Polymers, Volume 12, Issue 2 (February 2020) – 251 articles

Hydrogels are excellent candidates for the sustained local delivery of anticancer drugs, as they possess tunable physicochemical characteristics that enable to control drug release kinetics and potentially tackle the problem of systemic side effects in traditional chemotherapeutic delivery. Yet, current systems often involve complicated manufacturing or covalent bonding processes that are not compatible with regulatory or market reality. Here, we developed a novel gelatin methacryloyl (GelMA)-based drug delivery system (GelMA-DDS) for the sustained local delivery of paclitaxel-based Abraxane^®, for the prevention of local breast cancer recurrence following mastectomy. GelMA-DDS readily encapsulated Abraxane^® with a maximum of 96% encapsulation efficiency. The mechanical properties of the hydrogel system were not affected by drug loading. Tuning of the physical properties, by varying GelMA concentration, allowed tailoring of GelMA-DDS mesh size, where decreasing the GelMA concentration provided overall more sustained cumulative release (significant differences between 5%, 10%, and 15%) with a maximum of 75% over three months of release, identified to be released by diffusion. Additionally, enzymatic degradation, which more readily mimics the in vivo situation, followed a near zero-order rate, with a total release of the cargo at various rates (2–14 h) depending on GelMA concentration. Finally, the results demonstrated that Abraxane^® delivery from the hydrogel system led to a dose-dependent reduction of viability, metabolic activity, and live-cell density of triple-negative breast cancer cells in vitro. The GelMA-DDS provides a novel and simple approach for the sustained local administration of anti-cancer drugs for breast cancer recurrence. Full article

Herein, commercially available Dowex 5WX8, a cation exchange polymeric resin, was modified through solvent impregnation with t-butyl phosphate (TBP) to produce a solvent impregnated resin (SIR), which was tested for the removal of rhodamine B (RhB) from water in batch adsorption experiments. The effect of SIR dosage, contact time, and pH on RhB adsorption was studied and optimized by response surface methodology (RSM), interaction, Pareto, and surface plots. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were respectively used for characterizing SIR surface morphology and identifying active binding sites before and after RhB adsorption. SEM showed that the pristine SIR surface was covered with irregular size and shape spots with some pores, while RhB saturated SIR surface was non-porous. FTIR revealed the involvement of electrostatic and π–π interactions during RhB adsorption on SIR. Dosage of SIR, contact time, and their interaction significantly affected RhB adsorption on SIR, while pH and its interaction with dosage and contact time did not. The optimum identified experimental conditions were 0.16 g of SIR dose and 27.66 min of contact time, which allowed for 98.45% color removal. Moreover, RhB adsorption equilibrium results fitted the Langmuir isotherm with a maximum monolayer capacity (q_max) of 43.47 mg/g. Full article

Isolation and characterization of new biologically active substances affecting cancer cells is an important issue of fundamental research in biomedicine. Trehalose lipid was isolated from Rhodococcus wratislaviensis strain and purified by liquid chromatography. The effect of trehalose lipid on cell viability and migration, together with colony forming assays, were performed on two breast cancer (MCF7—low metastatic; MDA-MB231—high metastatic) and one “normal” (MCF10A) cell lines. Molecular modeling that details the structure of the neutral and anionic form (more stable at physiological pH) of the tetraester was carried out. The tentative sizes of the hydrophilic (7.5 Å) and hydrophobic (12.5 Å) portions of the molecule were also determined. Thus, the used trehalose lipid is supposed to interact as a single molecule. The changes in morphology, adhesion, viability, migration, and the possibility of forming colonies in cancer cell lines induced after treatment with trehalose lipid were found to be dose and time dependent. Based on the theoretical calculations, a possible mechanism of action and membrane asymmetry between outer and inner monolayers of the bilayer resulting in endosome formation were suggested. Initial data suggest a mechanism of antitumor activity of the purified trehalose lipid and its potential for biomedical application. Full article

