Anionic Ring Opening Research Articles

Alkylene oxide poylmerizations: identification of side reactions and by-products

In this study microwave-assisted anionic ring opening polymerization (ROP) of alkylene oxides is reported. Low molar mass polymers of propylene oxide (PO), butylene oxide (BO) and hexylene oxide (HO) are synthesized by anionic ring opening using various monohydric alcohols as initiators. The monohydric alcohols and lower molar masses allowed for monitoring of different types of possible unwanted by-products and their sources. Liquid chromatography at critical conditions (LCCC) and liquid adsorption chromatography (LAC) are used to determine the presence of oligomers other than targeted. Finally, MALDI-TOF MS of the products have clearly shown the trends and extents of different types of side reactions that are possible in anionic ring opening of alkylene oxides. Propylene oxide is most vulnerable to chain transfer reactions compared to higher alkylene oxide.

The role of particle surface functionality and microstructure development in isothermal and non-isothermal crystallization behavior of polyamide 6/cellulose nanocrystals nanocomposites

Polyamide 6 (PA6)/cellulose nanocrystal (CNC) and aminopropyl triethoxy silane (APS) - modified CNC nanocomposites were prepared by in situ anionic ring opening polymerization and subsequent melt extrusion. The morphological observation of these hybrid systems revealed that the non-modified nanocrystals developed a network-like fibrillar structure while the APS-modified CNCs were finely dispersed mostly as individual whiskers. The isothermal and non-isothermal crystallization kinetics was extensively studied with emphasis on the effects of CNC surface functionality and the subsequent microstructure development on crystallization behavior of these novel nanocomposite systems. The non-modified CNC particles with corresponding fibrillar microstructure were found significantly hinder the crystallization process and spherultic growth of polyamide 6 chains under both isothermal and non-isothermal conditions. On other hand, the surface modified cellulose nanocrystals with improved sub-micron dispersion enhance crystal nucleation in early stages of crystallization while imposing opposite effect in later stages of crystallization resulting in development of relatively smaller defective spherulitic structures.

Conventional Oxyanionic versus Monomer-Activated Anionic Copolymerization of Ethylene Oxide with Glycidyl Ethers: Striking Differences in Reactivity Ratios.

Detailed understanding of the monomer distribution in copolymers is essential to tailor their properties. For the first time, we have been able to utilize in situ 1H NMR spectroscopy to monitor the monomer-activated anionic ring opening copolymerization (AROP) of ethylene oxide (EO) with a glycidyl ether comonomer, namely, ethoxy ethyl glycidyl ether (EEGE). We determine reactivity ratios and draw a direct comparison to conventional oxyanionic ROP. Surprisingly, the respective monomer reactivities differ strongly between the different types of AROP. Under conventional oxyanionic conditions similar monomer reactivities of EO and EEGE are observed, leading to random structures (rEO = 1.05 ± 0.02, rEEGE = 0.94 ± 0.02). Addition of a cation complexing agent (18-crown-6) showed no influence on the relative reactivity of EO and EEGE (rEO = rEEGE = 1.00 ± 0.02). In striking contrast, monomer-activated AROP produces very different monomer reactivities, affording strongly tapered copolymer structures (rEO = 8.00 ± 0.16, rEEGE = 0.125 ± 0.003). These results highlight the importance of understanding reactivity ratios of comonomer pairs under certain polymerization conditions, at the same time demonstrating the ability to generate both random and strongly tapered P(EO-co-EEGE) polyethers by simple one-pot statistical anionic copolymerization. These observations may be generally valid for the copolymerization of EO and glycidyl ethers.

Oxidation-Responsive and "Clickable" Poly(ethylene glycol) via Copolymerization of 2-(Methylthio)ethyl Glycidyl Ether.

Poly(ethylene glycol) (PEG) is a widely used biocompatible polymer. We describe a novel epoxide monomer with methyl-thioether moiety, 2-(methylthio)ethyl glycidyl ether (MTEGE), which enables the synthesis of well-defined thioether-functional poly(ethylene glycol). Random and block mPEG-b-PMTEGE copolymers (Mw/Mn = 1.05-1.17) were obtained via anionic ring opening polymerization (AROP) with molecular weights ranging from 5 600 to 12 000 g·mol(-1). The statistical copolymerization of MTEGE with ethylene oxide results in a random microstructure (rEO = 0.92 ± 0.02 and rMTEGE = 1.06 ± 0.02), which was confirmed by in situ (1)H NMR kinetic studies. The random copolymers are thermoresponsive in aqueous solution, with a wide range of tunable transition temperatures of 88 to 28 °C. In contrast, mPEG-b-PMTEGE block copolymers formed well-defined micelles (Rh ≈ 9-15 nm) in water, studied by detailed light scattering (DLS and SLS). Intriguingly, the thioether moieties of MTEGE can be selectively oxidized into sulfoxide units, leading to full disassembly of the micelles, as confirmed by detection of pure unimers (DLS and SLS). Oxidation-responsive release of encapsulated Nile Red demonstrates the potential of these micelles as redox-responsive nanocarriers. MTT assays showed only minor effects of the thioethers and their oxidized derivatives on the cellular metabolism of WEHI-164 and HEK-293T cell lines (1-1000 μg·mL(-1)). Further, sulfonium PEG polyelectrolytes can be obtained via alkylation or alkoxylation of MTEGE, providing access to a large variety of functional groups at the charged sulfur atom.

