Ultrahigh Molecular Weights Research Articles

Bottlebrush DNA-Primed Rolling Circle Amplification for Sensitive Detection of Biomolecules

Development of nucleic acids containing unnatural moieties has expanded the scope of genetic materials, and modifications of nucleobases have been extensively explored and found broad applications. However, previous efforts have mainly focused on modifying nucleobases with small molecules, while nucleobase modification with macromolecules has barely been explored. In this work, we first demonstrated the construction of highly programmable bottlebrush-like DNA structures by enzymatic production of DNA containing nucleobases modified with coupling handles and chemical attachment of single-stranded DNAs onto these handles. Employing these bottlebrush DNAs (BDs), we then developed a method named bottlebrush DNA-primed rolling circle amplification (BDP-RCA), which could rapidly produce branched DNA products with ultrahigh molecular weights in a controllable manner. BDP-RCA generated up to approximately 20-fold more products than ordinary RCA within 10 min. Moreover, the BDP-RCA product demonstrated a netlike structure in aqueous solution and a structure consisted of uniformly sized nanoflowers with a diameter of approximately 0.7 μm when lyophilized. These observations suggested the great potential of BDP-RCA in the development of materials and methods for biosensing, which were demonstrated with several examples. First, ultrasensitive detection of human α-thrombin with a limit of detection (LOD) of 1.1 pM was achieved by using BDP-RCA to amplify the detection signal in an ELISA-like assay. Second, magnetic beads immobilizing the BDP-RCA product were successfully applied for the efficient capture, enrichment, and preservation of a protein or bacterial cells to be detected. The LOD for the detection of human α-thrombin with this method was 68.5 pM.

Non-stoichiometric effect in the superacid-catalyzed polyhydroxyalkylation of biphenyl and 1-propyl isatin

An experimental study on the superacid-catalyzed polyhydroxyalkylation of biphenyl (A2 monomer) and 1-propyl isatin (B2 monomer) at non-stoichiometric conditions is presented. The produced high-performance polymers were characterized by gel permeation chromatography matrix-assisted laser-desorption/ionization-time-of-flight (MALDI-TOF), nuclear magnetic resonance and diffusion-ordered spectroscopy (DOSY). High molecular weights (Mw > 150,000 Da) and ultra-high molecular weights (Mw ∼ 900,000 Da) are obtained when B2 is used in excess, which agrees with the behavior observed at non-stoichiometric conditions for other superacid catalyzed polyhydroxyalkylations, contrary to the case when A2 is used in excess, where a reduction in molecular weight is obtained, as reported in a previous study from our group. A, B, and M types of linear polymer molecules, as well as C-type cycles, were observed from the MALDI-TOF data.

Titanium Complexes Bearing NNO‐Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution†

Comprehensive SummaryA series of titanium amido complexes (1‐Ti(NMe2)2 to 4‐Ti(NMe2)2) bearing NNO‐tridentate ligands was synthesized from the reactions of phenoxy‐imine‐amine ligands with one equivalent of Ti(NMe2)4. Subsequently, titanium dichloride complexes (1‐TiCl2 to 4‐TiCl2) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2‐Ti(NMe2)2, 2‐TiCl2, and 4‐TiCl2 in the solid state were determined by single‐crystal X‐ray diffraction. Upon activation with MAO, titanium dichloride complexes as single‐site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3‐TiCl2/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 104 g∙mol−1) and very narrow distribution (Đ = 1.23). In the presence of 1‐octene as comonomer, linear low‐density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 104 g∙mol−1) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.

Self-assembly of POSS-Polystyrene Bottlebrush Block Copolymers on an Angle-Robust Selective Absorber for Enhancing the Purity of Reflective Structural Color.

