Polymerization Time Research Articles

Aqueous Dispersion Polymerization for the Development of Lamivudine-Polyacrylonitrile Nanoparticles through Quality by Design Approach.

The development of polymeric nanoparticles (NPs) from preformed polymers usually requires the use of organic solvents and is more expensive. Hence, in this work, the development of polymeric nanoparticles by in situ aqueous dispersion polymerization from the monomers was set as an objective. Acrylonitrile monomer based polymeric NPs comprising Lamivudine (LMV) as a model drug were prepared using the aqueous dispersion polymerization technique. A quality by design approach was applied to optimise various formulation and process factors viz. monomer concentration, initiator concentration, stabilizer concentration and polymerization temperature. Polymerization time (PT), entrapment efficiency (EE), particle size (PS), and drug release rate constant (k) were taken as the responses to define the quality of the prepared NPs. Design of experiments analysis followed by optimization was performed to identify the optimized combination of the factors. Later, the optimized formulation was studied for the physical state of the LMV in the nanoparticles, surface morphology of the NPs and cytotoxicity studies. The optimized formulation was found to have 91.7 min. of PT, 81.4% of EE, 253 nm of PS and a k value of 0.262 h-1 (18 h to release 99%). The cytotoxicity studies indicated that the NPs were highly safe to use. These results altogether inferred that LMV contained NPs were developed effectively from the acrylonitrile monomer by the aqueous dispersion polymerization method.

Polyaniline prepared by Fe3O4 catalysed eco-friendly synthesis as electrocatalyst for efficient water electrolysis

Preparing cost-effective and highly active catalysts for electrocatalytic hydrogen evolution reaction is crucial for developing hydrogen-based technologies. Hence, four conductive polyanilines, prepared by the environmentally-friendly approach using Fe3O4 nanoparticles/H2O2 as the catalyst/main oxidant system (PANI/Fe3O4), were investi¬gated for the first time as electrocatalysts for hydrogen evolution reaction (HER) in acidic media (0.1 M H2SO4) by using voltammetry and chronoamperometry. PANI/Fe3O4 electrodes exhibited Tafel slope values in the -171 to -246 mV dec-1 range depending on the synthesis conditions ‒ Fe3O4/aniline mass ratio and polymerization time. The sample PANI/Fe3O4-II(3) prepared with shorter reaction time and higher Fe3O4/aniline mass ratio showed the best electrocatalytic behaviour reflected in the lowest onset potential (-0.286 V), the lowest overpotential to reach a current density of -10 mA cm-2, the highest current density, the lowest HER activation energy (10 kJ mol-1), and the lowest charge-transfer resistance (5.3 Ω) under HER conditions. Materials were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photo¬electron spectroscopy and electrochemical impedance spectroscopy, and differences in their electrocatalytic HER performance were explained by differences in their content of Fe3O4, surface and electrical properties. Moreover, the possibility of using PANI/Fe3O4-II(3) as HER electrocatalyst in a wider range of pH (i.e. in alkaline media as well) and as a bifunc¬tional electrocatalyst, i.e., for oxygen evolution reaction beside HER, was also examined.

Impact of UV Light Exposure During Printing on Thermomechanical Properties of 3D-Printed Polyurethane-Based Orthodontic Aligners

Aim: Polyurethane-based aligners, created through photoinitiated free-radical polymerization, have been the subject of numerous studies focusing solely on their mechanical properties. In contrast, we investigate their thermomechanical properties, which are crucial for their efficacy. This paper aims to investigate the effects of different UV light exposure durations on the complex modulus of elasticity, tan delta, glass transition temperature, and the degree of conversion (DC). Methods: Aligners were printed using Tera Harz TC-85 and NextDent Ortho Flex resin with specific exposure times (2, 2.4, 3, 4, and 4.5 s for Tera Harz; 5, 6, 7, and 8 s for NextDent) and processed per manufacturer guidelines. The degree of conversion was analyzed using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, while Dynamic Mechanical Analysis (DMA) characterized the mechanical properties (complex modulus and tan delta) and the glass transition. Results: Tera Harz TC-85 showed a higher degree of conversion (90.29–94.54%), suggesting fewer residual monomers, which is potentially healthier for patients. However, its lower glass transition temperature (35.60–38.74 °C) might cause it to become rubbery in the mouth. NextDent Orto Flex, with a higher storage modulus (641.85–794.55 MPa) and Tg (49.36–50.98 °C), offers greater rigidity and stability at higher temperatures (greater than temperature in the oral cavity), ideal for orthodontic forces, though its lower degree of conversion raises health concerns. Conclusions: Tera Harz TC 85 generally achieves higher DC and more stable polymerization across different UV exposure times than NextDent Orto Flex. Optimal polymerization times significantly impact both the mechanical and thermal properties of these dental resins, with NextDent showing optimal properties at 7 s and Tera Harz benefiting from both very short and extended exposure times.

