Copolymer Solutions Research Articles

The Superhydrophobic State Stability of Coatings Based on Copolymers of Glycidyl Methacrylate and Alkyl Methacrylates on Cotton Fabric Surface

We suggest a simple and reproducible strategy for fabricating durable superhydrophobic coatings on the basis of series of functional random copolymers of alkyl methacrylates and glycidyl methacrylate on cotton fabric surface. The procedure consists of the fabric treatment by solutions of copolymers in methylethylketone and following heating at 140 °C. The initial contact angles of obtained coatings on fabric surface achieve 165°. The dependence of superhydrophobic properties of coatings based on copolymers of glycidyl methacrylate and alkyl (meth)acrylates (with alkyl radicals С4–С18 in side chains) attached to the cotton fabric surface was studied. The comparative analysis of superhydrophobic state stability of polymer coatings during long-term contacts with aggressive media is presented. We evaluated the contact angles stability as a function of prolonged contact of polymer coatings with water under saturated vapor conditions, organic solvents, and synthetic detergents. Polymeric coatings based on a copolymer of lauryl methacrylate (С12) and glycidyl methacrylate provide better stability of superhydrophobic properties compared with other copolymers of alkyl methacrylates.

A Study of Films Based on Acrylic Copolymers: Mesoscopic Simulation

Aqueous solutions of an acrylic copolymer and a low-molecular-weight anionic surfactant are studied using mesoscopic simulation by dissipative particle dynamics. The possibility of formation of a homogeneous film from the acrylic copolymer, where a domain structure is absent and a surfactant is separated from the polymer phase, is studied. A mesoscopic model taking into account the main structural features of the acrylic copolymer chain and the surfactant is proposed. It was shown that a change in the parameters of electrostatic interaction influences the fineness of the systems under study, but does not change the morphology of forming films. Conditions for the preparation of a film with homogeneous morphology are stated.

A rheo-optical study on the linear viscoelasticity and molecular dynamics of block copolymer solutions forming hexagonal close-packed cylindrical domains

The linear viscoelastic properties of block copolymer solutions forming hexagonal close-packed cylindrical domains and their relaxation dynamics were investigated by using a rheo-optical method based on simultaneous measurements of stress and strain-induced birefringence. The sample solution is composed of a PS-b-PI diblock copolymer and a mixed solvent of DOP and SALACOS 913, which are a neutral solvent for both PS and PI and a highly selective solvent for PI, respectively. The copolymer concentration was fixed, and the DOP fraction of the mixed solvent was increased to change the domain structure from a hexagonal close-packed cylindrical structure to a spherical structure. The sign of the complex strain-optical coefficient, which is the complex ratio of the oscillatory strain-induced birefringence to the strain, varied with frequency, indicating that the viscoelastic relaxation spectra include multiple relaxation modes. Four relaxation modes were successfully estimated with the aid of the modified stress-optical rule. The four modes were assigned to (1) reorientation of corona chains, (2) reorientation of core chains, (3) deformation of domains, and (4) reorientation of grains. The intrinsic birefringence of the cylindrical structure was found to be 1.7 × 10−5. By assuming entropic stress of grain reorientation, the grain size was estimated to be ~0.2 μm from the viscoelastic intensity. The linear viscoelastic properties of block copolymer solutions forming hexagonal close-packed cylindrical domains were investigated by using a rheo-optical method. Based on the modified stress-optical rule, the complex shear modulus was separated to four relaxation modes. Considering the sign and magnitude of the stress-optical coefficient associated with each mode, the four modes were assigned to (1) reorientation of corona chains, (2) reorientation of core chains, (3) deformation of domains, and (4) reorientation of grains. The results were compared with those for spherical domains.

