Anionic Ring-opening Polymerization Research Articles

Tough omni-dynamic silicone rubbers with excellent self-healing, elasticity, remoldability, and degradability

Combining different reversibly connecting mechanisms in a single system constitutes an efficient method to multi-functionalize dynamic polymer materials but normally requires complicated molecular designs. Herein we report a class of omni-dynamic silicone elastomers that can be directly prepared via simple anionic ring-opening polymerization (AROP) of octamethylcyclotetrasiloxane (D4) with bis(tetramethylammonium)oligodimethyl siloxanediolate (BTMASA) as the bifunctional initiator. The polymerization leads to the formation of telechelic polydimethylsiloxanes (PDMS) that would immediately undergo microphase separation to form elastic products. On the one hand, the tetramethylammonium siloxanolate (TMASA) terminals of the telechelic PDMS aggregate into charged domains serving as dissociative supramolecular crosslinking interactions in the products. On the other hand, the TMASA groups maintain their activities after polymerization and can catalyze associative chain exchange reactions among PDMS chains. Such a unique structure endows the silicone elastomers with good solubility in solvents like tetrahydrofuran (THF), appealing mechanical properties (elastic, stretchable, tough), and excellent degradability. In this system, the BTMASA plays multiple roles, including an initiator for AROP, a building block for supramolecular crosslinking, and a catalyst for chain exchange. We believe such a one-to-three concept will open a new direction for the design of novel dynamic polymer materials.

Mussel-Inspired Multiloop Polyethers for Antifouling Surfaces.

Despite the widespread use of polymers for antifouling coatings, the effect of the polymeric topology on the antifouling property has been largely underexplored. Unlike conventional brush polymers, a loop conformation often leads to strong steric stabilization of surfaces and antifouling and lubricating behavior owing to the large excluded volume and reduced chain ends. Herein, we present highly antifouling multiloop polyethers functionalized with a mussel-inspired catechol moiety with varying loop dimensions. Specifically, a series of polyethers with varying catechol contents were synthesized via anionic ring-opening polymerization by using triethylene glycol glycidyl ether (TEG) and catechol-acetonide glycidyl ether (CAG) to afford poly(TEG-co-CAG)n. The versatile adsorption and antifouling effects of multiloop polyethers were evaluated using atomic force microscopy and a quartz crystal microbalance with dissipation. Furthermore, the crucial role of the loop dimension in the antifouling properties was analyzed via a surface force apparatus and a cell attachment assay. This study provides a new platform for the development of versatile antifouling polymers with varying topologies.

Organocatalyzed Synthesis and Degradation of Functionalized Poly(4-allyloxymethyl-β-propiolactone)s

The chemical synthesis of degradable poly(β-hydroxyalkanoate) (PHA) produced by microorganisms allows the control of the solubility, crystallinity, hydrophobicity, degradability, thermal, and mechanical properties by introducing functionality on the side chain. Herein, we synthesized a PHA derivative containing a pendant allyl group via the anionic ring-opening polymerization of a 4-allyloxymethyl-β-propiolactone (AMPL) monomer, which was prepared via the carbonylation of allyl glycidyl ether. The AMPL monomer was subjected to various organocatalysts in bulk to yield poly(4-allyloxymethyl-β-propiolactone) (PAMPL) with controllable molecular weight and dispersity. The prepared PAMPL polymers were characterized via 1H and 13C NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) analyses. A photoactivated thiol–ene reaction allowed the postpolymerization modification of PAMPLs with varying substituents. Functionalized PAMPL polymers degraded under chemical and thermal conditions, and importantly, cross-linked PAMPL films degraded during exposure to soil and seawater under a wide range of degradation kinetics. This study provides the future potentials of the chemically synthesized and functionalized PHA for replacing conventional petroleum-derived polymers.

Facile Access to Functionalized Poly(thioether)s via Anionic Ring-Opening Decarboxylative Polymerization of COS-Sourced α-Alkylidene Cyclic Thiocarbonates

Herein, a series of α-alkylidene cyclic thiocarbonates (αCTCs) have been selectively synthesized from carbonyl sulfide (COS) and primary propargylic alcohols and polymerized via anionic ring-openin...

Sulfanion-initiated open-vessel anionic ring-opening polymerization (AROP) of N-sulfonyl aziridines

Sulfanion-initiated open-vessel anionic ring-opening polymerization (AROP) of N-sulfonyl aziridines

Polyether-Based Diblock Terpolymer Micelles with Pendant Anthracene Units-Light-Induced Crosslinking and Limitations Regarding Reversibility.

