Anionic Ring-opening Polymerization Research Articles

Convenient Access to α-Amino-ω-Hydroxyl Heterobifunctional PEG and PPO via a Sacrificial Hexahydro-Triazine Star Strategy.

The anionic ring opening polymerizations of ethylene oxide (EO) and propylene oxide (PO) are performed by using 1,3,5-triethanol hexahydro-1,3,5-triazine (TrAz) as a "sacrificial" trifunctional initiator. Well-defined three-arm star polymers are obtained with a narrow molecular weight distribution (M w /M n < 1.1). Molecular weights range from 3-15 kg mol-1 . Since these star polymers possess an acid-labile hexahydro-triazine core, acidic hydrolysis leads to cleavage of the arms. This gives access to well-defined α-amino-ω-hydroxyl heterobifunctional poly(ethylene glycol) (PEG) and poly(propylene oxide) (PPO) in the molecular weight range of 1-5 kg mol-1 and low dispersity M w /M n < 1.1. The α,ω-heterobifunctional polyethers are valuable structures for bioconjugation. Furthermore, an acid-labile triazine star polymer is directly used as a polyol component for the synthesis of a polyurethane network, which is stable under ambient conditions but degrades rapidly under acidic conditions.

Poly(ethylene glycol) with Multiple Aldehyde Functionalities Opens up a Rich and Versatile Post-Polymerization Chemistry

Two novel epoxide monomers 3,3-dimethoxy-propanyl glycidyl ether (DMPGE) and 3,3-dimethoxy-2,2-dimethylpropanyl glycidyl ether (DDPGE) were developed for the introduction of multiple aldehyde functionalities into the poly(ethylene glycol) (PEG) backbone. The acetal protecting group for the aldehyde functionality is stable against the harsh, basic conditions of the anionic ring-opening polymerization. Both monomers could be homopolymerized as well as copolymerized randomly with ethylene oxide (EO) in a controlled fashion. Copolymers with molecular weights (Mn) in the range of 4500–20100 g/mol and low dispersity (Mw/Mn) between 1.06 and 1.14 were obtained. The polymers were characterized by size exclusion chromatography, 1H NMR spectroscopy, and by differential scanning calorimetry regarding their thermal properties. The controlled character of the copolymerization was verified by MALDI-TOF. To study the distribution of the acetal-protected aldehyde functionalities at the polyether chains, the copolymerizat...

Direct access to poly(glycidyl azide) and its copolymers through anionic (co-)polymerization of glycidyl azide

Glycidyl azide polymer or poly(glycidyl azide) which is considered as an excellent energetic binder or plasticizer in advanced solid propellants is generally obtained by post-modification or azidation of poly(epichlorohydrin). Here we report that glycidyl azide can be directly homopolymerized through anionic ring-opening polymerization to access poly(glycidyl azide) using onium salts as initiator and triethyl borane as activator. Molar masses of poly(glycidyl azide) up to 11.0 Kg/mol are achieved in a controlled manner with a narrow polydispersity index (PDI ≤ 1.2). Similarly, alternating poly(glycidyl azide carbonate) are also prepared through alternating copolymerization of glycidyl azide with carbon dioxide. Lastly, the copolymerization of glycidyl azide with other epoxide monomers is carried out; the azido functions carried by glycidyl azide which are successfully incorporated into the backbones of polyethers and polycarbonates based on cyclohexene oxide and propylene oxide subsequently served to introduce other functions by click chemistry.

Synthesis of dual-responsive polymer via convertible RAFT and ring-opening polymerizations in one-pot

The synthesis and applications of dual- or multi stimuli-responsive polymers have gained increasing attention. One-pot strategy by combination two different polymerization mechanisms is promising for the synthesis of dually stimuli-responsive polymers in a rapid route. In this work, we report a convertible anionic ring-opening and RAFT polymerization by using asymmetrical trithiocarbonate as both an initiator for the anionic ring-opening polymerization and a chain transfer agent for RAFT polymerization to produce poly(propylene sulfide) (PPS)- poly(N-isopropylmethacrylamide) block-like copolymers. Furthermore, the ROS and temperature responsibility of the formed copolymer are also evaluated.