Unusually large hysteresis in temperature-responsive phase-transition behavior of aqueous solutions of isotactic copolymers comprising N-ethylacrylamide and N-isopropylacrylamide

Radical copolymerizations of N-ethylacrylamide (NEAAm) and N-isopropylacrylamide (NIPAAm) at various ratios were conducted in N-ethylacetamide at −40 °C to prepare isotactic copolymers with mm triad contents of 48.7%–50.8%. The temperature-induced phase transition behaviors of their aqueous solutions were investigated using light transmittance (500 nm) and dynamic light scattering. Reversible and sharp phase transitions were observed in the transmittance of aqueous solutions (1.0 wt%) of copolymers with NIPAAm compositions of ≤9.1 mol%. The phase transition temperatures in both the heating and cooling processes gradually decreased with increasing hydrophobic NIPAAm composition. However, copolymers with NIPAAm compositions of 13.9–28.0 mol% exhibited large hystereses (ca. 40 °C) in which the phase transition temperature in the cooling process dramatically decreased. Furthermore, the copolymer with NIPAAm composition of 37.8 mol% was insoluble in water. Syndiotactic poly(NEAAm-co-NIPAAm)s were soluble in water and showed reversible and sharp phase transitions regardless of the NIPAAm composition, which indicates that stereostructure plays an important role in the induction of unusually large hysteresis. Dynamic light scattering analysis suggested that the dehydrated polymers were swollen in the cooling process, even below the phase transition temperature in the heating process, likely because of the cross-linking domain formed by isotactic NIPAAm segments with hydrophobic interaction in the dehydrated state.

Triblock Copolymers Based on Sucrose Methacrylate and Methyl Methacrylate: RAFT Polymerization and Self‐Assembly

AbstractABA and BAB triblock amphiphilic copolymers based on sucrose methacrylate and methyl methacrylate are synthesized by sequential reversible addition–fragmentation chain transfer polymerization using S,S′‐bis(R,R′‐dimethyl‐R′′‐acetic acid)‐trithiocarbonate as a chain transfer agent. The copolymers present narrow molar mass dispersity, controlled molar mass and architecture as determined by gel permeation chromatography and 1H and 13C nuclear magnetic resonance. The copolymers with molar and mass fractions of poly(sucrose methacrylate) block ranging from 1 to 22 mol% and 3 to 52 wt%, respectively, and different molar masses present characteristics of a surfactant such as self‐assembly. The self‐assembly of the triblock copolymers in water, N,N‐dimethylformamide (DMF), dichloromethane, tetrahydrofuran, or benzene results mostly in vesicles as confirmed by scanning electron microscopy images and small‐angle X‐ray of the dispersions. Moreover, the copolymers present the capability to stabilize aromatic molecules (Nile Red dye) and nonpolar solvents in an aqueous phase and polar ionic molecules (methylene blue) and water in a nonpolar medium, suggesting the potential for application in drug encapsulation, environmental remediation systems, and molecular extraction in liquid–liquid immiscible systems, for example. Films prepared by casting from copolymer solutions in DMF present a lamellar structure with the lamellar thickness varying according to the copolymer molar mass.

Asymmetric Reactions in Water Catalyzed by L-Proline Tethered on Thermoresponsive Ionic Copolymers

L-Proline was covalently tethered on thermoresponsive ionic block copolymers that formed micelles in aqueous solutions. The block copolymers consisted of a poly(N-isopropylacrylamide) (PNIPAAm) segment and an anionic or cationic polymer segment. These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 35-40°C, and achieved thermal stimuli-induced formation and dissociation of micelles. The copolymer generated micelles in aqueous solution at a higher temperature, where a catalytic aldol reaction proceeded with high diastereo- and enantioselectivities. The micelles dissociated at lower temperature to form a clear solution such that the products could be efficiently extracted from the aqueous reaction mixture. Extraction of the aldol product with an organic solvent from the aqueous solution of the anionic copolymer was more efficient than from the nonionic copolymer solution.

Correction to: Self-organization in aqueous solutions of thermosensitive star-shaped and linear gradient copolymers of 2-ethyl-2-oxazoline and 2-isopropyl-2-oxazoline

The author noticed that the published paper contained error. Unfortunately, the author name “Tatyana Kirila” of the article was repeated twice. Given in this paper is the correct list of authors.

Formation and Regulation of Multicompartment Vesicles from Cyclic Diblock Copolymer Solutions: A Simulation Study.