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. Full article

Lecithin-encapsulated carvacrol has been incorporated into poly (vinyl alcohol) (PVA) for the purpose of obtaining active films for food packaging application. The influence of molecular weight (Mw) and degree of hydrolysis (DH) of the polymer on its ability to retain carvacrol has been analysed, as well as the changes in the film microstructure, thermal behaviour, and functional properties as packaging material provoked by liposome incorporation into PVA matrices. The films were obtained by casting the PVA aqueous solutions where liposomes were incorporated until reaching 0 (non-loaded liposomes), 5 or 10 g carvacrol per 100 g polymer. The non-acetylated, high Mw polymer provided films with a better mechanical performance, but less CA retention and a more heterogeneous structure. In contrast, partially acetylated, low Mw PVA gave rise to more homogenous films with a higher carvacrol content. Lecithin enhanced the thermal stability of both kinds of PVA, but reduced the crystallinity degree of non-acetylated PVA films, although it did not affect this parameter in acetylated PVA when liposomes contained carvacrol. The mechanical and barrier properties of the films were modified by liposome incorporation in line with the induced changes in crystallinity and microstructure of the films. Full article

Ceramifiable silicone rubber composites play important roles in the field of thermal protection systems (TPS) for rocket motor cases due to their advantages. Ceramifiable silicone rubber composites filled with different contents of ZrSi₂ were prepared in this paper. The fffects of ZrSi₂ on the vulcanization, mechanical and ablation resistance properties of the composites were also investigated. The results showed that the introduction of ZrSi₂ decreased the vulcanization time of silicone rubber. FTIR spectra showed that ZrSi₂ did not participate in reactions of the functional groups of silicone rubber. With the increasing content of ZrSi₂, the tensile strength increased first and then decreased. The elongation at break decreased and the permanent deformation increased gradually. The thermal conductivity of the composite increased from 0.553 W/(m·K) to 0.694 W/(m·K) as the content of the ZrSi₂ increased from 0 to 40 phr. In addition, the thermal conductivity of the composite decreased with the increase of temperature. Moreover, thermal analysis showed that the addition of ZrSi₂ increased the initial decomposition temperature of the composite, but had little effect on the peak decomposition temperature in nitrogen. However, the thermal decomposition temperature of the composite in air was lower than that in nitrogen. The addition of ZrSi₂ decreased the linear and mass ablation rate, which improved the ablative resistance of the composite. With the ZrSi₂ content of 30 phr, the linear and mass ablation rate were 0.041 mm/s and 0.029 g/s, decreasing by 57.5% and 46.3% compared with the composite without ZrSi₂, respectively. Consequently, the ceramifiable silicone rubber composite filled with ZrSi₂ is very promising for TPS. Full article

A Zn/Al layered double hydroxides (LDHs) hosting carbon nanotubes (80% of CNTs) was synthesized and dispersed into a commercial biodegradable highly amorphous vinyl alcohol polymer at different loading (i.e., 1; 3; 5; 10 wt %). In order to improve the degree of dispersion of the filler into the polymer matrix, an ionic liquid (IL) based on 1-hexadecyl-3-methylimidazolium dimethyl-5-sodiosulfoisophthalate was added to the composites’ mixtures. Structural characterization of filler and polymeric composites was carried out. The analysis of thermal, mechanical and electrical properties of the composites, resulted improved compared to the unfilled material, allowed to hypothesize a good dispersion of the LDH-CNTs lamellar filler into the polymer matrix-assisted by the ionic liquid. This was demonstrated comparing electrical conductivity of composite at 5% of LDH-CNTs in the presence and in the absence of IL. The experimental results showed that the electrical conductivity of the sample with IL is four orders of magnitude higher than the one without IL. Furthermore, the percolation threshold of the whole system resulted very low—0.26% of LDH-CNTs loading, which is 0.21% of CNTs. Full article

