Anionic Ring-opening Copolymerization Research Articles

Complete depolymerization of poly(ester-alt-thioether)s under mild conditions into AB functional monomers

Full depolymerization of functional poly(ester-alt-thioether)s by methanolysis at room temperature and subsequent step-growth repolymerization.

Closed-loop chemically recyclable covalent adaptive networks derived from elementary sulfur.

The development of sulfur-rich polymers derived from elementary sulfur provides an innovative approach to industrial waste valorization. Despite significant advancements in polymerization techniques and promising applications beyond traditional polymers, polysulfide networks are still primarily stabilized by diene crosslinkers, forming robust C-S bonds that hinder the degradation of sulfur-based polymers. In this study, the anionic ring-opening copolymerization of chemically homologous S8 and cyclic disulfides was explored to yield robust sulfur-rich copolymers with high molecular weight. The incorporation of polysulfide segments not only efficiently activated the crosslinked networks for excellent reprocessability and mechanical adaptability but also endowed the resulting copolymer with high optical transparency in the near-infrared region. More importantly, the dynamic disulfide crosslinking sites promoted the chemical closed-loop recyclability of the polysulfide networks via reversible S-S cleavage. This innovative inverse vulcanization strategy utilizing dynamic disulfide crosslinkers offers a promising pathway for the advanced applications and upcycling of high-performance sulfur-rich polymers.

Poly(dimethyl-diphenyl-imide)siloxane/phenolic-based double network hybrid resin coatings for ablation thermal protection

Organic-inorganic hybridization is an important way to improve ablation resistance of phenolic resin coatings (PR). However, long molecular chain silicone by copolymerization is less compatible with PR and hybrid resin will form sea-island phase, which is not favorable for further improvement of ablation resistance. Therefore, how to achieve a combination of long chain and compatibility is a major challenge. In this work, the poly(dimethyl-diphenyl-imide)siloxane (PMPI) containing imide and phenyl was synthesized by anionic ring-opening polymerization and copolymerization. Then, it was hybridized with PR to obtain PMPI/PR-based double network hybrid resin coatings with nano co-continuous phase. The oxyacetylene ablation test suggests that the resin coatings with medium phenyl content has the lowest linear ablation rate (0.055 mm/s), which is 74 % lower compared to PR (0.21 mm/s). In addition, the mechanism by which PMPI enhances ablation resistance is discussed. This work provides a promising approach to develop higher performance ablative-resistant resin coatings.

In Situ Kinetics Reveal the Influence of Solvents and Monomer Structure on the Anionic Ring‐Opening Copolymerization of Epoxides

AbstractIn‐depth understanding of copolymerization kinetics and the resulting polymer microstructure is crucial for the design of materials with well‐defined properties. Further, insights regarding the impact of solvents on copolymerization kinetics allows for precisely tuned materials. In this regard, in situ 1H NMR spectroscopy enables precise monitoring of the living anionic ring‐opening copolymerization (AROP) of ethylene oxide (EO) with the glycidyl ethers allyl glycidyl ether (AGE) and ethoxy vinyl glycidyl ether (EVGE), respectively. Determination of reactivity ratios reveals slightly higher reactivity of both glycidyl ethers compared to EO, emphasizing a pronounced counterion chelation effect by glycidyl ethers in AROP. Implementation of density functional theory (DFT) calculations further illustrates the complexation capability of ether‐containing side groups in glycidyl ethers, in analogy to crown ethers (“crown ether effect”). Investigation of the copolymerization in i) THF‐d8 and ii) DMSO‐d6 shows an increasing disparity of reactivity ratios for both glycidyl ethers compared to EO, clearly related to decreasing solvent polarity.

Using Triethylborane to Manipulate Reactivity Ratios in Epoxide-Anhydride Copolymerization: Application to the Synthesis of Polyethers with Degradable Ester Functions.

The anionic ring-opening copolymerization (ROCOP) of epoxides, namely of ethylene oxide (EO), with anhydrides (AH) generally produces strictly alternating copolymers. With triethylborane (TEB)-assisted ROCOP of EO with AH, statistical copolymers of high molar mass including ether and ester units could be obtained. In the presence of TEB, the reactivity ratio of EO (rEO), which is normally equal to 0 in its absence, could be progressively raised to values lower than 1 or higher than 1. Conditions were even found to obtain rEO equal or close to 1. Samples of P(EO-co-ester) with minimal compositional drift could be synthesized; upon basic degradation of their ester linkages, these samples afforded poly(ethylene oxide) (PEO) diol samples of narrow molar mass distribution. In other cases where rEO were lower or higher than 1, the PEO diol samples eventually isolated after degradation exhibited a broader distribution of molar masses because of the compositional drift of initial P(EO-co-ester) samples.

