. The reduction of the soil permeability by the polymer is the most obvious effect. When FIR = 40%, VR = 0.1 and SIR = 30%, the conditioned sand undergoes an appropriate state with good flow plasticity, with relatively low rotational torque and SD because the agglomeration effect of the polymer improves the homogeneity of the sandy soil. The engineering application of this soil conditioning scheme, which was based on laboratory test results, ensured the smooth completion of the tunnel.

First report of Schiff-base nickel nanoparticle-catalyzed oligomerization and polymerization of norbornene

Ten novel Schiff-base functionalized nickel nano-systems were synthesized to investigate the capping ability of the ligands as well as the stability of the resulting nanoparticles. All four ligands employed were found to be capable and comparable stabilizers to produce monodispersed nanoparticles. These nanoparticles were further evaluated as catalysts in the polymerization of norbornene, using MAO or MMAO as a co-catalyst. All ten nanomaterials were active polymerization catalysts, resulting in the first ever reported nanoparticle-assisted polymerization processes. It was shown that the nano-catalyst can facilitate either oligomerization or polymerization depending on the co-catalyst employed. Other than vinyl polynorbornene, hydroxy functionalized oligomer stabilized nanocomposite products were also obtained. The oligomers could be cleaved from the nanoparticle surface, depending on its intended application. The vinyl polymers obtained gave high molecular weights and low polydispersity indices, whereas the hydroxy oligomers gave low molecular weight oligomers that were monodispersed. It was shown that the metal to ligand concentration, i.e. the extent of the nanoparticle surface stabilization, has little influence on the catalytic activity but rather influenced the polymer selectivity. A higher ligand to metal ratio resulted in higher molecular weight polymers with lower polydispersity indices compared to the lower metal to ligand ratio analogues. The effect of the type of ligand employed, is also investigated.

Condensed Tannins as Antioxidants in Ruminants-Effectiveness and Action Mechanisms to Improve Animal Antioxidant Status and Oxidative Stability of Products.

Simple SummaryCondensed tannins (CTs) are secondary plant metabolites known for their antinutritional properties but also for their beneficial attributes for animal health and food quality, including antioxidant activity. Condensed tannins sources, such as plants and agro-industrial by-products or extracts prepared from these vegetal materials, have been used in ruminant diets to improve the animal antioxidant status and the oxidative stability of their products. However, this nutritional strategy has shown inconsistent results. Furthermore, unlike other phenolic compounds with low molecular weight, CTs are high molecular weight oligomers and polymers with poor bioavailability, which limit their absorption into circulation and direct antioxidant effect in living animals and post-mortem. Therefore, the action mechanism by which dietary CT exerts an antioxidant effect on ruminants is poorly understood. So, this review briefly presents the chemical structure of tannins, with particular emphasis on CT chemical structure, summarizes several studies focused on the effect of dietary CT sources on ruminants’ antioxidant status and oxidative stability of their products, and discusses the possible action mechanisms by which CT can exert such effects.Condensed tannins (CTs) are widely distributed in plants, and due to their recognized antioxidant activity are considered as possible natural antioxidants for application in ruminant diets. A wide range of CT-rich sources has been tested in ruminant diets, and their effects on animal antioxidant status and oxidative stability of their products are reviewed in the present work. Possible mechanisms underlying the CT antioxidant effects in ruminants are also discussed, and the CT chemical structure is briefly presented. Utilization of CT-rich sources in ruminant feeding can improve the animals’ antioxidant status and oxidative stability of their products. However, the results are still inconsistent. Although poorly understood, the evidence suggests that CTs can induce an antioxidant effect in living animals and in their products through direct and indirect mechanisms, which can occur by an integrated and synergic way involving: (i) absorption of CTs with low molecular weight or metabolites, despite CTs’ poor bioavailability; (ii) antioxidant action on the gastrointestinal tract; and (iii) interaction with other antioxidant agents. Condensed tannins are alternative dietary antioxidants for ruminants, but further studies should be carried out to elucidate the mechanism underlying the antioxidant activity of each CT source to design effective antioxidant strategies based on the use of CTs in ruminant diets.

