Search Results (125)

Herein, electrospun nanofibers composed of polyaniline (PANI), polyethylene oxide (PEO), and Luffa cylindrica (LC) cellulose, reinforced with titanium dioxide (TiO₂) nanoparticles, were synthesized via electrospinning to investigate the effect of TiO₂ nanoparticles on PANI/PEO/LC nanocomposites and the effect of conductivity on nanofiber morphology. Cellulose extracted from luffa was added to the PANI/PEO copolymer solution, and two different ratios of TiO₂ were mixed into the PANI/PEO/LC biocomposite. The morphological, vibrational, and thermal characteristics of biocomposites were systematically investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). As anticipated, the presence of TiO₂ enhanced the electrical conductivity of biocomposites, while the addition of Luffa cellulose further improved the conductivity of the cellulose-based nanofibers. FTIR analysis confirmed chemical interactions between Luffa cellulose and PANI/PEO matrix, as evidenced by the broadening of the hydroxyl (OH) absorption band at 3500–3200 cm⁻¹. Additionally, the emergence of characteristic peaks within the 400–1000 cm⁻¹ range in the PANI/PEO/LC/TiO₂ spectra signified Ti–O–Ti and Ti–O–C vibrations, confirming the incorporation of TiO₂ into the biocomposite. SEM images of the biocomposites reveal that the thickness of nanofibers decreases by adding Luffa to PANI/PEO nanofibers because of the nanofibers branching. In addition, when blending TiO₂ nanoparticles with the PANI/PEO/LC biocomposite, this increment continued and obtained thinner and smother nanofibers. Furthermore, the incorporation of cellulose slightly improved the crystallinity of the nanofibers, while TiO₂ contributed to the enhanced crystallinity of the biocomposite according to the XRD and DCS results. Similarly, the TGA results supported the DSC results regarding the increasing thermal stability of the biocomposite nanofibers with TiO₂ nanoparticles. These findings demonstrate the potential of PANI/PEO/LC/TiO₂ nanofibers for advanced applications requiring conductive and structurally optimized biomaterials, e.g., for use in humidity or volatile organic compound (VOC) sensors, especially where flexibility and environmental sustainability are required. Full article

L-asparaginase (L-ASNase) remains a vital chemotherapeutic agent for acute lymphoblastic leukemia (ALL), primarily due to its mechanism of depleting circulating asparagine essential for leukemic cell proliferation. However, existing ASNases (including pegylated ones) face limitations including immunogenicity, rapid clearance, and off-target toxicities. Earlier, we have shown that the conjugation of L-ASNase with the polyamines and their copolymers results in significant enhancement of the antiproliferative activity due to accumulation in tumor cells. We suggested that this effect is probably mediated by polyamine transport system (PTS) receptors that are overexpressed in ALL cells. Here, we investigated the effect of competitive inhibitors of PTS receptors to the L-ASNase interaction with cancer cells (L5178Y, K562 and A549). L-ASNase from Rhodospirillum rubrum (RrA), Erwinia carotovora (EwA), and Escherichia coli (EcA) were conjugated with natural polyamines (spermine—spm, spermidine—spd, putrescine—put) and a synthetic branched polymer, polyethyleneimine 2 kDa (PEI2 ), using carbodiimide chemistry. Polyamine conjugation with L-ASNase significantly increased enzyme binding and cellular uptake, as quantified by fluorimetry and confocal microscopy. This increased cellular uptake translated into increased cytotoxicity of L-ASNase conjugates. The presence of competitive ligands to PTS receptors decreased the uptake of polyamine-conjugated enzymes-fatty acid derivatives of polyamines produced the strongest suppression. Simultaneously with this suppression, in some cases, competitive ligands to PTS significantly promoted the uptake of the native unconjugated enzymes, “equalizing” the cellular access for native vs conjugated ASNase. The screening for competing inhibitors of PTS receptor-mediated endocytosis revealed spermine and caproate/lipoate derivatives as the most potent inhibitors or antagonists, significantly reducing the cytostatic efficacy of polyamine-conjugated ASNases. The results obtained emphasize the complex, cell-type-dependent and inhibitor-specific nature of these interactions, which highlights the profound involvement of PTS in L-ASNase internalization and cytotoxic activity. These findings support the viability of polyamine conjugation as a strategy to enhance L-ASNase delivery and therapeutic efficacy by targeting the PTS. Full article

