Search Results (61)

Functional hydrogels have significant potential for applications in the pharmaceutical, agricultural, and environmental sectors. This study focuses on the synthesis of polyampholytic hydrogels through free radical polymerization using functionalized chitosans. The chitosan was modified with mono and disulfonic groups at different temperatures (25 °C and 60 °C) and reaction times (1, 8, 24 h), followed by further modification with glycidyl methacrylate to introduce vinyl groups into the polymers structure. The modified polymers were analyzed using proton nuclear magnetic resonance, Fourier transform infrared, scanning electron spectroscopy, thermogravimetric analysis, and solubility tests. Specifically, 0.74 mmol/g and 1.58 mmol/g of the primary amine groups available in the chitosan chain (out of a total of 4.93 mmol/g) were substituted with mono- and disulfonic groups, respectively. Following treatment with glycidyl methacrylate, 3.39 mmol/g and 2.21 mmol/g of the remaining primary amine groups in the mono- and disulfonic polymers, respectively, were substituted. The hydrogels obtained by the modified polymers at optimal conditions of 1 h and 25 °C, were characterized by the techniques already mentioned in addition to rheological tests, and water absorption studies across different pHs. The hydrogels demonstrated potential for environmental remediation, particularly in adsorptions of ciprofloxacin (CPX) and copper (Cu²⁺) from aqueous solutions at pH 7, achieving adsorption efficiencies of 24–25% for CPX and 83% for Cu²⁺. The results suggest that the synthesized hydrogels could provide an eco-friendly and efficient solution to challenges in wastewater treatment. Full article

The interest in macromolecular alkoxysilyl-functionalized hybrids (self-assembling or nanostructured), which could be used as precursors in biomimetic silica precipitation and for the synthesis of hollow spherical silica particles, is growing. Nevertheless, reports on all-organosilicon systems for bioinspired silica precipitation are scarce. Therefore, a new kind of polyalkoxysilane macromonomer–linear polysilsesquioxane (LPSQ) of ladder-like backbone, functionalized in side chains with trimethoxysilyl groups (LPSQ-R-Si(OMe)₃), was designed following this approach. It was obtained by photoinitiated thiol-ene addition of 3-mercaptopropyltrimethoxysilane to the vinyl-functionalized polysilsesquioxane precursor, carried out in situ in tetraethoxysilane (TEOS). The mixture of LPSQ-R-Si(OMe)₃ and TEOS (co-monomers) was used in a sol–gel process conducted under acidic conditions (0.5 M HCl/NaCl) in the presence of Pluronic^® F-127 triblock copolymer as a template. LPSQ-R-Si(OMe)₃ played a key role for the formation of microparticles of a spherical shape that were formed under the applied conditions, while their size (as low as 3–4 µm) was controlled by the stirring rate. The hybrid materials were hydrophobic and showed good thermal and oxidative stability. Introduction of zinc acetate (Zn(OAc)₂) as an additive in the sol–gel process influenced the pH of the reaction medium, which resulted in structural reinforcement of the hybrid microparticles owing to more effective condensation of silanol groups and a relative increase of the content of SiO₂. The proposed method shows directions in designing the properties of hybrid materials and can be translated to other silicon–organic polymers and oligomers that could be used to produce hollow silica particles. The established role of various factors (macromonomer structure, pH, and stirring rate) allows for the modulation of particle morphology. Full article