Polymer-Lipid Hybrid Materials.

Hierarchic self-assembly underpins much of the form and function seen in synthetic or biological soft materials. Lipids are paramount examples, building themselves in nature or synthetically in a variety of meso/nanostructures. Synthetic block copolymers capture many of lipid's structural and functional properties. Lipids are typically biocompatible and high molecular weight polymers are mechanically robust and chemically versatile. The development of new materials for applications like controlled drug/gene/protein delivery, biosensors, and artificial cells often requires the combination of lipids and polymers. The emergent composite material, a "polymer-lipid hybrid membrane", displays synergistic properties not seen in pure components. Specific examples include the observation that hybrid membranes undergo lateral phase separation that can correlate in registry across multiple layers into a three-dimensional phase-separated system with enhanced permeability of encapsulated drugs. It is timely to underpin these emergent properties in several categories of hybrid systems ranging from colloidal suspensions to supported hybrid films. In this review, we discuss the form and function of a vast number of polymer-lipid hybrid systems published to date. We rationalize the results to raise new fundamental understanding of hybrid self-assembling soft materials as well as to enable the design of new supramolecular systems and applications.

Optimization of physico-chemical and membrane filtration processes to remove high molecular weight polymers from produced water in enhanced oil recovery operations

Polymer flooding is an enhanced oil recovery technique to extract the large portion of leftover subsurface oil following conventional extraction methods. In the flooding process, a long-chain polymer, such as partially hydrolyzed polyacrylamide (HPAM), is added to the displacing fluid to increase the mobility and extraction of the oil phase. Nevertheless, the challenge of managing produced water from polymer flooding operations is high because residual HPAM results in significantly high viscosity and organic content in the stream. Commonly used methods for produced water treatment, such as gravity settling and flotation, cannot be applied to obtain a purified stream efficiently, while innovative techniques are not yet feasible in practical operations. In this work, a simple method of polymer precipitation prompted by divalent ions is evaluated, optimized, and compared to membrane ultrafiltration. The physico-chemical properties of the HPAM are investigated and polymer precipitation tests are conducted by varying the main operational parameters, including pH, salinity, temperature, calcium and/or magnesium concentration, and polymer concentration. Response surface developed by central composite design method is used to optimize the process and identify the correct dosage of divalent cations coagulants and pH, the two main factors promoting HPAM separation. The removal of HPAM is well-described and maximized (>85%) by the model, which is also validated on three synthetic samples representing real wastewaters from polymer flooding applications. Optimized ultrafiltration, using ceramic membranes with surface pore size of 15 kDa, also shows the ability to remove HPAM effectively from water, but the precipitation method seems to be more versatile and easier to apply. The two processes, precipitation and ultrafiltration, may potentially be used in sequence as they complement each other in several ways.

Development of poly(ethyleneimine) grafted amphiphilic copolymers: Evaluation of their cytotoxicity and ability to complex DNA

Poly(ethyleneimine) (PEI) is one of the most widely used cationic polymers for gene delivery. The high molecular weight polymer, which is commercially available, is highly efficient but also very cytotoxic. The reduction in charge density by using nonlinear architectures based on low molecular weight (LMW) PEI is a promising approach to produce safer DNA-vectors. Herein, a group of cationic graft copolymers with different composition containing a hydrophobic biocompatible backbone and LMW linear PEI (lPEI) grafts obtained by ring opening polymerization and click chemistry was studied. The self-assembly and DNA complexation behavior of these materials was analyzed by the gel retardation assay, zeta potential measurements, and dynamic light scattering. The copolymers formed positively charged particles in water with average sizes between 270 and 377 nm. After they were added to DNA in serum-free medium, these particles acquired negative/near-neutral charges and increased in size depending on the N/P ratio. All copolymers showed reduced cytotoxicity compared to the 25 kDa lPEI used as reference, but the transfection efficiency was reduced. This result suggested that the cationic segments were too small to fully condense the DNA and promote cellular uptake, even with the use of several grafts and the introduction of hydrophobic domains. The trends found in this research showed that a higher degree of hydrophobicity and a higher grafting density can enhance the interaction between the copolymers and DNA. These trends could direct further structural modifications in the search for effective and safe vectors based on this polycation.

