Anionic Ring Opening Research Articles

Molecular Orientation and Thermal Conductivity in Liquid Crystalline Epoxy Resins by Anionic Ring-Opening Polymerization

Molecular Orientation and Thermal Conductivity in Liquid Crystalline Epoxy Resins by Anionic Ring-Opening Polymerization

Anionic Ring-Opening Polymerization of ε-Caprolactam above the Crystallization Temperature of Polyamide 6: A Study on the Effects of the Activator and Catalyst

Anionic Ring-Opening Polymerization of ε-Caprolactam above the Crystallization Temperature of Polyamide 6: A Study on the Effects of the Activator and Catalyst

Preparation of Allyl-Containing PDMS Telehelics by the Anionic Ring-Opening Polymerization

The synthesis of allyl-containing PDMS telechelics from octamethylcyclotetrasiloxane and 1,3-diallyl-1,1,3,3-tetramethyldisiloxane as a stopper by the anionic ring-opening of a siloxane ring is presented. A series of the polymers with the molecular weights from 1000 to 12000 were obtained and characterized by gel permeation chromatography and 1H NMR spectroscopy. The molecular weights of the resulting polymers correspond to the given ones.

Cyclic carbamates based on (R)-(+)-limonene oxide for ring-opening polymerization

A novel synthetic pathway for synthesizing isocyanate-free polyurethanes is reported here. β-Amino alcohols were efficiently synthesized from the aminolysis of the epoxide ring of (R)-(+)-limonene oxide with different primary amines as nucleophiles and hot water as catalysts. The regio- and diastereoselectivities of the reactions were investigated and supported by computational studies. DFT calculations were performed to understand the experimental results more deeply. It confirmed the crucial roles of water molecules and the nature of the nucleophile in forming the products. The formation of the product is entirely driven by the free energy of activation that affects the reaction rate. Cyclic carbamates were prepared from β-amino alcohols using the dialkyl carbonate (DAC) chemistry. An oligourethane was obtained from Anionic Ring-Opening Polymerization (AROP) of a cyclic carbamate derived from (R)-(+)-limonene-oxide. All the products were characterized by employing 1H and 13C NMR spectroscopies. The assignments of the signals in 1H and 13C NMR spectra were also supported by 2D NMR spectroscopy.

Mastering Macromolecular Architecture by Controlling Backbiting Kinetics during Anionic Ring-Opening Polymerization

Mastering Macromolecular Architecture by Controlling Backbiting Kinetics during Anionic Ring-Opening Polymerization

Ferrocene functionalized oligomeric siloxane building blocks as potential linkers for biological active molecules

Despite the fact, that biologically active molecules (e.g., antioxidants, antibiotics and antiviral reagents) were investigated intensively in the last decades, new linker molecules and building blocks, which can enhance the activity and change the polarity of compounds is still a growing field in pharmaceutic research. The application of a ferrocene moiety in combination with a siloxane linker attached to a biological active molecule is realized in the present study for the first time. A method is introduced that uses mono- (FcLi) and dilithioferrocene (FcLi2) to perform anionic ring opening reactions of hexamethylcyclotrisiloxane (D3). The formation of lithium silanolate species αDnLi (α = Fc, D3 = (SiMe2O)3) was observed, followed by the termination of the ring opening reactions with chlorosilanes Cl–ω to obtain siloxane oligomers of type αDnω. Approaches were investigated to enable ω = SiMe2H and ω = SiMe2Cl functionality. It was shown, that oligomeric siloxanes were able to undergo further hydrosilylation reactions with the introduction of a phenol moiety.

Naloxone-initiated mechanochemical synthesis of poly(lactic acid)

A mechanochemical approach was utilized for the synthesis of Naloxone covalently linked poly(lactic acid) and nanoparticles. This preparation was achieved using lactide as a monomer in anionic ring opening polymerization,...

High energy barrier hydroxyl radical dissociation mechanism of a low shock sensitivity dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) explosive.