The development of high-impact denture base formulations that are suitable for digital light processing (DLP) 3D printing is demanding. Indeed, a combination of high flexural strength/modulus and high fracture toughness is required. In this contribution, eight urethane macromonomers (UMs1-8) were synthesized in a one-pot, two-step procedure. Several rigid diols were first reacted with two equivalents of trimethylhexamethylene diisocyanate. The resulting diisocyanates were subsequently end-capped with a free-radically polymerizable monomer bearing a hydroxy group. UMs1-8 were combined with the monofunctional monomer (octahydro-4,7-methano-1H-indenyl)methyl acrylate and a poly(ε-caprolactone)-polydimethylsiloxane-poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer (BCP1) as a toughening agent. The double-bond conversion, glass transition temperature (T_g), and mechanical properties (flexural strength/modulus, fracture toughness) of corresponding light-cured materials were measured (cured in a mold using a light-curing unit). The results showed that the incorporation of BCP1 was highly efficient at significantly increasing the fracture toughness, as long as the obtained networks exhibited a low crosslink density. The structure of the urethane macromonomer (nature of the rigid group in the spacer; nature and number of polymerizable groups) was demonstrated to be crucial to reach the desired properties (balance between flexural strength/modulus and fracture toughness). Amongst the evaluated macromonomers, UM1 and UM2 were particularly promising. By correctly adjusting the BCP1 content, light-cured formulations based on those two urethane dimethacrylates were able to fulfill ISO20795-1:2013 standard requirements regarding high-impact materials. These formulations are therefore suitable for the development of 3D printable high-impact denture bases. 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

The synthesis of poly(acrylic acid-co-acrylamide) was investigated to enhance its rheological properties. Syntheses were conducted in both aqueous and supercritical fluid media, with and without the incorporation of a novel star-shaped macromonomer. The macromonomer, synthesized from a Boltorn H30 core with PEGMA⁵⁰⁰ arms and modified to contain a single vinyl group, was copolymerized with acrylic acid and acrylamide. Comprehensive polymer characterization was performed using FTIR, NMR, and SEC-MALS-dRI techniques. Rheological assessments revealed that copolymers containing the star-shaped monomer exhibited significantly higher viscosities than those lacking the hyperbranched component, a result attributed to the inter- and intrachain interactions facilitated by the PEGMA⁵⁰⁰ arms. Additionally, purification studies demonstrated that dialysis was necessary to remove short-chain polymers, particularly for samples synthesized in supercritical media, to achieve optimal rheological performance. Polymers synthesized in a supercritical CO₂–ethyl acetate mixture exhibited higher viscosities compared to their water-synthesized counterparts. The integration of the novel star-shaped macromonomer into HPAM-like polymers offers substantial potential for enhanced oil recovery applications. Full article

Photocurable materials offer a rapid transition from a liquid to a solid state, and have recently received great interest in the medical field. However, while dental resins are very popular, only a few materials have been developed for soft tissue repair. This study aims to synthesize a difunctional methacrylate monomer using a dibutyltin dilaurate which is suitable for the photocuring of soft materials. These soft materials were compared with PhotoBioCure^® (Szczecin, Poland) material with a similar molecular weight, of Mn ~7000 g/mol on average. Infrared spectroscopy was used to monitor the two-step synthesis catalyzed with dibutyltin dilaurate, while spectroscopic and chromatographic methods were used to determine the chemical structure and molecular weight of the monomers. Photopolymerization kinetics under varying light intensities were explored in a nitrogen atmosphere for representative difunctional monomers. The mechanical testing of the resulting elastomeric films confirmed tensile strength and modulus values consistent with soft tissue parameters in the range of 3–4 MPa. The 3D printability of the macromonomers was also assessed. Additionally, cytotoxicity assessments using cultured cells showed a high cell viability (97%) for all new materials. Overall, we demonstrate that difunctional methacrylate monomers converted to flexible solids during photopolymerization show great potential for biomedical applications. Full article

Anionic thermo- and pH-responsive copolymers were synthesized by photoiniferter reversible addition–fragmentation chain transfer polymerization (PI-RAFT). The thermo-responsive properties were provided by oligo(ethylene glycol)-based macromonomer units containing hydrophilic and hydrophobic moieties. The pH-responsive properties were enabled by the addition of 5–20 mol% of strong (2-acrylamido-2-methylpropanesulfonic) and weak (methacrylic) acids. Upon initiation by visible light at 470 nm and in the absence of radical initiators, yields from the ternary copolymers reached 94% in 2.5 h when the process was carried out in continuous flow mode using 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid as a light-sensitive RAFT agent. The polymers were characterized using size exclusion chromatography, IR and NMR spectroscopy, and differential scanning calorimetry. The copolymers featured a sufficiently high molecular weight (93–146 kDa) consistent with theoretical values and satisfactory dispersities in the range of 1.18–1.45. The pH-responsive properties were studied in deionized water, saline, and buffer solutions. Dramatic differences in LCST behavior were observed in strong and weak acid-based polyelectrolytes. The introduction of sulfonic acid units, even in very small amounts, completely suppressed the LCST transition in deionized water while maintaining it in the saline and buffer solutions, with a negligible LCST dependence on the pH. In contrast, the incorporation of weak methacrylic acid demonstrated a pronounced pH dependence. The peculiarities of micelle formation in aqueous solutions were investigated and critical micelle concentrations and their ability to retain pyrene, a hydrophobic drug model, were determined. It was observed that anionic molecular brushes formed small micelles with aggregation numbers of 1–2 at concentrations in the order of 10⁻⁴ mg/mL. These micelles have a high ability to entrap pyrene, which makes them a promising tool for targeted drug delivery. Full article

