Showing papers on "Copolymer published in 2023"

Polymers Derived from Isobutylene. Synthesis, Properties, Application

Abstract: Part 1 Scientific and technological aspects of isobutylene production: properties and production of isobutylene - physical properties, chemical properties, methods of isobutylene production, production of isobutylene in industry, special methods of isobutylene production, analysis of isobutylene isobutylene polymerization - general ideas of polymerization, catalysts, polymerization mechanism, initiation, chain propagation, limiting of the chain propagation, problems of cationic polymerization of isobutylene, molecular engineering, features of fast polymerization processes, problems of kinetics of fast polymerization processes, kinetic features of isobutylene polymerization macrokinetics of isobutylene polymerization -modelling of isobutylene polymerization as a fast chemical reaction, macroscopic features of isobutylene polymerization, novel fundamental regularities, on existence of several macroscopic regimes, on connection between geometrical size of the reaction zone and kinetic and hydrodynamic parameters, influence of linear flow motion rate on molecular-mass characteristics of resulting polymer, influence of the methods of catalyst transmission on molecular-mass characteristics of resulting polymer, heat regime of fast isobutylene polymerization, heat regime of polymerization in the absence of heat elimination, heat regime of polymerization with reaction mass boiling, efficiency of external heat elimination, optimization of molecular-mass characteristics of polymer in fast isobutylene polymerization, the zone model, estimation of molecular-mass polyisobutylene characteristics in the absence of heat elimination at the multistage catalyst delivery into the reacting turbulent zone. (Part contents).

Visible-Light-Mediated Controlled Radical Branching Polymerization in Water.

Abstract: Hyperbranched polymethacrylates were synthesized by green-light-induced atom transfer radical polymerization (ATRP) under biologically relevant conditions in the open air. Sodium 2-bromoacrylate (SBA) was prepared in situ from commercially available 2-bromoacrylic acid and used as a water-soluble inibramer to induce branching during the copolymerization of methacrylate monomers. As a result, well-defined branched polymethacrylates were obtained in less than 30 min with predetermined molecular weights (36 000 ˂ Mn ˂ 170 000), tunable degree of branching, and low dispersity values (1.14 ≤ Đ ≤ 1.33). Moreover, the use of SBA inibramer enabled the synthesis of bioconjugates with a well-controlled branched architecture.

Growth of single-crystal imine-linked covalent organic frameworks using amphiphilic amino-acid derivatives in water

Abstract: A core feature of covalent organic frameworks (COFs) is crystallinity, but current crystallization processes rely substantially on trial and error, chemical intuition and large-scale screening, which typically require harsh conditions and low levels of supersaturation, hampering the controlled synthesis of single-crystal COFs, particularly on large scales. Here we report a strategy to produce single-crystal imine-linked COFs in aqueous solutions under ambient conditions using amphiphilic amino-acid derivatives with long hydrophobic chains. We propose that these amphiphilic molecules self-assemble into micelles that serve as dynamic barriers to separate monomers in aqueous solution (nodes) and hydrophobic compartments of the micelles (linkers), thereby regulating the polymerization and crystallization processes. Disordered polyimines were obtained in the micelle, which were then converted into crystals in a step-by-step fashion. Five different three-dimensional COFs and a two-dimensional COF were obtained as single crystals on the gram scale, with yields of 92% and above.

Membranized Coacervate Microdroplets: from Versatile Protocell Models to Cytomimetic Materials