This work focuses on developing a novel method to optimize the fabrication conditions of polyamide (PA) thin film composite (TFC) membranes using the multi-objective genetic algorithm II (MOGA-II) method. We used different fabrication conditions for formation of polyamide layer—trimesoyl chloride (TMC) concentration, reaction time (t), and curing temperature (Tc)—at different levels, and designed the experiment using the factorial design method. Three functions (polynomial, neural network, and radial basis) were used to generate the response surface model (RSM). The results showed that the radial basis predicted good results (R² = 1) and was selected to generate the RSM that was used as the solver for MOGA-II. The experimental results indicate that TMC concentration and t have the highest influence on water flux, while NaCl rejection is mainly affected by the TMC concentration, t, and Tc. Moreover, the TMC concentration controls the density of the PA, whereas t confers the PA layer thickness. In the optimization run, MOGA-II was used to determine optimal parametric conditions for maximizing water flux and NaCl rejection with constraints on the maximum acceptable levels of Na₂SO₄, MgSO₄, and MgCl₂ rejections. The optimized solutions were obtained for longer t, higher Tc, and different TMC concentration levels. Full article

Composite materials are widely used for their peculiar combination of excellent structural, mechanical, and damping properties. This work presents an experimental study on the dissipation properties of disk-shaped composite specimens exploiting vibration tests. Two different polymer matrix composites with the same number of identical laminae, but characterized by different stacking sequences, namely unidirectional and quasi-isotropic configurations, have been evaluated. An ad-hoc steel structure was designed and developed to reproduce an in-plane torsional excitation on the specimen. The main idea of the proposed approach relies on deriving the damping properties of the disks by focusing on the modal damping of the overall vibrating structure and, in particular, using just the first in-plane torsional deformation mode. Experimental torsional damping evaluations were conducted by performing vibrational hammer excitation on the presented setup. Two methods were proposed and compared, both relying on a single-degree-of-freedom (SDOF) approximation of the measured frequency response function (FRF). Full article

There has been increased interest to develop protective fabrics and clothing for protecting the wearer from hazards such as chemical, biological, heat, UV, pollutants etc. Protective fabrics have been conventionally developed using a wide variety of techniques. However, these conventional protective fabrics lack breathability. For example, conventional protective fabrics offer good protection against water but have limited ability in removing the water vapor and moisture. Fibers and membranes fabricated using electrospinning have demonstrated tremendous potential to develop protective fabrics and clothing. These fabrics based on electrospun fibers and membranes have the potential to provide thermal comfort to the wearer and protect the wearer from wide variety of environmental hazards. This review highlights the emerging applications of electrospinning for developing such breathable and protective fabrics. Full article

Bonding of carbon fiber reinforced polymer (CFRP) plates to a concrete member is a widely used strengthening method. CFRP plates used in construction degrade due to harsh environmental conditions such as high temperature or alkaline solution seepage from concrete. However, the adhesive between CFRP plates and concrete may have a positive effect on the durability performance of CFRP plates. In this paper, the long-term performance of both naked and adhesive coated CFRP pultruded plates subjected to different-temperature water or alkaline solution (20, 40 and 60 °C) are investigated to evaluate the protective effect of adhesive on CFRP plates. It is found that the adhesive coating can slow the deterioration of mechanical properties especially the tensile properties and fiber-matrix interfacial properties. The water absorption mechanism of CFRP plates was also investigated. Full article

Poly (butyl methacrylate) (PBMA) was blended with a series of phenolic resins (PR) to study the effect of PR molecular weight on dynamic mechanical properties of PBMA/PR composites. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) found a similar variation of glass transition temperature (T_g). The maximum loss peak (tanδ_max) improved in all PBMA/PR blends compared with the pure PBMA. However, tanδ_max reduced as the molecular weight increased. This is because PR with higher molecular weight is more rigid in the glass transition zone of blends. The hydrogen bonding between PBMA and PR was characterized by Fourier transform infrared spectroscopy (FTIR). Lower molecular weight PR formed more hydrogen bonds with the matrix and it had weaker temperature dependence. Combined with the results from DMA, we studied how molecular weight affected hydrogen bonding and thus further affected tanδ_max. Full article