Hybrid copolymerization via mechanism interconversion between radical vinyl-addition and anion ring-opening polymerization

Here, we report a new hybrid copolymerization via an interconvertible living free radical and anion ring-opening polymerization mechanism, in which the copolymerization of cyclic monomers and vinyl-type monomers can be achieved.

Aziridines and azetidines: building blocks for polyamines by anionic and cationic ring-opening polymerization

The synthesis of aziridine and azetidine monomers and their ring-opening polymerizationviadifferent mechanisms is reviewed.

Recyclable sulfone-containing polymersviaring-opening polymerization of macroheterocyclic siloxane monomers: synthesis, properties and recyclability

The first recyclable sulfone-containing polysiloxanes were synthesizedviaan anionic ring-opening polymerization of macroheterocyclic siloxane monomers.

Fast Screening of Diol Impurities in Methoxy Poly(Ethylene Glycol)s (mPEG)s by Liquid Chromatography on Monolithic Silica Rods.

The determination of diol impurities in methoxy poly(ethylene glycol)s (mPEG)s is of high importance, e.g., in the area of pharmaceutical applications, since mPEGs are considered the gold standard—based on properties of biocompatibility, stealth effect against the immune system, and well-established procedures used in PEGylation reactions. Herein, we communicate a straightforward and fast approach for the resolution of the PEGdiol impurities in mPEG products by liquid chromatography on reversed-phase monolithic silica-rods. Thus, we utilize fine, in-house prepared and narrow dispersity mPEGs (Ð ≤ 1.1) and commercial PEGdiol standards as a reference. Most efficient analysis of diol impurities becomes possible with reversed-phase liquid chromatography that results in selective elution of the PEGdiol from mPEG macromolecule populations in partition/adsorption mode. We do this by a minimum selectivity of the population of macromolecules characterizing the narrow molar mass distributions of mPEG. Control experiments with intentionally added water at the start of the well-controlled mPEG synthesis via the living anionic ring opening polymerization of ethylene oxide clearly reconciled the existence of PEGdiol impurity in chromatographed samples. The here-demonstrated methodology allows for the resolution of diol impurities of less than one percent in elution times of only a few minutes, confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) of the collected elution fractions. The unique combination of the open flow-through pore structure of the monolithic silica rods and resultant varying accessibility of C18-derivatized pore surfaces indicates beneficial properties for robust and end-group-specific adsorption/partition liquid chromatography of synthetic macromolecules.

Preparation of nanochitin-contained magnetic chitosan microfibers via continuous injection gelation method for removal of Ni(II) ion from aqueous solution

In this study, nanochitin-contained magnetic chitosan (FPCC) microfibers were prepared successfully via continuous injection gelation method and employed to remove Ni(II) ion from aqueous solution. Firstly, Fe3O4-nanoparticles were encapsulated into ε-caprolactam (CL) monomer solution in the presence of polystyrene (PSE), followed by CL anionic ring-opening polymerization and PSE removal, and obtained magnetic polyamide 6 (PA 6) microparticles (FP). After that, the economical FPCC microfibers can be prepared by adding FP microparticles and nanochitin (n-CT) into poly(vinyl alcohol)/chitosan hybrids (PVA/CTS). The obtained FPCC microfibers had shown significant advantages in production, separation, and adsorption when compared to the hydrogel beads prepared by the traditional method (instantaneous gelation method). Within 10 h, 99.7% Ni(II) could be adsorbed by FPCC magnetic microfibers (adsorbent dosage: 1 g, pH: 4.1, and temperature: 293 K). More attractively, the hybridized microfibers could be easily separated from the aqueous solution through a magnetic separation method after Ni(II) adsorption. Ni(II) adsorption behaviors of the hybrid microfibers conform to the Langmuir isotherm model and pseudo-second-order kinetic model. Besides, the possible adsorption mechanism was also discussed.