Abstract: Conspectus Although complex coacervate microdroplets derived from associative phase separation of counter-charged electrolytes have emerged as a broad platform for the bottom-up construction of membraneless, molecularly crowded protocells, the absence of an enclosing membrane limits the construction of more sophisticated artificial cells and their use as functional cytomimetic materials. To address this problem, we and others have recently developed chemical-based strategies for the membranization of preformed coacervate microdroplets. In this Account, we review our recent work on diverse coacervate systems using a range of membrane building blocks and assembly processes. First, we briefly introduce the unusual nature of the coacervate/water interface, emphasizing the ultralow interfacial tension and broad interfacial width as physiochemical properties that require special attention in the judicious design of membranized coacervate microdroplets. Second, we classify membrane assembly into two different approaches: (i) interfacial self-assembly by using diverse surface-active building blocks such as molecular amphiphiles (fatty acids, phospholipids, block copolymers, protein–polymer conjugates) or nano- and microscale objects (liposomes, nanoparticle surfactants, cell fragments, living cells) with appropriate wettability; and (ii) coacervate droplet-to-vesicle reconfiguration by employing auxiliary surface reconstruction agents or triggering endogenous transitions (self-membranization) under nonstoichiometric (charge mismatched) conditions. We then discuss the key cytomimetic behaviors of membranized coacervate-based model protocells. Customizable permeability is achieved by synergistic effects operating between the molecularly crowded coacervate interior and surrounding membrane. In contrast, metabolic-like endogenous reactivity, diffusive chemical signaling, and collective chemical operations occur specifically in protocell networks comprising diverse populations of membranized coacervate microdroplets. In each case, these cytomimetic behaviors can give rise to functional microscale materials capable of promising cell-like applications. For example, immobilizing spatially segregated enzyme-loaded phospholipid-coated coacervate protocells in concentrically tubular hydrogels delivers prototissue-like bulk materials that generate nitric oxide in vitro, enabling platelet deactivation and inhibition of blood clot formation. Alternatively, therapeutic protocells with in vivo vasoactivity, high hemocompatibility, and increased blood circulation times are constructed by spontaneous assembly of hemoglobin-containing cell-membrane fragments on the surface of enzyme-loaded coacervate microdroplets. Higher-order properties such as artificial endocytosis are achieved by using nanoparticle-caged coacervate protocell hosts that selectively and actively capture guest nano- and microscale objects by responses to exogenous stimuli or via endogenous enzyme-mediated reactions. Finally, we discuss the current limitations in the design and programming of membranized coacervate microdroplets, which may help to guide future directions in this emerging research area. Taken together, we hope that this Account will inspire new advances in membranized coacervate microdroplets and promote their application in the development of integrated protocell models and functional cytomimetic materials.

Temperature‐Triggered Dynamic Janus Fabrics for Smart Directional Water Transport

Abstract: In this study, thermosensitive amino‐silica@PDVB/PNIPAM Janus particles (JPs) are synthesized by seed emulsion polymerization‐induced phase separation and selective modification methods. Amino‐modified silica moieties are covalently bonded to a diverse choice of substrates to achieve robust composite coatings, and a PDVB/PNIPAM abdomen forms a micro‐nano‐scale hierarchical surface. PNIPAM has a lower critical solution temperature (LCST), which allows the hydrophilic and hydrophobic properties of the coating to reverse with a change in temperature. When the fabrics are coated with the thermosensitive Janus particles, water repellency is observed above 32 °C, while hydrophilicity is revealed below 32 °C. Then, after the composite fabric is worn, the side next to the skin becomes hydrophobic due to the high temperature, and the side facing the environment is hydrophilic. Therefore, sweat can be pumped from the hydrophobic side to the hydrophilic side through the dynamic Janus fabric. The dynamic hydrophobic–hydrophilic Janus structure enables the efficient and fast evaporation of sweat. The perspiration rate of Janus fabrics is five times higher than that of commercial cotton fabrics. While the wettability of the composite coating remains reversible after 20 temperature cycles and 20 tape adhesion cycles, showing good mechanical durability. The reversible thermal sensitivity remains after repeated rubbing and ultrasonic immersion.

