Injectable hydrogels offer promising alternatives for scaffold-based tissue engineering due to their minimally invasive delivery and in situ forming capability. In this study, we reported the first development of an injectable hydrogel scaffold combining carboxymethyl cellulose (CMC), poly(ethylene glycol) (PEG), and poly(ε-caprolactone) (PCL) into a single system. This novel approach integrated the biocompatibility of CMC, tunable responsiveness of PEG, and mechanical robustness/degradability of PCL, which had not been previously reported. A pH- and temperature-responsive carboxymethyl cellulose (CMC) grafted with a methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) [CMC-g-(mPEG-b-PCL)] system was synthesized. The diblock copolymers were first prepared by ring-opening polymerization of ε-caprolactone using a poly(ethylene glycol) methyl ether (mPEG) in combination with a stannous octoate initiator, followed by grafting onto the pH-responsive CMC backbone using simple 1-ethyl-3-(3-(dimethylamino)propyl carbodiimide)/N-hydroxysuccinimide (EDC/NHS) coupling chemistry in N,N-dimethylformamide (DMF). Structural characterization by 1H NMR and FTIR spectroscopy confirmed the presence of characteristic functional groups from both CMC and mPEG-b-PCL. Aqueous CMC-g-(mPEG-b-PCL) hydrogels were subsequently formulated, with 32 wt % CMC-g-(mPEG17-b-PCL12) showing the most favorable sol-gel phase-transition behavior based on the test tube inversion. Rheological analysis demonstrated that the hydrogel remained injectable in the sol state and formed a stable gel under physiological conditions, with the range of storage moduli comparable to that of early stage cartilage tissue. In addition, the hydrogel exhibited an interconnected porous structure, as observed by scanning electron microscopy. Cytocompatibility was validated through MTT and live/dead staining assays using L929 fibroblasts and MG63 osteoblast-like cells. The results showed that the cell morphology was preserved, and the cell viability was stable throughout 5 days of incubation. These findings support the cytocompatibility of the synthesized CMC-g-(mPEG-b-PCL) graft copolymer and suggest its potential for further investigation as an injectable hydrogel scaffold for bone and cartilage tissue engineering applications.

Driven by both environmental concerns and economic considerations, the demand for biomass-derived monomers in polymer development has significantly increased in recent years. Bio-based plastics, in particular, have emerged as a leading focus area and have consistently ranked among the top priorities in discussions of breakthrough technologies for advancing a circular economy. In this study, one of the goals is to assess the effectiveness of various esterification catalysts. For this purpose, different bio-based homopolyesters using 1,3-propanediol and malonic acid as raw materials and six catalysts (titanium (IV) butoxide (TBT), titanium (IV) isopropoxide (TTIP), tin (II) 2-ethylhexanoate (stannous octoate, Sn(Oct)2), antimony (III) oxide (Sb2O3), stannous chloride dehydrate (SnCl2.2H2O) and aluminum chloride (AlCl3)) were synthesized. The synthesized polymers were chemically characterized by NMR and FTIR. The thermal properties were investigated by DSC and TGA. The FTIR results confirmed that the homopolyesters were successfully synthesized, and a Tg of approximately -48 °C was detected by DSC. The maximum working temperatures, where loss of 50 wt % occurs, were around 365 °C.

With aging, harsh working conditions or sports injuries, the meniscus can degrade, causing pains to the patient. Nowadays, the treatment consists of the surgical replacement of this cartilage. Since this procedure can lead to complications due to open wounds and potential infections, synthesizing a polyurethane-based injectable joint filler represents an interesting alternative. In this study, poly(δ-decalactone)triol oligomers and Lysine diisocyanate were chosen as starting monomers to create an isocyanate-based prepolymer, because of their biocompatibility and liquid state at room temperature. Nevertheless, to fully replace the meniscus, the joint filler must crosslink in vivo, and this should occur in a short time window. Accordingly, in this work, we studied the catalytic activity of a range of relatively safe compounds for the alcohol/isocyanate addition reaction. A preliminary 1H NMR kinetic study of the catalyzed addition of 1-butanol or 3-pentanol on lysine diisocyanate ethyl ester at body temperature has been performed to reach this objective. Among catalysts, stannous octoate was the most effective with either primary or secondary alcohol, allowing them to reach 92 and 80% alcohol conversion, respectively. In addition, the conversion of the primary and secondary isocyanates of lysine diisocyanate ethyl ester was monitored for all the catalysts and revealed different behaviors depending on the catalyst employed. Stannous octoate, unlike the others, showed a similar reactivity for primary and secondary isocyanates with conversions of 49 and 47%, respectively. Finally, when employing the most effective catalyst, curing of the poly(δ-decalactone) triisocyanate with glycerol at 35 °C provided a polyurethane elastomer that exhibits an elastic modulus of 519 kPa and a swelling index lower than 3% in PBS, making it suitable for injectable polyurethane joint filler application.

