Trimethylolpropane Trimethacrylate Research Articles

Using maturity method to predict compressive strength of acrylic polymer concrete containing TMPTMA or silane at sub-zero curing temperatures

Acrylic polymer concrete (APC) is a fast-setting and high-strength material with low freezing point, and can gain strength even at sub-zero temperatures, making it an excellent option for repairing pavements and roads during cold weather. Accurately estimating the compressive strength of APC is critical for determining safety time to open the pavement to traffic. Unfortunately, traditional maturity methods, such as those recommended by ASTM C1074 for Portland cement concrete, cannot be applied directly for strength estimation of APC. In order to estimate the compressive strength of APC containing 0–5 phr trimethylolpropane trimethacrylate (TMPTMA) or 0–2 phr silane cured at sub-zero temperatures, the Arrhenius equation-based maturity method has been modified and utilized for the first time in this study. An exponential function is adopted to characterize strength development of APC cured at different temperatures (-20-0 °C), with the assumption that the ultimate compressive strength of APC is independent of curing temperature. The corresponding activation energies (Ea) for APC are determined using Arrhenius equation. The findings indicate that the Ea value of APC without any additives is 39.65 kJ/mol. Moderate amount addition of TMPTMA (0–1 phr) enhances the temperature sensitivity, however, silane incorporation alone significantly reduces Ea value by 7–12 kJ/mol. The Ea values are also utilized to estimate the compressive strength of APC, based on the equivalent time at the reference temperature (0 °C). The modified maturity method effectively predicts the compressive strength of APC cured under sub-zero temperatures. The estimated values closely match experimental data with errors controlled in ±10%. This work will provide basis and instruction on estimating strength and determining the safe timing for traffic opening when APC is used as a patch repair for roads and pavements.

Photocrosslinking of ethylene‐vinyl acetate (EVA)–polyethylene‐octene (POE) copolymer containing halogen‐free flame retardants

AbstractPhotocrosslinking of polymers for industrial applications show undoubted advantages related to the mild conditions needed and the economical equipment. However, some issues include: the use of (i) mercury lamps as light sources, which poses concerns about safety and energy consumption, (ii) typical additives, such as halogen‐free flame‐retardant fillers (HFFR) are powdered materials, which can scatter UV photons and avoid a deep penetration of the light. In this study, we explore the UV‐curing of an innovative EVA‐POE blend containing hydrotalcite and aluminum hydroxide as HFFR in the presence of a 370‐nm UV LED, namely Ekopren® XI1321, a plastic used as coverage for electric cables. Two commercially available photoinitiators (benzophenone and ethyl Michler's ketone) were analyzed as well as two crosslinking coagents widely used in industry, that is, triallyl cyanurate and trimethylolpropane trimethacrylate. A comparison with pure EVA and LDPE was performed to show a higher cross‐linked content of the proposed blend, even in the presence of light scattering mineral fillers at high concentration.

Novel Ion-imprinted Polymer as a Tool for Selective Determination of SbIII in Natural Waters

A novel SbIII-imprinted polymer was synthesized via radical copolymerization of methacrylic acid and trimethylolpropane trimethacrylate in the presence of 2-mercapto-N-(2-naphthyl)acetamide as a chelating ligand forming the functionality of specific binding sites. The extent of ligand incorporation in the active centres was evaluated by elemental analysis and found to be 73.6%. The IIP was utilized as a sorbent material for selective solid-phase extraction of SbIII in drinking waters after optimization of sorption and desorption processes in a batch mode. Excellent separation of SbIII and SbV was accomplished at pH 8 followed by elution of SbIII with 0.5 M thiocarbamide. Analytical procedure for non-chromatographic speciation and determination of SbIII was developed demonstrating very good precision (RSD 7–11%) and recoveries between 97–105%. This procedure enabled up to 25-fold reconcentration and completely met the requirements of EU legislation for the quality of water intended for human consumption.