Next Generation Low-Cost NMP/PVDF-Free Fast-Charging Ni-Rich NMC Cathode Electrodes for High Power Energy Storage Device Applications

Longer range, faster charging, safer, and more durable and affordable batteries are required in order to promote the shift to an EV society powered by renewable energy. However, the current battery performance is limited by the conventional PVDF-NMP processing based cathode, which has lower electrical and ionic conductivity. The high molecular weight PVDF binders are the main cause of non-uniform porosity distribution, material agglomeration in active layer, and poor electrical conductivity. This problem is more prominent in high mass loading thick cathodes (>5 mg/cm2) that are required in high energy density battery designs. For examples, these cathode electrodes are not compatible with fast charging as they have high impedance and do not allow moderate to high C-rates in both charge and discharge.Nanoramic has re-invented how electrodes are manufactured by completely removing high molecular weight polymers such as PVDF and the toxic NMP solvent from the active layer of electrode. This dramatically improves Li-ion battery and Li-metal battery cell performance while decreasing the cost of manufacturing and the capital expenditures related to mixing, coating and drying, NMP solvent recovery, and calendering. In the Neocarbonix™ electrodes, a 3D nanocarbon matrix works as a mechanical scaffold for the electrode active material and mimics the polymer chain entanglement. The engineered surface chemistry of the nanocarbon materials, active materials (NMC), and the current collector promotes excellent mechanical stability for the resulting electrode architecture. As opposed to PVDF polymer, the 3D nanocarbon matrix is highly electrically conductive, allows for significantly thicker cathode active layer while improving the electrical conductivity of the electrode. By using eco-friendly solvents that are easily evaporated, the electrode throughput is higher, and more importantly, the energy consumption from electrode drying process is reduced by 30% due to reduction of temperature from 150 ⁰C-180 ⁰C required by the NMP to 60-70 ⁰C.In the Neocarbonix cathode electrodes the 3D carbon matrix is formed during a proprietary slurry preparation: high aspect ratio 1D and 2D carbon materials are properly dispersed and chemically functionalized using a 2-step proprietary slurry preparation process. The chemical functionalization is designed to form an organized self-assembled structure with the surface of active material particles (e.g. NMC particles). The so formed slurry is usually based on low-boiling point environmental green solvents for Ni-Rich NMC cathodes and are very easily evaporated and handled.After coating and drying, the electrodes undergo a calendering to control the density and porosity of the active material. In NMC811 cathode electrodes, densities of ≥3.6 g/cc and ≤20% porosity can be achieved. Depending on mass loading and battery cell requirements, the porosity can be optimized. Nanoramic projects a reduction in $/kWh of up to 20% with such cathode design. Figure below displays the preliminary results comparing the Neocarbonix (NX) NMP-PVDF free Ni-Rich NMC cathode electrodes with the conventional PVDF based NMC cathode electrodes in Li-Metal based half pouch cells (Li metal is the counter electrodes). Preliminary data shows that NX electrodes can maintain 62-66% capacity retention under 7C-Rate while the PVDF based electrodes can only maintain ~39% of initial capacity, which proves 27% improvement under high C-Rate discharge power performance. Also the NX NMC622 electrodes shows excellent fast-charging capability with 87.1% charge capacity within 15 mins constant current (CC) region fast-charge. Even for the higher areal loading NMC811 cathode (5.2-5.6 mAh/cm2) under 3.4C-Rate fast-charging, NX NMC811 displays 77.3% capacity retention within 17 mins CC region fast-charge, while the PVDF NMC811 control electrode only shows 35.9% capacity retention under 3.4C-Rate fast-charging, which proves that high capacity loading ~5.6 mAh/cm2 Neocarbonix Ni-rich NMC cathode can improve >2X in high-rate 15mins fast-charging capability compared with conventional PVDF electrodes in the electric vehicle (EV) applications. Figure 1