Ring-opening polymerization of caprolactone initiated by tin octoate catalyst

Preparation and characterization of sugar palm (Arenga pinnata) starch grafted with oligo(lactic acid) via ex situ oligomerization.

Poly(?-caprolactone) (PCL) is a biodegradable polymer extensively used in biomedical and industrial applications due to its biocompatibility, mechanical flexibility, and processability. Among various synthesis methods, ring-opening polymerization (ROP) of ?-caprolactone (?-CL) has emerged as a preferred approach for producing high-molecular-weight polymers with low polydispersity and controlled structures. This review compares polycondensation, chemical ROP and enzymatic ROP strategies, evaluating their efficiency, environmental impact and scalability. Chemical ROP using catalysts such as stannous octoate and zinc alkoxides achieves molecular weights up to 45,000 g/mol and >85% conversion but involves toxic residues and complex purification. Enzymatic ROP, particularly with immobilized Candida antarctica lipase B (CALB), offers metal-free synthesis with molecular weights up to 80,000 g/mol and conversion rates exceeding 95% under mild, solvent-free conditions. Recent advances in bioreactor technologies including packed-bed and microreactor systems enable rapid conversion (up to 98%) and enzyme reuse, supporting industrial scalability. This review synthesizes recent developments across catalytic systems and reactor configurations, which reveals the potential of enzymatic ROP as a sustainable alternative for industrialscale PCL production.

ABSTRACTHydroxyl‐terminated polybutadiene (HTPB), a linear liquid rubber with terminal hydroxyl groups, is a cornerstone binder in polymer‐bonded explosives (PBX) and composite propellants. Its cross‐linking with hexamethylene diisocyanate trimer (HDI‐trimer), a trifunctional isocyanate crosslinker, faces critical challenges in balancing pot life and curing rates for industrial scalability. Traditional single‐catalyst systems, such as dibutyl tin dilaurate (DBTDL) and tin octoate (TECH), exhibit high catalytic activity and a relatively short pot life, which limit the industrial application. This study aims to resolve these limitations by engineering blended catalyst systems to synergistically modulate cross‐linking kinetics and expand industrial adaptability. Five catalysts, namely TECH, FeAA (iron acetylacetonate), DABCO (1,4‐Diazabicyclo[2.2.2]octane), TPB (triphenyl bismuth), and nano‐ZnO, were blended pairwise at 0.05 w.t.% (1:1 functional group molar ratio) within HTPB/HDI‐trimer binder systems. Viscosity build‐up of the binder systems during the curing process was monitored via rotational viscometry at 45°C (rotor #29, 0.5 rpm), with Arrhenius modeling to quantify rheological reaction rates (kη) and pot life. Full curing at 45°C was achieved within 24 h, eliminating energy‐intensive thermal curing. This work pioneers a multi‐site catalytic strategy for HTPB systems, enabling energy‐efficient room‐temperature curing, which is a paradigm shift for PBX and solid composite propellant manufacturing. The composite catalysts significantly reduce energy consumption costs and provide tunable pot life to accommodate industrial processing requirements. Commercial applications span defense, aerospace, and automotive sectors, where rapid processing and material stability are paramount.

Abstract Cyclic anhydride and epoxide ring‐opening copolymerization is a versatile and controlled route to make polyesters, gaining attention in different application sectors. But so far, the chemical recycling of these polyesters to cyclic monomers is under‐explored. Here, the catalytic chemical recycling of aliphatic polyesters to selectively form 16‐ and 18‐membered lactones is presented. The recycling reactions are catalyzed using commercial tin(II) octoate and conducted in the polymer melt (230 °C) resulting in high conversions to the macrolactones (>90%). The recycled macrolactones undergo catalyzed ring‐opening polymerizations to produce polyesters with equivalent properties to the virgin materials.