Formation of long chain branches (LCB) in polyethylene (PE), via incorporation of in situ generated vinyl macromonomers, is known to affect material properties dramatically, making their detection and quantification of primary importance. ¹³C NMR spectroscopy is the archetypal technique for the analysis of polymer microstructure, yet it suffers from major limitations in the analysis of LCB in polyethylene, primarily in terms of resolution. Herein, we propose a simple and effective methodology for detecting and quantifying LCB based on the analysis of C atoms in β-position with respect to the branching point. By analyzing model ethylene/α-olefin copolymers bearing methyl, ethyl, butyl, hexyl or tetradecyl chain branches, we show how the C_β resonances can be used to discriminate between shorter or longer branches. Importantly, the proposed method allows the most critical discrimination between hexyl-type branches and LCB, with an up to three-fold detection enhancement with respect to previously proposed procedures based on the analysis of the methine carbons. The proposed approach is then tested on a representative industrial sample of HDPE, proving that it is suitable to detect very small amounts of LCB. 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

Stimuli-responsive polymeric nanostructures are compelling vectors for a wide range of application opportunities. The objective we sought was to broaden the array of self-assembling amphiphilic copolymers with stimuli-responsive characteristics by introducing a hydrophilic tunable monomer, (2-dimethylamino)ethyl methacrylate (DMAEMA), together with a hydrophilic one, lauryl methacrylate (LMA), within linear and branched copolymer topologies. Size exclusion chromatography was used to evaluate the resultant linear and hyperbranched copolymers’ molecular weight and dispersity, and FT-IR and ¹H-NMR spectroscopy techniques were used to delineate their chemical structure. The structural changes in the obtained self-organized supramolecular structures were thoroughly investigated using aqueous media with varying pH and salinity by dynamic light scattering (DLS), fluorescence spectroscopy (FS), and transmission electron microscopy (TEM). The nanoscale assemblies formed by the amphiphiles indicate significant potential for applications within the field of nanotechnology. Full article

In this study, modification of poly(adipic anhydride) through branching its chains was carried out via melt condensation polymerization with D-mannitol. The percentage of mannitol was varied (3, 4, 5, 10, 15, and 20 Wt.%) and the resulting copolymers were purified and characterized by FT-IR and ¹³C-NMR. These analyses indicated that linear chains of poly(adipic anhydride) can react with strong nucleophiles and dissociate to produce highly branched poly(adipic anhydride-co-mannitol adipate) which confirms the validity of the proposed mechanism. The copolymer’s molecular weight characteristics have been also examined using GPC analysis. Thermal properties of copolymers were also investigated using TGA, DTG, and DCS analyses. TGA/DTG revealed that the thermal degradation of copolymers proceeds in multi-stage decomposition, whereas the shift and pattern change of the melting point peak of DSC curves can identify the weight percentage of mannitol for homogenous copolymers. Two non-isothermal models, the Flynn–Wall–Ozawa and Kissinger methods, have been also employed to analyze thermogravimetric data collected from the thermal decomposition of the copolymers and found that Flynn–Wall–Ozawa method provides better results with R² correlation up to 99.3%. The activation energy in the region of T_max was determined and found that an increase in mannitol contents in copolymer has a positive impact on its thermal stability. Full article

Biodegradable polyesters have been researched intensively over the last two decades because of their biodegradability and superb physical properties. However, the use of linear biodegradable polyesters, for the preparation of drug delivery systems (DDS), is hampered by several limitations. In view of this, scientific attention has been shifted to the employment of branched-chain (co-)polymers. In this context, we present herein the development of new melatonin (MLT) tablet formulations, using novel branched polylactide (PLA)-based copolymers of different architectures. Specifically, three PLA-polyol branched polyesters, namely, a three-arm copolymer based on glycerol (PLA-glycerol), a four-arm copolymer based on pentaerythritol (PLA-pentaerythritol), and a six-arm copolymer based on sorbitol (PLA-sorbitol), were utilized. The presence of these polyesters in the formulations was found to be crucial, as the sought MLT release, regarding its use in confronting sleep onset and/or sleep maintenance dysfunctions, was achieved. The copresence of the other excipients in the matrix tablets (lactose monohydrate, hydroxypropylmethylcellulose, microcrystalline cellulose, and sodium alginate) led to a concentration-dependent synergistic effect on the MLT release. To the best of our knowledge, this is the first investigation with these specific polymeric materials, concerning MLT modified release from matrix tablets. Full article