Design of thermally programmable 3D shape memory polymer-based devices tailored for endovascular treatment of intracranial aneurysms

Despite recent technological advancements in endovascular embolization devices for treating intracranial aneurysms (ICAs), incomplete occlusion and aneurysm recanalization remain critical challenges. Shape memory polymer (SMP)-based devices, which can be manufactured and tailored to patient-specific aneurysm geometries, possess the potential to overcome the suboptimal treatment outcome of the gold standard: endovascular coiling. In this work, we propose a highly porous patient-specific SMP embolic device fabricated via 3D printing to optimize aneurysm occlusion, and thus, improve the long-term efficacy of endovascular treatment. To facilitate device deployment at the aneurysm via Joule-heating, we introduce a stable, homogeneous coating of poly-pyrrole (PPy) to enhance the electrical conductivity in the SMP material. Using an in-house pulse width modulation circuit, we induced Joule-heating and characterized the shape recovery of the PPy-coated SMP embolic devices. We found that the employed PPy coating enables enhanced electrical and thermal conductivity while only slightly altering the glass transition temperature of the SMP material. Additionally, from a series of parametric studies, we identified the combination of catalyst concentration and pyrrole polymerization time that yielded the shape recovery properties ideal for ICA endovascular therapy. Collectively, these findings highlight a promising material coating for a future coil-free, personalized shape memory polymer (SMP) embolic device, designed to achieve long-lasting, complete occlusion of aneurysms.

Wear and roughness analysis of two highly filled flowable composites.

This in vitro study aimed to evaluate surface roughness and wear of highly filled flowables and traditional packable composites. Additionally, the effect of polymerization time on these parameters was evaluated. Two flowable higly filled composites (CMf-Clearfil Majesty ES flow-low viscosity, Kuraray and GUf-Gaenial Universal Injectable, GC) and two packable composites (CM-Clearfil Majesty ES-2, Kuraray and GU-Gaenial A'CHORD, GC) were used to create 160 specimens (n = 40;8 × 6×4mm). For each tested material, two subgroups were considered according to the polymerization time (n = 20): 10s or 80s. After setting, the specimens were subjected to chewing simulations (240.000 cycles, 20N), and wear was measured by the laser integrated in the chewing simulator. The surface roughness was measured using a rugosimeter, before and after chewing cycles. Two representative specimens per group were observed under scanning electron microscope (SEM). Data were collected and statistically analyzed (p < 0.05). Wear analysis highlighted statistically significant differences between the groups: CMf10-CMf80 (p = 0.000), CMf10-CM10 (p = 0.019), CMf10-GUf10 (p = 0.002), CM10-CM80 (p = 0.000), CM80-GUf80 (p = 0.02), GUf10-GUf80 (p = 0.000), GUf10-GU10 (p = 0.043) and GU10-GU80 (p = 0.013). Statistically significant differences in surface roughness were highlighted between the groups: CMf10-CMf80 (p = 0.038), CMf80-CM80 (p = 0.019), CMf80-GU80 (p = 0.010), CM80-GUf80 (p = 0.34) and GUf80-GU80 (p = 0.003). Surface roughness and wear of highly filled flowable composites were comparable to that of traditional paste composites. Furthermore, a longer curing time leads to an improvement in the mechanical properties of the composites. Highly filled flowables can be a valid alternative to paste composites in occlusal areas due to its similar surface roughness and wear values, especially when overcured.