Extraction-assisted voltammetric determination of homocysteine using magnetic nanoparticles modified with molecularly imprinted polymer

Amagnetic graphite-epoxy composite (m-GEC) electrochemical sensor is presentedbased on magnetic imprinted polymer (mag-MIP) to determine homocysteine (Hcy). Mag-MIP was synthesized via precipitation polymerization, using functionalized magnetic nanoparticles (Fe3O4) together with the template molecule (Hcy), the functional monomer 2-hydroxyethyl methacrylate (HEMA), and the structural monomer trimethylolpropane trimethacrylate (TRIM). For mag-NIP (magnetic non-imprinted polymer), the procedure was the same in the absence of Hcy. Morphological and structural properties of the resultant mag-MIP and mag-NIP were examined usingTEM, FT-IR, and Vibrating Sample Magnetometer. Under optimized conditions, the m-GEC/mag-MIP sensor showed a linear range of 0.1-2µmol L-1, with alimit of detection (LOD) of 0.030µmol L-1. In addition, the proposed sensor responded selectively to Hcy compared to several interferents present in biological samples. The recovery values determined by differential pulse voltammetry (DPV) were close to 100% for natural and synthetic samples, indicating good method accuracy. The developed electrochemical sensor proves to be a suitable device for determining Hcy, with advantages related to magnetic separation and electrochemical analysis.

Molecular Imprinting of Benzylpiperazine: A Comparison of the Self-Assembly and Semi-Covalent Approaches

Molecularly imprinted polymers (MIPs) for benzylpiperazine (BZP, 1), an illicit designer drug, were developed by using both self-assembly and semi-covalent approaches. From an array of potential functional monomers (FMs) and using a combination of pre-synthetic interaction studies (by molecular modelling and NMR analysis) and binding assays, the highest performing self-assembly 1-MIPs were confirmed to result from methacrylic acid (7) as FM, ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TRIM) as crosslinkers and chloroform as the porogen and rebinding solvent at template (T): FM ratios of 1:1 and 1:2, giving imprinting factors (IF) 3 to 7. The semi-covalent 1-MIPs were designed using benzylpiperazine (4-vinylphenyl) carbamate (16) as the template-monomer adduct in combination with either EDGMA or TRIM. Our comparative analysis showed the semi-covalent polymers to have a stronger affinity for 1 (significantly lower Kd values and higher IFs) and faster uptake than the self-assembly systems. Both approaches have comparable cross-reactivity: marginal to low against cocaine (17) and morphine (18) and high against ephedrine (19) and phenylpiperazine (20). They also have comparable selectivity: highly selective towards 1 against 17, moderate against 18 and non-selective against 19. EGDMA-based self-assembly MIPs displayed a greater imprinting effect (higher IFs and NIP-to-MIP Kd ratios) than TRIM-based MIPs, while the TRIM-based semi-covalent MIP outperformed its EGDMA-based equivalent. By virtue of its modest selectivity against the test illicit drugs, 1-MIPs could potentially be used as a dummy MIP for the broad-based capture and enrichment of illicit drug blends for subsequent laboratory analysis.

Synthesis and thermal characterization of porous polymeric microspheres functionalized with thiol groups

The paper presents a method of the preparation and functionalization of polymer microspheres consisting of glycidyl methacrylate (GMA) and crosslinking agents: 1,4-dimethacryloyloxybenzene (1,4DMB) and trimethylolpropane trimethacrylate (TRIM). Poly(GMA-co-1,4DMB) and poly(GMA-co-TRIM) microspheres were obtained by seed swelling polymerization. To introduce thiol groups into the microspheres structure, the reaction with thiocarboxylic acids was performed. The chemical structure of parent and modified microspheres was confirmed by FTIR and Raman spectroscopy. Elemental composition of microspheres after functionalization was determined by elemental analysis. The analysis showed the percentage of sulfur in the range of 2.78–4.51%, which corresponds to a concentration of thiol group in the range of 0.87–1.41 mmol g−1. Additionally, the porous structure of the copolymers was investigated using the low-temperature nitrogen adsorption–desorption method. The starting microspheres are characterized by a specific surface in the range of 150–160 m2 g−1, whereas functionalized copolymers indicate slightly lower surface area, of about 130 m2 g−1. The thermal stability of the materials was determined by the method of differential scanning calorimetry and thermogravimetric analysis. The course of the thermal degradation under oxidative conditions of modified microspheres is different from the starting copolymers. The functionalized microspheres showed much higher thermal stability (approximately 270 °C) compared to the starting microspheres (230–250 °C).

