Search Results (11)

Functional polymers, a significant class of compounds with diverse applications, are synthesized by incorporating functional groups into polymer matrices. Poly(epichlorohydrin) (PECH) is a pivotal polymer due to its reactive chloromethyl group, which readily enables its transformation into various functional polymers. Our study is focused on theoretically unraveling the mechanism behind modifying PECH through menthol grafting. We optimized and characterized various stationary states using density functional theory (DFT) at the B3LYP/6-311++G** level. These calculations were conducted in both the gas phase and a solution environment (THF). To anticipate the specific sites within our polymer that would be subject to grafting, we calculated various reactivity indices at the same computational level. Full article

In order to improve the performance of the anion exchange membrane (AEM) used in acid recovery from industrial wastewater, this study adopted a new strategy in which brominated poly (2,6-dimethyl-1,4-phenyleneoxide) (BPPO) and polyepichlorohydrin (PECH) were used as the polymer backbone of the prepared membrane. The new anion exchange membrane with a net structure was formed by quaternizing BPPO/PECH with N,N,N,N-tetramethyl-1,6-hexanediamine (TMHD). The application performance and physicochemical property of the membrane were adjusted by changing the content of PECH. The experimental study found that the prepared anion exchange membrane had good mechanical performance, thermostability, acid resistance and an appropriate water absorption and expansion ratio. The acid dialysis coefficient (U_H⁺) of anion exchange membranes with different contents of PECH and BPPO was 0.0173–0.0262 m/h at 25 °C. The separation factors (S) of the anion exchange membranes were 24.6 to 27.0 at 25 °C. Compared with the commercial BPPO membrane (DF-120B), the prepared membrane had higher values of U_H⁺ and S in this paper. In conclusion, this work indicated that the prepared BPPO/PECH anion exchange membrane had the potential for acid recovery using the DD method. Full article

Recently, there have been several studies done regarding anion exchange membranes (AEMs) based on polyepichlorohydrin (PECH), an attractive polymer enabling safe membrane fabrication due to its inherent chloromethyl groups. However, there are still undiscovered properties of these membranes emerging from different compositions of cast solutions. Thus, it is vital to explore new membrane properties for sustainable energy generation by reverse electrodialysis (RED). In this study, the cast solution composition was easily tuned by varying the ratio of active polymer (i.e., blend ratio) and quaternary agent (i.e., excess diamine ratio) in the range of 1.07–2.00, and 1.00–4.00, respectively. The membrane synthesized with excess diamine ratio of 4.00 and blend ratio of 1.07 provided the best results in terms of ion exchange capacity, 3.47 mmol/g, with satisfactory conductive properties (area resistance: 2.4 Ω·cm², electrical conductivity: 6.44 mS/cm) and high hydrophilicity. RED tests were performed by AEMs coupled with the commercially available Neosepta CMX cation exchange membrane (CEMs). Full article

The development of the most effective, suitable and economic ion-exchange membranes is crucial for reverse electrodialysis (RED)—the most widely studied process to harvest salinity gradient energy from mixing seawater and river water. RED utilizes two types of membranes as core elements, namely cation exchange membranes (CEM) and anion exchange membranes (AEM). Since the preparation of AEMs is more complex compared to CEMs, the design and development of anion exchange membranes have been the focus in this study. Homogeneous AEMs based on two types of polyepichlorohydrin (PECH) with different chlorine amounts (PECH-H, 37 wt% and PECH-C, 25 wt%) were synthesized, and first-time benchmarking of the membrane properties was conducted. In addition to physicochemical membrane properties, some instrumental analyses such as SEM, FTIR and DSC were investigated to characterize these anion-exchange membranes. Based on the results, although the PECH-H-type membrane had enhanced ion-exchange properties, PECH-C-based anion-exchange membranes exhibited a higher power density of 0.316 W/m² in a lab-scale RED system. Evidently, there is room for the development of new types of PECH-C-based AEMs with great potential for energy generation in the RED process. Full article