RNA-Inspired and Accelerated Degradation of Polylactide in Seawater.

Marine plastic pollution is a worldwide challenge making advances in the field of biodegradable polymer materials necessary. Polylactide (PLA) is a promising biodegradable polymer used in various applications; however, it has a very slow seawater degradability. Herein, we present the first library of PLA derivatives with incorporated “breaking points” to vary the speed of degradation in artificial seawater from years to weeks. Inspired by the fast hydrolysis of ribonucleic acid (RNA) by intramolecular transesterification, we installed phosphoester breaking points with similar hydroxyethoxy side groups into the PLA backbone to accelerate chain scission. Sequence-controlled anionic ring-opening copolymerization of lactide and a cyclic phosphate allowed PLA to be prepared with controlled distances of the breaking points along the backbone. This general concept could be translated to other slowly degrading polymers and thereby be able to prevent additional marine pollution in the future.

New way of anionic ring-opening copolymerization of \u03b2-butyrolactone and \u03b5-caprolactone: determination of the reaction course

Poly(ε-caprolactone)-block-poly(β-butyrolactone) copolymers were prepared in two-step synthesis. Firstly, poly(ε-caprolactone) (PCL) was obtained by anionic ring-opening polymerization of CL initiated with anhydrous KOH activated 12-crown-4 cation complexing agent. Reaction was carried out in tetrahydrofuran solution and argon atmosphere at room temperature. Then, β-butyrolactone (BL) and 18-crown-6 were added to the system, resulting in PCL-block-PBL copolymer, which contains after methylation hydroxyl starting group and methyl ester end group. The main product was contaminated with PCL and PBL homopolymers formed in a side reactions. 13C NMR technique was used for determination of chemical structure of polymers obtained. The course of the studied processes was proposed. MALDI-TOF technique was used to reveal the macromolecules’ architecture where several series were found. The identified series shown that mainly copolymeric macromolecules were formed with scare contribution of homopolymeric polybutyrolactone with trans-crotonate starting groups and polycaprolactone, which is congruent with the proposed reaction mechanism. Moreover, critical approach concerning previously reported PCL-block-PBL copolymer synthesis by use of NaH as initiator was also presented.

"Dumb" pH-Independent and Biocompatible Hydrogels Formed by Copolymers of Long-Chain Alkyl Glycidyl Ethers and Ethylene Oxide.

The formation and rheological properties of hydrogels based on amphiphilic ABA triblock polyether copolymers are described, relying solely on the hydrophobic interaction of long-chain alkyl glycidyl ether (AlkGE)- based A-blocks that are combined with a hydrophilic poly(ethylene glycol) (PEG) midblock. Via anionic ring-opening copolymerization (AROP), ethylene oxide (EO) and long-chain alkyl glycidyl ethers (AlkGEs) were copolymerized, using deprotonated poly(ethylene glycol) (PEG) macroinitiators (Mn of 10, 20 kg mol-1). The polymerization afforded amphiphilic ABA triblock copolymers with molar masses in the range of 21-32 kg mol-1 and dispersities (Đ) of Đ = 1.07-1.17. Kinetic studies revealed random copolymerization of EO and AlkGE, indicating random spacing of the hydrophobic AlkGE units by polar EO units. Following this approach, the hydrophobicity of the apolar blocks of amphiphilic ABA triblock polyethers can be tailored. Detailed rheological measurements confirmed the successful formation of hydrogels at different pH values as a consequence of nonpolar interactions and alkyl chain crystallization. Hydrogel formation was also observed at different ionic strengths (i.e., varied salt concentration), based on the hydrophobic aggregates. This behavior is in contrast to other often-used supramolecular cross-linking strategies, such as Coulomb interactions, complexation, or hydrogen bonding. Micro-differential scanning calorimetry (μ-DSC) measurements of the hydrogels revealed crystalline hydrophobic domains with melting temperatures in the physiological temperature range. In 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide (MTT) assays, diblock copolymers possessing structural analogy to the triblock copolymers were studied to assess the general cytotoxicity of amphiphilic polyethers bearing long alkyl chains at the polyether backbone, using splenic immune cells. At intermediate polymer concentrations, no cytotoxic effects were observed. This indicates that long-chain alkyl glycidyl ethers are promising for the introduction of highly hydrophobic as well as crystalline motifs at the polyether backbone in hydrogels for biomedical purposes.