A facile approach for improving color purity is explored by the introduction of an angle-robust selective absorber (ARSA) into bottlebrush block copolymer (BBCP)-based one-dimensional (1D) photonic crystals (PCs). The BBCPs of poly[(3-(12-(cis-5-norbornene-exo-2,3-dicarboximido)dodecanoylamino)propyl POSS)-block-(norbornene-graft-styrene)], Px (x = 1-4), with ultrahigh molecular weights (Mn ∼ 2260 kDa) and low dispersities (D̵ ∼ 1.07) are synthesized by ring-opening metathesis polymerization. The 1D PCs of the lamellar structure are fabricated by self-assembly of the BBCP with different periodicities for full color-generation (blue, green, and red). The optically tailored substrate (i.e., ARSA) is used to modulate the spectral line shape with selective absorption in the near-infrared range. Optical simulation proposes the optimized 1D PC structures on the ARSA, and it provides the reproducibility of the predictable color. The simulated structures are well matched with the experimental results, verifying the enhancement of color saturation even at various incident angles (0-70°).

Improved Enhanced Oil Recovery Polymer Selection Using Field-Flow Fractionation

Summary Various polyacrylamide polymers have been successfully applied in chemical enhanced oil recovery (EOR) projects. These polymers are characterized by high molecular weights (MWs) to achieve high viscosifying power. The selection of polymers for chemical EOR is a crucial step in the field testing and implementation of such EOR projects. The reason is that per-pattern operating expenditures (OPEX) are one of the sensitive cost drivers for such projects. The important parameters for the selection of polymers are the filtration ratio, viscosifying power, polymer retention, and stability of the polymers at reservoir conditions. The MW distribution (MWD) of the polymers has a major impact on polymer properties and performance. Measuring the MWD is challenging using conventional methods. Field-flow fractionation (FFF) enables the determination of the distribution to select and quality check various polymers. Multiangle light scattering (MALS) was used as the main detector. Polymers with high MWs (>1 MDa) are used for EOR to obtain highly viscous aqueous solutions. The MWD of the polymers is crucial for the solution characteristics. Conventional analysis of polymers is performed using either viscometry, which is able to determine the average MW but does not give information on MWD, or size-exclusion chromatography (SEC), which is restricted to MWs of <20 MDa. FFF is based on the analytes flowing at different speeds in a channel-dependent on their size and mass. This effect leads to separation, which is then used to determine the MWD. FFF allows determining the MW and MWD of various ultrahigh MW polyacrylamides (HPAAMs). The FFF measurements showed that, despite similar MWs being claimed, substantial differences in MWD are observed. This technology allowed the quantification of the MWD of HPAAMs up to an MW of 5 GDa. Furthermore, gyration radii of the HPAAM molecules were determined. Selecting polymers on viscosifying power only is not addressing issues related to different MWs and MWDs such as selective polymer retention and degradation of the high molar mass part of the distribution. The results were used to improve the polymer selection for chemical EOR projects. In addition to viscosifying power and price, also the MWD and changes of the MWD in the porous medium are considered in the selection of the polymer. Overall, this work presents a new technique for the analysis of ultrahigh MW EOR polymers, which enables the possibility to determine the full range of polymer MWDs. This available information enhances the EOR polymer selection process addressing selective polymer retention and mechanical degradation in addition to the viscosifying power of polymers.

Trifluoromethoxy-substituted nickel catalysts for producing highly branched polyethylenes: impact of solvent, activator andN,N′-ligand on polymer properties

Highly branched and narrowly dispersed polyethylenes with high or ultra-high molecular weights are accessible using the depicted nickel precatalyst/activator combinations.

Living Aqueous Microemulsion Polymerization of Ethylene with Robust Ni(II) Phosphinophenolato Catalysts.

Due to chain transfer events being competitive with chain growth, ethylene polymerization by P,O-chelated Ni(II) complexes usually affords low molecular weight polymers or oligomers. We now show that appropriately bulky substituted phosphinophenolato Ni(II) can polymerize in a living fashion, virtually devoid of chain transfer. Aqueous polymerizations with microemulsions of [κ2-P,O-2-(2-(2',6'-(MeO)2C6H3)C6H4)(Ph)P-6-(3',5'-(CF3)2C6H3)C6H3O-NiMe(pyridine)] (3) at 30 °C yield polyethylenes with narrow molecular weight distributions (Mw/Mn 1.02 to 1.34) and ultrahigh molecular weights (up to 2 × 106) in the form of aqueous nanoparticle dispersions. Catalyst stability and activity are maintained up to 70 °C in water.

