Ring-opening Polymerization Research Articles

Exploring the Catalytic Efficiency of Lithium Bis(trimethylsilyl)amide (LiHMDS) in Lactide Polymerization

The exploration of efficient catalysts for the ring-opening polymerization of cyclic esters has significant implications for the synthesis of biocompatible and biodegradable polymers. In this work, the simple catalyst lithium bis(trimethylsilyl)amide (LiHMDS) with high activity was explored in detail for the synthesis of polylactide (PLA). Using LiHMDS as the catalyst, various cyclic esters were polymerized to obtain diverse sustainable polyesters, such as poly(lactide), poly(δ-valerolactone), and poly(caprolactone), with controlled molecular weights and narrow molecular weight distributions. PLA synthesis was accomplished in just a few minutes at room temperature, contributing to the sustainable advancement of this polymer.

A Bio-Redox Dynamic Pickering Emulsion from Nature to Nature.

The biosafety issue of Pickering emulsions has gradually become public. It is shown that the particles that make up Pickering emulsions, previously thought to be non-physiologically toxic, may also pose a potential threat to human life and health, as well as to ecosystems, due to their inherent emulsifying capacity. Hence, the principle of "from nature to nature" is proposed, which refers to emulsifiers that are of natural origin and can be metabolized by natural biological processes to eliminate their emulsifying ability. A feasible pathway by which the natural small molecule, thioctic acid, is exploited for the preparation of Pickering emulsions is also presented. The strategy of calcium ion-induced aggregation and ring-opening polymerization of sodium thioctate is utilized for the preparation of particulate emulsifiers, thus forming stable O/W-type Pickering emulsions. Benefiting from the antioxidant property of the thioctic acid moiety and the transdermal capacity of the emulsion itself, it combines protection of the bioactive substance with transdermal delivery. Furthermore, the particulate emulsifiers that are prepared, abundantly enriched with dynamic disulfide bonds, can be integrated into the natural metabolic pathway, specifically by being reduced through the involved glutathione, thereby facilitating their natural degradation and effectively mitigating any potential biological hazards.

Synthesis of hyperbranched polyethers with diverse structures based on “A1 + B2” ring-opening polymerization

Synthesis of hyperbranched polyethers with diverse structures based on “A1 + B2” ring-opening polymerization

Effect of pressure and monomer concentration on ring-opening enzymatic polymerization of globalide in pressurized propane

Effect of pressure and monomer concentration on ring-opening enzymatic polymerization of globalide in pressurized propane

The construction of a stable physical–chemical multi-crosslinking structure through a simplified FROMP strategy synergistically enhances the flame retardancy and mechanical properties of PDCPD

The enhancement of the flame retardancy of polydicyclopentadiene (PDCPD) while maintaining its excellent mechanical properties has long been an important and critical technical challenge for many years. In this contribution, we designed and synthesized a new flame-retardant monomer containing double norbornene groups (NB-PDP) which can undergo the frontal ring-opening metathesis polymerization (FROMP) with dicyclopentadiene (DCPD) and 5-dicyclopentadiene-2-carboxylic acid (NB-COOH). Through the formulation optimization, the flame retardancy and mechanical properties of the copolymers could be easily regulated. To investigate the influencing mechanism of the NB-PDP and NB-COOH on the properties of the copolymers, the thermodynamics and kinetics of the FROMP, as well as the micro-structures, mechanical properties, and flame-retardant performance of the PDCPD/NB-PDP/NB-COOH copolymers were systematically studied. The findings suggest that the integration of NB-PDP and NB-COOH resulted in a diverse array of physical and chemical cross-linking networks within the system. Consequently, the tensile strength of the copolymers reached a maximum of 63.1 MPa and the elongation at break achieved up to 28.5%, representing the increases of 43.0% and 154.0% compared to that of PDCPD without any modification, respectively. It is worth mentioning that except the flame-retardant NB-PDP, NB-COOH could also serve as the carbon source to enhance the char formation and further improve the flame-retardant properties, such as the limiting oxygen index (LOI), peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP). These phenomena indicate that the material exhibits excellent mechanical properties and conspicuous flame retardancy. This work provided an efficient method for the preparation of the intrinsically flame-retardant PDCPD materials and a new strategy for the constructing of the thermosetting materials with excellent comprehensive performance.