A novel lignocellulose-based poly(butylene 3-propyladipate-co-furanoate) (PBA_pF) was synthesized from lignocellulose-derived 3-propyladipic acid (3PAA), 1,4-butanediol (BDO), and 2,5-furandicarboxylic acid (FDCA). The copolyesters were characterized by ¹H NMR, GPC, DSC, TGA, XRD, DMA, rotational rheology, tensile tests, and enzymatic degradation tests. They were random copolymers whose composition was well controlled, and the number-average sequence lengths of the copolyesters were around 1.35–4.33. By combining the results of tensile tests and DMA, the elongation at break of PBA_pF₄₅ (1865%) had a much greater value than that of PBAF₄₅ (1250%), i.e., the branching incorporated into the linear polymer increased the melt strength and conferred tension-hardening properties, which helped to enhance the elongation of the polymer. In addition, the influences of 3PAA content on enzymatic degradation were studied in terms of weight loss; when the content of 3PAA was 55 mol%, the copolyesters exhibited good biodegradability. Thus, depending on their composition, PBA_pF_S might find end applications as biodegradable elastomers or impact modifiers for other polymers. Full article

In this study, we report the synthesis of amphiphilic hyperbranched poly[(2-dimethylaminoethyl methacrylate)-co-(benzyl methacrylate)] statistical copolymers with two different stoichiometric compositions using the reversible addition–fragmentation chain transfer polymerization (RAFT) technique. The selection of monomers was made to incorporate a pH and thermoresponsive polyelectrolyte (DMAEMA) component and a hydrophobic component (BzMA) to achieve amphiphilicity and study the effects of architecture and environmental factors on the behavior of the novel branched copolymers. Molecular characterization was performed through size exclusion chromatography (SEC) and spectroscopic characterization techniques (¹H-NMR and FT-IR). The self-assembly behavior of the hyperbranched copolymers in aqueous media, in response to variations in pH, temperature, and ionic strength, was studied using dynamic light scattering (DLS), electrophoretic light scattering (ELS), and fluorescence spectroscopy (FS). Finally, the efficacy of the two novel copolymers to encapsulate curcumin (CUR), a hydrophobic, polyphenolic drug with proven anti-inflammatory and fluorescence properties, was established. Its encapsulation was evaluated through DLS, UV–Vis, and fluorescence measurements, investigating the change of hydrodynamic radius of the produced mixed copolymer–CUR nanoparticles in each case and their fluorescence emission properties. Full article

The homopolymerization of norbornene and the copolymerization of norbornene and ethylene were carried out using the neutral α-sulfonate-β-diimine nickel catalyst SD-Ni. The neutral α-sulfonate-β-diimine catalyst is highly active in the homopolymerization of norbornene, producing vinyl-addition polynorbornene (PNB) with a high molecular weight. The copolymerization of norbornene (NB) and ethylene (E) using the catalyst SD-Ni was also investigated. The α-sulfonate-β-diimine catalyst SD-Ni shows distinctive catalytic copolymerization properties to produce high-molecular-weight E-NB copolymers with low norbornene incorporation. Importantly, microstructure analyses confirm that the resultant E-NB copolymers are branched cyclo-olefin copolymers (COCs) with branched polyethylene units. Full article

In recent years, the design and synthesis of high-performing conjugated materials for the application in organic photovoltaics (OPVs) have achieved lab-scale devices with high power conversion efficiency. However, most of the high-performing materials are still synthesised using complex multistep procedures, resulting in high cost. For the upscaling of OPVs, it is also important to focus on conjugated polymers that can be made via fewer simple synthetic steps. Therefore, an easily synthesised amorphous thiophene−quinoxaline donor polymer, TQ1, has attracted our attention. An analogue, TQ-EH that has the same polymer backbone as TQ1 but with short branched side-chains, was previously reported as a donor polymer with increased crystallinity. We have synthesised copolymers with varied ratios between octyloxy and branched (2-ethylhexyl)oxy-substituted quinoxaline units having the same polymer backbone, with the aim to control the aggregation/crystallisation behaviour of the resulting copolymers. The optical properties, glass transition temperatures and degree of crystallinity of the new copolymers were systematically examined in relation to their copolymer composition, revealing that the composition can be used to fine-tune these properties of conjugated polymers. In addition, multiple sub-T_g transitions were found from some of the polymers, which are not commonly or clearly seen in other conjugated polymers. The new copolymers were tested in photovoltaic devices with a fullerene derivative as the acceptor, achieving slightly higher performances compared to the homopolymers. This work demonstrates that side-chain modification by copolymerisation can fine-tune the properties of conjugated polymers without requiring complex organic synthesis, thereby expanding the number of easily synthesised polymers for future upscaling of OPVs. Full article