Ring-opening polymerization of \u03b2-butyrolactone in the presence of alkali metal salts: investigation of initiation course and determination of polymers structure by MALDI-TOF mass spectrometry

Several alkali metal salts that activated 18-crown-6 were applied as initiators of β-butyrolactone anionic ring-opening polymerization in tetrahydrofuran at room temperature. Some of them, i.e., Ph2PK, Ph3HBK, (Me3Si)2NK, and t-BuOK, deprotonate the monomer which results in macromolecules with trans-crotonate starting group. Other salts, for example, MeOK, i-PrOK, PhCH2OK, and CbK (Cb denotes carbazolyl group), deprotonate monomer or open its ring in the acyl-oxygen position. After ring-opening KOH forms as intermediate and initiates further polymerization. Ph3CK and monopotassium salt of ethylenediaminetetraacetic acid also deprotonate monomer and open its ring, however, in the alkyl-oxygen position. Monopotassium salts of glycolic acid, diglycolic acid, or malonic acid initiate polymerization mainly by ring opening in the alkyl-oxygen position. It results in the formation of polymers with two reactive terminal groups. The salts used react with the monomer as strong bases, nucleophilic bases, or nucleophiles. It determines unsaturation of the polymers obtained in the wide range of 2–100 mol%.

Lithium hexamethyldisilazide initiated superfast ring opening polymerization of alpha-amino acid N-carboxyanhydrides

Polypeptides have broad applications and can be prepared via ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs). Conventional initiators, such as primary amines, give slow NCA polymerization, which requires multiple days to reach completion and can result in substantial side reactions, especially for very reactive NCAs. Moreover, current NCA polymerizations are very sensitive to moisture and must typically be conducted in a glove box. Here we show that lithium hexamethyldisilazide (LiHMDS) initiates an extremely rapid NCA polymerization process that is completed within minutes or hours and can be conducted in an open vessel. Polypeptides with variable chain length (DP = 20–1294) and narrow molecular weight distribution (Mw/Mn = 1.08–1.28) were readily prepared with this approach. Mechanistic studies support an anionic ring opening polymerization mechanism. This living NCA polymerization method allowed rapid synthesis of polypeptide libraries for high-throughput functional screening.

Synthesis and Antifungal Activities of Amphiphilic PDMS-b-QPDMAEMA Copolymers on Rhizoctonia solani

Cationic polymers are prospective fungicidal agents for inhibiting plant diseases because of the controllability of their structure and properties. This study investigates the effect of the hydrophobic-hydrophilic balance on the antifungal activities of antimicrobial polymers against phytopathogenic fungi (Rhizoctonia solani Kühn AG-1(IA)), the pathogen of rice sheath blight (RShB). A series of polydimethylsiloxane-polymethacrylate block copolymers containing quaternary ammonium salts (PDMS-b-QPDMAEMA, labeled as SnQm; n and m represent 1000th of the molecular weight of the PDMS and QPDMAEMA chain, respectively) were synthesized via anionic ring-opening polymerization and atom transfer radical polymerization (ATRP). The abilities of the quaternary ammonium salts to adsorb onto the surface of R. solani sclerotia and permeate the R. solani sclerotia were investigated on the basis of static water contact angles and fluorescence labeling. The results indicated that the moderately hydrophobic PDMS chain helped stabilize the attachment of the hydrophilic QPDMAEMA chain and then help it penetrate the R. solani sclerotia. Its antifungal properties toward R. solani were characterized by determining its minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) and the inhibition rate of R. solani sclerotia germination. The hydrophobic PDMS chains had a significant influence on the antifungal activities of amphiphilic SnQm against R. solani sclerotia. This work highlights the prospective application of amphiphilic antimicrobial polymers as antifungal agents for inhibiting plant diseases.

Synthesis, Characterization and Biodegradation of Poly(?-Methyl ?-Propiolactone)

Poly(α-methyl β-propiolactone) (PmPL) was synthesized through anionic ring-opening polymerization of the corresponding lactone. Structural characterization of PmPL was performed by using FTIR, 1H-NMR and MALDI-MS spectrometry. Thermal behavior of the polymer was investigated by using DSC and TGA. Glass transition, melting and thermal degradation temperatures of PmPL were determined as -36.7, 95.5 and 242.4 oC, respectively. Biodegradation studies were conducted at 37 oC in three different media, that is, pH 7.4 phosphate buffered saline (PBS), PBS containing pancreatic trypsin and PBS containing pancreatic lipase. The biodegradation kinetics and mechanism of the polymer were followed by gravimetric measurements and LC-MS analysis. Up to 65% mass loss in 5-week period was recorded for the buffer media in the presence of lipase and trypsin. LC-MS analysis of the residues in the media revealed that biodegradation undergoes mainly through ester bond hydrolysis.