Dielectric actuators (DEAs), because of their exceptional properties, are well-suited for soft actuators (or robotics) applications. This article studies a multi-stimuli thermo-dielectric-based soft actuator under large bending conditions. In order to determine the stress components and induced moment (or stretches), a nominal Helmholtz free energy density function with two types of hyperelastic models are employed. Non-linear electro-elasticity theory is adopted to derive the governing equations of the actuator. Total deformation gradient tensor is multiplicatively decomposed into electro-mechanical and thermal parts. The problem is solved using the second-order Runge-Kutta method. Then, the numerical results under thermo-mechanical loadings are validated against the finite element method (FEM) outcomes by developing a user-defined subroutine, UHYPER in a commercial FEM software. The effect of electric field and thermal stimulus are investigated on the mean radius of curvature and stresses distribution of the actuator. Results reveal that in the presence of electric field, the required moment to actuate the actuator is smaller. Finally, due to simplicity and accuracy of the present boundary problem, the proposed thermally-electrically actuator is expected to be used in future studies and 4D printing of artificial thermo-dielectric-based beam muscles. Full article

This study presents a method for the determination of the dynamic pressure-dependent solidification of polycarbonate (PC) during flow using high pressure capillary rheometer (HPC) measurements. In addition, the pressure-dependent solidification was determined by isothermal pressure-volume-temperature (pvT) measurements under static conditions without shear. Independent of the compression velocity, a linear increase of the solidification pressure with temperature could be determined. Furthermore, the results indicate that the relaxation time at a constant temperature and compression rate can increase to such an extent that the material can no longer follow within the time scale specified by the compression rate. Consequently, the flow through the capillary stops at a specific pressure, with higher compression rates resulting in lower solidification pressures. Consequently, in regard to HPC measurements, it could be shown that the evaluation of the pressure via a pressure hole can lead to measurement errors in the limit range. Since the filling process in injection molding usually takes place under such transient conditions, the results are likely to be relevant for modelling the flow processes of thin-walled and microstructures with high aspect ratios. Full article

The incorporation of double dynamic bonds into hydrogels provides an effective strategy to engineer their performance on demand. Herein, novel hydrogels were PREPARED by combining two kinetically distinct dynamic covalent bonds, boronate ester and acylhydrazone bonds, and the synergistic properties of the hydrogels were studied comprehensively. The functional diblock copolymers P(N-isopropyl acrylamide-co-N-acryloyl-3-aminophenylboronic acid)-b-(N-isopropyl acrylamide-co-diacetone acrylamide) (PAD) were prepared via reversible addition−fragmentation chain transfer (RAFT) polymerization. The hydrogel was constructed by exploiting dynamic reaction of phenyboronic acid moieties with polyvinyl alcohol (PVA) and ketone moieties with adipic dihydrazide (ADH) without any catalyst. The active boronate ester linkage endows the hydrogel with fast gelation kinetics and self-healing ability, and the stable acylhydrazone linkage can enhance the mechanical property of the hydrogel. The difference in kinetics endows that the contribution of each linkage to mechanical strength of the hydrogel can be accurately estimated. Moreover, the mechanical property of the hydrogel can be readily engineered by changing the composition and solid content, as well as by controlling the formation or dissociation of the dynamic linkages. Thus, we provide a promising strategy to design and prepare multi-responsive hydrogels with tunable properties. Full article