Raclopride-Molecularly Imprinted Polymers: A Promising Technology for Selective [11C]Raclopride Purification.

In this work, we developed a novel approach to purify [11C]Raclopride ([11C]RAC), an important positron emission tomography radiotracer, based on tailored shape-recognition polymers, with the aim to substitute single-pass HPLC purification with an in-flow trap & release process. Molecular imprinting technology (MIT) applied to solid phase extraction (MISPE) was investigated to develop a setting able to selectively extract [11C]RAC in a mixture containing a high amount of its precursor, (S)-O-Des-Methyl-Raclopride (DM-RAC). Two imprinted polymers selective for unlabeled RAC and DM-RAC were synthesized through a radical polymerization at 65 °C using methacrylic acid and trimethylolpropane trimethacrylate in the presence of template molecule (RAC or DM-RAC). The prepared polymer was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy and tested in MISPE experiments. The polymers were used in testing conditions, revealing a high retention capacity of RAC-MISPE to retain RAC either in the presence of similar concentrations of RAC and DM-RAC precursor (96.9%, RSD 6.6%) and in the presence of a large excess of precursor (90%, RSD 4.6%) in the loading solution. Starting from these promising results, preliminary studies for selective purification of [11C]Raclopride using this RAC-MISPE were performed and, while generally confirming the selectivity capacity of the polymer, revealed challenging applicability to the current synthetic process, mainly due to high backpressures and long elution times.

Binary systems for the trimethylolpropane triacrylate and trimethylolpropane trimethacrylate in supercritical carbon Dioxide: Experiment and modeling

The phase equilibrium data for two binary mixes of trimethylolpropane triacrylate (TMPTA) and trimethylolpropane trimethacrylate (TMPTMA) in supercritical CO2 are given. The mixture's experimental isotherms were determined at five different temperature windows, ranging from 313.2 K to 393.2 K, and maximum pressure of 32.23 MPa. The continuous critical mixture plot displayed by both binary mixtures indicates type-I behavior. At any temperature and composition, none of the systems under study exhibited three phases. The critical point for TMPTA + supercritical CO2 mixtures shifts to a higher pressure as temperature increases; however, no critical point was found for TMPTMA + supercritical CO2 mixture.Experimental phase behavior data is correlated with the Peng-Robinson two parameter cubic equation of state. Using two mixing parameters, all the isotherms in (P, x) space are predicted with satisfactory accuracy.

Cross-Linked Ionic Liquid Polymer for the Effective Removal of Ionic Dyes from Aqueous Systems: Investigation of Kinetics and Adsorption Isotherms.

In the current study, we have synthesized an imidazolium based cross-linked polymer, namely, 1-vinyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide (poly[veim][Tf2N]-TRIM) using trimethylolpropane trimethacrylate as cross linker, and demonstrated its efficiency for the removal of two extensively used ionic dyes-methylene blue and orange-II-from aqueous systems. The detailed characterization of the synthesized poly[veim][Tf2N]-TRIM was performed with the help of 1H NMR, TGA, FT-IR and FE-SEM analysis. The concentration of dyes in aqueous samples before and after the adsorption process was measured using an UV-vis spectrophotometer. The process parameters were optimised, and highest adsorption was obtained at a solution pH of 7.0, adsorbent dosage of 0.75 g/L, contact time of 7 h and dye concentrations of 100 mg/L and 5.0 mg/L for methylene blue and orange-II, respectively. The adsorption kinetics for orange-II and methylene blue were well described by pseudo-first-order and pseudo-second-order models, respectively. Meanwhile, the process of adsorption was best depicted by Langmuir isotherms for both the dyes. The highest monolayer adsorption capacities for methylene blue and orange-II were found to be 1212 mg/g and 126 mg/g, respectively. Overall, the synthesized cross-linked poly[veim][Tf2N]-TRIM effectively removed the selected ionic dyes from aqueous samples and provided >90% of adsorption efficiency after four cycles of adsorption. A possible adsorption mechanism between the synthesised polymeric adsorbent and proposed dyes is presented. It is further suggested that the proposed ionic liquid polymer adsorbent could effectively remove other ionic dyes and pollutants from contaminated aqueous systems.