Effect of Polymerization Time on Microhardness of Resin Cement

Effect of Polymerization Time on Microhardness of Resin Cement

Flexible and Multifunctional Pressure/Gas Sensors with Polypyrrole-Coated TPU Hierarchical Array.

A promising strategy is proposed for fabricating flexible pressure/gas sensors, which have a microprotuberance and microwrinkle structure at micropillars on their sensing substrates. The sensing substrates were prepared by compression molding thermoplastic polyurethane (TPU; an industrial grade polymer) and subsequent pyrrole polymerization. Benefiting from the hierarchical structure on the sensing substrates, the flexible sensors exhibit high performances in detecting both pressure and ammonia (NH3). Mechanism for the functionalities of the hierarchical structure of the pressure sensors was analyzed. Such unique hierarchical structure endows the interlocked pressure sensor by assembling the substrates prepared at 60 min polymerization time with a relatively high sensitivity in a wider linearity range (1.15 kPa-1, 0-800 Pa), a lower detection limit of 6.2 Pa, and shorter response and recovery times (26/28 ms). The combination of stronger interfacial interaction between the TPU and polypyrrole layer, the mutual support of the interlocked micropillars, and the inherent high resilience of TPU endows the pressure sensor with lower hysteresis, good repeatability and stability, and higher durability (10,000 cycles). The interlocked pressure sensor can detect full-range human physiological activities from weak physiological signals (such as face muscle contraction, heartbeat, and breath) to body movements (such as head, elbow, and foot movement). The gas sensor assembled with the hierarchical sensing substrate prepared at 60 min polymerization time exhibits selective, stable, and faster sensing responses to NH3. The proposed facile and cost-effective preparation strategy can be an excellent candidate for fabricating high-performance and multifunctional sensors.

Surface Engineering of N‐Doped Carbon Derived from Polyaniline for Primary Zinc‐Air Batteries

AbstractZinc‐air batteries (ZABs) with metal‐free cathodes are considered environmentally friendly and cost‐effective. However, more active and durable catalysts are required for this purpose. Herein, polyaniline (PANI)‐derived carbon materials were obtained to boost the oxygen reduction reaction (ORR) and, consequently, the performance of a primary ZAB. The developed porous N‐doped carbon (NDC) materials were engineered by varying the polymerization time and calcination temperature (500–900 °C). SEM micrographs and BET surface areas showed that the polymerization of aniline under cold conditions (5 °C) at 6, 8, or 24 h did not have a significant effect on the morphology or surface area. The fibrous structure of PANI was engineered by temperature, resulting in a progressive increase in the surface area until a three‐dimensional porous structure was achieved at 900 °C with the highest area of 601.9 m2 g−1. The surface doping of nitrogen species shifted from PANI‐rich N species to enriched graphitic N from 12.69 % (500 °C) to 24.26 % at 900 °C. The NDC 900 °C presented a voltage of 1.4 V and power density of 56 mW cm−2 (only 7 mW cm−2 lower than that of Pt/C). The results demonstrate that this material is an excellent candidate for high‐performance primary ZABs.

Controlled two-step synthesis of n-type conjugated ladder polymers using a flow reactor

The coplanar backbone of conjugated ladder polymers (cLPs) enhances electron transfer and π-π interactions, making cLPs promising materials for various applications in organic electronics and optoelectronics. Nevertheless, the limited solubility and intricate synthetic processes for cLPs make it challenging to control their molecular weight and corresponding properties, and pose as significant obstacles to their widespread application. Here, an n-type cLP, PNDI-2BocL, was synthesized using a flow reactor for the first time, with controlled molecular weights. The polymerization reaction conditions to synthesize a precursor polymer, PNDI-2Boc, were first optimized in flow, followed by sequential ladderization in batch through the injection of an acid solution. The reaction time of polymerization was varied from 7.5 to 15 min, yielding soluble PNDI-2BocL with a number-averaged molecular weight (Mn) ranging from 9.8 to 54.0 kg/mol with a deviation of 11 %. Additionally, 15 min of polymerization and ladderization were successfully conducted in a single flow system sequentially for the first time. In the molecular weight-dependent studies, higher optical absorption at longer wavelengths, increased degrees of crystallinity, and higher electron mobilities in organic field-effect transistors (OFETs) were observed for higher molecular weight PNDI-2BocL. Our results highlight the importance of controlling the molecular weights of cLPs and demonstrate that the flow synthesis technique provides a viable solution for synthesizing soluble cLPs in a controlled, reproducible, and rapid manner.