N-heterocyclic carbene stabilized indenyl scandium di-alkyl complex: Preparation of ultra-high molecular weight polyolefin

By using iPr2Im as a Lewis base ligand, β-H elimination reactions of propylene polymerization were suppressed at −30 °C. Polypropylene and its block copolymers with ethylene possessing ultra-high molecular weights (Mn > 1,000,000 g/mol) were successfully obtained in high TOFs (PP > 104 mol molSc−1 h−1). DFT calculations suggested that the delocalized electrons in the strongly conjugated system of iPr2Im could significantly reduce the electro positivity of active sites. This method provides a convenient strategy for tuning the electronic properties of active sites.

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions

Synthesis of Ethylene/1-Octene Copolymers with Ultrahigh Molecular Weights by Zr and Hf Complexes Bearing Bidentate NN Ligands with the Camphyl Linker

Ultrahigh molecular weight polyethylene (UHMWPE) is a class of high-performance engineering plastics, exhibiting a unique set of properties and applications. Although many advances have been achieved in recent years, the synthesis of UHMWPE is still a great challenge. In this contribution, a series of zirconium and hafnium complexes, [2,6-(R1)2-4-R2-C6H2-N-C(camphyl)=C(camphyl)-N-2,6-(R1)2-4-R2-C6H2]MMe2(THF) (1-Zr: R1 = Me, R2 = H, M = Zr; 2-Zr: R1 = Me, R2 = Me, M = Zr; 1-Hf: R1 = Me, R2 = H, M = Hf; 2-Hf: R1 = Me, R2 = Me, M = Hf), bearing bidentate NN ligands with the bulky camphyl backbone were synthesized by the stoichiometric reactions of α-diimine ligands with MMe4 (M = Hf or Zr). All Zr and Hf metal complexes were analyzed using 1H and 13C NMR spectroscopy, and the molecular structures of complexes 1-Zr and 1-Hf were determined by single-crystal X-ray diffraction, revealing that the original α-diimine ligand was selectively reduced into the ene-diamido form and generated an 1,3-diaza-2-metallocyclopentene ring in the metal complexes. Zr complexes 1-Zr and 2-Zr showed moderate activity (up to 388 kg(PE)·mol−1(M)·h−1), poor copolymerization ability, but unprecedented molecular weight capability toward ethylene/1-octene copolymerization. Therefore, copolymers with ultrahigh molecular weights (>600 or 337 × 104 g∙mol−1) were successfully synthesized by 1-Zr or 2-Zr, respectively, with the borate cocatalyst [Ph3C][B(C6F5)4]. Surprisingly, Hf complexes 1-Hf and 2-Hf showed negligible activity under otherwise identical conditions, revealing the great influence of metal centers on catalytic performances.

Probing Thermoresponsive Polymerization-Induced Self-Assembly with Variable-Temperature Liquid-Cell Transmission Electron Microscopy

Summary We directly initiate and visualize the formation of polymeric nanomaterials via variable-temperature liquid-cell transmission electron microscopy (VT-LCTEM). With temperature control in the liquid cell, reversible addition-fragmentation chain transfer polymerization was thermally initiated, leading to the formation of amphiphilic block copolymers that assemble upon dispersion polymerization-induced self-assembly (PISA). In combination with traditional ex situ analyses, VT-LCTEM enabled not only the characterization of the nanoparticles in situ but also the observation of a thermal phase transition. Critically, because these assemblies form from thermoresponsive components, any temperature changes during sample preparation and analysis can alter morphologies, necessitating direct in situ characterization of reaction progression. We believe that the findings and the technique described herein will lead to unprecedented possibilities for the development and characterization of self-organizing soft matter.

