Conventional Polymerization Research Articles

Construction of a Homogeneous Enzyme-Free Autocatalytic Nucleic Acid Machinery for High-Performance Intracellular Imaging of MicroRNA

Construction of a Homogeneous Enzyme-Free Autocatalytic Nucleic Acid Machinery for High-Performance Intracellular Imaging of MicroRNA

Supramolecular Polysulfide Polymers with Metal‐Ligand Interactions

AbstractWe report the first preparation of a supramolecular polysulfide polymer using metal‐ligand interactions. The supramolecular polysulfide polymer was prepared by introducing 2,2’‐bipyridine (bpy) at both ends of linear sulfur and linking the bpy with Cu2+. The molecular weight of the supramolecular polysulfide polymer was higher than polysulfide polymer obtained via conventional polymerization. Disassembly and re‐assembly of the supramolecular polysulfide polymers were controlled by de‐metalation of Cu2+ from the complex between bpy and Cu2+ and re‐formation of the complex with the addition of chelating agents and Cu2+, respectively.

Light-regulated growth of polymer chains from the surface of RAFT agent primed mesoporous silica nanoparticles

Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the extensively explored and studied controlled radical polymerization methods. Recently, in comparison to the conventional RAFT polymerization process, visible light-regulated photo-induced electron/energy transfer (PET)-RAFT polymerization has picked up interest. With an ever-increasing desire for greener and more sustainable methods for synthesis, techniques such as PET-RAFT polymerization can be well adapted as an alternative approach for performing a variety of syntheses. Keeping this in mind we step forward with the synthesis of mesoporous silica nanoparticles containing an in-built RAFT agent using a stepwise co-condensation method. Herein, we report a facile synthesis of an organic-inorganic hybrid system in which surface-initiated RAFT polymerization was performed using several monomers (hydrophobic and hydrophilic) from RAFT agent primed mesoporous silica nanoparticles (RAFT-MSNs). The surface-initiated RAFT polymerization was carried through thermally initiated polymerization using AIBN and visible light-regulated PET-RAFT polymerization using Eosin Y as a photocatalyst. The light-regulated PET-RAFT polymerization was carried out smoothly in a shorter time frame as compared to the thermally initiated RAFT polymerization. A variety of characterization methods were used to confirm the successful grafting of polymeric chains from the surface of RAFT-MSNs. Hence, by appropriate polymer functionalization of mesoporous silica nanoparticles with stimuli-responsive polymers or polymers bearing functional groups, these organic-inorganic hybrids can be studied in a wide variety of applications such as drug delivery, catalysis, nanoconfinement, etc.

Polyamide-based membranes with structural homogeneity for ultrafast molecular sieving

Thin-film composite membranes formed by conventional interfacial polymerization generally suffer from the depth heterogeneity of the polyamide layer, i.e., nonuniformly distributed free volume pores, leading to the inefficient permselectivity. Here, we demonstrate a facile and versatile approach to tune the nanoscale homogeneity of polyamide-based thin-film composite membranes via inorganic salt-mediated interfacial polymerization process. Molecular dynamics simulations and various characterization techniques elucidate in detail the underlying molecular mechanism by which the salt addition confines and regulates the diffusion of amine monomers to the water-oil interface and thus tunes the nanoscale homogeneity of the polyamide layer. The resulting thin-film composite membranes with thin, smooth, dense, and structurally homogeneous polyamide layers demonstrate a permeance increment of ~20–435% and/or solute rejection enhancement of ~10–170% as well as improved antifouling property for efficient reverse/forward osmosis and nanofiltration separations. This work sheds light on the tunability of the polyamide layer homogeneity via salt-regulated interfacial polymerization process.

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

The impact of reversible deactivation in photo-inifierter RAFT polymerization on control and livingness of the process is investigated. The findings are used to create multiblock copolymers with high molecular weight and efficient chain extension.

Micropatterning of acoustic droplet vaporization in acoustically-responsive scaffolds using extrusion-based bioprinting