Water Domain Enabled Transport and Enhanced Stability in Aqueous Solid Polymer-in-Salt Electrolytes for Lithium-Ion Batteries

As lithium-ion batteries (LIBs) continue to grow in use for energy storage applications, concerns over their safety have influenced research for alternative materials, particularly solid-state electrolytes to replace the highly flammable and electrochemically unstable liquid organic electrolytes used in commercial LIBs. Aqueous-based solid polymer electrolytes (SPEs) offer a safer approach by using water as an abundant, cheap, and non-toxic solvent in an inherently nonflammable polymer matrix. This class of electrolyte also offers decreased cost and weight, ease of processibility, and increased long-term chemical and mechanical stability. However, widespread commercial adoption of SPEs for lithium-ion batteries has been hindered by subpar transport properties, namely, ionic conductivities <1 mS/cm at room temperature and slower Li+ transport compared to anion transport due to slow polymer chain mobility. The use of water as a solvent also lends to restrictive electrochemical stability windows (ESWs) due to its nonideal redox properties that lead to minimal anodic and cathodic limits, dominated by hydrogen evolution at potentials beyond common anode materials (>2 V vs. Li/Li+).To combat these challenges, our work builds upon the concept of super-concentrated salt systems. In the solid-state regime, highly concentrated “polymer-in-salt” systems can exhibit an ion cluster effect allowing for fast cationic transport decoupled from polymer chain segmental motion. In the aqueous regime, highly concentrated “water-in-salt” systems exhibit the formation of a passivating solid electrolyte interphase (SEI) through reduction of TFSI- to form LiF on the anode surface. The presence of water in the “water-in-salt” system also gives rise to a disproportionation of Li+ solvation environments, namely TFSI-rich and water-rich domains, allowing for fast cationic transport through the water domains. By including a highly concentrated “water-in-salt” system into a polymer matrix, the unique aqueous solid polymer-in-salt electrolyte (ASPE) demonstrates preferential Li+ transport compared to anion transport, high ionic conductivity, and extended ESW. This system also exhibits unique stability in air that eliminates the need for meticulously dry environments and solution processing, which is desirable to manufacturers for substantial savings in productions costs.We demonstrate that the ASPE comprised of poly(ethylene oxide) (PEO), water, and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) salt can achieve a high room temperature ionic conductivity of >1.75 mS/cm. Pulsed field gradient NMR shows a lithium transference number of 0.66, which was corroborated with electrochemical impedance spectroscopy. Molecular dynamic simulations reveal that the exceptional transport properties of the ASPE are likely due to decoupling of ion conduction from the polymer-assisted transport seen in typical SPEs, instead being dominated by water-assisted vehicular transport. The system exhibits stability to ~1.5 V vs. Li/Li+, enabling access to anode materials like LTO and LVPF previously incompatible with aqueous electrolytes. Cycling performance was assessed using LTO/LMO, a ~2.8 V output, to demonstrate the capability of the ASPE to promote intercalation and deintercalation in these electrodes.Further work demonstrates improvement to the ESW of the ASPE by changing the composition of the “water-in-salt” electrolyte to a highly concentrated hybrid aqueous/ionic liquid electrolyte and changing the polymer matrix. The inclusion of ionic liquid as a second, non-aqueous solvating molecule reduces the amount of water needed in the system and provides an alternative pathway for quality SEI formation. High molecular weight polymer offers a solvating matrix to reduce the overall concentration of water while simultaneously reducing water activity through changes in the hydrogen bonding structure. Additionally, the new polymer matrix exhibits superior thermodynamic stability at high voltages and aids in decoupling ionic mobility from polymer mobility, making it a strong choice for highly concentrated systems without sacrificing transport properties. This new class of ASPE demonstrates a remarkable extended cathodic limit <1 V vs. Li/Li+ and overall ESW >4 V with minimal electrochemical activity up to 5.5 V vs. Li/Li+. Cyclic voltammetry demonstrates compatibility with commercial LTO and TNO anodes, which when paired with appropriate high voltage cathode material can enable fast-charging systems with increased energy density.

