Search Results (178)

Polylactic acid (PLA) is a renewable biopolymer that has attracted considerable interest due to its ability to replace petroleum-based synthetic polymers, thereby offering a more sustainable alternative to global environmental concerns. This study focused on evaluating the effect of catalyst concentration and reaction time on the efficiency of PLA synthesis via the Ring-Opening Polymerization (ROP) technique. The process involved a lactic acid esterification stage (using 88% lactic acid) to obtain lactide, employing 40% and 60% (v/v) sulfuric acid concentrations, followed by polymerization at various reaction times (10, 15, 20, and 30 min). Analysis of variance (ANOVA) results revealed that the 40% catalyst concentration had a statistically significant effect on polymer yield (p = 0.032), whereas reaction time showed no statistical significance (p = 0.196), although the highest yields were recorded at 10 and 15 min. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of the characteristic functional groups of PLA, and Differential Scanning Calorimetry (DSC) revealed a semi-crystalline structure with a high melting temperature, indicating good thermal stability. These results validate the viability of PLA as a functional and sustainable biopolymer. Full article

In this study, poly-DL-lactic acid (PDLLA) was synthesized via ring-opening polymerization (ROP) to develop a biomedical scaffold for tissue engineering. A rotary evaporator with a two-stage vacuum pump under an inert atmosphere and constant stirring was used. A factorial design with three factors (oligomerization time, ROP time, and catalyst concentration) at two levels was applied. Polymers were characterized by FTIR, capillary viscometry, ¹H-NMR, DSC, and TGA. The kinetic study revealed a first-order model, indicating that the polymerization rate depends linearly on monomer concentration. The activation energy (70.5 kJ/mol) suggests a moderate energy requirement, consistent with ring-opening polymerization, while the high pre-exponential factor (6.93 × 10⁶ min⁻¹) reflects a significant frequency of molecular collisions. The scaffold was fabricated via extrusion and 3D printing, and its morphology, porosity, mechanical properties, and contact angle were studied. The highest molecular weight PDLLA was obtained with 6 h of oligomerization, 4 h of ROP, and 1% catalyst concentration. The samples exhibited thermal stability below 40 °C, while the scaffold reached 71.6% porosity, an 85.97° contact angle, and a compressive strength of 4.24 MPa with an elastic modulus of 51.7 MPa. These findings demonstrate the scaffold’s potential for biomedical applications. Full article

Recent advances in zinc complexes for stereoselective ring-opening polymerization (ROP) and copolymerization (ROCOP) highlight their pivotal role in synthesizing biodegradable aliphatic polyesters and polycarbonates. These materials address the urgent demand for sustainable alternatives to petroleum-based plastics, with stereochemical control directly impacting polymer crystallinity, thermal stability, and degradability. Zinc catalysts, leveraging low toxicity and versatile coordination chemistry, enable precise stereoregulation, whose performance is modulated by ligand steric/electronic effects, coordination geometry, and reaction conditions. This review summarizes the recent developments in zinc complexes for stereoselective ROP and ROCOP, focusing on ligand design strategies to enhance catalytic performance. Full article

Bacterially produced poly[(R)-3-hydroxybutyrate] (P3HB) was subjected to an alcoholysis reaction to produce low-molecular-weight (M_n ≈ 10,000 g mol⁻¹) hydroxy-terminated P3HB (LMPHB). Using diethyl zinc as a catalyst, LMPHB was reacted with the cyclic monomers ε-caprolactone and l-lactide in separate ring-opening polymerization (ROP) reactions to produce PHB-b-PCL (PHBCL) and PHB-b-PLA (PHBLA) AB-type crystalline–crystalline diblock copolymers with varying PCL and PLA block lengths. ¹H NMR and GPC were used to confirm the structure of the polymers. DSC was used to measure the thermal properties as well as assessing crystallization. A single-shifting T_g for PHBLA showed the two blocks to be miscible in the melt. The TGA results indicate enhanced thermal stability over the homopolymer P3HB. A study of the crystallization was undertaken by combining WAXD, a second DSC heating regime, and POM. POM showed that the crystallization in PHBCL to be dependent on the crystallization temperature more so than PHBLA, whose composition appeared to be the more definitive factor determining the spherulitic morphology. The results informed the crystallization temperatures used in the production of the melt-crystallized thin films that were imaged using AFM. AFM images showed unique surface morphologies dependent on the diblock copolymer composition, block length, and crystallization temperature. Finally, the enzymatic degradation studies showed these unique surface morphologies to influence how these block copolymers were degraded by enzymes. Full article