Acoustically-responsive scaffolds (ARSs) are composite hydrogels that respond to ultrasound in an on-demand, spatiotemporally-controlled manner due to the presence of a phase-shift emulsion. When exposed to ultrasound, a gas bubble is formed within each emulsion droplet via a mechanism termed acoustic droplet vaporization (ADV). In previous in vitro and in vivo studies, we demonstrated that ADV can control regenerative processes by releasing growth factors and/or modulating micromechanics in ARSs. Precise, spatial patterning of emulsion within an ARS could be beneficial for ADV-induced modulation of biochemical and biophysical cues. However, precise patterning is limited using conventional bulk polymerization techniques. Here, we developed an extrusion-based method for bioprinting ARSs with micropatterned structures. Emulsions were loaded within bioink formulations containing fibrin, hyaluronic acid and/or alginate. Experimental as well as theoretical studies elucidated the interrelations between printing parameters, needle geometry, rheological properties of the bioink, and the process-induced mechanical stresses during bioprinting. The shear thinning properties of the bioinks enabled use of lower extrusion pressures resulting in decreased shear stresses and shorter residence times, thereby facilitating high viability for cell-loaded bioinks. Bioprinting yielded greater alignment of fibrin fibers in ARSs compared to conventionally polymerized ARSs. Bioprinted ARSs also enabled generation of ADV at high spatial resolutions, which were otherwise not achievable in conventional ARSs, and acoustically-driven collapse of ADV-induced bubbles. Overall, bioprinting could aid in optimizing ARSs for therapeutic applications.

Preparation of mesocarbon microbeads as anode material for lithium-ion battery by co‑carbonization of FCC decant oil and conductive carbon black

Low yield and unremarkable electrochemical performance of MCMB prepared from conventional thermal polymerization are inevitable, which limits its large-scale application as anode material for lithium-ion batteries. Hence, in this work, MCMBs were prepared by co‑carbonization of low-valued FCC decant oil and conductive carbon black (CCB). CCB can enhance the nucleation, inhibit the growth of the mesophase spheres and adhere on the surface of spheres, thereby increasing the yields (38.9 wt%), influencing the microstructure and subsequent electrochemical performance of MCMB. The MCMBs prepared by doping with 3 wt% CCB exhibited a small particle size (15.0 μm) and moderate structural disorder degree with wide interlayer spacing (AD3/Aall = 18.15%, d002 = 3.5342 Å), which shortened the transport pathway of Li+ inside the microbeads. Besides, chain-like conductive carbon black connected to the surface of the MCMBs, forming a continuous and developed conductive network, which was benefit for increasing of electron conduction and enhancing the Li+ transport rate outside the microbead. Such MCMB delivered the superior long-term cyclability with specific capacity of 394.5 mAh g−1 at 0.5 A g−1 (over 400 cycles) and presented a high-rate capability with reversible capacity of 276.0 mAh g−1 at an ultra-high current density of 3 A g−1.

Synergizing radiation-induced emulsion graft polymerization of glycidyl methacrylate on polyethylene-coated polypropylene nonwoven fabric by addition of hydrophobic alcohols

The radiation-induced emulsion graft polymerization method is limited for applying concentrations higher than the monomer concentration that enables stable formation of monomer micelles. Furthermore, foaming may occur because of the presence of the surfactant, which is essential for the formation of micelles, resulting in likely splashing around a highly flammable monomer emulsion. In the present study, to overcome these issues, we investigate the effect of added alcohols on the grafting of glycidyl methacrylate (GMA) in emulsion graft polymerization. By adding hydrophobic alcohols to the GMA monomer emulsion of the given system, we succeeded in increasing polymerization rate at low monomer concentrations and developing a highly safe method of emulsion graft polymerization. By adding 0.5 wt% of hydrophobic alcohol such as 1-octanol to the GMA monomer emulsion, the degree of grafting was 4 times higher than in the case without addition. In addition, we successfully reduced the foamability of the GMA monomer emulsion deriving from the surfactant. This is a novel graft polymerization method with promising wide industrial application, as it brings improvements for the existing issues of the conventional emulsion graft polymerization method — (1) emulsion stability under low concentration monomer and (2) process stability due to foaming of the monomer emulsion during polymerization.

Interfacial polymerized polyamide nanofiltration membrane by demulsification of hexane-in-water droplets through hydrophobic PTFE membrane: Membrane performance and formation mechanism

• Emulsion mediated interfacial polymerization. • Demulsification of hexane-in-water droplets by hydrophobic PTFE membrane. • Controlled release of TMC during interfacial polymerization. Interfacial polymerization has been considered as a benchmark strategy for polyamide membrane fabrication. However, controlled reaction is still challengeable. Herein we propose a novel emulsion mediated interfacial polymerization strategy for controllable polyamide nanofiltration fabrication. Hexane micro-droplets containing trimesoyl chloride (TMC) molecules were adsorbed, demulsified and transported to the interface from hexane-in-water emulsion by a hydrophobic and oleophilic polytetrafluoroethylene (PTFE) membrane for further controlled reaction with piperazine (PIP). Surface morphologies, layer thickness, surface chemistry, crosslinking and water contact angle of resulted polyamide membranes were studied with varying reaction time, displaying the control for interfacial polymerization. PTFE membrane assisted interfacial polymerization strategy leads to smoother (Ra = 8.0 nm) and thinner (25 nm) polyamide layer compared with conventional interfacial polymerization. The resulted membrane exhibits comparable nanofiltration performances (water permeability: 7.3 Lm −2 h -1 bar −1 , Na 2 SO 4 rejection: 92.3%) with conventional membranes. The current study provided a new avenue for controllable interfacial polymerization.