Synthesis and ring-opening polymerization of bisubstituted ε-caprolactones bearing aryl and cyano groups

Synthesis and ring-opening polymerization of bisubstituted ε-caprolactones bearing aryl and cyano groups

Investigation of Amphiphilic PDMS-Hyperbranched Polyglycerol Copolymers to Tune the Fouling-Release Properties in a Moisture Curable Coating System.

Hyperbranched polyglycerol (HBPG) has been proven to be effective as a hydrophilic material when incorporated into amphiphilic copolymers, enhancing fouling-release properties. These amphiphilic polymers not only increase the effectiveness of coatings across a wide range of organisms but also impart antifouling characteristics without resorting to toxic chemicals. HBPGs exhibit high resistance to proteins and lead to the effective removal of marine organisms under low impact pressures. To enhance the effectiveness of HBPGs and facilitate polymer stratification onto the coating surface, copolymers with polydimethylsiloxane (PDMS) were synthesized through a ring-opening multibranching polymerization reaction. These amphiphilic polymers, with varying molecular weights of the PDMS block and different degrees of branching in the HBPG blocks, were incorporated into a urea-siloxane moisture-cure coating system at a concentration of 5 wt %. This study aimed to identify the optimal molecular weight of PDMS and the degree of branching in HBPG that provides the most improved fouling-release (FR) properties to the base coating. The amphiphilic copolymers underwent thorough characterization using Fourier transform infrared (FTIR), NMR, and surface tension measurements. Coatings were extensively characterized for their surface properties by using atomic force microscopy (AFM), photoinduced force microscopy (PiFM), X-ray photoelectron spectroscopy (XPS), moisture adsorption measurements, and contact angle measurements. To assess fouling-release and antifouling properties, laboratory biological assays were conducted with five common marine fouling organisms: Navicula incerta, Celluphaga lytica, Ulva linza, Chlorella vulgaris, and Amphibalanus amphitrite. Notably, 1k or 5k PDMS with a polyglycerol branching ratio of 10:1 or 15:1 emerged as the best performers across a diverse array of laboratory biological assays.

Rapid, Highly Sustainable Ring-Opening Polymerization via Resonant Acoustic Mixing

Rapid, Highly Sustainable Ring-Opening Polymerization via Resonant Acoustic Mixing

3D Porous Polycaprolactone with Chitosan-Graft-PCL Modified Surface for In Situ Tissue Engineering

Tissue engineering has emerged as a promising approach for improved regeneration of native tissue and could increase the quality of life of many patients. However, the treatment of injured tissue transitions is still in its early stages, relying primarily on a purely physical approach in medical surgery. A biodegradable implant with a modified surface that is capable of biological active protein delivery via a nanoparticulate release system could advance the field of musculoskeletal disorder treatments enormously. In this study, interconnected 3D macroporous scaffolds based on Polycaprolactone (PCL) were fabricated in a successive process of blending, annealing and leaching. Blending with varying parts of Polyethylene oxide (PEO), NaCl and (powdered) sucrose and altering processing conditions yielded scaffolds with a huge variety of morphologies. The resulting unmodified hydrophobic scaffolds were modified using two graft polymers (CS-g-PCLx) with x = 29 and 56 (x = PCL units per chitosan unit). Due to the chitosan backbone hydrophilicity was increased and a platform for a versatile nanoparticulate release system was introduced. The graft polymers were synthesized via ring opening polymerization (ROP) of ε-Caprolactone using hydroxy groups of the chitosan backbone as initiators (grafting from). The suspected impact on biocompatibility of the modification was investigated by in vitro cell testing. In addition, the CS-g-PCL modification opened up the possibility of Layer by Layer (LbL) coating with alginate (ALG) and TGF-β3-loaded chitosan tripolyphosphate (CS-TGF-β3-TPP) nanoparticles. The subsequent release study showed promising amounts of growth factor released regarding successful in vitro cell differentiation and therefore could have a possible therapeutic impact.

Nitroxide-Containing Poly(2-oxazoline)s Show Dual-Stimuli-Responsive Behavior and Radical-Trapping Activity.