Amphiphilic block copolymers with complex topologies (e.g., star and brush topologies) have attracted significant attention in drug delivery owing to their superior performance over linear micelles. However, their precise synthesis and structure–property relationships require further investigation. In this study, hydroxylated polybutadiene with adjustable topology and hydroxyl group density was employed as a macroinitiator to synthesize well-defined amphiphilic poly (ethylene oxide)-b-poly(ε-caprolactone-ran-δ-valerolactone) (PEO-b-P(CL-ran-VL)) copolymers via ring-opening polymerization (ROP). A series of linear, star, linear–comb, and star–comb copolymers were prepared as curcumin-loaded micellar carriers for the study. The self-assembly behavior, drug encapsulation efficiency, and in vitro release profiles of these copolymers in aqueous environments were systematically investigated. The results demonstrated that increasing the branch length of star–comb copolymers effectively reduced micelle size from 143 to 96 nm and enhanced drug encapsulation efficiency from 27.3% to 39.8%. Notably, the star–comb architecture exhibited 1.2-fold higher curcumin encapsulation efficiency than the linear counterparts. Furthermore, the optimized star–comb nanoparticles displayed sustained release kinetics (73.38% release over 15 days), outperforming conventional linear micelles. This study establishes a quantitative structure–property relationship between copolymer topology and drug delivery performance, providing a molecular design platform for programmable nanocarriers tailored to diverse therapeutic requirements of various diseases. Full article

In this study, novel triblock copolymers, including poly(N-isopropylacrylamide)-block-poly(ε-caprolactone)-block-poly(N-isopropylacrylamide) (PNIPAM-b-PCL-b-PNIPAM), poly(N-vinyl-pyrrolidone)-block-poly(ε-caprolactone)-block-poly(N-vinyl-pyrrolidone) (PNVP-b-PCL-b-PNVP), poly(N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate)-block-poly(ε-caprolactone)-block-poly(N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate) (P(DMAEMA-co-NIPAM)-b-PCL-b-P(NIPAM-co-DMAEMA)), and poly(N,N-dimethylacrylamide)-block-poly(ε-caprolactone)-block-poly(N,N-dimethylacrylamide) (PDMA-b-PCL-b-PDMA), were synthesized via a combination of ring-opening polymerization (ROP) and reversible addition–fragmentation chain transfer (RAFT) polymerization. The synthesis was performed using novel bifunctional PCL-based RAFT macro chain transfer agents (macroCTAs; MXTPCL-X1 and MXTPCL-X2) with a m-xylene-bis(2-mercaptoethyloxy) core. Initially, m-xylene-bis(1-hydroxy-3-thia-propane) (MXTOH), which has not previously been used in lactone polymerization, was synthesized via the reaction of α,α′-dibromo-m-xylene with 2-mercaptoethanol in the presence of sodium in ethanol. Subsequently, Sn(Oct)₂-catalyzed ROP of ε-caprolactone (ε-CL) using MXTOH as an initiator yielded PCL-diol (MXTPCLOH). The resulting PCL-diol underwent further functionalization through esterification and substitution reactions, leading to the formation of PCL-based RAFT macroCTAs. Triblock copolymers were synthesized using these macroCTAs with AIBN as an initiator. The synthesized products, along with their intermediates, were characterized using FTIR and ¹H NMR spectroscopy. The number average molecular weight (M_n) and polydispersity index (Ð) of PCL-based macroCTAs were determined by using GPC analysis. The sensor capabilities of the synthesized novel triblock copolymers were investigated on the determination of syringic acid and it was determined that the most sensitive polymer was PNVP-b-PCL-b-PNVP (MXTP2). The working range was between 1.5 µg/mL and 15 µg/mL and the limit of detection (LOD) was found to be 0.44 µg/mL using DPV on MXTP2 polymer sensor. Full article