Nonionic surfactants based on amphiphilic polyphosphonate copolymers prepared via anionic ring-opening copolymerization

Nonionic surfactants are omnipresent in our everyday life and used in modern drug delivery. The synthesis of degradable surfactants is crucial to simplify the purification of final products or reduce polymer waste. Here, we present the synthesis of a new amphiphilic 2-n-dodecyl-2-oxo-1,3,2-dioxaphospholane, a monomer for the anionic ring-opening polymerization towards poly(ethylene alkyl phosphonate)s. The novel monomer is copolymerized with 2-ethyl-2-oxo-1,3,2-dioxaphospholane to produce well-defined, water-soluble, and surface-active copolymers with molar masses up to 18,400 g mol−1, dispersities between 1.2 and 1.3, and critical aggregation concentrations below 0.07 g L−1. The reactivity ratios of the two comonomers indicate a random monomer incorporation with r1 = 1.46 and r2 = 0.68. Adjusting the comonomer ratio changes the amphiphilicity of the resulting copolymers. They are applied in the free radical miniemulsion polymerization to produce well-defined nanoparticles. The intrinsic hydrolytic degradability of polyphosphonates makes these polymers interesting candidates for use in, emulsion stabilization for drug delivery or cosmetics.

Hyperbranched Poly(ether-siloxane)s Containing Ammonium Groups: Synthesis, Characterization and Catalytic Activity.

In this article we report an easy synthetic route towards hyperbranched polyglycerols (Amm-HBPGs) containing trimethylammonium groups and siloxane or hydroxyl end-groups. Siloxane derivatives of Amm-HBPGs were synthesized in an efficient five-step procedure including an anionic ring opening copolymerization of the phthalimide-epoxy monomer with glycidol, followed by reactions with allyl bromide, hydrosililation with hydrogenheptamethyltrisiloxane, hydrazinolysis of phthalimide groups and quaternization of resulting amine groups with methyl iodide. Hydroxyl derivatives were obtained by quaternization of previously reported aminated HBPG’s with methyl iodide. Polymeric products were characterized using various NMR techniques, FTIR, and elemental analysis. Both Amm-HBPGs were shown to be effective in catalysis of addition of CO2 to oxirane. The hydrophilic catalysts showed higher efficiency but synthesis of ethylene carbonate was accompanied by formation of small amounts of ethylene glycol. The siloxane-containing catalyst was easily separable from reaction mixture showing high potential in the process of converting carbon dioxide into valuable chemical raw materials.

γ-Butyrolactone Copolymerization with the Well-Documented Polymer Drug Carrier Poly(ethylene oxide)-block-poly(ε-caprolactone) to Fine-Tune Its Biorelevant Properties.

Polymeric drug carriers exhibit excellent properties that advance drug delivery systems. In particular, carriers based on poly(ethylene oxide)-block-poly(ε-caprolactone) are very useful in pharmacokinetics. In addition to their proven biocompatibility, there are several requirements for the efficacy of the polymeric drug carriers after internalization, e.g., nanoparticle behavior, cellular uptake, the rate of degradation, and cellular localization. The introduction of γ-butyrolactone units into the hydrophobic block enables the tuning of the abovementioned properties over a wide range. In this study, a relatively high content of γ-butyrolactone units with a reasonable yield of ≈60% is achieved by anionic ring-opening copolymerization using 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a very efficient catalyst in the nonpolar environment of toluene with an incorporated γ-butyrolactone content of ≈30%. The content of γ-butyrolactone units can be easily modulated according to the feed ratio of the monomers. This method enables control over the rate of degradation so that when the content of γ-butyrolactone increases, the rate of degradation increases. These findings broaden the application possibilities of polyester-polyether-based nanoparticles for biomedical applications, such as drug delivery systems.

Acid-Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5.

PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (M n) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG‐co‐isoEPB)MA copolymer and the hydrogels showed pH‐dependent, rapid hydrolysis at pH 5–6 and long‐term storage stability at neutral pH (pH 7.4). By designing the degree of polymerization and content of degradable vinyl ether groups, the release time of an entrapped protein OVA‐Alexa488 can be tailored from a few hours to several days (hydrolysis half‐life time t 1/2 at pH 5: 13 h to 51 h).