In this study, the phase transition phenomena of linear poly(acrylic acid) (PAA) and linear or star-shaped poly(acrylic acid-co-methyl acrylate) (P(AA-co-MA)) in highly concentrated KCl solutions were investigated. The effects of polymer molecular weight, topology, and composition on their phase transition behavior in solution were investigated. The cloud point temperature (T_CP) of polymers drastically increased as the KCl concentration (C_KCl) and solution pH increased. C_KCl strongly influenced the temperature range at which the phase transition of PAA occurred: C_KCl of 1.0–2.2 M allowed the phase transition to occur between 30 and 75 °C. Unfortunately, at C_KCl above 2.6 M, the T_CP of PAA was too high to theoretically trigger the crystallization of KCl. The addition of hydrophobic methyl acrylate moieties decreased the T_CP into a temperature region where KCl crystallization could occur. Additionally, the hydrodynamic diameters (D_h) and zeta potentials of commercial PAA samples were examined at room temperature and at their T_CP using dynamic light scattering. The salt concentration (from 1 to 3 M) did not impact the hydrodynamic diameter of the molecules. D_h values were 1500 and 15 nm at room temperature and at T_CP, respectively. Full article

Thermal modification of wood causes chemical changes that significantly affect the physical, mechanical and biological properties of wood; thus, it is essential to investigate these changes for better utilization of products. Fourier transform infrared spectroscopy and size exclusion chromatography were used for evaluation of chemical changes at thermal treatment of oak wood. Thermal modification was applied according to Thermowood process at the temperatures of 160, 180 and 210 °C, respectively. The results showed that hemicelluloses are less thermally stable than cellulose. Chains of polysaccharides split to shorter ones leading to a decrease of the degree of polymerization and an increase of polydispersity. At the highest temperature of the treatment (210 °C), also crosslinking reactions take place. At lower temperatures degradation reactions of lignin predominate, higher temperatures cause mainly condensation reactions and a molecular weight increase. Chemical changes in main components of thermally modified wood mainly affect its mechanical properties, which should be considered into account especially when designing various timber constructions. Full article

When considering cellulose (UFC100) modification, most of the processes employ various solvents in the role of the reaction environment. The following article addresses a solvent-free method, thermal drying, which causes a moisture content decrease in cellulose fibers. Herein, the moisture content in UFC100 was analyzed with spectroscopic methods, thermogravimetric analysis, and differential scanning calorimetry. During water desorption, a moisture content drop from approximately 6% to 1% was evidenced. Moreover, drying may bring about a specific variation in cellulose’s chemical structure. These changes affected the cellulose-filled polymer composite’s properties, e.g., an increase in tensile strength from 17 MPa for the not-dried UFC100 to approximately 30 MPa (dried cellulose; 24 h, 100 °C) was observed. Furthermore, the obtained tensile test results were in good correspondence with Payne effect values, which changed from 0.82 MPa (not-dried UFC100) to 1.21 MPa (dried fibers). This raise proves the reinforcing nature of dried UFC100, as the Payne effect is dependent on the filler structure’s development within a polymer matrix. This finding paves new opportunities for natural fiber applications in polymer composites by enabling a solvent-free and efficient cellulose modification approach that fulfils the sustainable development rules. Full article

Modified ultra-high-molecular-weight polyethylene (UHMWPE) with calcium stearate (CS) and polyethylene wax (PEW) is a feasible method to improve the fluidity of materials because of the tense entanglement network formed by the extremely long molecular chains of UHMWPE, and a modified UHMWPE sheet was fabricated by compression molding technology. A Fourier-transform infrared spectroscopy test found that a new chemical bond was generated at 1097 cm⁻¹ in the materials. Besides, further tests on the thermal, thermomechanical, mechanical, and shape memory properties of the samples were also conducted, which indicates that all properties are affected by the dimension and distribution of crystal regions. Moreover, the experimental results indicate that the addition of PEW and CS can effectively improve the mechanical properties. Additionally, the best comprehensive performance of the samples was obtained at the PEW content of 5 wt % and the CS content of 1 wt %. In addition, the effect of temperature on the shape memory properties of the samples was investigated, and the results indicate that the shape fixity ratio (R_f) and the shape recovery ratio (R_r) can reach 100% at 115 °C and 79% at 100 °C, respectively, which can contribute to the development of UHMWPE-based shape memory polymers. Full article