Interaction of [Sn(OtBu)₄] with the acid 2,2′-diphenylgylcine, Ph₂C(X)CO₂H (X = NH₂), affords the complex {Sn[Ph₂C(NH₂)(CO₂)]₄}·2MeCN (1·2MeCN) after work-up, whereas when X = OH (benzilic acid), the complex {Sn[Ph₂C(O)(CO₂)]₂(CH₃CO₂H)₂} (2) is isolated. In 1·2MeCN, the four 2,2′-diphenylglycinate ligands adopt three different coordination modes (two N,O-chelates, an O,O-chelate, and a monodentate carboxylate ligand), whilst in 2, two cis-O,O-chelate ligands are present along with two acetic acid ligands, the latter being derived from hydrolysis of acetonitrile. Both 1 and 2 have been screened as catalysts for the ring opening polymerization of ε-caprolactone and δ-valerolactone; for comparison, the commercial catalyst [Sn(Oct)₂], where Oct = 2-ethylhexanoate, and the precursor [Sn(OtBu)₄] have been screened under similar conditions. The products were of low to high molecular weight for PCL and low to moderate molecular weight for PVL, with wide Ð values, and they comprised several types of polymer families, including OH-terminated, OH/OMe-terminated, and cyclic polymers. For both monomers, kinetic profiles indicated that [Sn(Oct)₂] outperformed 1, 2, and [Sn(OtBu)₄], though under certain conditions, 1 and 2 afforded high-molecular weight products with better control. Full article

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-PCL_x) 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. Full article

A series of poly(lactic acid) (PLA)/biochar (BC) bio-composites filled with low amounts (1–5 wt%) of BC were prepared and characterized. The synthesis involved the in situ ring-opening polymerization (ROP) of lactide in the presence of two different types of BC named SWP550 and SWP700, having been produced by pyrolysis of softwood pellets at two different temperatures, 550 and 700 °C, respectively. The bio-composites were characterized by complementary techniques. The successful synthesis of PLA and PLA/BC bio-composites was directly demonstrated by the formation of new bonds, most probably between PLA and BC. Indirect evidence for that was obtained by the systematic molar mass reduction in the presence of BC. BC was found by transmission electron microscopy (TEM) micrographs to be well dispersed at the nanosize level, indicating that in situ polymerization is a technique quite efficient for producing bio-composites with finely dispersed BC additive. The molecular dynamics mapping is performed here via dielectric spectroscopy, moreover, for the first time in these PLA/BC systems. The strong PLA/BC interactions (due to the grafting) led to a systematic deceleration of segmental mobility (elevation of the T_g) in the bio-composites despite the opposite effect expected by the decrease in molar mass with the BC content increasing. In addition, the same interactions and chain-length reduction are responsible for the slight suppression of the PLA’s crystallizability. The effects are slightly stronger for SWP700 as compared to SWP550. The crystal structure is rather similar between the unfilled matrix and the bio-composites, whereas, based on the overall data, the semicrystalline morphology is expected to be tighter in the bio-composites. The thermal stability and decomposition kinetics were also thoroughly studied. All materials exhibit good resistance to thermal degradation. Additionally, the mechanical properties of bio-composites were evaluated by tensile testing and found slightly enhanced at low biochar contents and decreasing thereafter due to the low molecular weight of bio-composites with the larger BC contents. Full article