Enhancement of the properties of carbon-black-filled natural rubber compounds containing soybean oil cured with peroxide through the addition of coagents

Due to the hazard of the commercial rubber processing oil such as distillate aromatic extract (DAE), many rubber researchers play attention to find the green alternatives. Vegetable oils seem to gain a lot of attraction for this. It is not just only due to their environmentally friendly nature but also their abundance and affordable cost. The use of soybean oil (SBO) for the carbon black-filled rubber compounds was focused here and comparatively discussed with the use of DAE. Furthermore, this work also proposed the way to improve the mechanical properties and environmental endurance of the rubber compounds containing SBO by adding coagents. There were two types of coagent including trimethylolpropane trimethacrylate (TMPTMA) and triallyl isocyanurate (TAIC) used here. It was found that the cure time, cure rate index, and cure reaction rate constant of SBO-added rubber compounds with and without coagents were higher than those of DAE-added rubber compounds, whereas the activation energy of SBO-added rubber compounds was lower than the one with DAE. Without coagent, the mechanical properties of rubber compounds with DAE and SBO are equal. However, the addition of coagents improved the mechanical properties of rubber compounds containing SBO. The modulus at 100% strain, modulus at 200% strain, and tensile strength of TMPTMA-added rubber compounds increased by 41%, 48%, and 15%, respectively, whereas the rubber compounds with TAIC increased by 7%, 8%, and 20%, respectively, when compared to the one with SBO alone. Interesting, the SBO-added rubber compounds with and without coagents showed better thermal aging and ozone resistances than the DAE-added rubber compounds. All results showed that the presence of coagents especially TMPTMA gave the SBO-added rubber compound with the superior performance to the DAE-added rubber compound and the SBO-added rubber compound without coagent.

Does Multifunctional Acrylate's Addition to Methacrylate Improve Its Flexural Properties and Bond Ability to CAD/CAM PMMA Block?

This study investigated the effects of a multifunctional acrylate copolymer-Trimethylolpropane Triacrylate (TMPTA) and Di-pentaerythritol Polyacrylate (A-DPH)-on the mechanical properties of chemically polymerized acrylic resin and its bond strength to a CAD/CAM polymethyl methacrylate (PMMA) disk. The methyl methacrylate (MMA) samples were doped with one of the following comonomers: TMPTA, A-DPH, or Trimethylolpropane Trimethacrylate (TMPTMA). The doping ratio ranged from 10 wt% to 50 wt% in 10 wt% increments. The flexural strength (FS) and modulus (FM) of PMMA with and without comonomer doping, as well as the shear bond strength (SBS) between the comonomer-doped PMMA and CAD/CAM PMMA disk, were evaluated. The highest FS (93.2 ± 4.2 MPa) was obtained when doped with 20 wt% of TMPTA. For TMPTMA, the FS decreased with the increase in the doping ratio. For SBS, TMPTA showed almost constant values (ranging from 7.0 to 8.2 MPa) regardless of the doping amount, and A-DPH peaked at 10 wt% doping (8.7 ± 2.2 MPa). TMPTMA showed two peaks at 10 wt% (7.2 ± 2.6 MPa) and 40 wt% (6.5 ± 2.3 MPa). Regarding the failure mode, TMPTMA showed mostly adhesive failure between the CAD/CAM PMMA disk and acrylic resin while TMPTA and A-DPH showed an increased rate of cohesive or mixed failures. Acrylate's addition as a comonomer to PMMA provided improved mechanical properties and bond strength to the CAD/CAM PMMA disk.