The self-assembly of a cyclic AB copolymer system with relatively long A blocks and short B blocks in B-selective solvents is investigated using a simulated annealing method. By investigating the effect of the lengths and solubilities of A and B blocks (NA and NB, εAS and εBS), the incompatibility between A and B blocks (εAB), as well as the polymer concentration (Cp) and the conditions for the formation of multicompartment vesicles in cyclic diblock copolymer solutions, is predicted. The phase diagrams in terms of NB, εAS, and Cp are constructed. The mechanism of the morphological transition is elucidated. It is shown that for cyclic copolymers the change in the above factors relating to the polymer and solvent properties all can lead to the transition from simple vesicles to multicompartment vesicles, but two different transition mechanisms are revealed. In addition, our simulations demonstrate that the self-assembly of cyclic copolymers could provide a powerful strategy for regulating the compartment number and the wall thickness of the multicompartment vesicles by adjusting the block solubilities and block lengths, respectively. These findings will facilitate the application of multicompartment architectures in cell mimicry, drug delivery, and nanoreactors.

Microparticles-in-Thermoresponsive/Bioadhesive Hydrogels as a Novel Integrated Platform for Effective Intra-articular Delivery of Triamcinolone Acetonide.

Intra-articular (IA) injection of thermoresponsive hydrogels coupled with microparticles (MPs) possess the benefit of sustaining the anti-inflammatory drug effect within the joint cavity for rheumatoid arthritis treatment. Star-shaped thermoresponsive poly(polyethylene glycol) methacrylate [Poly(PEGMA)] copolymers were synthesized using free radical polymerization technique and fully characterized. Triamcinolone acetonide (TA)-loaded PLA/mPEG-PDL MPs, previously optimized, were integrated into the synthesized copolymer solutions at various concentrations and tested for their gelation temperatures. The MPs-in-hydrogel formulations were characterized using scanning electron microscope (SEM), viscosity measurements, ex vivo bioadhesion, and in vitro release studies. The anti-inflammatory effect of integrated systems was assessed in adjuvant-induced monoarthritic rat knee joints and compared to Kenacort and TA-loaded MPs. Two copolymers were successfully synthesized; G-1 = poly(PEGMA188-ME-co-PEGMA475-ME) and G-2 = poly(PEGMA246-EE-co-PEGMA475-ME). Using the tube inversion technique, the gel formation was found dependent on copolymer concentration. An irreversible aggregation was obtained at copolymer concentrations ≤10% (w/v), while a gel was formed at 20 and 30% (w/v) of both copolymers upon increasing temperature. The MP-hydrogel formulations were optimized at 20 and 30% (w/v) of G-1 and G-2 with gelation temperatures of 33 and 37 °C, respectively. SEM images revealed the porous microstructures of hydrogels and their adsorption on MP surfaces. The integrated formulas showed pseudoplastic behaviors, while the bioadhesion study confirmed their bioadhesiveness on excised cartilage. The in vitro release study confirmed drug sustainment from MPs-hydrogels compared to MPs. In vivo studies proved the superiority of MP-in-hydrogels in treatment of induced arthritis, relative to Kenacort and MPs alone, suggesting the applicability of this integrated platform in IA drug delivery.

Drug carrier systems made from self-assembled glyco-nanoparticles of maltoheptaose-b-polyisoprene enhanced the distribution and activity of curcumin against cancer cells

Controlled self-assembly of polymeric systems behave according to their composition and physical-chemical properties. Inclusion of a guest molecule may influence interactions and response to the media and to other surfaces and bodies, for example, cells. Hence, loading the polymeric system with curcumin (CUR), a natural and anticancer drug, confer interesting features to the carrier material. Micelle formation was achieved, in aqueous solution of carbohydrate-based block copolymer consisting in maltoheptaose-block-polyisoprene (MH-b-PI3.8kDa), by adding a large amount of water (a selective solvent for maltoheptaose, MH) into a solution of well-dissolved MH-b-PI3.8kDa (THF/H2O 9:1 (% w/w)]. Morphology and size (ca. 89 nm) of these glyco-nanoparticles were characterized using light scattering (static and dynamic modes – SLS and DLS) complemented by nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The lyophilization efficiency was confirmed by measuring the relation between final and initial diameters (Sf/Si). CUR was successfully loaded into the nanoparticles with an entrapment efficiency of ca. 70%. CUR-charged nanoparticles showed stability into simulated gastric and intestinal fluids. Such micelles served as drug delivery system to carry CUR and presented a great role in wiping out unhealthy cells from many sorts.