A new root canal sealer was developed based on urethane acrylates using polycarbonate polyol (PCPO), a macrodiol prepared in the consumption of carbon dioxide as feedstock. The superior mechanical properties and biostability nature of PCPO-based urethane acrylates were then co-crosslinked with a difunctional monomer of tripropylene glycol diarylate (TPGDA) as sealers for resin matrix. Moreover, nanoscale silicate platelets (NSPs) immobilized with silver nanoparticles (AgNPs) and/or zinc oxide nanoparticles (ZnONPs) were introduced to enhance the antibacterial effect for the sealers. The biocompatibility and the antibacterial effect were investigated by Alamar blue assay and LDH assay. In addition, the antibacterial efficiency was performed by using Enterococcus faecalis (E. faecalis) as microbial response evaluation. These results demonstrate that the PCPO-based urethane acrylates with 50 ppm of both AgNP and ZnONP immobilized on silicate platelets, i.e., Ag/[email protected], exhibited great potential as an antibacterial composite for the sealer of root canal obturation. Full article

In this paper, solution casting method is used to prepare the PP (polypropylene) non-woven fabric based composite film filled with silicon dioxide/polyvinylidene fluoride (SiO₂/PVDF). The mechanical and thermodynamic properties of PP/SiO₂/PVDF composites were studied by a uniaxial tensile test under different temperature and combustion experiment. It is found that the stress of PP/SiO₂/PVDF composite film with 4 wt % SiO₂ is the maximum value, reaching 18.314 MPa, 244.42% higher than that of pure PP non-woven. Meanwhile, the thermal–mechanical coupling tests indicate that with the increase of temperature, the ultimate stress and strain of the composite decrease. At the same time, the thermal shrinkage property of the composite during the heating process is studied. The modified composite has good thermal stability under 180 °C. Scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric (TG) were used to characterize the pore shape, distribution and crystal phase change of the composite. The modified PP/SiO₂/PVDF composite film structure shows high strength and good thermal stability, and can better meet the requirements of strength and thermal performance of lithium-ion battery during the charging and discharging process. Full article

Nanocomposites based on transparent polymer matrices containing nanoparticles (NPs) of noble metals are modern-day materials that can be specially designed for photonics, linear and nonlinear optics, laser physics and sensing applications. We present the improved photosensitive nanocomposites doped with Au and Ag NPs allowing fabrication of high effective submicrometer dimensional diffraction structures using holographic method. A general approach for the fabrication of holographic structures using a two-component mixture of the monomers of different reactivity was developed. Two different methods, ex situ and in situ, were studied to introduce Au and Ag NPs in the polymer matrix. The diffusion model of the grating formation upon holographic exposure as well as the process of Ag NP synthesis in a polymer matrix is considered. The influence of the NP size on the polymerization process, material dynamic range and nonlinear properties were investigated. The mechanisms and characteristics of the nanocomposite nonlinear optical response are discussed. Full article