Morphological, structural, optical, broadband frequency range dielectric and electrical properties of PVDF/PMMA/BaTiO3 nanocomposites for futuristic microelectronic and optoelectronic technologies

Abstract: Polymer blend nanocomposite (PBNC) films consisted of fluoropolymer poly(vinylidene fluoride) (PVDF) and plexiglass polymer poly(methyl methacrylate) (PMMA) blend host matrix (fixed composition blend of PVDF/PMMA = 80/20 wt/wt%) with barium titanate (BaTiO3) ceramic nanofiller of varying concentrations (x = 0, 2.5, 5, 10, and 15 wt%) were prepared via a state-of-the-art solution-cast method. Scanning electron microscope (SEM) images evidenced high homogeneity of these PBNC films and a huge alteration in the spherulite morphology of the PVDF with the increase in dispersed BaTiO3 concentration in the polymer blend matrix. The X-ray diffraction (XRD) patterns identified the presence of electro-active polar β- and γ-phases of the PVDF crystallites in all the composite materials which are supported by the results of Fourier transform infrared (FTIR) spectra. The differential scanning calorimeter (DSC) thermograms explained the high melting temperature of these overlapped PVDF polymorphs and the degree of crystallinity altered anomalously with the variation of nanofiller concentration. The absorbance of ultraviolet-visible (UV-Vis) radiations enhanced while the direct energy band gap of the 80PVDF/20PMMA blend matrix and also the semiconducting BaTiO3 was found to decrease with the increased concentration of nanomaterial in the host polymer matrix. The ambient temperature broadband dielectric spectra covering the frequency range from 20 Hz to 1 GHz explain that the real part of complex dielectric permittivity reduced with a huge dispersion at higher radio frequencies where the dielectric loss tangent and electric modulus spectra exhibited an intense chain segmental relaxation process. The electrical conductivity of these PBNC films increased with frequency augmented and illustrated a small variation for different concentration composites. The experimental results demonstrated that these PVDF/PMMA/BaTiO3 films could be potential candidates for frequency tunable nanodielectric, electromagnetic interference shielders, a flexible dielectric substrate, thermal insulators, and bandgap regulated materials for futuristic microelectronic, capacitive energy storage, and optoelectronic technologies.

Combining Associative and Dissociative Dynamic Linkages in Covalent Adaptable Networks from Biobased 2,5-Furandicarboxaldehyde

Abstract: Covalent adaptable networks (CAN) emerged as a recent class of polymers that combine the most interesting advantages of thermosets and thermoplastics. In this frame, combining different dynamic linkages within the polymer network could be an interesting approach to finely tune the material properties and determine the extent of their behaviors. Here, we report the synthesis of novel dually crosslinked CAN in which dynamic associative imine linkages and dissociative Diels–Alder adducts were both obtained by exploiting the chemistry of a single biobased building block, 2,5-furandicarboxaldehyde (FDC). Thanks to the favorable chemical environment of the furan ring in a linear polyimine based on FDC, very fast coupling with maleimides in Diels–Alder reactions was reported, leading to the formation of polymer networks in remarkably short times. The obtained sustainable polymer systems were shown to have a behavior in-between those of vitrimers and dissociative CANs, with tunable mechanical behavior and excellent reprocessability.

Outer-Shell Self-Supported Nickel Catalysts for the Synthesis of Polyolefin Composites.

Abstract: In-situ heterogeneous olefin polymerization has attracted much attention for the synthesis of polyolefin composites. However, the complicated syntheses of specially designed catalysts or the detrimental effects of interactions between catalyst and solid supports pose great challenges. In this contribution, an outer-shell self-supporting strategy was designed to heterogenize nickel catalysts on different fillers via precipitation homopolymerization of ionic cluster type polar monomer. These catalysts demonstrated high activity, good product morphology control, and stable performances in ethylene polymerization and copolymerization. Moreover, various polyolefin composites with great mechanical and customized properties can be efficiently synthesized.

Autonomous discovery of emergent morphologies in directed self-assembly of block copolymer blends

Abstract: The directed self-assembly (DSA) of block copolymers (BCPs) is a powerful approach to fabricate complex nanostructure arrays, but finding morphologies that emerge with changes in polymer architecture, composition, or assembly constraints remains daunting because of the increased dimensionality of the DSA design space. Here, we demonstrate machine-guided discovery of emergent morphologies from a cylinder/lamellae BCP blend directed by a chemical grating template, conducted without direct human intervention on a synchrotron x-ray scattering beamline. This approach maps the morphology-template phase space in a fraction of the time required by manual characterization and highlights regions deserving more detailed investigation. These studies reveal localized, template-directed partitioning of coexisting lamella- and cylinder-like subdomains at the template period length scale, manifesting as previously unknown morphologies such as aligned alternating subdomains, bilayers, or a “ladder” morphology. This work underscores the pivotal role that autonomous characterization can play in advancing the paradigm of DSA.