Development of a nasal spray containing aminocaproic acid and a copolymer of N-vinylpyrrolidone and 2-methyl-5-vinylpyridine for use in the prevention of influenza and other viral respiratory infections

Objectives. Prevention of influenza and viral respiratory infections is one of the major public health problems today. The aim of the study was to develop the formulation and production conditions for a nasal spray that can be used in the prevention of influenza and other viral respiratory infections, based on aminocaproic acid and a copolymer of N-vinylpyrrolidone and 2-methyl-5-vinylpyridine.Methods. The influence of pH and temperature on the transparency of the copolymer solution was investigated using a turbidimeter to determine the optimal pH for the dosage form. The pH value was determined using a pH meter equipped with a combined glass electrode. The presence or absence of opalescence in the solution was determined visually, whereas the dynamic viscosity of the solution was determined at 25.0±0.5°С using a rotational viscometer. The optimal temperature and mixing speeds were selected as part of the technological development process. Quantitation of the active substances in the resulting drug was conducted using a previously reported high performance liquid chromatography method. A preliminary evaluation of the drug’s shelf life was performed via stability studies using the accelerated aging method.Results. Drug stability was ensured when the pH range of the dosage form was between 5.5 and 6.2. The addition of a thickening agent is not advisable due to undesired interactions between the excipients and the active substances during storage. Ideally, the drug composition for nasal use was aminocaproic acid (1 wt %) and the copolymer (0.5 wt %) in aqueous solution. A phosphate buffer solution with pH 5.5 was selected as the solvent for the dosage form to ensure the stability of the drug solution and ease-of-use without any disruptions in the normal functioning of the cilia in the nasal cavity. The optimal technology for drug production was determined, and the control parameters for this process were highlighted. Drug stability studies conducted via the accelerated aging method revealed that the estimated shelf life of the dosage form was 2 years. Conclusions. A new formulation and optimized production conditions were developed for a drug based on aminocaproic acid and a copolymer of N-vinylpyrrolidone and 2-methyl-5-vinylpyridine, in the form of a nasal spray, for the prevention of influenza and other viral respiratory infections.

Self-organization in aqueous solutions of thermosensitive star-shaped and linear gradient copolymers of 2-ethyl-2-oxazoline and 2-isopropyl-2-oxazoline

Thermosensitive star-shaped eight-arm poly-2-alkyl-2-oxazolines (M = 21,000 g mol−1) was synthesized. The arms were gradient copolymers of 2-ethyl-2-oxazoline (EtOx) and 2-isopropyl-2-oxazoline (iPrOx). The more hydrophilic EtOx units prevailed near the calix[8]arene core. For comparison, model linear gradient copolymer (M = 3800 g mol−1) was investigated. For both polymers, comonomer molar ratio was 1/1. The aqueous solutions of copolymers were studied by light scattering and turbidimetry. Self-organization of linear and star-shaped molecules in solution was different, but the phase separation temperatures for these copolymers coincided. In order to find out the influence of the distribution of EtOx and iPrOx units along the arms on the behavior of star-shaped polyalkyloxazolines, the behavior of investigated stars was compared with that for stars, whose arms was block copolymers poly-2-isopropyl-2-oxazoline and poly-2-ethyl-2-oxazoline. It was shown that the phase separation temperature for gradient copolymer solutions was higher than one for block copolymers.

Estimation of Reactivity Ratios in the Copolymerization of Styrene and VeoVa‐10

AbstractThe styrene and vinyl neodecanoate copolymerization system shows a strong tendency to form two separate homopolymers. In order to improve the feeding strategies and hence the copolymer uniformity, it is necessary to know the reactivity ratios between these monomers. The error‐in‐variables‐method (EVM) is the most recommended mathematical procedure for estimating these parameters. Experiments on free‐radical copolymerization in solution in sealed ampoules are carried out to provide data for the conversion (via gravimetry) and fractional monomer compositions (via Fourier transform mid‐infrared (mid‐FT‐IR) spectroscopy). These data allow estimation of the reactivity ratios. EVM appropriately takes into account the experimental errors in the data and allows determination of the reactivity ratio values by the Mayo–Lewis model (r1 = 28.60 and r2 = 1.23). The convergence and robustness of the method decrease considerably with a larger discrepancy between the reactivity values.