Building on our previous studies, which have demonstrated that homochiral propagating species—(R*,R*)-[Me₂Ga(µ-OCH(Me)CO₂R)]₂—were crucial for the heteroselectivity of [Me₂Ga(µ-OCH(Me)CO₂Me)]₂ in the ring-opening polymerization (ROP) of racemic lactide (rac-LA), we have investigated the effect of alkyl groups on the structure and catalytic properties of dialkylgallium alkoxides in the ROP of rac-LA. Therefore, we have isolated and characterized the rac-[R₂Ga(µ-OCH(Me)CO₂Me]₂ (R = Et (1), ⁱPr (2) and rac-[R₂Ga(µ-OCH(Me)C₅H₄N]₂ (R = Et (3), ⁱPr (4)) complexes, to demonstrate the effect of alkyl groups on the chiral recognition induced the formation of the respective homochiaral species—(R*,R*)-[R₂Ga(µ-OCH(Me)CO₂Me)]₂ and (R*,R*)-[R₂Ga(µ-OCH(Me)C₅H₄N]₂. Moreover, we have investigated the structure of (S,S)-[R₂Ga(µ-OCH(Me)CO₂Me]₂ (R = Et ((S,S)-1, R = ⁱPr ((S,S)-2,) and their catalytic activity in the ROP of rac-LA. With an increase in the bulkiness of alkyl substituents on gallium the following can be observed: (a) the tendency for the formation of homochiral complexes decreased, (b) the symmetry of homochiral (S,S)-[R₂Ga(µ-OCH(Me)CO₂Me]₂ (M = Me, Et (S,S)-1), ⁱPr (S,S)-2) changed, and both have resulted in (c) lower or no heteroselectivtity across these complexes in the ROP of rac-LA. Importantly, the results have confirmed the crucial role of the chiral-induced formation of homochiral asymmetric dimers on the heteroselectivity of dialkylgallium alkoxides in the ROP of rac-LA. Full article

The present work focuses on the synthesis and characterization of biobased lignin-poly(lactic) acid (PLA) composites. Organosolv lignin, extracted from beechwood, was used as a filler at 0.5, 1.0, and 2.5 wt% loadings, with ultrasonication reducing the lignin particle size to ~700 nm. The PLA–lignin composites were prepared via in situ ring-opening polymerization (ROP) of L-lactide in the presence of lignin. This method ensured uniform lignin dispersion in the PLA matrix due to grafting of PLA chains onto lignin particles, preventing aggregation. Strong polymer–filler interactions were confirmed through spectroscopic analysis (FTIR and XPS) and their effects on static and dynamic glass transitions (DSC). These interactions enhanced mechanical properties, including a two-fold increase in tensile strength and elongation at 1 wt% lignin. Crystallization was suppressed due to shorter PLA chains, and a 15% drop in dynamical fragility was observed via Broadband Dielectric Spectroscopy (BDS). Antioxidant activity improved significantly, with PLA–2.5% ultrasonicated organosolv lignin reducing DPPH• content to 7% after 8 h, while UV-blocking capability increased with lignin content. Full article

Considering the demand for the construction of a sustainable future, it is essential to endow the conventional thermoset silicone adhesive with reuse capability and recyclability. Although various research attempts have been made by incorporating reversible linkages, developing sustainable silicone adhesives by natural linkers is still challenging, as the interface between the natural linker and the silicone is historically difficult. We exploited the possibility of utilizing α-lipoic acid, a natural linker, to construct a sustainable silicone adhesive. Via the simultaneous ring-opening reaction between the COOH and epoxide-functionalized silicone and the polymerization of the α-lipoic acid, the resulting network exhibited dynamic properties. The shear strength of the LASA90 presented strong adhesion (up to 88 kPa) on various substrates including steel, aluminum, PET, and PTFE. Meanwhile, reversible adhesion was shown multiple times under mild heating conditions (80 °C). The rheology, TG-DTA, DSC, and ¹H NMR showed that the degradation of the LASA occurred at 150 °C via the retro-ROP of the five-membered disulfide ring, indicating their recyclability after usage. Conclusively, we envision that a silicone adhesive based on α-lipoic acid as a natural linker is more sustainable than conventional silicone thermosets because of its desired properties, strong adhesion, reversibility, and on-demand heat degradation. Full article