Cyclic anhydride and epoxide ring-opening copolymerization is a versatile and controlled route to make polyesters, gaining attention in different application sectors. But so far, the chemical recycling of these polyesters to cyclic monomers is under-explored. Here, the catalytic chemical recycling of aliphatic polyesters to selectively form 16- and 18-membered lactones is presented. The recycling reactions are catalyzed using commercial tin(II) octoate and conducted in the polymer melt (230°C) resulting in high conversions to the macrolactones (>90%). The recycled macrolactones undergo catalyzed ring-opening polymerizations to produce polyesters with equivalent properties to the virgin materials.

Abstract Poly(d,l‐lactide) is a biocompatible and biodegradable polymer with applications in the biomedical field (drug delivery, implants) and packaging. Conventional synthesis with stannous octoate is slow (>4 h) and can climb to over 30 h. In order to reduce reaction times, we developed a microwave reactor process to ring‐open polymerize d,l‐lactide to form poly(d,l‐lactide) in the presence of stannous octoate and an initiator, benzyl alcohol. We evaluated the suitability of toluene and tetrahydrofuran as solvents at 130, 150, and 170°C for the polymerization. Their respective dielectric loss values are 0.1 and 0.35. Compounds with larger dielectric loss values are better at converting microwave energy to heat. The microwave's power input peaked at 420 W to reach 170°C with toluene, whereas with tetrahydrofuran the peak was 330 W; afterwards, the power input to maintain that temperature was 10 W for both solvents. A reaction in toluene at 170°C after 1 h produced poly(d,l‐lactide) with a molecular weight of 31 kDa and a dispersity index of 1.5. In tetrahydrofuran, at the same temperature, the molecular weight peaked at 11 kDa after 4 h with a dispersity index of 1.2. Moreover, in the absence of microwaves the polymerization does not occur. Tetrahydrofuran is hygroscopic and water cleaves poly(d,l‐lactide) chains resulting in a lower molecular weight despite the longer reaction time and larger dielectric loss compared to toluene, a water immiscible solvent.

Due to the significant economic and environmental benefits, the demand for biomass-derived building blocks in polymer development has increased in recent years. Bio-based plastics, integral to advancing a circular economy, have consistently been a leading topic among emerging technologies. In this study, we aim to evaluate the effectiveness of different esterification catalysts. To achieve this, we synthesized a range of fully bio-based oligomers using glycerol and malonic acid as starting materials, along with three catalysts: tin(II) 2-ethylhexanoate (stannous octoate, Sn(Oct)2), stannous chloride dihydrate (SnCl2·2H2O), and aluminum chloride (AlCl3). The chemical structures of the synthesized oligomers were confirmed using NMR and FTIR spectroscopy. Thermal properties were assessed using DSC and TGA. FTIR analysis verified successful oligomer synthesis, and a glass transition temperature (Tg) of approximately -56 °C was determined via DSC. Additionally, the oligomers exhibited maximum working temperatures at around 278 °C, corresponding to a 50 wt% loss.

Abstract Despite the great successes achieved for the closed‐loop recyclable polymers in the last decade, thermoplastic elastomers (TPEs) with closed‐loop recyclability and good mechanical performances are largely underexplored. In this contribution, the preparation of PδVL‐b‐PβMVL‐b‐PδVL triblock copolymers via one‐pot sequential ring‐opening copolymerization of bio‐renewable β‐methyl‐δ‐valerolactone (βMVL) and δ‐valerolactone (δVL) is achieved. The obtained triblock copolymers behave as TPEs that exhibit superior tensile strength and toughness as well as comparable elasticity to the most previously reported polyester‐based and commercial styrenic copolymer‐based TPEs. Remarkably, these triblock copolymers can be depolymerized to recover pristine monomers with a high yield by simply heating the materials under reduced pressure in the presence of stannous octoate as the catalyst. The recovered monomers can be separated or directly used to prepare TPEs with comparable performances to original TPEs, thus establishing a closed‐loop life cycle.