2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) structures possess potent antioxidant activities for biomedical applications. TEMPO immobilization on hydrophilic polymers is a powerful strategy to improve its properties; however, it is mostly limited to reversible-deactivation radical polymerizations or postpolymerization approaches. Here, we immobilized TEMPO units on a hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) backbone through cationic ring-opening polymerization (CROP) of a new 2-oxazoline monomer bearing a methoxy-protected TEMPO 2-substituent with 2-ethyl-2-oxazoline (EtOx). The ratios of EtOx/TempOx were adjusted to optimize the nitroxide content while maintaining suitable water solubility of the resulting P(EtOxx-stat-TempOx-Oy•) copolymers upon deprotection. P(EtOx40-stat-TempOx-O10•) and P(EtOx33-stat-TempOx-O17•) showed a dual stimuli-responsive behavior and demonstrated significant radical-trapping activities in aqueous media. Particularly, a meaningful augmentation in the activity of TempOx-O• was observed when it was immobilized as P(EtOxx-stat-TempOx-Oy•). The P(EtOx40-stat-TempOx-O10•) system exhibited a longer-lasting activity in water, statistically comparable to that of the antioxidant ferrostatin-1 (Fer-1). Overall, this study introduces a biocompatible polymeric platform for TEMPO immobilization that augments its radical-trapping activity and offers controllable stimuli-responsive properties.

Anionic ring-opening polymerization of 2-oxabicyclo[2.1.1]hexan-3-one: manipulating topology and conformation for circular polymer design.

Polyesters featuring a linear topology and in-chain 1,3-cyclobutane rings, synthesized via ring-opening polymerization (ROP) of 2-oxabicyclo[2.1.1]hexan-3-one (4R-BL, R = Bu, Ph) through a coordination-insertion mechanism, display excellent thermal and hydrolytic stability, making them promising candidates for sustainable circular materials. However, achieving diverse topological and stereochemical structures remains challenging. Herein, we demonstrate precise control over linear and cyclic topologies of these polyesters and the conformation of in-chain cyclobutane rings through anionic ROP of 4R-BLwith appropriate catalysts or initiators. Usingtert-butoxide (tBuOK) as the catalyst, low loading (0.05-0.1 mol%) produces high-molar-mass cyclic polyester P(4R-BL) (up to 571 kg/mol), whereas high loading (2 mol%) promotes transesterification and isomerization, ultimately yielding cyclic oligomers. Remarkably, the tetramer(4Ph-BL)4undergoes conformationalturnoverof the puckered cyclobutane rings and can be repolymerized into polymerP(4Ph-BL). This establishes a "monomer ⇄ polymer ⇄ tetramer" dual closed-loop life cycle, enhancing the potential for a circular material economy.

Degradable thermosets via orthogonal polymerizations of a single monomer.

Crosslinked thermosets are highly durable materials, but overcoming their petrochemical origins and inability to be recycled poses a grand challenge1-3. Many strategies to access crosslinked polymers that are bioderived or degradable-by-design have been proposed, but they require several resource-intensive synthesis and purification steps and are not yet feasible alternatives to conventional consumer materials4-8. Here we present a modular, one-pot synthesis of degradable thermosets from the commercially available, biosourced monomer 2,3-dihydrofuran (DHF)9. In the presence of a ruthenium catalyst and photoacid generator, DHF undergoes slow ring-opening metathesis polymerization to give a soft polymer; then, exposure to light triggers strong acid generation and promotes the cationic polymerization of the same DHF monomer to spatially crosslink and strengthen the material10-12. By manipulating catalyst loading and light exposure, we can access materials with physical properties spanning orders of magnitude and achieve spatially resolved material domains. Importantly, the DHF-based thermosets undergo stimuli-selective degradation and can be recycled to themonomer under mild heating. The use of two distinct polymerization mechanisms on a single functional group allows the synthesis of degradable and recyclable thermoset materials with precisely controlled properties.

Zn(TFSI)2-Mediated Ring-Opening Polymerization for Electrolyte Engineering Toward Stable Aqueous Zinc Metal Batteries