Mechanism of \u03b5-caprolactone polymerization in the presence of alkali metal salts: investigation of initiation course and determination of polymers structure by MALDI-TOF mass spectrometry

Various alkali metal salts were applied as initiators for ε-caprolactone anionic ring-opening polymerization in tetrahydrofuran at room temperature. It was observed that potassium methoxide (MeOK), potassium isopropoxide (i-PrOK) and potassium tert-butoxide (t-BuOK) nonactivated or activated by 18-crown-6 (18C6) initiated polymerization mainly by deprotonation of the monomer. In the case of potassium hydride (KH), its basicity increased with the ability of the ligand for cation complexation. For example, KH without ligand or with weak ligands for K+ as 12C4 reacted exclusively by ring opening. However, in the presence of strong ligands, as 15C5, 18C6 or cryptand C222, basicity of H− increased with the ability of the ligand for cation complexation. In the last case, ~ 32% of the monomer was deprotonated. In these systems, gaseous H2 evolved during the initiation. Deprotonation of the monomer by some initiators resulted in macromolecules with reactive aldehyde group or lactone ring as starting groups. They took part in the reaction with potassium alkoxide active centers of growing chains leading to the formation of branched poly(ε-caprolactone)s. Sodium hydride (NaH) was inactive, but in the presence of 15-crown-5 or 18-crown-6 initiated polymerization exclusively by ring opening. MALDI-TOF mass spectrometry supported with 13C NMR and SEC was used for analysis of the polymers obtained. Mechanism of the studied processes was proposed and discussed.

“Green” ethers as solvent alternatives for anionic ring-opening polymerizations of ethylene oxide (EO): In-situ kinetic and advanced characterization studies

In the present work, the polymerization process of ethylene oxide (EO) leading to diphenyl-PEO-OH with a molar mass of 5000 and 10,000 g mol−1 in different ethers used as solvents was investigated. The aim was to gain access to the kinetics of the anionic ring-opening polymerization (AROP) of EO by an online and in-situ real-time method and to test alternative “greener” solvents in comparison to the well-established solvents, e.g. tetrahydrofuran (THF). For this purpose, we chose two promising “green” ethers, methyl tetrahydrofuran (MeTHF) and cyclopentyl methyl ether (CPME), with improved properties regarding reduced peroxide formation, higher boiling points, easier drying, and lower water solubility. During the AROP in the custom-built setup, in-situ IR measurements were performed and the final products were characterized by SEC, MALDI-TOF-MS, and 1H NMR measurements, as well as newly in-house developed liquid chromatography (LC) investigations for purity analysis and diol impurity content estimations. Results presented in this study show that the controlled polymerization of EO in the tested alternative solvents represents a viable alternative to commonly established ones, as based on our kinetic studies and product characterization results.

Toward industrial use of anionically activated lactam polymers: Past, present and future

Abstract This paper gives an overview of lactam-based polymers and related composites produced via anionic ring opening polymerization (AROP). Recent and past achievements, grouped into academic and industrial research works, and covering also the chemistry (initiator and activator systems) and modification possibilities of in situ polymerized e-caprolactam (CL) and ω-lauryllactam (LL) are presented and discussed. Special emphasis was put on the industrial applications of AROP of CL and LL resulting in polyamide-6 (PA6) and PA12, respectively. The results achieved are surveyed and highlighted according to the preparation and manufacturing techniques. Based on this state-of-art review, development trends for the future were concluded and their possible drivers suggested.