Design and synthesis of phenyl silicone rubber with functional epoxy groups through anionic copolymerization and subsequent epoxidation

In this paper, we have developed epoxidized phenyl silicone rubber (EMVPQ) with good oil and radiation resistance by anionic ring-opening copolymerization and further epoxidation modification. Silicone rubbers with both phenyl and epoxy groups were firstly synthesized and main properties of the material were characterized. When the phenyl content in EMVPQ was increased from 5% to 20%, the damping loss peak shifted to the high temperature by 36 °C and the effective damping temperature range was widened by 3 °C. The tensile strength of EMVPQ with 20% phenyl content did not change before and after irradiation. When the epoxy content is only 13%, the EMVPQ retained mechanical properties after immersion at 25 °C or 100 °C for 72 h, but a commercial sample substantially lost its mechanical properties. This work not only promotes the research of epoxidized phenyl silicone rubber, but also opens an effective way for the preparation of high-performance aerospace materials.

Monomer-activated Copolymerization of Ethylene Oxide and Epichlorohydrin: In Situ Kinetics Evidences Tapered Block Copolymer Formation

The monomer-activated anionic ring-opening copolymerization (AROP) of ethylene oxide (EO) and epichlorohydrin (ECH) using tetraoctylammonium bromide as an initiator and triisobutylaluminum (i-Bu3Al) as an activator was studied. The properties of the copolymers as well as the microstructure have been analyzed in detail via an in situ NMR kinetics study. The statistical copolymers exhibited molecular weights ranging from 2350 gmol−1 to 38000 gmol−1 (measured by SEC, PEG-standards) and moderate dispersities of 1.27–1.44. The thermal property tests revealed both a glass transition and melting for all copolymers, supporting a block-like nature. Applying in situ NMR kinetic measurements, the reactivity ratios of EO and ECH were determined to be strongly disparate, i.e., rEO = 9.2 and rECH = 0.10. This shows that the simple one-pot statistical anionic copolymerization of EO and ECH via the monomer-activated AROP resulted in the formation of strongly tapered, block-like structures. Furthermore, post-polymerization functionalization of the reactive chloromethyl groups by nucleophilic displacement was investigated for the copolymers. Copolymerization of EO and ECH offers a broad platform for further functionalization and therefore the possibility to prepare a variety of multifunctional PEGs.

Facile Synthesis of Functional Poly(ε-caprolactone) via Janus Polymerization

Functionalized aliphatic polyesters attract increasing attentions as biocompatible and biodegradable polymers with broad applications in biological science. In this contribution, we propose a facile and controllable synthetic technique for functional poly(ε- caprolactone) (PCL) via Janus polymerization, which comprises cationic ring-opening copolymerization (ROP) of ε-caprolactone (CL) with 3,3-bis(chloromethyl) oxacyclobutane (CO) and (coordinated) anionic ROP of CL at a single propagating chain by rare earth metal triflates (RE(OTf)3) and propylene oxide, thus generating block copolymers in one step. The compositions of the copolymers of poly(CLb-( CL-r-CO)) can be modulated by various RE(OTf)3. Scandium triflate catalyzes Janus polymerization to yield the copolymers containing the highest CO contents among all the RE(OTf)3 catalysts used with complete conversion of CL. The chlorine in CO repeating units is ready to be transferred into azide group which affords the modification sites to react with 9-ethynyl-9-fluorenol and mPEG-alkyne, respectively, via copper(I)-catalyzed azide-alkyne cycloaddition reaction with quantitative conversions of azides, as confirmed by FTIR analyses. According to NMR and SEC analyses, copolymers (PCC-g-PEG) bearing a homo-PCL block and a PEG-grafted block of poly(CO-co-CL) demonstrate well-defined chemical structures. The investigations on thermal properties reveal the strong phase separation between PCL and PEG blocks. The amphiphilic PCC-g-PEG is able to self-assemble into micelles in aqueous solution while cylindrical and lamellar morphologies are observed in bulk. We provide an efficient protocol to synthesize functional PCL combining onestep Janus polymerization and precise post-polymerization click reaction.

Anionic ring-opening copolymerization of styrene oxide with monosubstituted oxiranes: analysis of composition of prepared new copolyether-diols by MALDI-TOF mass spectrometry

Several new random copolyethers of styrene oxide (SO) and other monosubstituted oxirane as comonomer, i.e., propylene oxide (PO), isopropyl glycidyl ether (IPGE) or allyl glycidyl ether (AGE), were synthesized in THF solution at room temperature. As initiator monopotassium salt of dipropylene glycol activated by 18-crown-6 complexing agent was used. Synthesized copolyether-diols were characterized by SEC, 13C NMR and MALDI-TOF techniques. They were unimodal and had Mn = 3500–4600 and relatively low dispersity (Mw/Mn = 1.16–1.18). Low unsaturation of the products resulted from chain transfer reaction to styrene oxide. Composition of SO/PO-diol, SO/IPGE-diol and SO/AGE-diol copolymers was determined by MALDI-TOF mass spectrometry. Homopolymers were not formed during the processes.Graphical abstract