Achieving Ultrahigh Molecular Weights with Diverse Architectures for Unconjugated Monomers through Oxygen‐Tolerant Photoenzymatic RAFT Polymerization

AbstractAchieving well‐defined polymers with ultrahigh molecular weight (UHMW) is an enduring pursuit in the field of reversible deactivation radical polymerization. Synthetic protocols have been successfully developed to achieve UHMWs with low dispersities exclusively from conjugated monomers while no polymerization of unconjugated monomers has provided the same level of control. Herein, an oxygen‐tolerant photoenzymatic RAFT (reversible addition‐fragmentation chain transfer) polymerization was exploited to tackle this challenge for unconjugated monomers at 10 °C, enabling facile synthesis of well‐defined, linear and star polymers with near‐quantitative conversions, unprecedented UHMWs and low dispersities. The exquisite level of control over composition, MW and architecture, coupled with operational ease, mild conditions and environmental friendliness, broadens the monomer scope to include unconjugated monomers, and to achieve previously inaccessible low‐dispersity UHMWs.

Achieving Ultrahigh Molecular Weights with Diverse Architectures for Unconjugated Monomers through Oxygen-Tolerant Photoenzymatic RAFT Polymerization.

Achieving well-defined polymers with ultrahigh molecular weight (UHMW) is an enduring pursuit in the field of reversible deactivation radical polymerization. Synthetic protocols have been successfully developed to achieve UHMWs with low dispersities exclusively from conjugated monomers while no polymerization of unconjugated monomers has provided the same level of control. Herein, an oxygen-tolerant photoenzymatic RAFT (reversible addition-fragmentation chain transfer) polymerization was exploited to tackle this challenge for unconjugated monomers at 10 °C, enabling facile synthesis of well-defined, linear and star polymers with near-quantitative conversions, unprecedented UHMWs and low dispersities. The exquisite level of control over composition, MW and architecture, coupled with operational ease, mild conditions and environmental friendliness, broadens the monomer scope to include unconjugated monomers, and to achieve previously inaccessible low-dispersity UHMWs.

100th Anniversary of Macromolecular Science Viewpoint: Achieving Ultrahigh Molecular Weights with Reversible Deactivation Radical Polymerization.

Synthetic strategies for achieving ultrahigh molecular weights via reversible deactivation radical polymerization are discussed from the mechanistic, kinetic, and experimental aspects, and their applications as high-performance materials are highlighted. Further development of this field requires continuous effort to improve livingness and polymerization efficiency under greener conditions.

Kinetic model of hyperbranched polymers formed by self-condensing vinyl polymerization of inimers and trifunctional cores with different reactivities in a continuous-stirred tank reactor

A kinetic model is proposed to describe the formation of hyperbranched polymers, HBPs, by the self-condensing vinyl polymerization, SCVP, of inimers in a continuous stirred tank reactor, CSTR, with the addition of trifunctional cores. The dependence of the average degree of polymerization, DP, and the degree of branching, DB, on the Damköhler number, Da, is calculated by a generating function method. If the SCVP system has no core initiators, the flow in the CSTR may be stopped at a Da of approximately 0.5, which is caused by the formation of HBPs with ultrahigh molecular weights; then, the stable operating range becomes very narrow. The growth of HBPs in the SCVP can be retarded by adding the core with high reactivity into the CSTR. Therefore, formation of HBPs with ultrahigh molecular weights can be avoided even though the A groups are almost completely consumed at a high Da number. For example, the reduced weight-average DP is less than 1000 when the degree of conversion of the A group is 0.99, and only a few unreacted monomers remain in the product. The proposed model is useful for designing and optimizing a flow process for producing HBPs by the SCVP in a CSTR.

Crystallization rates of moderate and ultrahigh molecular weight polyethylene characterized by Flash DSC measurement

AbstractWe compared crystallization rates in three bulk commercial polyethylene samples separately consisting of two ultrahigh molecular weights and one moderate molecular weight. The lower‐end temperature of isothermal crystallization was expanded by means of Flash DSC measurement in order to approach the practically fast crystallization region. The results showed that, in the whole temperature range of our observations, ultrahigh molecular weights make polyethylene crystallization faster than moderate molecular weights. This behaviour is opposite to the general trend in linear polymers. In addition, ultrahigh molecular weights make polyethylene crystals resist fast heating before melting more than moderate molecular weights, due to high entanglement around the crystals. We discuss the possible mechanism of fast crystallization in ultrahigh molecular weight polyethylene, which is beneficial for prosthesis uses. © 2019 Society of Chemical Industry

Unpredictable Dynamics of Polymeric Reacting Flow by Comparison between Pre- and Post-Reaction Fluid Properties: Hydrodynamics Involving Molecular Diagnosis via ATR-FTIR Spectroscopy.