The synthesis of 9-methylanthracenyl glycidyl ether (AnthGE) as a crosslinkable monomer that can be applied in anionic ring opening polymerization is reported. Diblock terpolymers of the composition methoxy-poly(ethylene oxide)-block-poly(2-ethylhexyl glycidyl ether-co-9-methylanthracenyl glycidyl ether) (mPEO-b-P(EHGE-co-AnthGE) with 10 to 24 wt% of AnthGE are synthesized and characterized. Their micellization behavior, as well as their light-induced core-crosslinking via irradiation with UV light (λ = 365nm) is studied. The results are compared with studies on the dimerization, and the dimer cleavage via irradiation with UV-C light (λ = 254nm), of the same diblock terpolymer in organic solution, and the small-molecule model compound 9-methoxymethylanthracene. Differences in 1 H NMR spectra of the crosslinked or dimerized compounds and reaction kinetics of the dimerization reactions under different conditions suggest possible side reactions for the case of the core-crosslinking of micelles in aqueous solution. These side reactions limit the reversibility of the anthracene dimerization reaction in aqueous solutions, even if the anthracene molecule is encapsulated within the hydrophobic core of a polymeric micelle.

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.

Star-Shaped Poly(furfuryl glycidyl ether)-Block-Poly(glyceryl glycerol ether) as an Efficient Agent for the Enhancement of Nifuratel Solubility and for the Formation of Injectable and Self-Healable Hydrogel Platforms for the Gynaecological Therapies.

In this paper, we present novel well-defined unimolecular micelles constructed a on poly(furfuryl glycidyl ether) core and highly hydrophilic poly(glyceryl glycerol ether) shell, PFGE-b-PGGE. The copolymer was synthesized via anionic ring-opening polymerization of furfuryl glycidyl ether and (1,2-isopropylidene glyceryl) glycidyl ether, respectively. MTT assay revealed that the copolymer is non-cytotoxic against human cervical cancer endothelial (HeLa) cells. The copolymer thanks to furan moieties in its core is capable of encapsulation of nifuratel, a hydrophobic nitrofuran derivative, which is a drug applied in the gynaecology therapies that shows a broad antimicroorganism spectrum. The study shows high loading capacity of the copolymer, i.e., 146 mg of nifuratel per 1 g of copolymer. The load unimolecular micelles were characterized using DLS and TEM microscopy and compared with the reference glyceryl glycerol ether homopolymer sample. The presence of numerous 1,2-diol moieties in the shell of PFGE-b-PGG macromolecules enabled the formation of reversible cross-links with 2-acrylamidephenylboronic acid-based polyacrylamide. The obtained hydrogels were both injectable and self-healable, which was confirmed with a rheological study.

Synthesis and Application of New Multibranched–Linear–Multibranched Fluorinated Copolymer as Demulsifiers for Naphthenic Compounds Stabilized Emulsion

• A series of novel fluorinated copolymer with multibranched–linear–multibranched structure were prepared. • The demulsification process of the copolymers in naphthenic acids and sodium naphthenates stabilized emulsions were evaluated. • The relationship between polymer structure and demulsification performance was discussed. To deal with the demulsification of emulsion stabilized by naphthenic compounds, a series of multibranched–linear–multibranched (MLM) copolymer were designed and synthesized. The hydrophilic core with MLM structure is constructed by anionic ring-opening multibranching polymerization (ROMBP) of glycidol with poly (ethylene glycol). The amphophobic arms are grafted by atom transfer radical polymerization (ATRP) of 2, 2, 2-trifluoroethyl methacrylate (TFEMA). The demulsification performance of the MLM copolymer in n-octane/water emulsion stabilized by naphthenic acids (NAs) and sodium naphthenates (Na-NAs) were evaluated. The influences of copolymer dosage, temperature and Na-NAs/NAs ratio on the demulsification efficiency were investigated in detail. Compared with the blank sample settled for 90 min, the fluorinated MLM copolymer with medium HLB value promoted the demulsification efficiency from 50% to 92%. By analyzing the correlation between the polymer structure and demulsification performance, it can be considered that the PEG segment improved the low solubility of the fluorinated copolymer caused by the solvophobic nature of fluorinated groups. The amphophobic effect of the fluorinated group not only accelerates the diffusion process of polymer molecules from the bulk to the interface, but also reduces the rigidity of the interface film by repelling the original interface active material, and produces effective demulsification.