Color Stability Assessment of Single- and Multi-Shade Composites Following Immersion in Staining Food Substances.

Composite resins are the material of choice for direct restorations, and their success depends mainly on their color stability, since discoloration causes color mismatch, and consequent patient dissatisfaction. A single- and a multi-shade resin were compared in order to evaluate their pigmentation after immersion in staining substances and to investigate the effect of the polymerization time on their color stability. Two-hundred-and-forty composite specimens were created, half made of a single-shade (Group ONE, n = 120) and half of a multi-shade composite (Group OXP, n = 120). Each group was further divided into ONE30 (n = 60) and OXP30 (n = 60), polymerized for 30″, and ONE80 (n = 60) and OXP80 (n = 60), polymerized for 80″. Randomly, the specimens were immersed in turmeric solution, soy sauce, energy drink, or artificial saliva. By means of a spectrophotometer, ΔE00 and WId were calculated at 24 h (T0), at 7 (T1), and 30 (T2) days. Single-shade composites showed statistically significant differences in color change from the turmeric solution, energy drink, and soy sauce than the multi-shade composites (p < 0.005), showing a higher discoloration potential. The polymerization time did not have significative effects on color stability. Single-shade composites showed more color change than multi-shade systems after immersion in staining substances, and the curing time did not influence color variations.

Study on Preparation and Performance of Acid pH-Responsive Intelligent Self-Healing Coating.

In this paper, microcapsules with acidic pH stimulus responsiveness were prepared through a one-step in situ polymerization method and a layer-by-layer assembly method. The effects of factors such as chitosan (CS) concentration, polymerization time, polymerization process temperature, and the number of polymerization layers on the performance of microcapsules were explored, and microcapsules with optimal performance were prepared and added to the epoxy coating. The morphology and structure of the microcapsules were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and zeta potential testing. The thermal stability and sustained release properties of the microcapsules were studied through thermogravimetric analysis and sustained release curve testing. Through scratch experiments, immersion experiments, salt spray experiments, and electrochemical impedance spectroscopy tests, the impact of the added amount of microcapsules on the self-healing performance and anti-corrosion performance of the coating in complex environments was explored. The results show that the optimal preparation process of acidic pH-responsive microcapsules requires that the concentration of chitosan is 2 mg/mL, the polymerization time of the polyelectrolyte layer is 8 h, the heating temperature during the polymerization process is 75 °C, and the number of polyelectrolyte layers is three. The prepared acidic pH-responsive microcapsules have good morphology, pH sensitivity, and thermal stability. The average particle size is approximately 203 μm, the drug loading rate reaches 59.74%, and the encapsulation rate reaches 63.99%. The optimal added amount of the acidic pH-responsive microcapsule coating is 15 wt%. The coating has a dual-trigger mechanism underlying it stimulus response capability and has an obvious stimulus response to acidic pH. It can inhibit corrosion in non-scratch areas, and its anti-corrosion ability is significantly stronger than that of epoxy coatings and ordinary self-healing coatings. The coating has a stronger repair effect and anti-corrosion ability when the environmental pH becomes acidic.