Solid-State Synthesis of Water-Soluble Chitosan-g-Hydroxyethyl Cellulose Copolymers.

Graft copolymers of chitosan with cellulose ether have been obtained by the solid-state reactive mixing of chitin, sodium hydroxide and hydroxyethyl cellulose under shear deformation in a pilot twin-screw extruder. The structure and composition of the products were determined by elemental analysis and IR spectroscopy. The physicochemical properties of aqueous solutions of copolymers were studied as a function of the composition, and were correlated to the mechanical characteristics of the resulting films to assess the performance of new copolymers as coating materials, non-woven fibrous materials or emulsifiers for interface stabilization during the microparticle fabrication process.

Oxidation-Responsive Emulsions Stabilized with Poly(Vinyl Pyrrolidone-co-allyl Phenyl Sulfide).

Oxidation-responsive emulsions were obtained by stabilizing mineral oil droplets using amphiphilic poly(vinyl pyrrolidone-co-allyl phenyl sulfide) (P(VP-APS)). 1H nuclear magnetic resonance (NMR) spectroscopy revealed that P(VP-APS) whose APS content was 0%, 3.28%, 3.43% and 4.58% were successfully prepared by free radical reaction and the sulfide of APS was oxidized by H2O2 treatment. X-ray Photoelectron Spectroscopy (XPS) also disclosed that the sulfide of APS was oxidized to sulfone by the oxidizing agent. The optical density of copolymer solutions and the interfacial activity of the copolymers markedly decreased by H2O2 treatment possibly because the sulfide of APS was oxidized and the amphiphilicity of the copolymers were weakened. The increase rate of the oil droplet diameter of the emulsions was outstandingly promoted when H2O2 solution (10%, v/v) was used as an aqueous phase. The phase separation of the emulsions was also expedited by the oxidizing agent. The oxidation of APS and the weakened interfacial activity were thought to be a main reason for the demulsification of P(VP-APS)-stabilized emulsions.

Thermo-associating polymers based on cross-linked 2-acrylamido-methylpropane sulfonic acid, part A: Synthesis and solution behavior

A novel thermo-thickening hydrophilic copolymer (CGBA) was prepared by free-radical copolymerization of sodium 2-acrylamido-2-methylpropane sulfonic acid (NaAMPS) with a newly-synthesized thermo-sensitive macromonomer (BA) and cross-linking N,N’-methylenebisacrylamide (MBA) in aqueous solution under optimal conditions. Its aqueous solution viscosity behavior with respect to temperature was preliminarily evaluated in comparison with its cross-linked sulfonated copolymer (CPAMPS) counterpart (without BA side-chains). Particular attention is dedicated to the thermo-thickening of the aqueous copolymer solutions as studied by the viscosity measurements. In pure water, and above 0.5 wt.%, CGBA manifested an abrupt macroscopic property above the critical association temperature (Tcass), while CPAMPS exhibited shear-thinning behavior following an Arrhenius law under the same conditions. The composition and length of BA side-chains were identified as the key parameters to envision the self-assembling behavior of CGBA. The results obtained from complementary experiments, performed by proton nuclear magnetic resonance (1H-NMR), Differential scanning calorimetry (DSC), and pyrene fluorescence showed the phase transition of BA side-chains above the Tcass. In addition, well above the Tcass (70 and 80 °C), the oscillatory shear experiments proved that the storage and loss modulus could be fitted with the single relation time Maxwell model at low frequencies. Furthermore, the magnitude of the thickening effect and the Tcass could be modulated using external factors such as shear rates, salinity, and pH. This, in combination with the cost-effectiveness, and the need to further broaden the established theory of thermo-sensitive comonomer, make this copolymer especially interesting for application not only in polymer flooding, but also in drilling fluid.

Thermally Triggered Injectable Underwater Adhesives.