Visible Light Induced Conventional Step-Growth and Chain-Growth Condensation Polymerizations by Electrophilic Aromatic Substitution.

A novel visible light induced step-growth polymerization by electrophilic aromatic substitution between photochemically generated carbocations and dimethoxybenzene nucleophile is described. Conventional step-growth polymerization and chain-growth condensation polymerization (CCP) mechanisms are presented. It is found that by changing the molar ratios of the monomers slightly, the CCP mechanism becomes operative and relatively higher molecular weight polymers are obtained because of the higher reactivity of the end groups of the intermediates and oligomers than that of the monomers. The possibility of grafting onto polymers containing epoxide at their side chains by photoinduced chain end activation of poly(dimethoxyphenylene methylene) is demonstrated. This study is expected to promote potential applications of the combination of photoinduced electron transfer reactions and CCP in macromolecular synthesis and material science.

A Valuable Observation on Thickeners for Valuable Utilisation in the Printing of Different Textile Fabrics

Thickeners are high molecular weight polymers used to impart viscosity and plasticity to the printing paste. Thickeners play an essential role in any printing process. Their main purpose is to hold dyestuffs, chemicals, and other printing auxiliaries to the fabrics during the method of printing. The goodness of the resulting print depends on the chemical and physical properties of the thickeners applied. The depth, the brightness of the colours, and particularly the sharpness and smoothness of the print are influenced or even determined by them.

Selecting multi-enzyme composition and preparation conditions for strong wort

Abstract: Development of sustainable biotechnologies for deep processing of grain raw materials requires effective mechanisms of obtaining strong wort for alcohol production. To provide qualitative characteristics of biochemical composition and rheological properties of strong wort, it is necessary to select optimal enzyme systems and conditions for deep conversion of high-molecular weight polymers of the grain. Previous research has proven the efficiency of carbohydrases for processing grain raw materials. However, there is little evidence on the catalytic effect of phytase, including in combination with other hydrolytic enzymes, on the degree of hydrolysis of polymers in grain raw materials when preparing strong wort. This paper demonstrates the effect of proteases and phytases in a multi-enzyme composition, as well as the conditions of enzymatic processing of raw materials, on the rheological and biochemical parameters of strong wort. Wheat, rye and corn were investigated. The synergism of the combined effect of studied hydrolases, including phytolytic and proteolytic enzymes, contributed to an increase in polymer conversion in this grain raw material and the concentration of soluble dry substances of the wort by 1.5 times. Using the proteases and phytases in the multienzyme composition allowed the concentration of the following components in the wort to be increased: glucose – by 1.2–1.3 times; amine nitrogen – by 1.5–2.2 times; phosphorus ions – by 1.4–4.3 times. Additionally, in the wort samples, the content of amino acids in the free form increased by over 4 times. It is shown that the pretreatment of grain raw materials at a temperature of 80–90ºС for 6 hours and saccharification for 1–2 hours using a complete complex of enzymes containing α-amylase, glucoamylase, xylanase, protease and phytase, allows a strong wort with a dry matter content of over 30% to be obtained. Moreover, a significant decrease in viscosity was noted (particularly for rye wort – by 1.3–1.9 times). Our results confirm the essential role of enzymes exhibiting substrate specificity to protein and phytic polymers in grain raw materials.

Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters.