Highly Thermally Stable, Reversible and Flexible Main Chain-Type Benzoxazine Hybrid Incorporating Both Polydimethylsiloxane and Double-Decker-Shaped Polyhedral Silsesquioxane Units through Diels-Alder Reaction.

Abstract: We synthesized a new bifunctional furan derivative (PDMS-FBZ) through a sequence of hydrosilylation of nadic anhydride (ND) with polydimethylsiloxane (PDMS), reaction of the product with p-aminophenol to form PDMS-ND-OH, and its subsequent Mannich reaction with furfurylamine and CH2 O. We then prepared the main chain-type copolymer PDMS-DABZ-DDSQ through a Diels-Alder (DA) cycloaddition of PDMS-FBZ with the bismaleimide-functionalized double-decker silsesquioxane derivative DDSQ-BMI. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirmed the structure of this PDMS-DABZ-DDSQ copolymer; differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) revealed it to have high flexibility and high thermal stability (Tg = 177°C; Td10 = 441°C; char yield = 60.1 wt%); contact angle measurements revealed a low surface free energy (18.18 mJ/m2 ) after thermal ring-opening polymerization, because the inorganic PDMS and DDSQ units were dispersed well, as revealed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This PDMS-DABZ-DDSQ copolymer possessed reversible properties arising from the DA and retro-DA reactions, suggesting its possible application as a functional high-performance material. This article is protected by copyright. All rights reserved.

Amide-Functionalized Polyolefins and Facile Post-Transformations

Abstract: Direct copolymerization of olefins with polar monomers to produce functionalized polyolefins has attracted much attention; however, highly efficient incorporation of amide functions into polyolefins is a long-standing challenge because the amide function is pronounced to retard chain growth. In this contribution, Vince Lactam’s derivatives (VLH, VLMe, and VLBoc) that contain high ring strain and an amide moiety are utilized in ethylene copolymerization mediated by palladium catalysts. Amide-functionalized polyethylenes, poly(E-VLBoc)s, are accessible with key characteristics of high amide incorporations (up to 30.1 mol %), high copolymer molecular weights, and high catalytic activities. The incorporation of the amide comonomer converts crystalline poly(E-VLBoc)s (Tm = 115–125 °C) to noncrystalline and transparent poly(E-VLBoc)s (Tg = 98–196 °C, optical transmittance (T) = 87.6%–90.4%). Both characteristics of cyclic amide functions and high amide incorporations in poly(E-VLBoc) enable facile post-transformations under mild conditions to produce hydrogen bond-containing (-C(O)NH-) poly(E-VLH), difunctionalized (-COOH and -NHR) poly(E-VLNHBoc), and water-soluble ammonium-functionalized poly(E-VLNH3+). The ammonium functionality endows polyolefin with antibacterial properties.

The Fluorocarbene Exploit: Enforcing Alternation in Ring-Opening Metathesis Polymerization.

Abstract: Fluoroalkenes are known to be notoriously reluctant substrates for olefin metathesis due to the generation of thermodynamically stable Fischer-type fluorocarbene intermediates, which invariably fail to undergo further reaction. In the present disclosure, we find that fluorine substitution on the sp2 carbon also strictly suppresses homopolymerization of norbornene derivatives (NBEs), and this can be harnessed to achieve alternating ring-opening metathesis polymerization (ROMP) with an appropriately electron-rich comonomer. Dihydrofuran (DHF) is thereby shown to undergo alternating ROMP with fluorinated norbornenes, the perfectly alternating structure of the resulting copolymer having been unambiguously elucidated by 1H, 19F, and 13C NMR analyses. Furthermore, we find that the degradability of the resultant copolymers in acidic media via hydrolysis of enol ether moieties in the backbone can be predictably modulated by the number of fluorine atoms present in the NBE comonomer, affording an opportunity to engage with the desirable physical properties of fluorinated polymers while limiting their attendant environmental degradability issues.