A novel bioinspired underwater adhesive based on the injectable aqueous solution of a graft copolymer with a thermoresponsive backbone is reported, which turns into a sticky hydrogel just below body temperature. With this topology, the collapse of the backbones upon the thermal transition leads to the formation of a percolating network of strong hydrophobic domains. Similar to pressure-sensitive adhesives (PSAs), the hydrogel goes through fibrillation and extensive energy dissipation in large deformations, giving it an edge over conventional chemical hydrogels, which are typically elastic and inherently nonsticky. This capability comes from the hydrophobic nanoscaffold, which resists large deformations to minimize its contact with water. Since hydrophobic interactions are not weakened in water, the behavior of the hydrogel is maintained in aqueous medium. Chemistry-insensitive adhesion of this hydrogel offers a major advantage over current injectable adhesives, which rely on in situ chemical crosslinking reactions with tissues.

Thermoresponsive Poly(ε-Caprolactone)-Poly(Ethylene/Propylene Glycol) Copolymers as Injectable Hydrogels for Cell Therapies.

Injectable, thermoresponsive hydrogels are promising candidates for the delivery, maintenance and controlled release of adoptive cell therapies. Therefore, there is significant interest in the development of cytocompatible and biodegradable thermoresponsive hydrogels with appropriate gelling characteristics. Towards this end, a series of thermoresponsive copolymers consisting of poly(caprolactone) (PCL), poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) segments, with various PEG:PPG ratios, were synthesised via ring-opening polymerisation (ROP) of ε-caprolactone and epoxy-functionalised PEG and PPG derivatives. The resultant PCL–PEG–PPG copolymers were characterised via proton nuclear magnetic resonance (1H NMR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The thermoresponsive characteristics of the aqueous copolymer solutions at various concentrations was investigated using the inversion method. Whilst all of the copolymers displayed thermoresponsive properties, the copolymer with a ratio of 1:2 PEG:PPG exhibited an appropriate sol–gel transition (28 °C) at a relatively low concentration (10 wt%), and remained a gel at 37 °C. Furthermore, the copolymers were shown to be enzymatically degradable in the presence of lipases and could be used for the encapsulation of CD4+ T-cell lymphocytes. These results demonstrate that the thermoresponsive PCL–PEG–PPG hydrogels may be suitable for use as an adoptive cell therapy (ACT) delivery vehicle.

All niobia Bragg stacks for optical sensing of vapors

Vapor responsive all Nb2O5 Bragg stacks were prepared using spin-coating of alternating dense and porous films with quarter-wavelength thickness. The required porosity in the films was achieved by soft-templating method using micellar solution of Pluronic copolymer as an organic template. The surface morphology and structure of the films were studied by transmission electron microscopy and selected area electron diffraction, respectively, while optical characterization was performed by combination of ellipsometric and reflectance measurements. Vapor sensing response of the films was tested by reflectance measurements of the samples prior to and after exposure to acetone vapors selected as probe molecules. Incorporation of “defect” layer in the multilayered structures was firstly simulated theoretically and then realized experimentally aiming at improvement of the optical response to volatile organic compounds. Furthermore, the potential of all niobia stacks consisting of alternating dense and porous sol–gel Nb2O5 films as chemical sensors with optical read-out is demonstrated and discussed.

Self-Healing Metallo-Supramolecular Hydrogel Based on Specific Ni2+ Coordination Interactions of Poly(ethylene glycol) with Bistriazole Pyridine Ligands in the Main Chain.

In this study, a supramolecular hydrogel formed by incorporating the 2,6-bis(1,2,3-triazol-4-yl)-pyridine (btp) ligand in the backbone of a polymer prepared by copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) "click" polyaddition reaction of 2,6-diethynylpyridine and diazido-poly(ethylene glycol) is reported. The hydrogelation is selectively triggered by the addition of Ni2+ ions to aqueous copolymer solutions. The gelation and rheological properties could be tuned by the change of metal to ligand ratio and polymer concentration. Interestingly, the hydrogel exhibits a fast (within 2 min) and excellent repeatable autonomic healing capacity without external stimuli. This self-healing behavior may find potential applications for the repairing of metal coatings, in the future.