Levamisole (LEVA) is used to treat worm infections, but it can also inhibit cancer cell growth by inhibiting the aldehyde dehydrogenase pathway. Therefore, here, we developed a drug carrier targeting CD133, a biomarker overexpressed in ovarian cancer cells. The particle structure and cytotoxicity of the prepared LEVA-containing particles—called LEVA/PVP/PMMA microparticles (MPs) (because it used matrix material polyvinylpyrrolidone (PVP) and poly(methylmethacrylate) (PMMA))—were investigated in the ovarian cancer cell lines SKOV-3 and CP70. The particle size of the MPs was determined to be 1.0–1.5 µm and to be monodispersed. The hydrophilic property of PVP created a porous MP surface after the MPs were soaked in water for 20 min, which aided the leaching of the hydrophilic LEVA out of the MPs. The encapsulation efficiency of LEVA/PVP/PMMA MPs could reach up to 20%. Free-form LEVA released 50% of drugs in <1 h and 90% of drugs in 1 day, whereas the drug release rate of LEVA/PVP/PMMA MPs was much slower; 50% released in 4 h and only 70% of drugs released in 1 day. In the in vitro cell model test, 5 mM free-form LEVA and 0.1 g/mL CD133 targeted LEVA/PVP/PMMA MPs reduced SKOV-3 cell viability by 60%; 0.1 g/mL LEVA/PVP/PMMA MPs was equivalent to a similar dosage of the free drug. In addition, the cytotoxicity of CD133-conjugated LEVA/PVP/PMMA MPs shows a different cytotoxicity response toward cell lines. For SKOV-3 cells, treatment with free-form LEVA or CD133-conjugated LEVA/PVP/PMMA MPs exerted dose-dependent cytotoxic effects on SKOV-3 cell viability. However, CD133-conjugated LEVA/PVP/PMMA MPs demonstrated no significant dose-dependent cytotoxic efficacy toward CP70 cells. Full article

Various amounts of methacryl polyhedral oligomeric silsesquioxane (POSS) were explored to be incorporated into novel nano SiO₂ dental resin composites using light curing method. The scanning electron microscopy (SEM), optical microscopy, fourier transform infrared spectroscopy (FTIR), nanoindentation, nanoscratch and three-point flexure tests were performed. The volumetric shrinkage and mechanical properties such as hardness, elastic modulus, resistance, flexural strength and fracture energy were analyzed. With the additions of POSS, the volume shrinkage decreased and the mechanical properties initially increased. The effects of POSS on these properties were studied to provide a reference for clinically selecting a composite resin with excellent properties. Full article

A series of polystyrene nanoparticles (PS-1, PS-2, PS-3, and PS-4) in aqueous solutions were investigated in terms of morphological structure, size, and size distribution. Synchrotron small-angle X-ray scattering analysis (SAXS) was carried out, providing morphology details, size and size distribution on the particles. PS-1, PS-2, and PS-3 were confirmed to behave two-phase (core and shell) spherical shapes, whereas PS-4 exhibited a single-phase spherical shape. They all revealed very narrow unimodal size distributions. The structural parameter details including radial density profile were determined. In addition, the presence of surfactant molecules and their assemblies were detected for all particle solutions, which could originate from their surfactant-assisted emulsion polymerizations. In addition, dynamic light scattering (DLS) analysis was performed, finding only meaningful hydrodynamic size and intensity-weighted mean size information on the individual PS solutions because of the particles’ spherical nature. In contrast, the size distributions were extracted unrealistically too broad, and the volume- and number-weighted mean sizes were too small, therefore inappropriate to describe the particle systems. Furthermore, the DLS analysis could not detect completely the surfactant and their assemblies present in the particle solutions. Overall, the quantitative SAXS analysis confirmed that the individual PS particle systems were successfully prepared with spherical shape in a very narrow unimodal size distribution. Full article

Different hybrid epoxy formulations were produced and cold-cured, monitoring the properties development during low temperature curing and aging. All systems were based on silane functionalized bis-phenol A (DGEBA) resins (Part A), cured at ambient temperature with two amine hardeners (Part B). The different components of the formulations were selected on their potential capability to bring about enhancements in the glass transition temperature. The durability of the produced hybrids was probed in comparison to the corresponding neat epoxies by monitoring changes in glass transition temperature (T_g) and flexural mechanical properties after exposure to different levels of humidity and immersion in water and at temperatures slightly higher than the local ambient temperature, in order to simulate the conditions encountered during summer seasons in very humid environments. The thermal degradation resistance of the hybrid systems was also evaluated by thermogravimetric analysis. Full article