A variety of lithiated calix[n]arenes, for which n = 6 or 8, have been isolated, structurally characterized, and evaluated as catalysts for the ring-opening polymerization (ROP) of the cyclic esters ε-caprolactone (ε-CL), δ-valerolactone (δ-VL), and rac-lactide (r-LA). In particular, interaction of p-tert-butylcalix[6]areneH6 (L6H6) with LiOtBu in THF led to the isolation of [Li14(L6H)2(CO3)2(THF)6(OH2)6]·14THF (1·14THF), the core of which has a chain of five Li2O2 diamonds. Similar use of p-tert-butylcalix[8]areneH8 (L8H8) afforded [Li10(L8)(OH)2(THF)8]·7THF (2·7THF), where the core is composed of a six-rung Li-O ladder. Use of debutylated calix[8]areneH8 (deBuL8H8) led to an elongated dimer [Li18(deBuL8)2(OtBu)2(THF)14]·4THF (3·4THF) in which the calix[8]arenes possess a wavelike conformation forming bridges to link three separate LixOy clusters (where x and y = 6, ignoring the THF donor oxygens). Interaction of L8H8 with LiOH·H2O afforded [Li4(L8H4)(OH2)4(THF)6]·5.5THF (4·5.5THF), where intramolecular H-bond interactions involving Li, O, and H construct a cage in the core of the structure with six- and eight-membered rings. Lastly, addition of Me3Al to the solution generated from L8H8 and LiOtBu led to the isolation of [(AlMe2)2Li20(L8H2)2(OH2)4(O2-)4(OH)2(NCMe)12]·10MeCN (5·10MeCN) in which Li, O, Al, and N centers build a polyhedral core. These complexes have been screened for their potential to act as precatalysts in the ring-opening polymerization (ROP) of ε-CL, δ-VL, and r-LA. For the ROP of ε-CL, δ-VL, and r-LA, systems 1-4 exhibited moderate activity at 130 °C over 8 h. In the case of ROP using the mixed-metal (Li/Al) system 5, better conversions and high molecular weight polymers were achieved. In the case of the ROP of ω-pentadecalactone (ω-PDL), the systems proved to be inactive under the conditions employed herein.

Ultrasound-Assisted Transglutaminase Catalysis of the Cross-Linking and Microstructure of αs-Casein, β-Casein and κ-Casein

The effects of ultrasonic treatment (UT)-assisted transglutaminase (TGase) catalysis on the physicochemical properties of individual αs-casein (αs-CN), β-casein (β-CN), and κ-casein (κ-CN) were investigated. After 60 min of incubation at 30 °C, αs-CN, β-CN, and κ-CN were cross-linked with TGase (6.0 units/mL), and high molecular weight polymers (&gt;200 kDa) were formed. The use of TGase in conjunction with UT (20 kHz, power of 400 W, and amplitude 20%) led to an increase in the rate of αs-CN, β-CN, and κ-CN polymerization compared to the individual casein that contained TGase but did not undergo UT. SDS-PAGE scrutiny showed that the intensities of αs-CN, β-CN, and κ-CN incubation with regard to TGase and UT at 30 °C for 60 min noticeably decreased to 5.66 ± 0.39, 3.97 ± 0.43, and 26.07 ± 1.18%, respectively (p &lt; 0.05). Particle size analysis results indicated that the molecule size appropriation for the cross-linking of αs-CN, β-CN, and κ-CN ranged from 6000 to 10,000 nm after 60 min incubation with TGase and UT. Transmission electron microscopy investigation showed network structures of cross-linking αs-CN, β-CN, and κ-CN were formed from αs-CN, β-CN, and κ-CN, respectively. As our results show, the comprehensive utilization of TGase and UT will be a superior method for the polymerization of αs-CN, β-CN, and κ-CN.