The saline gradient present in river mouths can be exploited using ion-exchange membranes in reverse electrodialysis (RED) for energy generation. However, significant improvements in the fabrication processes of these IEMs are necessary to increase the overall performance of the RED technology. This work proposes an innovative technique for synthesizing anion exchange membranes (AEMs) via electrospinning. The AEM synthesis was carried out by applying a high voltage while ejecting a mixture of polyepichlorohydrin (PECH), 1,4-diazabicyclo [2.2.2] octane (DABCO^® 33-LV) and polyacrylonitrile (PAN) at room temperature. Different ejection parameters were used, and the effects of various thermal treatments were tested on the resulting membranes. The AEMs presented crosslinking between the polymers and significant fiber homogeneity with diameters between 1400 and 1510 nm, with and without thermal treatment. Good chemical resistance was measured, and all synthesized membranes were of hydrophobic character. The thickness, roughness, swelling degree, specific fixed-charge density and ion-exchange capacity were improved over equivalent membranes produced by casting, and also when compared with commercial membranes. Finally, the results of the study of the electrospinning parameters indicate that a better performance in electrochemical properties was produced from fibers generated at ambient humidity conditions, with low flow velocity and voltage, and high collector rotation velocity. Full article

The macromolecular dynamics of dendronized copolymer membranes (PECHs), obtained by chemical modification of poly(epichlorohydrin) with the dendron 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy] benzoate, was investigated. In response to a thermal treatment during membrane preparation, these copolymers show an ability to change their shape, achieve orientation, and slightly crystallize, which was also observed by CP-MAS NMR, XRD, and DSC. The phenomenon was deeply analyzed by dielectric thermal analysis. The dielectric spectra show the influence of several factors such as the number of dendritic side groups, the orientation, their self-assembling dendrons, and the molecular mobility. The dielectric spectra present a sub-Tg dielectric relaxation, labelled as γ, associated with the mobility of the benzyloxy substituent of the dendritic group. This mobility is not related to the percentage of these lateral chains but is somewhat hindered by the orientation of the dendritic groups. Unlike other less complex polymers, the crystallization was dismantled before the appearance of the glass transition (α_Tg). Only after that, clearing transition (α_Clear) can be observed. The PECHs were flexible and offered a high free volume, despite presenting a high degree of modifications. However, the molecular mobility is not independent in each phase and the self-assembling dendrons can be eventually fine-tuned according to the percentage of grafted groups. Full article

Single-chain polymeric nanoparticles (SCPNs) have great potential as functional nanocarriers for drug delivery and bioimaging, but synthetic challenges in terms of final yield and purification procedures limit their use. A new concept to modify and improve the synthetic procedures used to generate water-soluble SCPNs through amphiphilic interactions has been successfully exploited. We developed a new ultrahigh molecular weight amphiphilic polymer containing a hydrophobic poly(epichlorohydrin) backbone and hydrophilic poly(ethylene glycol) side chains. The polymer spontaneously self-assembles into SCPNs in aqueous solution and does not require subsequent purification. The resulting SCPNs possess a number of distinct physical properties, including a uniform hydrodynamic nanoparticle diameter of 10–15 nm, extremely low viscosity and a desirable spherical-like morphology. Concentration-dependent studies demonstrated that stable SCPNs were formed at high concentrations up to 10 mg/mL in aqueous solution, with no significant increase in solution viscosity. Importantly, the SCPNs exhibited high structural stability in media containing serum or phosphate-buffered saline and showed almost no change in hydrodynamic diameter. The combination of these characteristics within a water-soluble SCPN is highly desirable and could potentially be applied in a wide range of biomedical fields. Thus, these findings provide a path towards a new, innovative route for the development of water-soluble SCPNs. Full article

A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the high conductivity associated with the pendant API group. The chemical structure of QPECH/PAEK-API membranes was identified by ¹H nuclear magnetic resonace spectroscopy. A variety of membrane properties, such as anion conductivity, water uptake, length swelling percentage, and thermal, mechanical and chemical stability, were investigated. The QPECH/PAEK-API1 membrane showed quite high hydroxide ion conductivity, from 0.022 S cm⁻¹ (30 °C) to 0.033 S cm⁻¹ (80 °C), and excellent mechanical strength, associated with the low water uptake of less than 40%, even at 80 °C. Such high conductivity at relatively low water uptake is attributed to the concentrated cationic groups, in a cross-linked structure, facilitating feasible ion transport. Further, the QPECH/PAEK-API membranes showed thermal stability up to 250 °C, and chemical stability for 30 days in a 4 NaOH solution, without significant loss of ion exchange capacity. Full article