Dielectric elastomer sensor with high dielectric constant and capacitive strain sensing properties by designing polar-nonpolar fluorosilicone multiblock copolymers and introducing poly(dopamine) modified CNTs

The application of silicone rubber as dielectric elastomer sensor is limited by its poor strain sensing performance because of low dielectric constant (ε′). In this study, we designed and fabricated a fluorosilicone dielectric composite with high ε′ and capacitive strain sensing performance by designing polar-nonpolar multiblock fluorosilicone copolymer and introducing poly(dopamine)-modified nanotubes (CNT-PDA). Firstly, a polar (bis(3-aminopropyl)-terminated poly(3,3,3-trifluoropropyl) methylsiloxane (H2N-PFMS-NH2)) and a nonpolar (bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (H2N-PDMS-NH2)) silicone oligomers were synthesized by anionic ring opening polymerization. Then, a series of PFMS/PDMS multiblock copolymer were synthesized through a one-pot polycondensation reaction between isocyanate groups from methylene-bis(4-cyclohexylisocyanate) and amino groups from the as prepared H2N-PFMS-NH2 and H2N-PDMS-NH2. The hydrogen bonds between urea groups act as physical crosslinking points on the multiblock copolymer. The H2N-PFMS-NH2 chains with polar CF3 groups contribute to high dipole polarizability and thus a high ε’. A strong interfacial adhesion between CNT-PDA and the multiblock copolymer was obtained by hydrogen bonding between the urea groups of the multiblock copolymer and CNT-PDA, resulting in strong interfacial polarizability. The as-prepared composite exhibits a ε′ of about 86.7 at 103 Hz and a capacitance change (ΔC) of about 0.91 nF at 200% strain at only 0.3 vol% of CNT-PDA, which was increased by 23.8 and 8.1 times, respectively, compared with the CNT-PDA/commercial nonpolar reference SiR composites. The largely improved ε′ and capacitive strain sensing properties are mainly attributed to the synergistic polarization effect, which was discussed based on impedance analysis and calculating the contribution of each composition on ε’ and ΔC.

Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization.

Increasingly precise control of polymer architectures generated by “Living” Anionic Ring-Opening Polymerization (Living AROP) is leading to a broad range of commercial advanced material applications, particularly in the area of siloxane macromers. While academic reports on such materials remain sparse, a significant portion of the global population interacts with them on a daily basis—in applications including medical devices, microelectronics, food packaging, synthetic leather, release coatings, and pigment dispersions. The primary driver of this increased utilization of siloxane macromers is their ability to incorporate the properties of silicones into organic structures in a balanced manner. Compared to organic polymers, the differentiating properties of silicones—low Tg, hydrophobicity, low surface energy, and high free molal space—logically lend themselves to applications in which low modulus, release, permeability to oxygen and moisture, and tactile interaction are desired. However, their mechanical, structural and processing properties have until recently precluded practical applications. This review presents applications of “Living” AROP derived polymers from the perspective of historical technology development. Applications in which products are produced on a commercial scale—defined as not only offered for sale, but sold on a recurrent basis—are emphasized. Hybrid polymers with intriguing nanoscale morphology and potential applications in photoresist, microcontact printing, biomimetic soft materials, and liquid crystals are also discussed. Previously unreported work by the authors is provided in the context of this review.

Synthesis and intracellular drug delivery applications of hyperbranched polymers functionalized β-cyclodextrin

Hyperbranched polymers have been extensively investigated for different application for their specific structure, functional groups and biocompatibility. Herein, we reported synthesis of hyperbranched polymers (named as β-CD-HPG-EBA-HH) using β-cyclodextrin (β-CD) as the precursor through anionic ring-opening polymerization. The hydrazide groups were further introduced onto functionalized β-CD, that could form dynamic hydrazone bonds with anticancer agent epirubicin (EPI). After mixing β-CD-HPG-EBA-HH with EPI, drug-containing polymeric nanoparticles with excellent water dispersibility can be obtained. The drug loading efficiency could reach to about 42.5% and the drug release shows pH dependent behavior. Biological assays indicated that β-CD-HPG-EBA-HH-EPI complexes could enter into cells via endocytosis and maintained desirable antitumor effects. Based on this method, many other functional materials could also be fabricated and potentially applied in various biomedical fields because of their unique dendritic structure of hyperbranched polymers and inclusion properties of β-CD.