Practical Zn metal batteries have been hindered by several challenges, including Zn dendrite growth, undesirable side reactions, and unstable electrode/electrolyte interface. These issues are particularly more serious in low-concentration electrolytes. Herein, we design a Zn salt-mediated electrolyte with in situ ring-opening polymerization of the small molecule organic solvent. The Zn(TFSI)2 salt catalyzes the ring-opening polymerization of (1,3-dioxolane (DOL)), generating oxidation-resistant and non-combustible long-chain polymer (poly(1,3-dioxolane) (pDOL)). The pDOL reduces the active H2O molecules in electrolyte and assists in forming stable organic-inorganic gradient solidelectrolyte interphase with rich organic constituents, ZnO and ZnF2. The introduction of pDOL endows the electrolyte with several advantages: excellent Zn dendrite inhibition, improved corrosion resistance, widened electrochemical window (2.6V), and enhanced low-temperature performance (freezing point = - 34.9°C). Zn plating/stripping in pDOL-enhanced electrolyte lasts for 4200 cycles at 99.02% Coulomb efficiency and maintains a lifetime of 8200h. Moreover, Zn metal anodes deliver stable cycling for 2500h with a high Zn utilization of 60%. A Zn//VO2 pouch cell assembled with lean electrolyte (electrolyte/capacity (E/C = 41mL (Ah)-1) also demonstrates a capacity retention ratio of 92% after 600 cycles. These results highlight the promising application prospects of practical Zn metal batteries enabled by the Zn(TFSI)2-mediated electrolyte engineering.

Synthesis, characterization and cytotoxicity analyzes of novel AB-Type Amphiphilic Block Copolymers

AB-type novel amphiphilic poly(L-lactide)-block-(N-isopropylacrylamide) (PLLA-b-PNIPAM) and poly(L-lactide)-block-(N-vinyl-pyrrolidone) (PLLA-b-PNVP), diblock copolymers were synthesized through the combined use of ring-opening polymerization (ROP) and controlled/living radical polymerization (CRP) techniques. (PLLA-b-PNIPAM) block copolymer was prepared via combination of ROP and atom transfer radical polymerization (ATRP) using the novel PLLA-based ATRP macroinitiator. (PLLA-b-PNVP) block copolymer was synthesized via combination of ROP and reversible addition-fragmentation chain transfer (RAFT) polymerization using the PLLA-based RAFT macro chain transfer agent (CTA). For this purpose, at first 2,4-difluorobenzyl alcohol (1) was used to initiate the ROP of (L-LA) using tin(II) 2-ethylhexanoate Sn(Oct)2 as a catalyst at 120 ℃ for synthesis of PLLA-OH (2). Secondly, bromoester end-functionalized PLLA-based ATRP macroinitiator (3) was synthesized by esterification of hydroxyl end group of (2). The first block copolymer, (PLLA-b-PNIPAM) (5), was synthesized by ATRP of NIPAM using (3) in presence of copper(I) chloride/tris[2-(dimethylamino)ethyl]amine (CuCl/Me6TREN) as catalyst system in DMF/water at 25 °C. For the synthesis step of second block copolymer, at first PLLA macro chain transfer agent (CTA) (4) was then synthesized via substitution reaction of (3) with potassium ethyl xanthogenate (KEX) and finally PLLA-b-PNVP (6) diblock copolymer was prepared via RAFT polymerization of NVP using (4). The molecular structures of novel polymers (2-6) were elucidated by spectroscopic (FTIR and 1H NMR) methods. In the application phase of this study, the effectiveness of copolymers was examined on cervical cancer cells. Cytotoxicity effects were evaluated in vitro on HeLa cell lines.

Unveiling Proton Transfer as the Key Process to Understand and Promote the Ring-Opening Polymerization of N-Carboxyanhydrides

Unveiling Proton Transfer as the Key Process to Understand and Promote the Ring-Opening Polymerization of <i>N</i>-Carboxyanhydrides

Stabilizing Layered Oxide Cathodes Based on Universal Surface Residual Alkali Conversion Chemistry for Rechargeable Secondary Batteries.

Layered transition metal oxides (LTMOs) are attractive cathode candidates for rechargeable secondary batteries because of their high theoretical capacity. Unfortunately, LTMOs suffer from severe capacity attenuation, voltage decay, and sluggish kinetics, resulting from irreversible lattice oxygen evolution and unstable cathode-electrolyte interface. Besides, LTMOs accumulate surface residual alkali species, like hydroxides and carbonates, during synthesis, limiting their practical application. Herein, a universal strategy is suggested to in situ convert surface residual alkali into a stable polymer coating layer for LTMOs, thus turning wastes into treasure. The formation process of polymer coating involves NH4F treatment to consume residual alkali, then utilizing generated fluorides to induce the ring-opening polymerization of tetrahydrofuran. Implementing this strategy to Li-rich Mn-based cathode materials (LRM) results in a notable reduction in voltage hysteresis, along with enhanced kinetics and cycling stability in lithium-ion batteries. With this layer of encapsulation, surface lattice oxygen release and layered-to-spinel phase transition of LRM are significantly alleviated with minimal mechanical degradation and surface parasitic reactions. Such strategy can also be applied to air-sensitive sodium-rich LTMOs in sodium-ion batteries,which showcases superior universality. This work might provide a promising solution to overcome residual alkali and interfacial instability issues for LTMOs in practical application.