Anionic Ring Opening Polymerization of ε-Caprolactone Initiated by Lithium Silanolates

Ring-opening homo- and co-polymerization reactions of ϵ-caprolactone were performed by employing anionic polymerization (high vacuum techniques) and lithium silanolates (LS) as initiators. LS were obtained by reaction between hexamethyl(cyclotrisiloxane) and sec-Bu–Li+, or from living poly(dimethylsiloxanyl)lithium chains. The results indicated that LS are efficient initiators for the ring-opening polymerization of ϵ-caprolactone, providing the respective homogeneous polymers in good yields.

Fabrication and simulation of inverse poly(ferrocenylmethylvinylsilane)/silica opal structures and their optical properties

Photonic crystal structures were fabricated by the formation of periodic arrays of poly(ferrocenylsilane) (PFS) derivations and silica spheres. Here, we present the primary steps of a simulation-driven design of photonic crystal based on PFS as a potentially stimuli-responsive polymer, which can present predesigned color when subjected to the visible light. The poly(ferrocenylmethylvinylsilane) (PFMVS) was synthesized by photolytic anionic ring opening polymerization of methylvinylsila[1]ferrocenophane monomer under controlled condition and monodisperse silica spheres were synthesized by the Stober process. Bare silica opal was prepared by the convective self-assembly process of different sizes of silica spheres on glass substrate followed by infiltration of PFMVS to obtain PFMVS/silica opal and finally removal of the silica spheres by acid washing to attain the inverse PFMVS opal. The particle size of silica spheres along with the refractive indices contrast of different components forming photonic crystal played an important role in obtaining the maximum reflectance wavelength of the desired opal. Photonic crystal prepared by 210, 270, and 330 nm monodisperse silica spheres represents the blue, green, and red color, respectively. Simulation analyses of these opal structures were investigated by using the plane-wave expansion (PWE) method to assess the photonic crystal behavior versus the visible light. According to the simulation results, the photonic crystal structure was designed. The experimental reflectance outcomes of the three opal structures were in good agreement with the simulation analysis.

Synthesis, Characterization, and Evaluation of Petroleum Demulsifiers of Multibranched Block Copolymers

A series of multibranched block copolymers was synthesized by means of anionic ring opening polymerization (AROP) techniques, using different alkoxide salts obtained from molecules that present different numbers of alcohol functions as initiators. Propylene oxide (PO) and ethylene oxide (EO) were polymerized in two steps, with the intent of obtaining multibranched block copolymers (PO/EO) with demulsifying activity in petroleum. The characterization of the polymers was done by means of size exclusion chromatography (SEC), Fourier transformed infrared spectroscopy (FTIR), carbon-13 nuclear magnetic resonance (13C NMR), and thermogravimetric analysis (TGA). A theoretical study by semiempirical AM1/NDDO has been carried out in order to explain the growth of multiple branches from the initiators during the early stages of the anionic polymerization. These simulations revealed complex patterns of polymer growth and increasing polydispersities when initiators with a greater number of active sites were employed ...

Bioactive (co)oligoesters with antioxidant properties – synthesis and structural characterization at the molecular level

Anionic ring opening (co)polymerization of novel β-substituted β-lactones to bioactive (co)oligoesters with antioxidant properties.

Unravelling the binding energetics of a synthetic polymeric heparin antidote with heparin using isothermal titration calorimetry

Unravelling the binding energetics of a synthetic polymeric heparin antidote with heparin using isothermal titration calorimetry

Comparison of the Performance of Two Bifunctional Curing Agents for the Photopolymerization of Epoxy Resins and the Study of the Mechanical Properties of the Obtained Polymers

SummaryThis work presents a new method for photocuring epoxy resins using bifunctional curing agents. These curing agents are tertiary amines functionalized with allyl groups. The tertiary amines can cure the epoxy resins by anionic ring opening polymerization of the oxirane groups while the allyl groups react with an added multifunctional thiol by the thiol–ene mechanism. The results showed that the produced polythioethers enhanced the toughness of the obtained polyethers. The kinetics of photopolymerization and the analysis of mechanical properties of the polymers are presented.

