Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Polycaprolactone Polymer Mixtures Reinforced by Cellulose Nanocrystals: Experimental and Simulation Studies

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polycaprolactone (PHBV/PCL) polymer mixtures reinforced by cellulose nanocrystals (CNCs) have been obtained. To improve the CNC compatibility with the hydrophobic PHBV/PCL matrix, the CNC surface was modified by amphiphilic polymers, i.e., polyvinylpyrrolidone (PVP) and polyacrylamide (PAM). The polymer composites were characterized by FTIR, DSC, TG, XRD, microscopy, BET surface area, and tensile testing. The morphological, sorption, thermal, and mechanical properties of the obtained composites have been studied. It was found out that with an increase in the CNC content in the composites, the porosity of the films increased, which was reflected in an increase in their specific surface areas and water sorption. An analysis of the IR spectra confirms that hydrogen bonds can be formed between the CNC hydroxyl- and the –CO– groups of PCL and PHBV. The thermal decomposition of CNC in the PHBV/PCL/CNC composites starts at a much higher temperature than the decomposition of pure CNC. It was revealed that CNCs can either induce crystallization and the polymer crystallite growth or act as a compatibilizer of a mixture of the polymers causing their amorphization. The CNC addition significantly reduces the elongation and strength of the composites, but changes Young’s modulus insignificantly, i.e., the mechanical properties of the composites are retained under conditions of small linear deformations. A molecular-dynamics simulation of several systems, starting from simplest binary (solvent-polymer) and finishing with multi-component (CNC—polymer mixture—solvent) systems, has been made. It is concluded that the surface modification of CNCs with amphiphilic polymers makes it possible to obtain the CNC composites with hydrophobic polymer matrices.

Cement-polymer materials for well casing

The work shows the efficiency of using the SСADC reagent as an additive in cement-polymer mixtures. It also outlines physicomechanical properties of the cement slurry and the stone formed on their basis at temperatures of 22 C and 80 C. The main regularities of the formation of structures of various levels in cement-polymer solutions are revealed, depending on the degree of filling and the type of introduced modifications of the SСADC reagent. It was found that an entangled fibrous structure is formed between the hydrated cement minerals and the complex additive SСADC. At a concentration of 0.2%, it provides a self-healing effect for a damaged cement stone, and also improves the properties of cement-polymer grouting mixtures, contributing to a decrease in the filtration rate of the solution to 30%, an increase in bending strength by 25-27% and by 36-42% in ultimate strength for compression.

New Insights on Solvent Implications in the Design of Materials Based on Cellulose Derivatives Using Experimental and Theoretical Approaches

The current paper presents a strategic way to design and develop materials with properties adapted for various applications from biomedicine to environmental applications. In this context, blends of (hydroxypropyl)methyl cellulose (HPMC) and poly(vinylpyrrolidone) (PVP) were obtained to create new materials that can modulate the membrane properties in various fields. Thus, to explore the possibility of using the HPMC/PVP system in practical applications, the solubility parameters in various solvents were initially evaluated using experimental and theoretical approaches. In this frame, the study is aimed at presenting the background and steps of preliminary studies to validate the blends behavior for targeted application before being designed. Subsequently, the analysis of the behavior in aqueous dilute solution of HPMC/PVP blend offers information about the conformational modifications and interactions manifested in system depending on the structural characteristics of polymers (hydrophilicity, flexibility), polymer mixtures composition, and used solvent. Given this background, based on experimental and theoretical studies, knowledge of hydrodynamic parameters and analysis of the optimal compositions of polymer mixtures are essential for establishing the behavior of obtained materials and validation for most suitable applications. Additionally, to guarantee the quality and functionality of these composite materials in the targeted applications, e.g., biomedical or environmental, the choice of a suitable solvent played an important role.