Alternating copolymerization of bio-based N-acetylhomocysteine thiolactone and epoxides

The anionic ring-opening polymerizations (AROP) of bio-based N-acetyl homocysteine thiolactone (NHTL) and different epoxides were carried out using benzyl alcohol and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) as initiating system. This polymerization is a rare example of AROP in the presence of an acidic moiety (acetamido group). Well-defined alternating poly(ester-alt-sulfide)s are obtained with number-average molar masses Mn ranging from 1.7 to 13.0 kg mol−1 and dispersities as low as 1.14. The presence of one acetamido function in the lateral group on each repeating unit of the copolymers derived from NHTL results in very significant increases (up to 94 °C) of the glass transition temperature Tg compared to similar poly(ester-alt-sulfide) derived from petro-based γ-butyrothiolactone (BTL). These functional poly(NHTL-alt-epoxide)s are valuable structures with numerous potential applications due to the presence in each repeating unit of one cleavable ester group and one redox-sensitive thioether group.

Synthesis of functional and architectural polyethers via the anionic ring-opening polymerization of epoxide monomers using a phosphazene base catalyst

This focused review provides an overview of our recent work and related research regarding the precise anionic ring-opening polymerization (AROP) of substituted epoxides, including alkylene oxides, glycidyl ethers, and glycidyl amines, using t-Bu-P4 as the phosphazene base catalyst to produce functional polyethers, such as homopolymers, block copolymers (BCPs), and topologically unique polymers. First, the fundamental aspects and applicable monomer scope of t-Bu-P4-catalyzed AROP are discussed. Subsequently, the applications of well-defined polyethers prepared via t-Bu-P4-catalyzed AROP to develop functional materials, such as thermoresponsive polymers and Li+ conducting polymers, are discussed. Finally, the utility of t-Bu-P4-catalyzed AROP in the precise synthesis of star-shaped, cyclic, and multicyclic polymers is presented. Overall, we intend to illustrate the exploitable utility of the present polymerization system for fundamental and advanced polymer research. This focused review provides an overview of our recent work and related research regarding the precise anionic ring-opening polymerization (AROP) of substituted epoxides, including alkylene oxides, glycidyl ethers, and glycidyl amines, using t-Bu-P4 as the phosphazene base catalyst to produce functional polyethers, such as homopolymers, block copolymers (BCPs), and topologically unique polymers. First, the fundamental aspects and applicable monomer scope of the t-Bu-P4-catalyzed AROP are discussed. Subsequently, the applications of the AROP system for synthesizing functional materials and architectural polymers are presented.

PH-Responsive Amphiphilic Polyether Micelles with Superior Stability for Smart Drug Delivery.

Despite widespread interest in the amphiphilic polymeric micelles for drug delivery systems, it is highly desirable to achieve high loading capacity and high efficiency to reduce the side effects of therapeutic agents while maximizing their efficacy. Here, we present a novel hydrophobic epoxide monomer, cyclohexyloxy ethyl glycidyl ether (CHGE), containing an acetal group as a pH-responsive cleavable linkage. A series of its homopolymers, poly(cyclohexyloxy ethyl glycidyl ether)s (PCHGEs), and block copolymers, poly(ethylene glycol)-block-poly(cyclohexyloxy ethyl glycidyl ether)s (mPEG-b-PCHGE), were synthesized via anionic ring-opening polymerization in a controlled manner. Subsequently, the self-assembled polymeric micelles of mPEG-b-PCHGE demonstrated high loading capacity, excellent stability in biological media, tunable release efficiency, and high cell viability. Importantly, quantum mechanical calculations performed by considering prolonged hydrolysis of the acetal group in CHGE indicated that the CHGE monomer had higher hydrophobicity than three other functional epoxide monomer analogues developed. Furthermore, the preferential cellular uptake and in vivo therapeutic efficacy confirmed the enhanced stability and the pH-responsive degradation of the amphiphilic block copolymer micelles. This study provides a new platform for the development of versatile smart polymeric drug delivery systems with high loading efficiency and tailorable release profiles.

Magnetically Responsive PA6 Microparticles with Immobilized Laccase Show High Catalytic Efficiency in the Enzymatic Treatment of Catechol

Herewith we report the first attempt towards non-covalent immobilization of Trametes versicolor laccase on neat and magnetically responsive highly porous polyamide 6 (PA6) microparticles and their application for catechol oxidation. Four polyamide supports, namely neat PA6 and such carrying Fe, phosphate-coated Fe and Fe3O4 cores were synthesized in suspension by activated anionic ring-opening polymerization (AAROP) of ε-caprolactam (ECL). Enzyme adsorption efficiency up to 92% was achieved in the immobilization process. All empty supports and PA6 laccase complexes were characterized by spectral and synchrotron WAXS/SAXS analyses. The activity of the immobilized laccase was evaluated using 2,2’-Azino-bis-(3- ethylbenzothiazoline-6-sulfonic acid (ABTS) and compared to the native enzyme. The PA6 laccase conjugates displayed up to 105% relative activity at room temperature, pH 4, 40 °C and 20 mM ionic strength (citrate buffer). The kinetic parameters of the ABTS oxidation were also determined. The reusability of the immobilized laccase-conjugates was proven for five consecutive oxidation cycles of catechol.