As a representative of the new generation of high-energy explosives, TKX-50 has attracted widespread attention due to its remarkably low sensitivity toward shock. However, the reported decomposition barriers of TKX-50 (∼37 kcal mol-1) are comparable to those of commonly used explosives. The mechanism of its low shock sensitivity remains unclear. In this study, using an ab initio molecular dynamics method combined with a multiscale shock simulation technique and transition state calculations (at the B2PLYP-D3/Def2TZVP level), we discovered an unconventional reaction pathway of TKX-50 under shock, and its rate-controlling step is the dissociation of the hydroxyl radical (OH) from the anion ring after proton transfer, followed by ring rupture and the production of H2O and N2. The barrier for this OH dissociation reaction is as high as 51.9 kcal mol-1. In contrast, under thermal stimuli, TKX-50 prefers to open rings directly after proton transfer without losing the OH. The corresponding barrier is 35.4 kcal mol-1, which is in good agreement with previous studies. The reason for the unconventional reaction pathway of TKX-50 under shock may be the suppression of anion ring opening in thermal decomposition by steric hindrance upon shock compression. In addition, the dominant N2 generation pathway under shock releases less energy than pyrolysis which further explains the low shock sensitivity of TKX-50. This study comprehensively elucidates the different reaction mechanisms of TKX-50 under thermal and shock conditions and proposes a crucial reaction pathway leading to its low shock sensitivity. These findings will contribute to the understanding and application of tetrazole anionic energetic salts.

Contrasting Roles of Counterions in Anionic Ring-Opening Polymerization Mediated by Heterocycle Organocatalysts

Contrasting Roles of Counterions in Anionic Ring-Opening Polymerization Mediated by Heterocycle Organocatalysts

Ketyl Radical Anion Mediated Radical Polymerization and Anionic Ring-Opening Polymerization to Give Polymers with Low Molecular Weight Distribution.

The development of novel polymerization capable of yielding polymers with low molecular weight distribution (Đ) is essential and significant in polymer chemistry, where monofunctional initiator contains only one initiation site in these polymerizations generally. Here, ketyl radical anion species is introduced to develop a novel Ketyl Mediated Polymerization (KMP), which enables radical polymerization at carbon radical site and anionic ring-opening polymerization at oxygen anion site, respectively. Meanwhile, polymerization and corresponding organic synthesis generally couldn't be performed simultaneously in one pot. Through KMP, organic synthesis and polymerization are achieved in one pot, where small molecules (cyclopentane derivates) and polymers with low Đ are successfully prepared under mild condition simultaneously. At the initiation step, both organic synthesis and polymerization are initiated by single electron transfer reaction with ketyl radical anion formation. Cyclopentane derivates are synthesized through 3-3 coupling reaction and cyclization. Polystyrene and polycaprolactone with low Đ and a full monomer conversion are prepared by KMP via radical polymerization and anionic ring-opening polymerization, respectively. This work therefore enables both organic synthesis and two different polymerizations from same initiation system, which saves time, labour, resource and energy and expands the reaction mode and method libraries of organic chemistry and polymer chemistry.

Enhanced Mechanical Property of Polyamide-6/Graphite Sheet Composites with Segregated 3D Network Binary Structure for High Thermal Conductivity.

Segregated conductive polymer composites exhibit excellent electrical properties with a low percolation threshold. However, the mechanical properties of the segregated conductive polymer composites were always poor because the conductive fillers at the interfaces hinder polymer chain diffusion and thus lead to weak interfacial interaction between the conductive fillers and the polymer matrix. In this paper, polyamide-6 and polyamide-612 microspheres were synthesized via the in situ anionic ring opening of caprolactam and laurolactam. Segregated graphite sheets/polyamide-6(GS/PA6) and polyamide-612(PA612) composites with good mechanical properties were realized via high-pressure solid-phase compression molding. The microstructures of the composite samples were observed by scanning electron microscopy, which showed that the formation of a GS-conductive network at the PA6 granule interfaces in the segregated conductive structures and the adopting of PA612 considerably improved the interfacial adhesion of the composites. A superior impact strength of 5.1 kJ/m2 was achieved with 50 wt% PA612 loading owing to improvements in the interface compatibility between PA6 and GS. The composites possessed an ultralow percolation threshold, which was ascribed to the segregated network structure being successfully constructed inside the material. As for GS/PA6 composites, the combination of segregated GS-conductive networks achieved an ultralow percolation of 2.8 vol%. The percolation of 80PA6/20PA612-GS composites was slightly higher, measuring up to 3.2 vol%. Moreover, the thermal conductivity of the 80PA6/20PA612-GS composites increased from 0.26 to around 0.5 W/(m·K), which was 1.9 times larger than the pure polyamide.