Preparation of polymeric aluminum chloride from secondary aluminum dross and its water purification effect

ABSTRACT Aluminum dross is solid waste generated by the aluminum industry. Currently, a large amount of aluminum dross is produced annually year. Aluminum dross, a hazardous waste, contains harmful substances such as aluminum metal, aluminum nitride, fluoride and chlorine salts, which pose a serious threat to human health and also cause damage to the ecological environment. Thus, it is important to recycle secondary aluminum dross and realise its high-value utilisation. Polymeric aluminum chloride (PAC) is a polymer flocculant, at present, China's annual use of PAC in the field of water treatment is about 5 × 105 t, and with the continuous improvement of water purification requirements, the annual use of PAC increased year by year. Here secondary aluminum dross was used as a raw material to prepare PAC by hydrochloric acid (HCl) leaching, followed by the addition of sodium carbonate. The optimal conditions for the acid leaching of secondary aluminum dross for the preparation of PAC were as follows: HCl concentration, 18%; liquid-to-solid ratio, 4.5:1; stirring rate, 200 r/min; reaction temperature, 90 °C; and 60 min. An aluminum leaching rate of 85.5% was obtained under these conditions. The results showed that the acid leachate after adding sodium carbonate, under the conditions of polymerisation temperature of 70 °C, polymerisation time of 6 h, and polymerisation pH value of 3.0, the PAC prepared had an alumina content of 10.19%, salinity of 32.37%, density of 1.32 g/cm3, 1% aqueous solution pH 4.3. The water purification effect of the prepared PAC surpassed that of the commercially available PAC. The utilisation of secondary aluminum dross can reduce the environmental pollution caused by aluminum slag.

Molecularly Imprinted Microspheres in Active Compound Separation from Natural Product.

Molecularly Imprinted Microspheres (MIMs) or Microsphere Molecularly Imprinted Polymers represent an innovative design for the selective extraction of active compounds from natural products, showcasing effectiveness and cost-efficiency. MIMs, crosslinked polymers with specific binding sites for template molecules, overcome irregularities observed in traditional Molecularly Imprinted Polymers (MIPs). Their adaptability to the shape and size of target molecules allows for the capture of compounds from complex mixtures. This review article delves into exploring the potential practical applications of MIMs, particularly in the extraction of active compounds from natural products. Additionally, it provides insights into the broader development of MIM technology for the purification of active compounds. The synthesis of MIMs encompasses various methods, including precipitation polymerization, suspension polymerization, Pickering emulsion polymerization, and Controlled/Living Radical Precipitation Polymerization. These methods enable the formation of MIPs with controlled particle sizes suitable for diverse analytical applications. Control over the template-to-monomer ratio, solvent type, reaction temperature, and polymerization time is crucial to ensure the successful synthesis of MIPs effective in isolating active compounds from natural products. MIMs have been utilized to isolate various active compounds from natural products, such as aristolochic acids from Aristolochia manshuriensis and flavonoids from Rhododendron species, among others. Based on the review, suspension polymerization deposition, which is one of the techniques used in creating MIPs, can be classified under the MIM method. This is due to its ability to produce polymers that are more homogeneous and exhibit better selectivity compared to traditional MIP techniques. Additionally, this method can achieve recovery rates ranging from 94.91% to 113.53% and purities between 86.3% and 122%. The suspension polymerization process is relatively straightforward, allowing for the effective control of viscosity and temperature. Moreover, it is cost-effective as it utilizes water as the solvent.

Fabrication of organogel strain sensor with self-healing property and extreme temperature tolerance by using phytic acid-liquid metal as initiator

Wearable strain sensors have aroused myriad of interest in the domain of electronic skin, soft robotics, and biomedicine. Organogels for wearable strain sensors require desirable stretchability, sensing stability, self-healing property, and a wide working temperature range. However, the synthesis of such organogels typically involves complex and time-consuming processes. Herein, we proposed a rapid copolymerization method for organogels composed of poly(acrylic acid-co-acrylic amide) (P(AA-co-AM)), phytic acid (PA), liquid metal (LM), and polyethylene oxide (PEO). The dispersion of GaInSn in PA solution (GaInSn-PA) was synthesized and employed to initiate the copolymerization of acrylic acid (AA) and acrylic amide (AM), which significantly reduced polymerization time to 2–3 min at room temperature. The release of Ga3+ ions from the LM facilitated cross-linking of P(AA-co-AM) chains through coordination bonds, while also imparted conductivity to the organogel. The synergistic effect between hydrogen bonds and metal coordination bonds extensive within the polymer chains imparted exceptional stretchability (1079 % strain) and self-healing efficiency (98 % at 60 °C) to the organogel. Consequently, the resulting strain sensor demonstrated the ability to accurately monitor both subtle and large human motion, exhibiting remarkable repeatability and durability across a wide temperature range (-20 °C∼40 °C). In addition, the integration of strain sensors on limbs for robotic control through limb movements underscored its practical viability. This optimized fabrication approach and structural design strategy set a new precedent for the development of organogel strain sensors in various applications.