The Effect of Polymerization Temperature on the Properties of Polyvinyl Fluoride Polymerization in Supercritical Carbon Dioxide

The ongoing search for environmentally friendlier alternative to the organic solvents used in chemical processes has led to the development of technologies based on supercritical carbon dioxide (scCO2), which is non-flammable, non-toxic and relatively inert fluid. Polymer chemistry does not escape this trend. Fluoropolymers prepared in scCO2 have many special properties, which are different from fluoropolymers that use water as the reaction medium, this paper studies the effect of polymerization temperature on polyvinyl fluoride polymerization in supercritical carbon dioxide. The results show that as the polymerization temperature increases, the intrinsic viscosity and shear viscosity of the polymer gradually decreases; at the same time, the increasing of polymerization temperature leads to higher proportion of irregular structure of the polymer, which causes lower melting point and lower crystallinity, and the film prepared by the resin also exhibits a higher visible light transmittance. The above results show that the resin polymerized in supercritical carbon dioxide can impart better performance to conventional polymerization, which expands the potential application fields of the resin.

Ruthenium-alkylidene Initiated Cyclopolymerization and Tandem Ringopening/ Ring-closing Metathesis (RO/RCM) Polymerization: Facile Access to Cycloolefin-based Polymers

Synthesis of cycloolefin-based polymers via metathesis-accompanied cyclopolymerization and tandem Ring-Opening/Ring-Closing Metathesis (RO/RCM) polymerization are undergoing exciting developments and emerging as an area of great interest in the field of polymer synthesis. Among the conventional polymerization techniques, both cyclopolymerization and tandem polymerization give access to highly functional cycloolefin ring-based polymers. This review provides an overview of the synthesis of such cycloolefin-based conjugated and non-conjugated polymers following cyclopolymerization and tandem RO/RCM polymerization methodologies.

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.

Facile Synthesis of Novel Polyethyleneimine Functionalized Polymeric Protic Ionic Liquids (PolyE‐ILs) with Protagonist Properties for Acid Catalysis

AbstractPolyethyleneimine (PEI), a potent architecture backbone was explored for the synthesis of novel polymeric ionic liquids (PolyE‐ILs) with protagonist properties. The simple quaternization of PEI dendrimer with Bronsted acids (H2SO4, H3PO4, CH3SO3H, CF3COOH and TsOH) leads to formation of series of protic PolyE‐ILs with corresponding counter anions [HSO4]−, [H2PO4]−, [CH3SO3]−, [CF3COO]− and [TsO]−. The physicochemical properties of synthesized PolyE‐ILs were studied by using TGA, Hammett acidity, hydrodynamic radii, solubility, and elemental analysis. PolyE‐ILs showed characteristic Hammett acidity (0.94–1.78), good thermal stability (<250 °C) and enhanced hydrodynamic radii. However, use of PolyE‐IL can be promoted for their wide applications as an acid catalysts. The reported PolyE‐IL‐1 with sulfonic acid counter ion was explored as catalyst for esterification of (E)‐cinnamic acids and it showed good catalytic activity. The enhanced hydrodynamic radii due to the branched architecture of PEI dendrimers facilities the separation process via Nanofiltration (NF) membrane with no membrane fouling. Thus, PolyE‐ILs can be highly active, easily recoverable, and reusable catalyst for esterification reactions with superior sustainability and economics. In addition to this the present one pot PolyE‐IL synthesis process is non‐complex and simple as compared to conventional post polymerization, ion exchange, and nucleophilic addition etc., strategies for synthesis of PILs.

Impacts of Surface Hydrophilicity of Carboxylated Polyethersulfone Supports on the Characteristics and Permselectivity of PA-TFC Nanofiltration Membranes.