Ring-Opening Polymerization of Allyl-Functionalized Lactams

Aliphatic polyamides containing pendent allyl groups were prepared by anionic ring-opening copolymerization of e-caprolactam with monomer 1, the substituted lactam 3-(3-propenyl)-2-azepanone. Copolymerization experiments revealed that up to 11 mol % of 1 was integrated successfully into these novel polyamides, which ranged in molecular weight from 27 to 72 kDa. Relative to the well-known commercial polyamide-6 (PA-6), the degree of crystallinity of the copolymers decreased with incorporation of functional monomer. Moreover, the pendent allyl groups afforded rapid access to numerous functional aliphatic polyamides, using photoinitiated thiol–ene chemistry, providing a pathway to cross-linked polyamide films and gels.

Anionic Ring-Opening Polymerization of N-(tolylsulfonyl)azetidines To Produce Linear Poly(trimethylenimine) and Closed-System Block Copolymers.

The anionic ring-opening copolymerization of N-( p-tolylsulfonyl)azetidine ( pTsAzet) and N-( o-tolylsulfonyl)azetidine ( oTsAzet) produces poly( pTsAzet- co- oTsAzet) as a statistical copolymer. The pTsAzet/ oTsAzet copolymerization is living and allows for the synthesis of poly(sulfonylazetidine) of target molecular weights with narrow dispersities. 1H NMR spectroscopy was used to monitor the kinetics of the polymerization and estimate the monomer reactivity ratios. It was found that the reactivity ratios for oTsAzet and pTsAzetat 180 °Care 1.66 and 0.60, respectively. The tosyl groups of p( pTsAzet- co- oTsAzet) were reductively removed to produce linear poly(trimethylenimine) (LPTMI). This represents the first route to LPTMI of controlled molecular weight and low dispersity. Finally, the slow kinetics of the sulfonylazetidine polymerization facilitated the synthesis of a block copolymer without requiring the sequential addition of monomer. Specifically, pTsAzet, oTsAzet, and ( N- p-toluenesulfonyl-2-methylaziridine) ( pTsMAz) were combined in solution. pTsMAz selectively polymerizes to form the first block at moderate temperature. After consumption of pTsMAz, the temperature was increased to copolymerize pTsAzet and oTsAzet and produce the block copolymer p( pTsMAz)- b-p( pTsAzet- co- oTsAzet).

Behavior of poly(ε-caprolactone)-based diblock copolymers in a bulk state and in solution

A series of amphiphilic MOPEO-b-PCL copolymers (DBCs), based on biocompatible methoxypoly(ethylene oxide) with Mn=4.5 kDa and poly(ε-caprolactone) of a variable chain length, was synthesized by an anionic ring-opening block copolymerization. The structural investigations, performed by DSC and WAXS methods, revealed the microphase separation in DBC bulk structure and the existence of separate amorphous regions and microcrystalline domains of MOPEO and PCL blocks. Spectrophotometry and SLS were used to study the self-assembling of DBC macromolecules in selective dioxane/aqueous solution and to determine the main micellization parameters (CMC and -ΔG°). The DBC micelles morphology and their specific aggregation in mixed solvent were shown.

Hyperbranched polyglycerols containing amine groups — Synthesis, characterization and carbon dioxide capture

Abstract In this article we report an easy synthetic way towards hyperbranched polyglycerols containing primary amine groups (A-HBPGs). A-HBPGs were synthesized in a two-step procedure including an anionic ring opening copolymerization of the phthalimide-epoxy monomer with glycidol followed by hydrazinolysis of phthalimide groups. Polymeric products of both synthetic steps were characterized using NMR, MALDI-TOF, FTIR, viscosimetry and elemental analysis techniques. The maximum amount of the amine containing units in the products was estimated to be 31 mol%. Introduction of higher amounts of these units was limited by the reactivity (sterical) and viscosity reasons. A-HBPGs showed to be effective in CO2 capture from the ambient air. Adsorbents consisting of A-HBPGs and fumed silica in the 1 to 1 wt ratio were capable of adsorbing up to 85.6 mg of CO2, representing 0.82 mmol CO2 per gram or 36.3 mg CO2 per gram of adsorbent. The measurements confirmed that the amount of adsorbed carbon dioxide was proportional to the number of amine sites in a polymer. The obtained CO2 adsorbents could be regenerated upon by heating. Desorption took place above 80 °C, but the optimum temperature seemed to be at least 100 °C. The effect of easier CO2 desorption in presence of HBPG structures reported in the literature in case of our materials has not been confirmed.