Microstructural-mechanical properties relationship in single polymer laminate composites based on polyamide 6

This paper studies the flexural and the impact properties of polyamide 6-based knitted reinforced single polymer composites (KSPCs) prepared by compression molding of powder-coated textile structures. To prepare matrix component, polyamide 6 microparticles (MPs) were synthesized by activated anionic ring-opening polymerization of ε-caprolactam in solution and then used for powder-coating of the knitted structures. The influence of the reinforcements' architecture, plies orientation, stacking order and fiber content on the final mechanical properties of KSPCs were investigated. Rib1 × 1 and Jersey knitted structures were selected as reinforcements and treated by a stretching-annealing procedure to modify their mechanical properties. The anisotropic tensile and compression properties imparted by the knitted structures were found to be the major factors determining the impact and flexural behavior of KSPCs. Moreover, reinforcement's crossover points, the plies orientation and the presence of a transcrystalline layer at the matrix-reinforcement interface were identified as relevant parameters. The fracture mechanism of KSPCs was linked to the morphology and crystalline structure of the resulting composites and investigated by simulation and finite element analysis of knitted reinforcements.

A new cyclic initiator system for the synthesis of novel star-shaped polyether-polyols (PEPOs) for fabrication of rigid cross-linked polyurethanes

Application of novel potassium salts (from mono- to penta-potassium) of 2,2,6,6-tetrakis(hydroxymethyl) cyclohexanol-activated 18C6 for propylene oxide polymerization is investigated. The novelty of the research concerns utilization of the cyclic-structured initiator with various substitution levels applied for anionic ROP of oxiranes. It results in the formation of bimodal macropentols (Scheme 1) with molar mass values in the range of Mn 2100–13200 g/mol and unsaturation, which depends on the initial concentration of monomer and alkoxide groups. The mechanism of the studied processes is discussed. The newly synthesized polyether-polyols (PEPOs) were used for the synthesis of new rigid polyurethanes (PURs) in one-step process. Thermogravimetric analysis (TGA) showed that the analyzed polyurethanes based on star-shaped polyols were characterized by two-stage thermal degradation and higher thermal stability in comparison to the linear polyols. The first stage of thermal decomposition of the tested PURs is related to the breaking of the urethane bonds in the rigid chains, while during the second stage, oligo-diol and oligo-pentol chains break down. A significant amount of solid degradation residue is advantageous in terms of the flame retardation of the obtained PUR, as this is usually associated with less products released during the degradation process. It was shown that the higher content of rigid segments in the PUR structure results in higher thermal resistance. The thermal behavior of the PURs was also investigated by differential scanning calorimetry (DSC).

From D-sorbitol to five-membered bis(cyclo-carbonate) as a platform molecule for the synthesis of different original biobased chemicals and polymers

Bis(cyclo-carbonate) was successfully synthesized from D-sorbitol (Sorb-BisCC) through an environmentally friendly process with dimethyl carbonate (DMC) as a reactant. In agreement with green chemistry principles, solvent free reactions were catalyzed and took place at low temperature. The reaction yield was increased until 50%, with the use of 1.3.5-triazabicyclo[4.4.0]dec-5-ene as catalyst and a continuous DMC feed to limit the side-reactions or the loss of reactant by azeotropic flux with a reactional subsidiary product. The obtained Sorb-BisCC is a remarkable platform molecule which could compete with others polycyclic platform molecules (isosorbide). Sorb-BisCC can be e.g., used to synthesize different chemicals such as short and long polyols, or novel biobased non-isocyanate polyurethanes (NIPU). Two Sorb-BisCC molecules have been coupled to obtain novel cyclic diols with pendant side chains. Polyether polyols were also obtained by anionic ring opening polymerization. According to the synthesis conditions, these synthetized polyether polyols range from partially to highly cross-linked materials. Finally, NIPU were synthesized with short and biobased fatty diamines. These different modifications and synthesis highlight the versatility of the Sorb-BisCC and demonstrated its high potential as building block. Sorb-BisCC can be considered as a platform molecule to open the way to different original and biobased chemical architectures.

Biologically Active Branched Polysaccharide Mimetics: Synthesis via Ring-Opening Polymerization of a Maltose-Based β-Lactam.

Stereoregular poly-amido-saccharides bearing α-glucopyranose branches (Mal-PASs) are synthesized by anionic ring-opening polymerization of a maltose-based β-lactam monomer followed by debenzylation. The polymerization affords high molecular weight polymers (up to 31500 g/mol) with narrow dispersities (Đ < 1.1). Deprotected Mal-PASs are highly soluble in water and adopt a left-handed helical conformation in solution. Turbidimetric assay shows that Mal-PASs are multivalent ligands to lectin Concanavalin A.