Montmorillonite disperses in amorphous phase of RIM PA6 matrix via anionic ring opening polymerisation

The reaction injection moulding process was employed to prepare montmorillonite (O-MMT)/polyamide 6 (PA6) nanocomposites. O-MMT was functionalised by aminosilane in order to improve the compatibility and decrease the viscosity of caprolactam melts, which swell O-MMT. Small angle X-ray diffraction and transmission electron microscopy results demonstrated that PA6 was sufficiently polymerised via in situ anionic ring opening route at the interlayer of the premodified O-MMT that yields a disordered exfoliated structure. Wide angle X-ray diffraction, polarising optical microscopy and differential scanning calorimetry analysis indicated that the crystallinity of nanocomposites decreased as the loading of O-MMT increased. O-MMT can induce γ-phase crystals and eliminate perfect α-phase crystals into smaller imperfect crystals. The O-MMT primarily disperses in the amorphous phase of RIM PA6 matrix that improves the mechanical properties and heat distortion temperature (HDT) of nanocomposites. For the nanocomposite at 5 wt-% O-MMT, the HDT of neat RIM PA6 was improved from 78 to 163°C.

In situ polymerization to prepare graphene-toughened monomer cast nylon composites

Cetyltrimethylammonium bromide was utilized to modify graphene oxide (GO) which was synthesized by the improved Hummers method. Monomer casting (MC) nylon/modified GO composites were prepared by an in situ anionic ring opening polymerization in this paper. The dispersion of the modified GO in nylon matrix was studied along with the mechanical and thermal properties of the composites. The results showed that the amount of sodium hydroxide had notable effects on the dispersion of the modified GO. Specifically, the incorporation of the modified GO into MC nylon enhanced the crystallization as confirmed by differential scanning calorimetric. The impact strength of the composite was improved by 66 % when 0.2 wt% of the modified GO was incorporated in the nylon matrix. Meanwhile, the tensile strength and flexural strength increased by 5 and 1.4 %, respectively. The results tested by thermal gravimetric analysis indicated that the composites had higher decomposition temperature in comparison with neat MC nylon.

Bioreducible hyperbranched polyglycerols with disulfide linkages: Synthesis and biocompatibility evaluation

ABSTRACTIn this article, we describe the development of multifunctional, water‐soluble hyperbranched polyglycerols containing redox‐sensitive disulfide linkages as a new class of biodegradable polymers. The polymers were synthesized by the anionic ring opening multibranching (co)polymerization of glycidol with an epoxide monomer bearing disulfide groups, 2‐((2‐oxiran‐2‐ylmethoxy)ethyl)disulfanyl) ethan‐1‐ol. Polymerizations were optimized at 65 °C unlike the homopolymerization of glycidol. Both low (5–10 kDa) and high (100 kDa) molecular weight polymers were synthesized in a controlled manner with low polydispersity. The polymers underwent degradation in presence of reducing agents such as tris(2‐carboxyethyl)phosphine, dithiothreitol, and glutathione resulting in low molecular weight fragments with thiol groups. Blood compatibility analysis using coagulation, platelet activation, complement activation and red blood cell lysis assays as well as cell toxicity analysis using MTS assay revealed the excellent biocompatibility of these newly synthesized polymer architectures. All these features make these polymers suitable for intracellular delivery of therapeutic molecules. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2104–2115

Well-defined polymethylene-based block co/terpolymers by combining anthracene/maleimide diels–alder reaction with polyhomologation

Well-defined co/terpolymers of polymethylene (PM) with poly(d,l-lactide) (PLA), polycaprolactone (PCL) and polyethylene glycol (PEG) were synthesized by combining polyhomologation, anionic ring opening polymerization and anthracene(Ant)/maleimide(MI) Diels–Alder reaction.

바이오 기반 ε-Caprolactam과 Morpholinone을 사용하여 중합한 나일론 6-모폴리논 랜덤 공중합체의 제조와 특성평가

Bio-based nylon 6-morpholinone random copolymers were prepared by the anionic ring opening polymerization of e-caprolactam and morpholinone, both of which were prepared from lysine and glucose, respectively. From this work, a new biomass based nylon 6 with improved hydrophilicity was prepared. Optimizing the polymerization condition, copolymer with a viscosity-average molecular weight of 30000 g/mol was prepared, with a yield of 80%. It was possible to improve the hydrophilicity of nylon 6 by its copolymerization with morpholinone. The prepared nylon 6-morpholinone random copolymers were then characterized using several analytical methods such as DSC, TGA, XRD, viscosity measurement with U-shaped glass capillary viscometer and contact angle measurement.