Urushiol is recognized as a sustainable coating material with superior properties; however, it faces significant challenges in applications such as petrochemicals and marine engineering due to surface oil contamination. This study aimed to enhance the cleanability of urushiol-based coatings through hydrophilic modification. Polyethylene glycol monooleate (PEGMO) was identified as an appropriate hydrophilic macromonomer and utilized as a modifier to develop a novel urushiol-based coating, termed P(U-PEGMO), via thermal curing. The results indicated that copolymerization occurred between urushiol and PEGMO during the curing process, forming a stable urushiol copolymer with favorable compatibility. The incorporation of PEGMO greatly improved the surface hydrophilicity of the coatings, as evidenced by a reduction in the water contact angle to below 30° when the modifier content reached 30% or higher, demonstrating a high degree of surface hydrophilicity. This enhanced property imparted the modified coating with underwater superoleophobicity and reduced oil adhesion, thereby facilitating the removal of oil. The cleaning performance was evaluated using a simple water rinsing method, after which, less than 2.5 wt% of oil residues remained on the surface of the modified coating. The high hydrophilicity is considered responsible for the coating’s easy-cleaning capability. In addition, the modified coatings exhibited improved flexibility and impact resistance, albeit with a slight decrease in hardness. Full article

Conjugated polymers (CPs), in particular poly(p-phenylene vinylene)s (PPVs), are recognized as “smart” materials with potential applications ranging from optoelectronic devices to emergent technologies and to precision medicine. The present communication reports on the synthesis and structural characterization of new dibrominated macromonomers and their derived PPVs, of rod–graft–coil architecture, whose grafted, biocompatible and hydrophilic side chains are either PEG-2000 or poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline). The Suzuki–Heck cascade reaction was used for PPVs’ obtainment. After PPVs’ structural characterization using specific techniques (such as ¹H-NMR; GPC), the micellar, fluorescent nanoparticles formed by spontaneous self-assembling during simple direct dissolution in water were evaluated using dynamic light scattering for their size, complementarily combined with Atom Force Microscopy (AFM) for their shape assessing. The PPV micelles’ photophysical properties were revealed using UV-vis spectroscopy and fluorescence measurements. Full article

In this work, comb homopolymers as well as comb-type copolymers of thermo-responsive oligo(ethylene glycol methyl ether methacrylate)s, OEGMAs, with various chain lengths (DEGMA, PEGMA₅₀₀, and PEGMA₉₅₀ containing 2, 9, or 19 repeating ethylene glycol units, respectively) were synthesized through free radical (co)polymerization. For the copolymers, either the functional hydrophobic glycidyl methacrylate (GMA) or the inert hydrophilic N,N-dimethylacrylamide (DMAM) were selected as comonomers. The self-assembly and thermo-responsive behavior of the products was investigated through Nile Red fluorescence probing, turbidimetry, and dynamic light scattering (DLS). Interestingly, it was found that all OEGMA-based homopolymers exhibit a tendency to self-organize in aqueous media, in addition to thermo-responsiveness. The critical aggregation concentration (CAC) increases with the number of repeating ethylene oxide units in the OEGMA macromonomers (CAC was found to be 0.003, 0.01, and 0.03% w/v for the homopolymers PDEGMA, PPEGMA₅₀₀, and PPEGMA₉₅₀, respectively). Moreover, the CAC of the copolymers in aqueous media is highly affected by the incorporation of hydrophobic GMA or hydrophilic DMAM units, leading to lower or higher values, respectively. Thus, the CAC decreases down to 0.003% w/v for the GMA-richest copolymer of PEGMA₉₅₀, whereas CAC increases up to 0.01% w/v for the DMAM-richest copolymer of DEGMA. Turbidimetry and DLS studies proved that the thermo-sensitivity of the polymers is governed by several parameters such as the number of repeating ethylene glycol groups in the side chains of the OEGMAs, the molar percentage of the hydrophobic or hydrophilic comonomers, along with the addition of salts in the aqueous polymer solutions. Thus, the cloud point of the homopolymer PDEGMA was found at 23 °C and it increases to 33.5 °C for the DMAM-richest copolymer of DEGMA. Lastly, the formation of a hydrogel upon heating aqueous mixtures of the GMA-comprising copolymers with silica nanoparticles overnight is strong evidence of the functional character of these polymers. Full article