Precision Synthesis of Polypeptides via Living Anionic Ring-Opening Polymerization of N-Carboxyanhydrides by Tri-thiourea Catalysts.

The chemistry of α-amino acid N-carboxyanhydrides (NCAs) has a history of over 100 years, but precise and efficient ring-opening polymerization methods for NCAs remain highly needed to facilitate the studies of polypeptides─that is, mimics of natural proteins─in various disciplines. Moreover, the universally accepted NCA polymerization mechanisms are largely limited to the "amine" and the "activated monomer" mechanisms, and the anionic ring-opening polymerization of NCAs has so far not been invoked. Herein, we show an unprecedented anion-binding catalytic system combining tripodal tri-thiourea with sodium thiophenolate that enables the fast and selective anionic ring-opening polymerization of NCAs. This method leads to the precision construction of various polypeptides with living polymerization behavior and is evidenced by narrow molecular weight distributions (Mw/Mn < 1.2), chain extension experiments, and minimal "activated monomer" pathway. Calculations and experimental results elucidate a living anionic polymerization mechanism, and high selectivities for monomer propagation relative to other deleterious side reactions, such as the "activated monomer" pathway, are attributed to the enhanced stabilization of the propagating carbamate anion, which is enforced by an intramolecular hydrogen bond within the tri-thiourea structure.

A road map on synthetic strategies and applications of biodegradable polymers.

Biodegradable polymers have emerged as fascinating materials due to their non-toxicity, environmentally benign nature and good mechanical strength. The toxic effects of non-biodegradable plastics paved way for the development of sustainable and biodegradable polymers. The engineering of biodegradable polymers employing various strategies like radical ring opening polymerization, enzymatic ring opening polymerization, anionic ring opening polymerization, photo-initiated radical polymerization, chemoenzymatic method, enzymatic polymerization, ring opening polymerization and coordinative ring opening polymerization have been discussed in this review. The application of biodegradable polymeric nanoparticles in the biomedical field and cosmetic industry is considered to be an emerging field of interest. However, this review mainly highlights the applications of selected biodegradable polymers like polylactic acid, poly(ε-caprolactone), polyethylene glycol, polyhydroxyalkanoates, poly(lactide-co-glycolide) and polytrimethyl carbonate in various fields like agriculture, biomedical, biosensing, food packaging, automobiles, wastewater treatment, textile and hygiene, cosmetics and electronic devices.

Synthesis of Functional Polyesters N-(2,3-epoxypropyl)-4,5,6,7-tetrahydroindole by Anionic Ring-Opening Polymerization.

The functional polyethers of N-(2,3-epoxypropyl)-4,5,6,7-tetrahydroindole (in up to 61% yield, Mw = 8.7–11.7 kDa) and copolymers with ethylene glycol methylglycidyl ether (Mw = 5.6–14.2 kDa) and ethylene glycol vinylglycidyl ether (Mw = 6.4–12.3 kDa) have been synthesized via anionic ring-opening polymerization in the presence of KOH without solvent. The polymerization involves the opening of the epoxy ring to deliver the linear polyethers bearing free tetrahydroindole rings and oxyethylene or vinyloxy groups in the side chain. The polyethers are soluble in ethanol, benzene, chloroform, dioxane, DMF, and DMSO. The polyethers obtained exhibit the properties of high-resistance organic semiconductors: their electrical conductivity reaches 10−14 S/cm.

One‐Pot Covalent Functionalization of 2D Black Phosphorus by Anionic Ring Opening Polymerization

AbstractIn this work, a one‐pot approach for the covalent functionalization of few‐layer black phosphorus (BP) by anionic ring opening polymerization of glycidol to obtain multifunctional BP‐polyglycerol (BP‐PG) with high amphiphilicity for near‐infrared‐responsive drug delivery and biocompatibility is reported. Straightforward synthesis in combination with exceptional biological and physicochemical properties designates functionalized BP‐PG as a promising candidate for a broad range of biomedical applications.