Heat-Resistant Phthalonitrile-Based Resins for 3D Printing via Vat Photopolymerization

In this study, a maleimide/phthalonitrile bifunctional monomer PNB-M was used in vat photopolymerization via the maleimide group to obtain phthalonitrile-containing polymers suitable for further thermal postcuring. A high concentration (40 wt %) and low viscosity (less than 500 mPa·s at 25 °C) photopolymer resin was prepared from the phthalonitrile monomer PNB-M with 4-acryloylmorpholine as comonomer and trimethylolpropane trimethacrylate as cross-linker. Photo-DSC, NMR, and FTIR tests revealed free-radical photoinduced copolymerization of the maleimide with the acrylic groups during 3D printing. Postprinting thermal curing of the phthalonitrile groups was performed with different curing agents as well as via self-initiation by PNB-M. The developed phthalonitrile-containing polymerizable compositions made it possible to increase glass transition temperatures of the 3D printed polymer materials up to 351 °C after additional thermal postcuring. Moreover, mechanical properties of the 3D printed materials have been improved after curing of the phthalonitrile monomer in the maleimide–acrylate copolymer.

Degradation by Electron Beam Irradiation of Some Composites Based on Natural Rubber Reinforced with Mineral and Organic Fillers.

Composites based on natural rubber reinforced with mineral (precipitated silica and chalk) and organic (sawdust and hemp) fillers in amount of 50 phr were obtained by peroxide cross-linking in the presence of trimethylolpropane trimethacrylate and irradiated by electron beam in the dose range of 150 and 450 kGy with the purpose of degradation. The composites mechanical characteristics, gel fraction, cross-linking degree, water uptake and weight loss in water and toluene were evaluated by specific analysis. The changes in structure and morphology were also studied by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Based on the results obtained in the structural analysis, possible mechanisms specific to degradation are proposed. The increasing of irradiation dose to 450 kGy produced larger agglomerated structures, cracks and micro voids on the surface, as a result of the degradation process. This is consistent with that the increasing of irradiation dose to 450 kGy leads to a decrease in crosslinking and gel fraction but also drastic changes in mechanical properties specific to the composites’ degradation processes. The irradiation of composites reinforced with organic fillers lead to the formation of specific degradation compounds of both natural rubber and cellulose (aldehydes, ketones, carboxylic acids, compounds with small macromolecules). In the case of the composites reinforced with mineral fillers the degradation can occur by the cleavage of hydrogen bonds formed between precipitated silica or chalk particles and polymeric matrix also.

Molecular Dynamic Study of Mechanism Underlying Nature of Molecular Recognition and the Role of Crosslinker in the Synthesis of Salmeterol-Targeting Molecularly Imprinted Polymer for Analysis of Salmeterol Xinafoate in Biological Fluid.

The rational preparation of molecularly imprinted polymers (MIPs) in order to have selective extraction of salmeterol xinafoate (SLX) from serum was studied. SLX is an acting β-adrenergic receptor agonist used in the treatment of asthma and has an athletic performance-enhancing effect. Molecular dynamics were used for the simulation of the SLX-imprinted pre-polymerization system, to determine the stability of the system. The computational simulation showed that SLX as a template, 4-hydroxyethyl methacrylate (HEMA) as a monomer, and trimethylolpropane trimethacrylate (TRIM) as a crosslinker in mol ratio of 1:6:20 had the strongest interaction in terms of the radial distribution functional. To validate the computational result, four polymers were synthesized using the precipitation polymerization method, and MIP with composition and ratio corresponding with the system with the strongest interaction as an MD simulation result showed the best performance, with a recovery of 96.59 ± 2.24% of SLX in spiked serum and 92.25 ± 1.12% when SLX was spiked with another analogue structure. Compared with the standard solid phase extraction sorbent C-18, which had a recovery of 79.11 ± 2.96%, the MIP showed better performance. The harmony between the simulation and experimental results illustrates that the molecular dynamic simulations had a significant role in the study and development of the MIPs for analysis of SLX in biological fluid.

Three-dimensional ordered macroporous imprinted polymer for bisphenol A recognition.