Our current study experimentally evaluates the impacts of surface hydrophilicity of supports on the properties of polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes. A series of “carboxylated polyethersulfone” (CPES) copolymers with an increasing “molar ratio” (MR) of carboxyl units were used to prepare supports with diverse surface hydrophilicities by the classical nonsolvent-induced phase separation (NIPS) method. Then, the PA-TFC NF membranes were finely fabricated atop these supports by conventional interfacial polymerization (IP) reactions. The linkages between the surface hydrophilicity of the supports and the characteristics of the interfacially polymerized PA layers as well as the permselectivity of NF membranes were investigated systematically. The morphological details of the NF membranes indicate that the growth of PA layers can be adjusted through increasing the surface hydrophilicity of the supports. Moreover, the separation results reveal that the NF membrane fabricated on the relatively hydrophobic support exhibits lower permeability (7.04 L·m−2·h−1·bar−1) and higher selectivity (89.94%) than those of the ones prepared on the hydrophilic supports (14.64~18.99 L·m−2·h−1·bar−1 and 66.98~73.48%). A three-stage conceptual scenario is proposed to illustrate the formation mechanism of the PA layer in NF membranes, which is due to the variation of surface hydrophilicity of the supports. The overall findings specify how the surface hydrophilicity of the supports influences the formation of PA layers, which ultimately defines the separation performances of the corresponding NF membranes.

Benign fabrication process of hierarchal porous polyurea microspheres with tunable pores and porosity: Their Pd immobilization and use for hexavalent chromium reduction

Developing new strategies for fabrication of porous materials with tunable morphology which have fewer environmental impacts is highly desired. Herein, conventional precipitation polymerization of polyurea (PU) synthesis is converted to interfacial polymerization via simple microfluidics and hierarchically porous and uniform PU microspheres (PPM) are prepared by the reaction of toluene diisocyanate and water, eliminating the use of toxic amines and organic solvents. The morphology and porosity of PPM are probed. The size of PPM is controlled by changing the diameter of flow channels of microfluidic device and their pore size and porosity are tuned by optimizing the polymerization conditions. Moreover, palladium (Pd) is immobilized on PPM by impregnation and subsequent reduction approach to get Pd@PPM. The hybrid composite, Pd@PPM, is used for catalytic reduction of toxic Cr6+ to benign Cr3+ by formic acid as a reductant along with sodium format as a promoter in aqueous system. Pd@PPM exhibited high catalytic activity and good stability for Cr6+ reduction and their large size with high uniformity eased their recovery to reuse them in subsequent Cr6+ reduction. Porous PU with controllable shape and morphology are rarely available. This work therefore provides new strategy to synthesis PPM with controllable porous morphology and their use as an effective support for catalysis.

Synthesis of Conjugated Polymers via Transition Metal Catalysed C-H Bond Activation.

Transition metal catalysed C-H bond activation chemistry has emerged as an exciting and promising approach in organic synthesis. This allows us to synthesize a wider range of functional molecules and conjugated polymers in a more convenient and more atom economical way. The formation of C-C bonds in the construction of pi-conjugated systems, particularly for conjugated polymers, has benefited much from the advances in C-H bond activation chemistry. Compared to conventional transition-metal catalysed cross-coupling polymerization such as Suzuki and Stille cross-coupling, pre-functionalization of aromatic monomers, such as halogenation, borylation and stannylation, is no longer required for direct arylation polymerization (DArP), which involve C-H/C-X cross-coupling, and oxidative direct arylation polymerization (Ox-DArP), which involves C-H/C-H cross-coupling protocols driven by the activation of monomers' C(sp2 )-H bonds. Furthermore, poly(annulation) via C-H bond activation chemistry leads to the formation of unique pi-conjugated moieties as part of the polymeric backbone. This review thus summarises advances to date in the synthesis of conjugated polymers utilizing transition metal catalysed C-H bond activation chemistry. A variety of conjugated polymers via DArP including poly(thiophene), thieno[3,4-c]pyrrole-4,6-dione)-containing, fluorenyl-containing, benzothiadiazole-containing and diketopyrrolopyrrole-containing copolymers, were summarized. Conjugated polymers obtained through Ox-DArP were outlined and compared. Furthermore, poly(annulation) using transition metal catalysed C-H bond activation chemistry was also reviewed. In the last part of this review, difficulties and perspective to make use of transition metal catalysed C-H activation polymerization to prepare conjugated polymers were discussed and commented.

Acetal-Based Functional Epoxide Monomers: Polymerizations and Applications.