In reacting flows, changes in fluid properties induced by the chemical reaction can alter the flow dynamics. Generally, these changes in fluid properties are evaluated by comparison between their pre- and post-reaction properties. If a fluid property such as viscosity decreases between pre- and post-reaction, we expect a decrease in viscosity to occur in the reacting flow. However, this study demonstrates a reacting polymeric liquid flow where a remarkable increase in the viscoelasticity temporally occurs despite the viscosity slightly decreasing after the reaction. We elucidated the underlying reaction mechanism, which involves a structural change in the side functional group (carboxyl) in polyacrylamide at ultrahigh molecular weights ( Mw > 106) with ultralow concentrations ([polymer] < 1 wt %) by using ATR-FTIR spectroscopy. This study demonstrates the existence of a reacting flow in which examination of microscopic molecular structure is required to understand the macroscopic flow dynamics. The findings will be valuable not only for industrial application such as reactor designs and rheology control but also for opening a new research area: chemically reacting flow involving the diagnosis of molecule structure.

Influence of residual impurities on ring‐opening metathesis polymerization after copper(I)‐catalyzed alkyne‐azide cycloaddition click reaction

ABSTRACTBottlebrush polymers (BBPs) are three‐dimensional polymers with great academic and industrial potential owing to their highly tunable and intricate architecture. The most popular method to synthesize BBPs is ring‐opening metathesis polymerization (ROMP) with Grubbs' catalyst, allowing living grafting‐through polymerization of macromonomers of up to ultrahigh molecular weights with narrow molecular weight distribution. In this case, it has been well recognized that the purity of macromonomers (MMs) is critical for a successful ROMP reaction. For MMs synthesized from reversible‐deactivation radical polymerization, Grubbs and Xia demonstrated that the better control of ROMP reaction can be achieved when they are prepared via “growth‐then‐coupling” method that is coupling a norbornenyl group to end‐functionalized prepolymers. However, these MMs can also contain various residual impurities from previous synthetic steps, which can potentially poison the catalyst and hamper the ROMP reaction. Herein, we intentionally doped possible impurities into purified MMs to identify the most poisoning species. As a result, it was found that alkyne‐functionalized norbornene most significantly retarded the ROMP reaction due to a formation of Ru‐vinyl‐carbene intermediates having low catalytic reactivity, whereas the other reagents such as solvent, Cu‐catalyst, ligands, and azido‐terminated prepolymers were relatively inert. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 726–737

Precise Synthesis of Bottlebrush Block Copolymers from ω-End-Norbornyl Polystyrene and Poly(4-tert-butoxystyrene) via Living Anionic Polymerization and Ring-Opening Metathesis Polymerization

A facile and efficient synthetic grafting-through strategy for preparing well-defined bottlebrush block copolymers (BBCPs) was developed through a combination of living anionic polymerization (LAP) and ring-opening metathesis polymerization (ROMP). ω-End-norbornyl polystyrene (NPSt) and poly(4-tert-butoxystyrene) (NPtBOS) were synthesized by LAP using terminator of chlorine moiety containing silane-protecting amine and coupled with a subsequent amidation using norbornyl activated ester. Bottlebrush homopolymers of NPSt were obtained by ROMP with ultrahigh molecular weights (MWs, Mw = 2928 kDa) and narrow molecular weight distributions (MWDs, Đ = 1.07) at high degree of polymerizations (DPw = 1084). Well-defined BBCPs with ultrahigh MWs (Mw ∼ 3055 kDa) and narrow MWDs (Đ ∼ 1.13) were synthesized through sequential ROMP of NPSt with NPtBOS. The effect of ultrahigh MWs was investigated by self-assembly of the BBCPs in which the phase-separated BBCPs presented periodic lamellar structures and exhibited structural colors from blue to pink.

Periodic polymers based on a self-accelerating click reaction

Self-accelerating click chemistry was used to prepare sequence-controlled periodic polymers with ultrahigh molecular weights or a cyclic molecular topology.