Research and Application of Gangue for the Preparation of Polymerized Aluminum Magnesium Chloride Flocculant

Polymerized aluminum magnesium chloride (PAMC) flocculant was prepared from gangue as a raw material, and the effects of pH, the polymerization time, and the polymerization temperature on the performance of the PAMC were investigated by a one-factor test, based on which, orthogonal experiments (three-factor and two-level) were conducted to optimize the relevant parameters. Meanwhile, FTIR and SEM were used to characterize the polymerized aluminum magnesium chloride, and the sample was applied in printing and dyeing wastewater treatment. The results showed that a pH value of 2.2 and a reaction at 60 °C for 4.5 h were the optimal preparation conditions; the characterization analysis showed that the synthesized product was polymerized aluminum magnesium chloride; the turbidity removal rate of the PAMC for printing and dyeing wastewater was increased by 2.1%, the COD removal rate was increased by 3.1%, the ammonia nitrogen removal rate was increased by 2.1%, and the chromaticity removal rate was increased by 9.2% compared with that of PAC.

The preparation of polystyrene/nickel core-shell particles for anisotropic conductive films (ACFs)

The use of core-shell conductive microspheres as conductive fillers for anisotropic conductive films (ACFs) has broad application prospects for high-precision circuit connections. However, existing preparation methods suffer from environmental pollution and a relatively long processing procedure. Therefore, we propose a bio-inspired, simple, and environmentally friendly method for preparing PS/Ni core-shell conductive particles suitable for ACFs. Specifically, this study utilized the oxidative self-polymerization of dopamine (DA) to modify the surface of polystyrene (PS) microspheres. The catechol groups in polydopamine (PDA) act as both reducing agents and anchor groups for palladium (Pd) atoms to catalyze the electroless nickel plating. Results indicated that the amount of (PDA) on the PS surface and the morphology of the formed nickel-phosphor (NiP) layer were regulated by adjusting the DA polymerization time and concentrations. The prepared PS-PDA/Ni conducting particles with an average diameter of 2 ± 0.2 μm has a low density (1.5 g/cm3) and can be applied to ACFs. The application of the prepared ACFs was demonstrated by bonding two flexible print circuits (FPC) with a line spacing of 200 μm. Good adhesion, conductivity, and anisotropic properties were observed in the bonded FPC-200s. This study provides useful information for producing suitable conductive particles with easy synthesis for ACFs applications.

PS@poly(NIPAM-co-AA) core@shell nanoparticles: size control and tuning of LCST

Here, we demonstrate a synthetic approach to precise size control of PNIPAM-based core@shell nanoparticles prepared by microemulsion polymerization as well as control of low critical solution temperature (LCST) of their water dispersions. The size of the PS-core can be tuned to ∼30 nm by a simple increase of mechanical stirring up to 1200 rpm, while the thickness of the thermoresponsive @poly(N-isopropyl acrylamide-co-acrylamide) shell can be controlled by varying the polymerization time. The effect of not only a molar ratio or co-monomer nature but also a strong influence of a thermoresponsive shell thickness on the LCST was found.

XPS Depth-Profiling Studies of Chlorophyll Binding to Poly(cysteine methacrylate) Scaffolds in Pigment-Polymer Antenna Complexes Using a Gas Cluster Ion Source.