Protecting group chemistry is essential for various organic transformation and polymerization processes. In particular, conventional anionic ring-opening polymerization (AROP) often requires proper protecting group chemistry because it is typically incompatible with most functional groups due to the highly basic and nucleophilic conditions. In this context, many functional epoxide monomers with proper protecting groups are developed, including the acetal group as a representative example. Since the early introduction of ethoxyethyl glycidyl ether, there is significant development of acetal-based monomers in the polyethers. These monomers are now utilized not only as protecting groups for hydroxyl groups under AROP conditions but also as pH-responsive moieties for biomedical applications, further expanding their utility in the use of functionalized polyethers. Recent progress in this field is outlined from their synthesis, polymerization, and biomedical applications.

Utilizing RAFT Polymerization for the Preparation of Well-Defined Bicontinuous Porous Polymeric Supports: Application to Liquid Chromatography Separation of Biomolecules

Polymer-based monolithic high-performance liquid chromatography (HPLC) columns are normally obtained by conventional free-radical polymerization. Despite being straightforward, this approach has serious limitations with respect to controlling the structural homogeneity of the monolith. Herein, we explore a reversible addition-fragmentation chain transfer (RAFT) polymerization method for the fabrication of porous polymers with well-defined porous morphology and surface chemistry in a confined 200 μm internal diameter (ID) capillary format. This is achieved via the controlled polymerization-induced phase separation (controlled PIPS) synthesis of poly(styrene-co-divinylbenzene) in the presence of a RAFT agent dissolved in an organic solvent. The effects of the radical initiator/RAFT molar ratio as well as the nature and amount of the organic solvent were studied to target cross-linked porous polymers that were chemically bonded to the inner wall of a modified silica-fused capillary. The morphological and surface properties of the obtained polymers were thoroughly characterized by in situ nuclear magnetic resonance (NMR) experiments, nitrogen adsorption-desorption experiments, elemental analyses, field-emission scanning electron microscopy (FESEM), scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS) as well as time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealing the physicochemical properties of these styrene-based materials. When compared with conventional synthetic methods, the controlled-PIPS approach affects the kinetics of polymerization by delaying the onset of phase separation, enabling the construction of materials with a smaller pore size. The results demonstrated the potential of the controlled-PIPS approach for the design of porous monolithic columns suitable for liquid separation of biomolecules such as peptides and proteins.

New Concept of Thin-Film Composite Nanofiltration Membrane Fabrication Using a Mist-Based Interfacial Polymerization Technique

The conventional interfacial polymerization (CIP) technique used for preparing thin-film composite (TFC) nanofiltration membranes typically requires a large amount of monomers during polyamide (PA) synthesis where most of the monomers are discarded after cross-linking. Thus, a new fabrication concept is proposed in this work to synthesize a PA layer via a mist-based interfacial polymerization (MIP) technique where only a small amount of aqueous solution is dispersed as mist. This approach also eliminates the rubber-rolling step in CIP. In addition to forming a thinner and looser PA structure, the piperazine solution required in the IP reaction is significantly reduced, that is, 17 times lower than that of CIP. The microdroplet dispersion approach in MIP could form a higher cross-linked PA due to the high polymerization interface besides forming a higher free-volume selective layer due to the disruption in the PA repeat structure. Our findings revealed that the newly developed mist-based TFC membrane could achieve 9.08 L/m2·h·bar pure water permeability and 97.2% Na2SO4 rejection coupled with a complete flux recovery rate. As a comparison, the conventional TFC membrane only attained 2.84 L/m2·h·bar and 95.7%, respectively. The MIP technique could also be potentially considered for developing a nanofiller-incorporated TFC membrane due to the absence of the rubber-rolling step.

Synthesis of succinic acid‐based polyamide through direct solid‐state polymerization method: Avoiding cyclization of succinic acid

AbstractSuccinic acid is an important synthetic monomer but it is difficult to use it as a precursor for synthesizing high molecular weight polyamide, due to its tendency to perform intra‐cyclization reaction at high temperature. In order to solve this problem, in this paper, the direct solid‐state polymerization (DSSP) method with the initial reactant, nylon salt which was composed of 1, 5‐diaminopentane, succinic acid, and terephthalic acid, was applied to synthesize the bio‐based copolyamide PA 5T/54. In comparison with the conventional melting polymerization method, the DSSP method can prevent the cyclization reaction of succinic acid effectively due to the lower reacting temperature as well as the restriction effect of the nylon salt. As a result, the product fabricated by DSSP method has higher molecular weight and much lighter color from red to white. Therefore, the DSSP method is advantageous for the synthesis of the polymers or copolymers composed of the succinic acid as the monomer. Furthermore, the polymerization mechanism proposed in this work can serve as a guidance for the design of the molecular structure and control of the polymerization process.