Strength, Carbonation Resistance, and Chloride-Ion Penetrability of Cement Mortars Containing Catechol-Functionalized Chitosan Polymer

There have been numerous recent studies on improving the mechanical properties and durability of cement composites by mixing them with functional polymers. However, research into applying modified biopolymer such as catechol-functionalized chitosan to cement mortar or concrete is rare to the best of our knowledge. In this study, catechol-functionalized chitosan (Cat-Chit), a well-known bioinspired polymer that imitates the basic structures and functions of living organisms and biological materials in nature, was synthesized and combined with cement mortar in various proportions. The compressive strength, tensile strength, drying shrinkage, accelerated carbonation depth, and chloride-ion penetrability of these mixes were then evaluated. In the ultraviolet–visible spectra, a maximum absorption peak appeared at 280 nm, corresponding to catechol conjugation. The sample containing 7.5% Cat-Chit polymer in water (CPW) exhibited the highest compressive strength, and its 28-day compressive strength was ~20.2% higher than that of a control sample with no added polymer. The tensile strength of the samples containing 5% or more CPW was ~2.3–11.5% higher than that of the control sample. Additionally, all the Cat-Chit polymer mixtures exhibited lower carbonation depths than compared to the control sample. The total charge passing through the samples decreased as the amount of CPW increased. Thus, incorporating this polymer effectively improved the mechanical properties, carbonation resistance, and chloride-ion penetration resistance of cement mortar.

MODIFIED WITH VARIOUS ADDITIVES ARYLALYCLIC COPOLYIMIDES AND COMPOSITE FILMS BASED ON THEIR BASIS

lopment of arylalicyclic copolyimides based on alicyclic dianhydride, aromatic dianhydrides of benzophenone- and diphenyloxidetetracarboxylic acids with 4,4'-diaminodiphenyl oxide at various ratios of alicyclic and aromatic dianhydrides, as well as various compositions based on these copolymers with low- or other high-molecular compounds that enhance the characteristics of the polymer matrix. Composite films were formed from solutions of the obtained polymer mixtures, and their properties were studied. It was noted that at optimal ratio of components, the films have improved thermal and strength properties, etc., exceeding the analogous properties of the initial arylalicyclic copolymer, while the elasticity has acceptable values for such material. The best characteristics had the composite films formed from a ternary composition of copo-lyimide-polyethylene glycol-alkylated montmorillonite. Metal-containing composite films, along with higher thermal stability compared to unmodified copolyimide, were resistant to aggressive reagents, lower values of specific volume and surface resistance, higher viscosity values, and different colors depending on the nature of the salt. By introducing a silicon-containing compound into the copolyimide solution, the new polymer systems have been obtained, and the porous films could be formed.

Fabrication of Novel and Potential Selective 4-Cyanophenol Chemical Sensor Probe Based on Cu-Doped Gd2O3 Nanofiber Materials Modified PEDOT:PSS Polymer Mixtures with Au/µ-Chip for Effective Monitoring of Environmental Contaminants from Various Water Samples

Herein, a novel copper-doped gadolinium oxide (Cu-doped Gd2O3; CGO) nanofiber was synthesized by a simple solution method in the basic phase and successfully characterized. We have used Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Energy-Dispersive Spectroscopy (EDS) techniques for characterization of the CGO nanofiber. The CGO nanofiber was used later to modify Au-coated μ-Chips with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer mixtures (coating binder) to selectively detect 4-cyanophenol (4-CP) in an aqueous medium. Notable sensing performance was achieved with excellent sensitivity (2.4214 µAµM−1 cm−2), fast response time (~12 s), wide linear dynamic range (LDR = 1.0 nM–1.0 mM: R2 = 0.9992), ultra-low detection limit (LoD; 1.3 ± 0.1 pM at S/N = 3), limit of quantification (LoQ; 4.33 pM), and excellent reproducibility and repeatability for CGO/Au/μ-Chip sensor. This CGO modified Au/μ-chip was further applied with appropriate quantification and determination results in real environmental sample analyses.

Mechanism and kinetic regularities of crystallization of nanocomposites based on bentonite and polymer mixtures of random polypropylene with butadiene nitrile rubber

The paper presents the results of a study of the dilatometric properties of thermoplastic elastomer nanocomposites based on mixtures of random polypropylene, nitrile butadiene rubber, a compatibilizer - copolymer of polypropylene with maleic anhydride. Nanosized bentonite particles were used as a filler. The concentration of bentonite nanoparticles was varied in the range of 1.0-20 wt %. The values of the free and occupied specific volumes of nanocomposites were determined depending on the temperature and concentration of bentonite. The mechanism and kinetic regularities of the crystallization process of nanocomposites are established.