Salinity gradient power is a renewable, non-intermittent, and neutral carbon energy source. Reverse electrodialysis is one of the most efficient and mature techniques that can harvest this energy from natural estuaries produced by the mixture of seawater and river water. For this, the development of cheap and suitable ion-exchange membranes is crucial for a harvest profitability energy from salinity gradients. In this work, both anion-exchange membrane and cation-exchange membrane based on poly(epichlorohydrin) and polyvinyl chloride, respectively, were synthesized at a laboratory scale (255 $\mathrm{c}$ $\mathrm{m}$ ²) by way of a solvent evaporation technique. Anion-exchange membrane was surface modified with poly(ethylenimine) and glutaraldehyde, while cellulose acetate was used for the cation exchange membrane structural modification. Modified cation-exchange membrane showed an increase in surface hydrophilicity, ion transportation and permselectivity. Structural modification on the cation-exchange membrane was evidenced by scanning electron microscopy. For the modified anion exchange membrane, a decrease in swelling degree and an increase in both the ion exchange capacity and the fixed charge density suggests an improved performance over the unmodified membrane. Finally, the results obtained in both modified membranes suggest that an enhanced performance in blue energy generation can be expected from these membranes using the reverse electrodialysis technique. Full article

In this work, a series of heptaphenyl siloxane trisilanol/polyhedral oligomeric silsesquioxane (T₇-POSS) modified by polyols with different molecular weights were synthesized into liquid-like nanoparticle–organic hybrid materials using the grafted-from method. All grafted POSS nanoparticles changed from solid powders to liquid at room temperature. Polyurethane (PU) nanocomposites with POSS contents ranging from 1.75 to 9.72 wt % were prepared from these liquefied polyols-terminated POSS with polyepichlorohydrin (POSS–PECH). Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the morphology of the POSS–PECH/PU nanocomposites. The results showed that the polyol-terminated POSS particles overcame the nanoagglomeration effect and evenly disperse in the polymeric matrix. The damping factor (tan δ) of resultant nanocomposites increased from 0.90 to 1.16, while the glass transition temperature decreased from 15.8 to 9.4 °C when POSS contents increased from 0 to 9.75 wt %. The gel content, tensile strength and Fourier transform infrared (FTIR) analyses demonstrated that the molecular thermal movement ability of the polyurethane (PU) matrix increased with increasing POSS hybrid content. Therefore, the improvement of the damping properties of the composites was mainly due to the friction-related losses occurring in the interface region between the nanoparticles and the matrix. Full article

A novel surface acoustic wave (SAW) sensor array based on wireless communication network is prepared. The array is composed of four SAW sensors, a wireless communication network module, and a global positioning system (GPS) module. The four SAW sensors of the array are coated with triethanolamine, polyepichlorohydrin, fluoroalcoholpolysiloxane, and L-glutamic acid hydrochloride to detect hydrogen sulfide (H₂S), 2-chloroethyl ethyl sulfide (CEES), dimethylmethylphosphonate (DMMP), and ammonia (NH₃) at film thicknesses of 50–100 nm. The wireless communication network module consists of an acquisition unit, a wireless control unit, and a microcontroller unit. By means of Zigbee and Lora technologies, the module receives and transmits the collected data to a PC work station in real-time; moreover, the module can control the sensor array’s working mode and monitor the working status. Simultaneously, the testing location is determined by the GPS module integrated into the SAW sensor array. H₂S, CEES, DMMP, and NH₃ are detected in 300 m at different concentrations. Given the practical future application in environment in the future, the low, safe concentrations of 1.08, 0.59, 0.10, and 5.02 ppm for H₂S, CEES, DMMP, and NH₃, respectively, are detected at the lowest concentration, and the sensitivities of different sensors of the sensor array are 32.4, 14.9, 78.1 and 22.6 Hz/ppm, respectively. With the obtained fingerprints and pattern recognition technology, the detected gases can be recognized. Full article