Polylactide (PLA) is one of the most promising bioplastics and is therefore often quoted as a solution to fight today's global plastics crisis. However, current PLA production via the ring-opening polymerization (ROP) of lactide is not yet sustainable since it heavily relies on the toxic catalyst tin octoate. To overcome the hurdles in scale-up and to accelerate the transition of promising new non-toxic alternative ROP catalysts from laboratory to industry, model-based analysis is a highly effective tool. Herein, our previously introduced kinetic model for the ROP of L-lactide using a non-toxic and robust Zn guanidine "asme"-type catalyst under industrially relevant melt conditions is expanded upon using two new co-initiators. The experimental data is evaluated using "traditional" kinetic analysis following pseudo-first-order kinetics to approximate a relationship between co-initiator concentration and the rate of polymerization. The range of validity of these findings is considerably expanded by taking model data into account to compare the performance of the different co-initiators in lactide ROP.

To prepare novel biodegradable copolymers with functional substituents that are distributed statistically or randomly over the macromolecule chain and have improved characteristics compared to homopolymers, we conducted a series of synthetic experiments with a novel cyclic monomer, 5-(benzyloxy)-1,3-dioxepan-2-one (4). This compound was synthesized, and its homopolymer, as well as its copolymers with L-lactide, ε-caprolactone and trimethylene carbonate, were prepared in a polymerization solution with stannous octoate as the initiator. The formation of the copolymers was confirmed using NMR spectroscopy and DSC data. The distribution of the monomeric units of the substituted 7CC in the copolymers with L-lactide and ε-caprolactone is random, as it is close to a statistical distribution. The copolymer with TMC is a gradient copolymer due to the different rates of monomer polymerization. The copolymer with a composition of 10(ε-CL):1(carbonate 4) can be considered a promising polymer after the deprotection of the hydroxy group for the inoculation of the functional substituents due to its convenience of preparation and properties similar to those of poly(ε-caprolactone).

Extraction and processing of polyether polyols derived from petrochemicals, commonly used as surfactants during polyurethane foam (PUF) production, contribute to carbon emissions and raises the issue of long-term sustainability given that petrochemicals are non-renewable resources. Here, 5 mg and 4 mg of neem seed oil are employed to form flexible and rigid PUF, classified purposefully based on their divergent usage. To find an environmentally friendly replacement, flexible PUF whose mass, volume, density, compression, tensile strength, cream time, foam rise and rising time are 0.0047 kg m3, 16.52 kg/m3, 8.10%, 39.28 kN/m2, 60s, 10s and 60s is formed by mixing 1.25 kg polyol, 5mg silicon oil and 10g calcium carbonate (CaCO3). Likewise, by mixing 1.2 kg polyol, 4mg silicon oil and 8g CaCO3, a rigid PUF with 0.005kg, m3, 16.2 kg/m3, 8.15%, 40.72 kN/m2, 50s, 15 cm and 58s key, physical and mechanical property as respectively listed under the flexible PUF formulation is produced. Both foams were produced using equal amounts of toluene diisocyanate, water, stannous octoate and methylene chloride, resulting in PUF that can be used in insulation, cushioning and construction support applications based on their characteristic height, density, tensile strength and compressive strength. As the surfactant, neem seed oil's potential in the synthesis of PUF cannot be overemphasized. The study of the kinetics of PUF production is limited and should trigger the adoption of biobased surfactants for industrial applications in the future.

Abstract Temporary plugging fracturing technology is an effective method for extending the range of segmented fracturing in horizontal wells and improving the utilization between fractures in low-permeability reservoirs. In this study, a controllable degradable temporary plugging agent was synthesized by graft copolymerization of PGA and PLA with a material ratio of 3:1, under the catalysis of stannous octoate at 150°C. This approach allows for controlled degradation of the temporary plugging materials by protecting PLA, which has good affinity to water, and adjusting the molecular weight of the product. It reduces the initial degradation rate while increasing the later degradation rate. To consider the heterogeneity of natural fractures and reservoir physical permeability in shallow sea reservoirs, a numerical model for temporary plugging and fracturing of horizontal wells was developed. The model investigates the influence of parameters such as displacement and cluster spacing on crack propagation, resulting in the formation of a simulation method suitable for temporary plugging fracturing of horizontal wells in heterogeneous reservoirs. The research findings indicate that crack length and width gradually increase with the increase of displacement. The maximum crack spread area is achieved at a displacement of 5~8m3/min. Temporary plugging can be implemented when the cluster spacing is ≤12m, allowing for the full expansion of cracks that have not effectively expanded. The largest crack spread area is observed at a crack spacing of 5~8m.