Monomer Design Enables Mechanistic Mapping of Anionic Ring‐Opening Polymerization of Aromatic Thionolactones

Degradable chalcogenide polyesters, e.g., polythioesters (PTEs), typically exhibit improved thermal, mechanical, and optical properties. Anionic ring‐opening polymerization (ROP) of thionolactones, an intrinsically promising yet underexplored approach to accessing PTEs, however, is still limited by: intolerance of metal catalysts, inadequate control over chain growth, and the absence of aromatic system. Monomer design‐boosted mechanistic studies may address the above challenges. Here, we present a new and highly reactive thionolactone synthesized from 1,1′‐binaphthyl‐2,2′‐diol (BINOL). Our investigations into polymerization kinetics and thermodynamics have underscored the importance of rapid initiation, eventually leading to the discovery of tetrabutylammonium 2‐naphthyl‐thiocarboxylate as a distinctive initiator that enables genuinely controlled and living polymerization of thionolactones. Ultimately, the atropisomerism inherent in BINOL has resulted in the creation of axially chiral PTE materials with tailored molecular weights, enantiomeric compositions, and topologies.

Acidity Reversal Enables Site-Specific Ring-Opening Polymerization of Epoxides from Biprotonic Compounds.

Polyethers are versatile materials extensively used in advanced as well as everyday applications. The incorporation of primary amine functionality into polyethers is particularly attractive due to its well-established coupling chemistries. However, the inherent nucleophilicity of amine group poses a challenge in the anionic ring-opening polymerization (ROP) of epoxides and requires the use of robust protecting groups that can withstand the harsh conditions of ROP without triggering undesirable side reactions. In this work, we present streamlined synthesis of amino-functionalized polyethers using classic N-carbamate-protected aminoalcohols as initiators for the ROP of epoxides. A Lewis acid-excess two-component organocatalytic system is found to trigger efficient anionic ROP of epoxides while preserving the integrity of the carbamate protection. Despite the higher intrinsic acidity of the carbamate group compared to the hydroxyl group, it is noncompetitive in both the deprotonation and ring-opening steps. This is due to an intriguing acidity-reversing effect of the catalyst, which allows site-specific ethoxylation to proceed exclusively from the hydroxyl group. The resulting poly(propylene oxide) and poly(ethylene oxide) exhibit the targeted molar mass, low dispersity, and well-defined end groups. The fidelity of the amino functionalities is further corroborated and utilized in construction of polypeptoide-based hybrid block copolymers using the synthesized polyethers as macroinitiators.

Monomer Design Enables Mechanistic Mapping of Anionic Ring-Opening Polymerization of Aromatic Thionolactones.

Degradable chalcogenide polyesters, e.g., polythioesters (PTEs), typically exhibit improved thermal, mechanical, and optical properties. Anionic ring-opening polymerization (ROP) of thionolactones, an intrinsically promising yet underexplored approach to accessing PTEs, however, is still limited by: intolerance of metal catalysts, inadequate control over chain growth, and the absence of aromatic system. Monomer design-boosted mechanistic studies may address the above challenges. Here, we present a new and highly reactive thionolactone synthesized from 1,1'-binaphthyl-2,2'-diol (BINOL). Our investigations into polymerization kinetics and thermodynamics have underscored the importance of rapid initiation, eventually leading to the discovery of tetrabutylammonium 2-naphthyl-thiocarboxylate as a distinctive initiator that enables genuinely controlled and living polymerization of thionolactones. Ultimately, the atropisomerism inherent in BINOL has resulted in the creation of axially chiral PTE materials with tailored molecular weights, enantiomeric compositions, and topologies.

Chain transfer to monomer – the main chain-growth termination reaction in radical ring-opening polymerization of ketene acetals

Chain transfer to monomer – the main chain-growth termination reaction in radical ring-opening polymerization of ketene acetals