Tailoring the Hydroxyl Density of Glass Surface for Anionic Ring-Opening Polymerization of Polyamide 6 to Manufacture Thermoplastic Composites.

Reactive thermoplastics matrices offer ease of processing using well-known molding techniques (such as Resin Transfer Molding) due to their initially low viscosity. For Polyamide 6 (PA6)/glass composites, the hydroxyl groups on the glass surface slow down the anionic ring-opening polymerization (AROP) reaction, and can ultimately inhibit it. This work aims to thoroughly control the hydroxyl groups and the surface chemistry of glass particulates to facilitate in situ AROP-an aspect that has been barely explored until now. A model system composed of a PA6 matrix synthesized by AROP is reinforced with calcinated and silanized glass microparticles. We systematically quantify, by TGA and FTIR, the complete particle surface modification sequence, from the dehydration, dehydroxylation and rehydroxylation processes, to the silanization step. Finally, the impact of the particle surface chemistry on the polymerization and crystallization of the PA6/glass composites was quantified by DSC. The results confirm that a careful balance is required between the dehydroxylation process, the simultaneous rehydroxylation and silane grafting, and the residual hydroxyl groups, in order to maintain fast polymerization and crystallization kinetics and to prevent reaction inhibition. Specifically, a hydroxyl concentration above 0.2 mmol OH·g−1 leads to a slowdown of the PA6 polymerization reaction. This reaction can be completely inhibited when the hydroxyl concentration reaches 0.77 mmol OH·g−1 as in the case of fully rehydroxylated particles or pristine raw particles. Furthermore, both the rehydroxylation and silanization processes can be realized simultaneously without any negative impact on the polymerization. This can be achieved with a silanization time of 2 h under the treatment conditions of the study. In this case, the silane agent gradually replaces the regenerated hydroxyls. This work provides a roadmap for the preparation of reinforced reactive thermoplastic materials.

Anionic Ring-Opening Polymerization of a Functional Epoxide Monomer with an Oxazoline Protecting Group for the Synthesis of Polyethers with Carboxylic Acid Pendants

Anionic Ring-Opening Polymerization of a Functional Epoxide Monomer with an Oxazoline Protecting Group for the Synthesis of Polyethers with Carboxylic Acid Pendants

Episulfide Anionic Ring-Opening Polymerization Initiated by Alcohols and Primary Amines in the Presence of γ-Thiolactones

Episulfide Anionic Ring-Opening Polymerization Initiated by Alcohols and Primary Amines in the Presence of γ-Thiolactones

Fluoride-initiated Anionic Ring-opening Polymerization: Mono- or Difunctional Polydimethylsiloxanes with Different Termini

Fluoride-initiated Anionic Ring-opening Polymerization: Mono- or Difunctional Polydimethylsiloxanes with Different Termini

Janus Polymerization: A One‐Shot Approach towards Amphiphilic Multiblock Poly(ester‐acetal)s Directly from 1,3‐Dioxolane with ε‐Caprolactone

Comprehensive SummaryJanus polymerization consists of anionic and cationic ring opening polymerizations (AROP and CROP) at the two ends of a single propagating polymer chain, followed by a self‐triggered chain extension generating multiblock copolymers (MBCPs) in one step. In the contribution, Janus polymerization by Tm(OTf)3 or Er(OTf)3 catalyst with an epoxy initiator is applied to synthesize MBCPs of semi‐crystalline poly(ε‐caprolactone) (PCL) blocks from coordinated AROP and poly(1,3‐dioxolane‐co‐ε‐caprolactone) (P(DO‐co‐CL)) blocks from CROP of DO with CL. Meanwhile, amorphous random copolymers [P(DO‐r‐CL)] are synthesized as control by employing other rare earth triflates [RE(OTf)3, RE = Y, Nd, Gd and Lu] as catalysts or in the absence of an initiator via CROP. On account of the distinguishable chemical structures and thermal properties between Janus MBCPs and cationic random copolymers, Janus features are confirmed including the CROP and AROP at a single propagating chain. The resultant amphiphilic copolymers self‐assemble to nanoparticles in aqueous solution with designable diameters with the corresponding ratios of hydrophilic and hydrophobic segments. MBCPs exhibit good shape memory properties with appropriate deformation temperature close to human body's, providing a prospect on the applications in biomedical devices.