Poly(L-lactic acid) (PLLA) and poly(ε-caprolactone) (PCL), two biodegradable and biocompatible polymers that are commonly used for biomedical applications, are, respectively, the result of the ring-opening polymerization of LA and ε-CL, cyclic esters, which can be produced according to several mechanisms (cationic, monomer-activated cationic, anionic, and coordination-insertion), except for L-lactide, which is polymerized only by anionic, cationic, or coordination-insertion polymerization. A series of well-defined PLLA-b-PCL block copolymers have been obtained starting from the same PLLA homopolymer, having a molar mass of 2500 g·mol-1, and being synthesized by coordination-insertion in the presence of tin octoate. PCL blocks were obtained via a cationic-activated monomer mechanism to limit transesterification reactions, and their molar masses varied from 1800 to 18,500 g·mol-1. The physicochemical properties of the copolymers were determined by 1H NMR, SEC, and DSC. Moreover, a series of nanoparticles (NPs) were prepared starting from these polyester-based copolymers by an emulsification/evaporation method. The sizes of the obtained NPs varied between 140 and 150 nm, as a function of the molar mass of the copolymers. Monomodal distribution curves with PDI values under 0.1 were obtained by Dynamic Light Scattering (DLS) and their spherical shape was confirmed by TEM. The increase in the temperature from 25 to 37 °C induced only a very slight decrease in the NP sizes. The results obtained in this preliminary study indicate that NPs have a temperature stability, allowing us to consider their use as drug-loaded nanocarriers for biomedical applications.

'Anode-free' Li metal batteries offer the highest possible energy density but face low Li coulombic efficiency when operated in carbonate electrolytes. Here we report a performance improvement of anode-free Li metal batteries using p-block tin octoate additive in the carbonate electrolyte. We show that the preferential adsorption of the octoate moiety on the Cu substrate induces the construction of a carbonate-less protective layer, which inhibits the side reactions and contributes to the uniform Li plating. In the mean time, the reduction of Sn2+ at the initial charging process builds a stable lithophilic layer of Cu6Sn5 alloy and Sn, improving the affinity between the Li and the Cu substrate. Notably, anode-free Li metal pouch cells with tin octoate additive demonstrate good cycling stability with a high coulombic efficiency of ~99.1%. Furthermore, this in situ p-block layer plating strategy is also demonstrated with other types of p-block metal octoate, as well as a Na metal battery system, demonstrating the high level of universality.

Polymerization of six-membered propylene oxalate

Polyalcohol liquefaction can be performed by acid or base catalysis, producing polyols with different properties. This study compared the mechanical properties of foams produced using polyols from liquefied Cytisus scoparius obtained by acid and base catalysis and using two different foam catalysts. The differences were monitored using FTIR analysis. Acid-catalyzed liquefaction yielded 95.1%, with the resultant polyol having an OH index of 1081 mg KOH/g, while base catalysis yielded 82.5%, with a similar OH index of 1070 mg KOH/g. Generally, compressive strength with dibutyltin dilaurate (DBTDL) ranged from 16 to 31 kPa (acid-liquefied polyol) and 12 to 21 kPa (base-liquefied polyol), while with stannous octoate (TIN), it ranged from 17 to 42 kPa (acid) and 29 to 68 kPa (base). Increasing water content generally decreased the compressive modulus and strength of the foams. Higher water content led to a higher absorption at 1670 cm-1 in the FTIR spectrum due to the formation of urea. Higher isocyanate indices generally improved compressive strength, but high amounts led to unreacted isocyanate that could be seen by a higher absorption at 2265 cm-1 and 3290 cm-1. DBTL was shown to be the best foam catalyst due to higher trimer conversion seen in the spectra by a higher absorption at 1410 cm-1. Acid- and base-derived polyols lead to different polyurethane foams with different FTIR spectra, particularly with a higher absorption at 1670 cm-1 for foams from acid-derived liquefaction.