Ethylene/1-octene copolymers exhibit enhanced flexibility and impact resistance compared to polyethylene, which makes them well suited for applications in advanced plastics and elastomers. United-atom molecular dynamics (MD) simulations were conducted to explore the mechanical behavior and deformation mechanisms of ethylene/1-octene copolymers under uniaxial tensile loading. This study systematically examined the influence of temperature, polymer chain length, chain quantity, and strain rate, with a specific focus on how hexyl branch content impacts the mechanical properties of amorphous ethylene/1-octene copolymers. The simulation results indicate that as the branch content increases, the yield strength and elastic modulus decrease, suggesting a trade-off between flexibility and mechanical strength. Energy decomposition analysis reveals that copolymers with more branched chains undergo greater changes in van der Waals energy. Additionally, as the branch content increases, the reduction in dihedral angle energy in the strain hardening region becomes more gradual, and the rate and the extent of the transition of dihedral angles from gauche to trans conformation decrease under deformation. Ethylene/1-octene copolymers exhibit higher chain entanglement parameters compared to linear polyethylene, with these parameters increasing as the branch content rises. Moreover, increasing the branch content results in a less pronounced increase in chain orientation along the loading direction. Full article

Double hydrophilic, random, hyperbranched copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) utilizing ethylene glycol dimethacrylate (EGDMA) as the branching agent. The resulting copolymers were characterized in terms of their molecular weight and dispersity using size exclusion chromatography (SEC), and their chemical structure was confirmed using FT-IR and ¹H-NMR spectroscopy techniques. The choice of the two hydrophilic blocks and the design of the macromolecular structure allowed the formation of self-assembled nanoparticles, partially due to the pH-responsive character of the DMAEMA segments and their interaction with -COOH end groups remaining from the chain transfer agent. The copolymers showed pH-responsive properties, mainly due to the protonation–deprotonation equilibria of the DMAEMA segments. Subsequently, a nanoscopic polymer–lipid (lipomer) mixed system was formulated by complexing the synthesized copolymers with cosmetic amphiphilic emulsifiers, specifically glyceryl stearate (GS) and glyceryl stearate citrate (GSC). This study aims to show that developing lipid–polymer hybrid nanoparticles can effectively address the limitations of both liposomes and polymeric nanoparticles. The effects of varying the ionic strength and pH on stimuli-sensitive polymeric and mixed polymer–lipid nanostructures were thoroughly investigated. To achieve this, the structural properties of the hybrid nanoparticles were comprehensively characterized using physicochemical techniques providing insights into their size distribution and stability. Full article

A novel elastomer-modified multicomponent, multiphase waste-sourced biocomposites, was prepared for converting waste biomass and plastic into value-added products. The effects of blending elastomer–olefin block copolymer (OBC) and maleic anhydride (MAH), and divinylbenzene (DVB) co-grafting of recycled polypropylene (rPP) matrix on the adhesion interface, structure, and properties of high wood flour-filled (60 wt.%) composites were thoroughly investigated. The results indicated that DVB introduced branched structures into the polymer matrix molecular chain and increased the MAH grafting rate. Co-grafting rPP/OBC blends enhanced the interfacial adhesion among rPP, OBC, and wood flour. Additionally, MAH-grafted OBC was prone to encapsulating rigid wood flour, thereby forming an embedded structure. Notably, the tensile modulus and impact strength of the final three-component composites increased by 60% and 125%, respectively, compared with the unmodified composites. Additionally, dynamic mechanical analysis revealed that DVB-induced branching promoted the formation of microvoids in the OBC shell layer surrounding the wood, which in turn induced significant plastic deformation in the polymer matrix. This work offers a facile and efficient method for preparing high-toughness, high-stiffness, and low-cost waste PP-based composites for automotive interiors, and indoor and outdoor decoration. Full article

A comparative study of the structural integrity of an opaque recycled poly(ethylene terephthalate) (rPET-O) has been carried out with two types of modified rPET-O by applying reactive extrusion techniques, namely (a) using a multi-epoxide reactive agent (REx-rPET-O) and (b) a 90/10 (wt/wt) rPET-O/polycarbonate (PC) blend. The chemical modifications introduced during reactive extrusion were confirmed using differential scanning calorimetry (DSC) and rheological dynamic analysis (RDA). For the quantification of the fracture parameters, an instrumented pendulum impact testing machine was used using specimens in SENB configuration. The structural modifications generated during reactive extrusion promote an increase of between 16 (REx-rPET-O) and 20% (rPET-O/PC) in the stress-intensity factor (K_Q) compared to unmodified rPET-O. The most significant differences between both modifications are registered in the “specific work of fracture” (w_f) (alternative parameter to the standardized impact strength), where an increase of 61% is reached for the case of rPET-O/PC and only 11% for REx-rPET-O. This trend can be attributed to the type of reactive modification that is generated, namely chain branching (REx-rPET-O) vs. the generation of a random copolymer “in situ” (rPET-O/PC). This copolymer decreases the crystallization capacity and degree of crystalline perfection of rPET-O, promoting an increase in the critical hydrostatic stress conditions for the generation of crazing and crack propagation. Full article