Direct ink write 3D printing of high solids loading bimodal distributions of particles

AbstractAs additive manufacturing (AM) expands as a processing technology for structurally customizable materials, there is increasing interest in printing with high particle contents. For suspensions with particle contents of over 50 vol%, there are significant formulation and processing challenges due to increased interparticle friction and suspension complexity. We focus on suspensions with bimodal particle distributions and two common binder systems, a high molecular weight polymer in a solvent that solidifies via solvent evaporation and a monomer mixture that cures via ultraviolet irradiation. We examine the interplay between formulation and processing and show that the formulation effects are particularly important at optimal printing parameters, but that they are overcome by processing‐related defects at sub‐optimal parameters. By understanding the processing and formulation effects specific to direct ink write AM of high solids suspensions, new customized inks can be designed for a wide range of applications, including construction, energetics, and ceramics.

Identifying a critical micelle temperature in simulations of disordered asymmetric diblock copolymer melts

In melts of highly asymmetric diblock copolymers, copolymers self-assemble into spherical micelles. Indirect evidence has long suggested the existence of two distinct characteristic temperatures in such materials: A critical micelle temperature (CMT) at which a dense fluid of micelles appears over a narrow range of temperatures and an order disorder transition (ODT) temperature at which micelles crystallize. In this article, molecular dynamics simulations are used to definitively confirm the correctness of this picture in melts of high molecular weight polymers, and to show that the CMT occurs very near where self-consistent field theory predicts the ODT to occur.

Effects of dye doping on electro-optical, thermo-electro-optical and dielectric properties of polymer dispersed liquid crystal films

In this study, polymer dispersed liquid crystal (PDLC) films comprising a phase separated low molecular weight thermotropic liquid crystal (LC) and high molecular weight polymer were, prepared using the polymer–induced phase separation method. In order to enhance the optical efficiency of the PDLC films, LC was doped with dichroic azo dye. Various characterization techniques were employed to determine the properties of the components and, the operating principles of the dye–doped PDLC (DPDLC) films. Morphological studies using polarizing optical microscopy and scanning electron microscopy indicated that the LC droplet configuration changed with various dye concentrations and voltages. Electro-optical analysis showed that the performance of the DPDLC film with a low dye concentration (0.007%) was excellent, with a high contrast ratio (241) and transmittance difference (ΔT = 98.57%), low threshold (VTH = 0.85 V/μm) and saturation voltages (VSAT = 1.45 V/μm), and a minimum hysteresis effect. The effects of temperature on the electro-optical properties of the DPDLC films were studied. Absorbance analyses were conducted using ultraviolet–visible spectrophotometry to complement the transmittance analyses. Dielectric relaxation spectroscopy was employed to measure relaxation frequency/time of DPDLC films. Debye and Cole – Cole modeling were conducted to understand nature of the relaxation process. The zero values of the distribution parameter (α) for all of the DPDLC composite films confirmed their Debye type relaxation process.

Influences of Ligand Backbone Substituents on Phosphinecarbonylpalladium and -nickel Catalysts for Ethylene Polymerization and Copolymerization with Polar Monomers.

A series of phosphinecarbonylpalladium and -nickel catalysts bearing various substituents on the ligand backbone were prepared, characterized, and used in ethylene polymerization and copolymerization with polar monomers. The Pd and Ni catalysts can achieve high activities as well as high polymer molecular weights in both ethylene polymerization and copolymerization with polar monomers. The electron-donating group from the carbonyl side can effectively increase the polymer molecular weights. Utilization of a cyclic backbone structure can increase the catalytic activities at the expense of the polymer molecular weights. Moreover, installation of a pyridyl moiety in the ligand backbone can enable Lewis acid responsiveness and can enhance the polymerization activities. These results suggest the importance of the ligand backbone for the properties of catalysts in ethylene polymerization and copolymerization reactions.

Supramolecular hydrogelation via host-guest anion recognition: Lamellar hydrogel materials for the release of cationic cargo

Supramolecular hydrogelation via host-guest anion recognition: Lamellar hydrogel materials for the release of cationic cargo