X-ray photoelectron spectroscopy (XPS) depth-profiling with an argon gas cluster ion source (GCIS) was used to characterize the spatial distribution of chlorophyll a (Chl) within a poly(cysteine methacrylate) (PCysMA) brush grown by surface-initiated atom-transfer radical polymerization (ATRP) from a planar surface. The organization of Chl is controlled by adjusting the brush grafting density and polymerization time. For dense brushes, the C, N, S elemental composition remains constant throughout the 36 nm brush layer until the underlying gold substrate is approached. However, for either reduced density brushes (mean thickness ∼20 nm) or mushrooms grown with reduced grafting densities (mean thickness 6-9 nm), elemental intensities decrease continuously throughout the brush layer, because photoelectrons are less strongly attenuated for such systems. For all brushes, the fraction of positively charged nitrogen atoms (N+/N0) decreases with increasing depth. Chl binding causes a marked reduction in N+/N0 within the brushes and produces a new feature at 398.1 eV in the N1s core-line spectrum assigned to tetrapyrrole ring nitrogen atoms coordinated to Zn2+. For all grafting densities, the N/S atomic ratio remains approximately constant as a function of brush depth, which indicates a uniform distribution of Chl throughout the brush layer. However, a larger fraction of repeat units bound to Chl is observed at lower grafting densities, reflecting a progressive reduction in steric congestion that enables more uniform distribution of the bulky Chl units throughout the brush layer. In summary, XPS depth-profiling using a GCIS is a powerful tool for characterization of these complex materials.

Investigating oligo(ethylene glycol) methacrylate thermoresponsive copolymers

Methacrylate-based polymers are frequently used in the development of thermoresponsive smart materials for biomedical applications. Among all the routes to such polymers, reversible addition fragmentation chain transfer (RAFT) copolymerisation is one of the most widely used. This paper reports the synthesis of thermoresponsive copolymers comprising oligo(ethylene glycol) methyl ether methacrylate with Mn of 300 (OEGMA300) and di(ethylene glycol) methyl ether methacrylate (DiEGMA). Polymers of molecular weight up to 100 kDA were obtained via RAFT polymerisation, mediated by a dithiobenzoate chain transfer agent (CTA) at 70 °C. An appropriate solvent, ratio of initiator to monomers, and minimum reaction polymerisation time were essential to provide optimum polymers. The synthesis of homogenous p(OEGMA300-co-DIEGMA) polymers with PDI of 1.1–1.2 was achieved in toluene with ≥10 h of reaction. Increasing the molecular weight of the p(OEGMA300-co-DiEGMA) polymers decreases the polydispersity index. p(OEGMA300-co-DiEGMA) polymers with Mw of 50,000 Da were successfully synthesised with lower critical solution temperatures (LCSTs) of 41.3 °C, 43.0 °C and >45 °C for OEGMA300:DiEGMA molar ratios of 2:8, 3:7 and 4:6, respectively. Further, the LCST was not found to be affected by the polymer molecular weight. The p(OEGMA300-co-DiEGMA) polymers showed no cytotoxicity to Caco-2 cells at a concentration of 1 mg mL−1, whereas a decrease of HDF cell viability by up to 26.5 % was seen. These polymers could be beneficial for several biomedical applications, such as developing formulations for temperature-triggered drug delivery.

Surface Modification of Polyethylene Terephthalate Track-Etched Membranes by 2,2,3,3,4,4,5,5,6,6,7,7-Dodecafluoroheptyl Acrylate for Application in Water Desalination by Direct Contact Membrane Distillation.

In this work, the surfaces of poly (ethylene terephthalate) track-etched membranes (PET TeMs) with pore sizes of 670-1310 nm were hydrophobized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA) by photoinitiated graft polymerization. Attenuated total reflection FTIR spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDX), and contact angle measurements were used to identify and characterize the TeMs. The optimal parameters for graft polymerization were determined as follows: polymerization time of 60 min, monomer concentration of 30%, and distance from the UV source of 7 cm. The water contact angle of the modified membranes reached 97°, which is 51° for pristine membranes. The modified membranes were tested for water desalination using direct contact membrane distillation (DCMD) method. The effects of membrane pore size, the degree of grafting, and salt concentration on the performance of membrane distillation process were investigated. According to the results obtained, it has been concluded that large pore size hydrophobic TeMs modified by using DFHA could be used for desalinating water.