A novel kind of three-dimensional ordered macroporous molecular imprinted polymer (3DOM MIP) was prepared and studied. Monodisperse silica microspheres were used to form silica crystal template via simple centrifuge. In the presence of template molecule, acrylamide and trimethylolpropane trimethacrylate were co-polymerized in the interstices of crystal template bisphenol A (BPA). Hydrofluoric acid were employed to etch silica crystal and the mixed solvent of methanol with acetic acid were employed to extract template molecule. The results of SEM and FTIR confirmed the successful synthesis of 3DOM MIP. The obtained 3DOM MIP exhibited a rapid adsorption kinetics and a specific adsorption capacities toward template molecule because of the small size of MIP wall, which possessed much more effective imprinted cavies. Meanwhile, 3DOM MIP could selective recognized BPA from its structural analogues.

Crosslinked 4-Vinylpyridine Monodisperse Functional Microspheres for Sorption of Ibuprofen and Ketoprofen

Nowadays, ibuprofen and ketoprofen are widely used over-the-counter medications to treat inflammation, fever, or pain. Their high consumption and improper disposal cause them to get into the environment and often pollute surface water. In this study, the new polymeric porous microspheres based on 4-vinylpyridine (4VP) are presented as effective sorbents for ibuprofen and ketoprofen preconcentration and removal. The porous microspheres were obtained via seed swelling polymerization with the use of two types of methacrylate crosslinkers, i.e., trimethylolpropane trimethacrylate (TRIM) and 1,4-dimethacryloiloxybenzene (14DMB). Additionally, as a reference sorbent, a copolymer of styrene and divinylbenzene was obtained. Porous structure investigations showed that the microspheres possess a specific surface area of about 100 m2/g, but noticeable differences were observed in their internal topography depending on the type of crosslinker used. Moreover, the porous structure of dry and swollen microspheres differs significantly. Swollen copolymers reveal the presence of micropores. The 4VP microspheres are characterized by high thermal stability; their initial decomposition temperature is about 300 °C. The performance of the 4VP copolymers as sorbents in aqueous solutions of drugs was evaluated in static and dynamic modes at three pH values of 3, 7, and 11. The highest sorption efficiency was obtained for ibuprofen and ketoprofen in pH 3. Both 4VP copolymers indicate the high sorption capacity in a static sorption as follows: towards ketoprofen of about 40 mg/g whereas towards ibuprofen of about 90 mg/g and 75 mg/g on copolymer crosslinked with trimethylolpropane trimethacrylate and 1,4-dimethacryloiloxybenzene, respectively. The recovery of ibuprofen and ketoprofen after dynamic sorption experiments was higher than 90%.

EGDMA- and TRIM-Based Microparticles Imprinted with 5-Fluorouracil for Prolonged Drug Delivery.

Imprinted materials possess designed cavities capable of forming selective interactions with molecules used in the imprinting process. In this work, we report the synthesis of 5-fluorouracil (5-FU)-imprinted microparticles and their application in prolonged drug delivery. The materials were synthesized using either ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TRIM) cross-linkers. For both types of polymers, methacrylic acid was used as a functional monomer, whereas 2-hydroxyethyl methacrylate was applied to increase the final materials’ hydrophilicity. Adsorption isotherms and adsorption kinetics were investigated to characterize the interactions that occur between the materials and 5-FU. The microparticles synthesized using the TRIM cross-linker showed higher adsorption properties towards 5-FU than those with EGDMA. The release kinetics was highly dependent upon the cross-linker and pH of the release medium. The highest cumulative release was obtained for TRIM-based microparticles at pH 7.4. The IC50 values proved that 5-FU-loaded TRIM-based microparticles possess cytotoxic activity against HeLa cell lines similar to pure 5-FU, whereas their toxicity towards normal HDF cell lines was ca. three times lower than for 5-FU.

Cobalt (II)-Mediated Molecularly Imprinted Polymer as a Monolithic Stationary Phase for Separation of Racemic Citronellal by Liquid Chromatography.