Secondary reactions in radical polymerization pose a challenge when creating kinetic models for predicting polymer structures. Despite the high impact of these reactions in the polymer structure, their effects are difficult to isolate and measure to produce kinetic data. To this end, we used solvation-corrected M06-2X/6-311+G(d,p) ab initio calculations to predict a complete and consistent data set of intrinsic rate coefficients of the secondary reactions in acrylate radical polymerization, including backbiting, β-scission, radical migration, macromonomer propagation, mid-chain radical propagation, chain transfer to monomer and chain transfer to polymer. Two new approaches towards computationally predicting rate coefficients for secondary reactions are proposed: (i) explicit accounting for all possible enantiomers for reactions involving optically active centers; (ii) imposing reduced flexibility if the reaction center is in the middle of the polymer chain. The accuracy and reliability of the ab initio predictions were benchmarked against experimental data via kinetic Monte Carlo simulations under three sufficiently different experimental conditions: a high-frequency modulated polymerization process in the transient regime, a low-frequency modulated process in the sliding regime at both low and high temperatures and a degradation process in the absence of free monomers. The complete and consistent ab initio data set compiled in this work predicts a good agreement when benchmarked via kMC simulations against experimental data, which is a technique never used before for computational chemistry. The simulation results show that these two newly proposed approaches are promising for bridging the gap between experimental and computational chemistry methods in polymer reaction engineering. Full article

This study conducts a theoretical exploration of the free radical polymerization of polydimethylsiloxane homopolymers with a methyl methacrylate end group (PDMS-MA). To achieve this, a methodology is developed to model and simulate experimental data previously reported by one of the authors. The model incorporates a typical chain reaction mechanism, encompassing initiation, propagation, chain transfer, and termination stages. The resulting ordinary differential equations from this mechanistic approach are numerically integrated over time. Employing a semi-heuristic procedure, the study derives estimated values for the diffusive steps of termination (k_td) and propagation (k_pd). Methodological accuracy is assessed through a comparison of the mathematical model results and experimental data. This evaluation includes the estimation of conversion and the average molecular weight (both number (M_n) and weight (M_w)) at three distinct monomer concentrations, considering a 4.78% mol initiator-to-monomer ratio. The theoretical results obtained from this study contribute to a better understanding of the evolution of diffusion coefficients. These coefficients play a crucial role in influencing the behavior of the studied reactions, particularly in relation to the absence of the autoacceleration effect in these reactions. Full article