Competition between Hydrolysis and Radical Ring-Opening Polymerization of MDO in Water. Who Makes the Race?

Abstract: A major challenge in modern society is the reduction of microplastics created by polymers having stable C–C backbones. The chemistry of radical ring-opening copolymerization of cyclic ketene acetals (CKAs) with vinyl monomers in introducing degradable ester units into the C–C backbone is highly promising. Although the corresponding reaction in an aqueous medium should provide biodegradable primary dispersions, the bottleneck is the hydrolytic instability of CKAs. Therefore, in-depth hydrolysis kinetics of CKA (2-methylene-1,3-dioxepane, MDO) at different pH values and temperatures under homogenous and heterogenous conditions are studied to get a “sweet spot” under which emulsion polymerization of MDO might be possible. Depending on the pH, the hydrolysis of MDO undergoes three different mechanisms with slowed hydrolysis kinetics under alkaline conditions. Besides 4-hydroxy-1-butylacetate (4-HBA), other co-hydrolysis products were detected, leading to the autocatalysis effect. The fast MDO hydrolysis during emulsion copolymerization with vinyl acetate led to the formation of polymers with extremely less incorporation of ring-opened MDO units. Degradation tests of the corresponding emulsion copolymers compared with copolymers prepared in solution confirmed the low incorporation ratio of MDO. The results and discussion presented in this work will be a strong guideline for future emulsion copolymerizations of CKAs.

Fluorine‐phosphate copolymerization waterborne acrylic resin coating with enhanced anticorrosive performance

Abstract: The modified waterborne acrylic resin was synthesized successfully by emulsion polymerization with octafluoropentyl methacrylate and phosphate functional monomer as monomers, showing an improved anti-corrosion performance of the resin coating. The existence and general distribution of the elements of the modified monomer in the emulsion were explored, and the anti-corrosion mechanism was disclosed. The results show that the modification of octafluoropentyl methacrylate and phosphate functional monomers improved the water resistance, corrosion resistance and thermal stability of acrylic resins. Compared with unmodified acrylic resin, the contact angle of the modified resin was increased from 74.23° to 83.51°, and the initial decomposition temperature was increased from 264 to 305 °C. At the same time, the corrosion voltage of the modified resin was increased, the corrosion current density was decreased, and the salt spray resistance was improved. This study provides a new way for the preparation of environmentally friendly, stable, and corrosion-resistant waterborne acrylic resins.

Synthesis of Block Copolymers Containing Stereoregular Pendant Electroactive Blocks.

Abstract: The stereoregular nonconjugated pendant electroactive polymer (NCPEP) poly((N-carbazolylethylthio) propyl methacrylate) (PCzETPMA) has recently shown charge carrier mobilities that are on par with conjugated polymers. Here, we increased the complexity of the architecture for this NCPEP by introducing a polystyrene (PS) block via an anionic, living polymerization yielding a family of PS-b-PCzETPMA block copolymers as the first examples of NCPEP-block-copolymers with controlled stereoregularity of the NCPEP-blocks. Through this methodology we were able to control the molar masses, PS to PCzETPMA block ratios, and tacticities of the PCzETPMA-blocks. We found all three parameters to significantly impact the hole mobilities (μh) of the resulting copolymers, which increased with higher molar masses, longer PCzETPMA-blocks, and higher isotacticity of the PCzETPMA-block, giving the best μh of 2.33 × 10-5 cm2/V·s after annealing at 150 °C for the highest molar mass copolymer with a dominant isotactic PCzETPMA-block. This work is the first reported synthesis of a block copolymer bearing a NCPEP-block with a controlled tacticity and demonstrates that such complex polymer architectures can be realized with NCPEPs while maintaining control over their stereoregularity and without significantly suppressing the hole mobility in the resulting copolymers.