Nonequilibrium Anionic Ring-opening Polymerization of Tetraphenyltetramethylcyclotetrasiloxane (D4Me,Ph) Initiated by Sodium Isopropoxide

GRAPHICAL ABSTRACT

Synthetic strategies for the generation of ABCA' type asymmetric tetrablock terpolymers

We report the synthesis of poly(lactide)-b-poly(styrene)-b-poly(butadiene)-b-poly(lactide) (LSBL′) and poly(styrene)-b-poly(isoprene)-b-poly(ethylene oxide)-b-poly(styrene) (SIOS′) tetrablock terpolymers with asymmetrically sized end blocks. A combination of anionic polymerization and ring opening transesterification polymerization (ROTEP) of (±)-lactide was used to synthesize LSBL′ while SIOS′ was prepared by a combination of anionic polymerization and reversible addition–fragmentation chain transfer (RAFT) polymerization. All intermediate and final products were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) techniques and specific control experiments for the LSBL′ tetrablock confirmed the successful synthesis.

Precise synthesis of undecenyl poly(ethylene oxide) macromonomers as heterofunctional building blocks for the synthesis of linear diblocks or of branched materials

Heterofunctional α-undecenyl-ω-hydroxy poly(ethylene oxide) (PEO) macromonomers could be designed by initiation. For their synthesis via Anionic Ring-Opening Polymerization (AROP) of ethylene oxide, a potassium alcoholate, prepared in situ by reaction of 10-undecene-1-ol with a stoichiometric amount of diphenylmethyl potassium (DPMK), was used. The applicability of the same initiator but in powder form was evaluated for the polymerization of ethylene oxide. This initiator is well-suited for, e.g., automated high-throughput screening approaches by simply weighing in the amount of initiator needed. The macromonomers were characterized by SEC, 1H NMR, MALDI-TOF MS and light scattering. Independent from the applied approach, well-defined heterobifunctional PEO macromonomers could be obtained. Their solution behavior was investigated in water and methanol by Dynamic Light Scattering (DLS) and in water by critical micelle concentration (cmc) measurements. Chemical modification of the hydroxyl end-group by methyl methacrylate or by propargyl bromide could be achieved leading to heterobifunctional PEO macromonomers. These PEOs offer a great potential as building blocks in macromolecular engineering. PI-b-PEO diblocks or comb-shaped PEOs represent typical examples.

Hybrid Organic-Inorganic Nanocomposites Based on Poly(ϵ-Caprolactone)/Polyhedral Oligomeric Silsesquioxane: Synthesis and In Vitro Evaluations

Hybrid poly(ϵ-caprolactone) (PCL) containing nanocomposites and non-hybrid linear PCL diols were synthesized by anionic ring opening polymerization of ϵ-caprolactone on a POSS or ethylene glycol central blocks, respectively. Monolith scaffolds were then fabricated from the hybrid nanocomposites and non-hybrid linear PCL diols via non-solvent induced phase separation technique. The effects of inclusion of POSS nanocage in the polymer chain structure on specific surface area and pore size of the scaffolds was investigated by multipoint BET method. This perfect scrutiny will introduce an excellent nanoparticle pendent to the PCL chains to promote the in vitro properties of the implants potentially applicable in tissue engineering.

Preparation, chemical, and thermal characterization of nylon 4/6 copolymers by anionic ring opening polymerization of 2-Pyrrolidone and ε-Caprolactam

Nylon 4/6 copolymers based on 2-pyrrolidone (C4) and e-caprolactam (C6) were synthesized and characterized as part of ongoing efforts to develop thermally stable, melt-processable 2-pyrrolidone (C4) based Nylons. Copolymers of various compositions were synthesized at between 50 and 100 °C via the anionic ring opening polymerization of C4 and C6 using a potassium tert-butoxide catalyst and a benzoyl chloride initiator. The polymers were characterized by NMR spectroscopy, DSC, TGA, GPC, intrinsic viscosity measurements, and X-ray scattering (SAXS and WAXS). Their chemical compositions and sequence distributions were obtained by 1H- and 13C-NMR spectroscopies, respectively. X-ray scattering was used to investigate the lamellar morphologies and the crystal structures of solvent cast films of the copolymers. WAXS revealed the presence of α-phase crystals in the copolymers. TGA data coupled with molecular weight and sequence distribution information indicated that the polymers’ thermal stability depended on both their chemical composition and their sequence distribution.