In this study, a biodegradable, cheap and durable recycled high-density polyethylene (rHDPE) polymer reinforced with rice husk (RH) fibre was fabricated into a foam structure through several processes, including extrusion, internal mixing and hot pressing. The effect of filler loading on the properties of the foam and the influence of RH surface treatments on the filler–matrix adhesion and mechanical properties of the composite foam were investigated. The morphological examination shows that 50 wt.% filler content resulted in an effective dispersion of cells with the smallest cell size (58.3 µm) and the highest density (7.62 × 1011 sel/cm³). This small cell size benefits the mechanical properties. Results indicate that the tensile strength and the Young’s modulus of the alkali-treated RH/rHDPE composite foam are the highest amongst the treatments (10.83 MPa and 858 MPa, respectively), followed by UV/O₃, which has shown considerable increments compared with the untreated composite. The flexural and impact tests also show the increment in strength for the composite foam after chemical treatment. Although the UV/O₃ surface treatment has minor influence on the mechanical enhancement of the composite foam, this method may be a reliable surface treatment of the fibre-reinforced composite. Full article

Cyclodextrin-grafted polymers are attractive biomaterials that could bring together the host–guest complexing capability of pristine cyclodextrin and the pharmaceutical features of the polymeric backbone. The present paper is aimed at characterizing the potential application of ammonium–chitosan grafted with 2-methyl-β-cyclodextrin (N⁺-rCh-MCD) as the functional macromolecular complexing agent for the oral administration of the neuropeptide dalargin (DAL). Specific NMR characterization procedures, along with UV and fluorescence techniques, as well as biological in vitro assessments have been performed. The results indicate that N⁺-rCh-MCD forms water-soluble complexes with DAL, with a prevalent involvement of Tyr or Phe over Leu and Ala residues. The association constant of DAL with the polymeric derivative is one order of magnitude higher than that with the pristine cyclodextrin (K_a: 2600 M⁻¹ and 120 M⁻¹, respectively). Additionally, N⁺-rCh-MCD shields DAL from enzymatic degradation in gastrointestinal in vitro models with a three-fold time delay, suggesting a future pharmaceutical exploitation of the polymeric derivative. Therefore, the greater affinity of N⁺-rCh-MCD for DAL and its protective effect against enzymatic hydrolysis can be attributed to the synergistic cooperation between cyclodextrin and the polymer, which is realized only when the former is covalently linked to the latter. Full article

Studies on control of and preventive measures against asphalt pavement moisture damage have important economic and social significance due to the multiple damage and repair of pavements, the reasons for which include the poor interfacial adhesive ability between acidic aggregates and asphalts. Anti-stripping agent is used in order to improve the poor adhesion, and decomposition temperature is regarded as being important for lots of anti-stripping products, because they always decompose and lose their abilities under the high temperature in the mixing plant before application to the pavement. A novel anti-stripping composite, montmorillonoid/Polyamide (OMMT/PAR), which possesses excellent thermal stability performance and is effective in preventing moisture damage, especially for acidic aggregates, was prepared. Moreover, the modification mechanisms and pavement properties were also investigated with reference to the composites. The results show that OMMT/PAR was prepared successfully, improving the interfacial adhesion between the acidic aggregate and the modified asphalt. Due to the nanostructure of OMMT/PAR, the thermal stability was enhanced dramatically and the interfacial adhesion properties were also improved. Furthermore, asphalts modified with OMMT/PAR and their mixtures showed excellent properties. Finally, the moisture damage process and the mechanisms by which OMMT/PAR improves the interfacial adhesion properties are explained through adhesion mechanism analyses. Full article

The focus of this paper is the realization and verification of a modified fiber bundle pull-out test setup to estimate the adhesion properties between threads and elastic matrix materials with a more realistic failure mode than single fiber debond techniques. This testing device including a modified specimen holder provides the basis for an adequate estimation of the interlaminar adhesion of fiber bundles including the opportunity of a faster, easier, and more economic handling compared to single fiber tests. The verification was done with the single-fiber and microbond test. Overall, the modified test setup showed the typical pull-out behavior, and the relative comparability between different test scales is given. Full article