Herein, a series of ternary amphiphilic amide-containing bottlebrushes were synthesized by photoiniferter (PI-RAFT) polymerization of macromonomers in continuous-flow mode using trithiocarbonate as a chain transfer agent. Visible light-mediated polymerization of macromonomers under mild conditions enabled the preparation of thermoresponsive copolymers with low dispersity and high yields in a very short time, which is not typical for the classical reversible addition–fragmentation chain transfer process. Methoxy oligo(ethylene glycol) methacrylate and alkoxy(C₁₂–C₁₄) oligo(ethylene glycol) methacrylate were used as the basic monomers providing amphiphilic and thermoresponsive properties. The study investigated how modifying comonomers, acrylamide (AAm), methacrylamide (MAAm), and N-methylacrylamide (-MeAAm) affect the features of bottlebrush micelle formation, their critical micelle concentration, and loading capacity for pyrene, a hydrophobic drug model. The results showed that the process is scalable and can produce tens of grams of pure copolymer per day. The unmodified copolymer formed unimolecular micelles at temperatures below the LCST in aqueous solutions, as revealed by DLS and SLS data. The incorporation of AAm, MAAm, and N-MeAAm units resulted in an increase in micelle aggregation numbers. The resulting bottlebrushes formed uni- or bimolecular micelles at extremely low concentrations. These micelles possess a high capacity for loading pyrene, making them a promising choice for targeted drug delivery. Full article

The presented work deals with the photocuring of telechelic macromonomers derived from plant-based fatty acids to obtain a soft polymer network. Compositions were made by mixing macromonomers with three different concentrations (0.5, 1, and 2%) of two type I photoinitiators (Omnirad 2022 and Omnirad 819). All formulations were then subjected to photopolymerization studies by applying UV-assisted differential scanning calorimetry (UV-DSC) measurements at isothermal conditions at 37 °C with a narrow light source wavelength of 365 nm and irradiation (light intensity) of 20 and 50 mW/cm². The percentage conversions, reaction orders, and constants were estimated based on autocatalytic Sestak–Berggen and Avrami models. In this work, for the first time, the influence of the curing conditions on the photopolymerization process, such as the photoinitiator concentration, light intensity, and oxygen presence/absence, were investigated for these novel systems. The results indicated significant differences between the two commercially available photoinitiators and their effects on photopolymerization kinetics. The maximum reaction rate was found to be considerably higher for Omnirad 2022 (which is a blend of three different compounds), especially at a lower light intensity, i.e., 20 mW/cm², compared to Omnirad 819. However, it led to lower maximum conversion in an air atmosphere. The dynamic thermomechanical analysis (DMTA) revealed that light intensity, photoinitiator concentration, and oxygen presence had a strong effect on the storage modulus and loss modulus values. It was concluded that the chemical structure of the photoinitiator and curing conditions had a strong effect on the photopolymerization kinetics and properties of the prepared soft polymer networks. Full article

The hydrophilic extractives isolated from black alder (Alnus glutinosa) bark through hot water extraction were characterized as novel renewable macromonomers capable of forming polyurethane (PU) networks based on a commercial polyisocyanate, with partial or complete replacement of petroleum-derived polyol polyether. The bark-sourced bio-polyol mainly consists of the xyloside form of the diarylheptanoid oregonin, along with oligomeric flavonoids and carbohydrates, resulting in a total OH group content of 15.1 mmol·g⁻¹ and a molecular weight (M_n) of approximately 750 g∙mol⁻¹. The ³¹P NMR data confirmed a similar proportion of aliphatic OH and phenolic groups. Three-component PU compositions were prepared using polyethylene glycol (M_n = 400 g∙mol⁻¹), bio-polyol (up to 50%), and polymeric diphenylmethane diisocyanate, which were pre-polymerized in tetrahydrofuran (THF) solution with tin organic and tertiary amine catalysts. The resulting mixture was cast and subjected to thermal post-curing. Calculation and experimental data confirmed the crosslinking activity of the bark-sourced bio-polyol in PU, leading to an increase in glass transition temperature (Tg), a decrease in sol fraction yield upon leaching of cured PU networks in THF, a significant increase in Young’s modulus and tensile strength. The macromonomers derived from bark promoted char formation under high temperature and oxidative stress conditions, limiting heat release during macromolecular network degradation compared to bio-polyol-free PU. It was observed that amine catalysts, which are active in urethane formation with phenolic groups, promoted the formation of PU with higher Tg and modulus at tensile but with less limitation of heat liberation during PU macromolecular structure degradation. The high functionality of the bark-derived bio-polyol, along with the equal proportion of phenolic and aliphatic OH groups, allows for further optimization of PU characteristics using three variables: increasing the substitution extent of commercial polyethers, decreasing the NCO/OH ratio, and selecting the type of catalyst used. Full article