Solvent-Free Glycidyl Carbamate Oligomerization and Solvent Affinity of Oligomers

Polyglycerols are a class of multifunctional polymers obtained from the polymerization of glycidol and its derivatives. Unlike poly(ethylene glycol) (PEG), which is the most common polyether, polyglycerols can exhibit many functionalities on their side chains and can be obtained from renewable resources, mainly glycerol. Hereby, this study will focus on glycidyl carbamates, a new class of monomers readily available from glycerol carbonate, which combines the chemical functionalities of both glycidol and urethane. The polymerization of these glycidyl ethers directly leads to linear poly(glycidyl carbamates), thus avoiding several protection and deprotection steps of the monomers or polymers. This study hence gives a first approach to glycidyl carbamate polymerization. Commonly used initiators in anionic ring-opening polymerization (alkali metal alkoxides) lead to ill-defined compounds after full conversion of the monomers, whereas pyridine derivative initiators lead to oligomers whose structures could be thoroughly described. The results suggest that low basicity and high nucleophilicity are the most suitable conditions to polymerize glycidyl carbamates because of the sensitivity of the urethane moiety. Additionally, a study of the obtained poly(glycidyl carbamates) affinity toward the solvent has been conducted to further describe the properties of these novel original polyethers.

Core-Cross-linked Fluorescent Worm-Like Micelles for Glucose-Mediated Drug Delivery.

We herein report the fabrication of core-crosslinked, fluorescent, and surface-functionalized worm-like block copolymer micelles as drug delivery vehicles. The polyether-based diblock terpolymer [allyl-poly(ethylene oxide)-block-poly(2-ethylhexyl glycidyl ether-co-furfuryl glycidyl ether)] was synthesized via anionic ring opening polymerization, and self-assembly in water as a selective solvent led to the formation of long filomicelles. Subsequent cross-linking was realized using hydrophobic bismaleimides as well as a designed fluorescent cross-linker for thermally induced Diels-Alder reactions with the furfuryl units incorporated in the hydrophobic block of the diblock terpolymer. As a fluorescent cross-linker, we synthesized and incorporated a cyanine 5-based bismaleimide in the cross-linking process, which can be used for fluorescence tracking of the particles. Furthermore, we covalently attached glucose to the allyl end groups present on the surface of the micelles to investigate active glucose-mediated transport into suitable cell lines. First studies in 2D as well as 3D cell culture models suggest a glucose-dependent uptake of the particles into cells despite their unusually large size compared to other nanoparticle systems used in drug delivery.

Mechanochemical Drug Conjugation via pH-Responsive Imine Linkage for Polyether Prodrug Micelles.

Prodrug-type polymer-drug conjugates based on highly biocompatible functional polyethers are developed through mechanochemical post-polymerization modification. Herein, we design functional epoxide monomers of ethoxyethyl glycidyl ether (EEGE) and azidohexyl glycidyl ether (AHGE) and synthesize diblock copolyethers of PEEGE-b-PAHGE via sequential anionic ring-opening polymerization. Subsequent conversion of the functional monomers to the corresponding hydroxyl and amine groups allows for the preparation of double hydrophilic block copolyethers. Most notably, mechanochemical modification allows for the conjugation of these polymers with a highly hydrophobic and potent anticancer agent, cinnamaldehyde, through an imine linkage. The self-assembly of the resulting polymer-drug conjugates into polymeric micelles is characterized by dynamic light scattering and atomic force microscopy. The pH-responsive cleavage of the imine linkages under acidic conditions leads to the release of cinnamaldehyde with a concomitant disassembly of the polymeric micelles. The superior biocompatibility coupled with the solvent-less mechanochemical conjugation approach provides a convenient means to introduce various therapeutics for smart drug delivery.

TEMPO-Substituted Poly(ethylene sulfide) for Solid-State Electro-Chemical Charge Storage.

A poly(ethylene sulfide) backbone is introduced as the main chain of a radical polymer. Anionic ring-opening polymerization of an episulfide monomer substituted with 2,2,6,6tetramethylpiperidin1oxyl (TEMPO), a robust nitroxide radical, yields the corresponding polythioether. Compared to the traditional poly(ethylene oxide) backbone, the new polymer shows a lower glass transition temperature (-10 °C), and about threefold higher solid-state ionic conductivity. The polythioether is also shown to improve the charge/discharge properties of a cathode in solid-state lithium-ion batteries.