Hydrogels with low toxicity, antimicrobial potency and shear-thinning behavior are promising materials to combat the modern challenges of increased infections. Here, we report on 8-arm star block copolypeptides based on poly(L-lysine), poly(L-tyrosine) and poly(S-benzyl-L-cysteine) blocks. Three star block copolypeptides were synthesized with poly(S-benzyl-L-cysteine) always forming the outer block. The inner block comprised either two individual blocks of poly(L-lysine) and poly(L-tyrosine) or a statistical block copolypeptide from both amino acids. The star block copolypeptides were synthesized by the Ring Opening Polymerization (ROP) of the protected amino acid N-carboxyanhydrides (NCAs), keeping the overall ratio of monomers constant. All star block copolypeptides formed hydrogels and Scanning Electron Microscopy (SEM) confirmed a porous morphology. The investigation of their viscoelastic characteristics, water uptake and syringe extrudability revealed superior properties of the star polypeptide with a statistical inner block of L-lysine and L-tyrosine. Further testing of this sample confirmed no cytotoxicity and demonstrated antimicrobial activity of 1.5-log and 2.6-log reduction in colony-forming units, CFU/mL, against colony-forming reference laboratory strains of Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, respectively. The results underline the importance of controlling structural arrangements in polypeptides to optimize their physical and biological properties. Full article

Polyesters (PEs) are sustainable alternatives for conventional polymers owing to their potential degradability, recyclability, and the wide availability of bio-based monomers for their synthesis. Herein, we used a one-pot, one-step self-switchable polymerization linking the ring-opening alternating copolymerization (ROAC) of epoxides/cyclic anhydrides with the ring-opening polymerization (ROP) of L-lactide (LLA) to synthesize PE-based hot-melt adhesives with a high bio-based content. In the cesium pivalate-catalyzed self-switchable polymerization of glutaric anhydride (GA), butylene oxide (BO), and LLA using a diol initiator, the ROAC of GA and BO proceeded whereas the ROP of LLA simultaneously proceeded very slowly, resulting in a copolyester consisting of poly(GA-alt-BO) and poly(L-lactide) (PLLA) segments with tapered regions, that is, PLLA-tapered block-poly(GA-alt-BO)-tapered block-PLLA (PLLA-tb-poly(GA-alt-BO)-tb-PLLA). Additionally, a series of tapered-block or real-block copolyesters consisting of poly(anhydride-alt-epoxide) (A segment) and PLLA (B segment) with AB-, BAB-, (AB)₃-, and (AB)₄-type architectures of different compositions and molecular weights were synthesized by varying the monomer combinations, alcohol initiators, and initial feed ratios. The lap shear tests of these copolyesters revealed an excellent relationship between the adhesive strength and polymer structural parameters. The (AB)₄-type star-block copolyester (poly(GA-alt-BO)-tb-PLLA)₄ exhibited the best adhesive strength (6.74 ± 0.64 MPa), comparable to that of commercial products, such as PE-based and poly(vinyl acetate)-based hot-melt adhesives. Full article

Selective polymerization with heterogeneous catalysts from mixed monomers remains a challenge in polymer synthesis. Herein, we describe that nano-sized zinc glutarate (ZnGA) can serve as a catalyst for the selective copolymerization of phthalic anhydride (PA), propylene oxide (PO) and lactide (LA). It was found that the ring-opening copolymerization (ROCOP) of PA with PO occurs firstly in the multicomponent polymerization. After the complete consumption of PA, the ring-opening polymerization (ROP) of LA turns into the formation of block polyester. In the process, the formation of zinc–alkoxide bonds on the surface of ZnGA accounts for the selective copolymerization from ROCOP to ROP. These results facilitate the understanding of the heterogeneous catalytic process and offer a new platform for selective polymerization from monomer mixtures. Full article