A metal-mediated molecularly imprinted polymer (MMIP) monolithic column was prepared as the stationary phase for high-performance liquid chromatography (HPLC) and applied to the enantiomeric separation of rac-citronellal. MMIP column was prepared through in situ copolymerizations with the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate/[BMIM][BF4] as the primary pore-forming agent and cobalt(II) acetate as the metal pivot. Interactions between polymer components in the synthesized monolith were assessed by FTIR to identify the functional groups. The monolith morphology was characterized with SEM, and the template removal was detected by UV Spectrophotometry at 253 nm. In this study, (R)-(+)-citronellal was used as a template, whereas 4-vinylpyridine (4-VP) was employed as the functional monomer with two monomer crosslinkers, trimethylolpropane trimethacrylate (TRIM), and ethylene glycol dimethacrylate (EDMA). The ternary mixture of porogenic solvent consisted of [BMIM][BF4], dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) with the applied ratio of 1 : 1:1 (v/v) and 10 : 1:5 (v/v) for the preparation of MMIP using TRIM and EDMA crosslinkers, respectively. Co(II) ion was added to the porogenic solvent before being mixed with the functional monomer and the crosslinker mixtures. Separating the rac-citronellal was achieved on the synthesized MMIP, showing better selectivity than the monolithic metal-mediated nonimprinted polymer (MNIP), nonimprinted polymer (NIP), and molecularly imprinted polymer (MIP).

Poly(acrylic acid)-Based Hydrogel Actuators Fabricated via Digital Light Projection Additive Manufacturing

Electroactive polymers that exhibit controlled deformation under an applied electric field, either in liquid or air, have great potential as soft robotic actuators. However, materials for soft robotics currently face challenges, including slow response, high actuation potential, and a lack of underlying mechanistic understanding. Additionally, fabrication of soft robotic actuators with complex design features has historically been restricted by two-dimensional fabrication methods. In this work, we investigate cross-linked poly(acrylic acid)-based actuators prepared utilizing digital light projection (DLP), an additive manufacturing technique that enables fabrication of actuators with complex geometries. A series of photopolymerizable inks are prepared incorporating acrylic acid (monomer), trimethylolpropane trimethacrylate (cross-linker), and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator). Soft actuators are 3D-printed utilizing a commercial DLP 3D printer operating under 405 nm UV light. These 3D-printed actuators exhibit large deformation (up to 43°), high actuation speed (up to 1.08°/s), and stable actuation performance for bending cycles under relatively low actuation voltage (4–6 V). Factors such as acrylic acid content, cross-linker concentration, actuator thicknesses, and electric field strength are varied, and their impact on the 3D-printed actuators are evaluated and discussed. Lastly, a membrane valve actuator is fabricated, and its ability to open and close under applied potential is demonstrated.

Bleed-out suppression of silicone rubber by electron beam crosslinking

A silicone rubber with a highly crosslinked surface layer was synthesized by a two-step crosslinking reaction with thermal processing and subsequent electron beam (EB) irradiation. The effect of the EB irradiation on the silicone rubber was evaluated by measuring the volume swelling ratio, shore hardness, tensile breaking strength, and water contact angle of the EB-crosslinked silicone rubber. The silicone rubber was effectively crosslinked as the EB irradiation increased. The optimal EB irradiation dose to form the EB-crosslinked structure in the silicone rubber was 500 kGy. Insufficient EB irradiation does not form a sufficient EB-crosslinked structure, while excessive EB irradiation dose would decompose the silicone rubber. The finer crosslinked structures of the surface layer of the silicone rubber formed by EB irradiation could function as a leak-proof filter to prevent the bleed-out of low-molecular-weight siloxanes inside the silicone rubber. The effect of the type of EB-crosslinking agent on the bleed-out suppression effect was investigated. The bleed-out suppression effect was improved in the following order: no EB-crosslinking agent < ethylene glycol dimethacrylate < silicone diacrylate < trimethylolpropane trimethacrylate (TMPTMA). The thermally and EB-crosslinked silicone rubber with TMPTMA successfully reduced the bleed-out ratio by approximately 60%, compared to the thermally crosslinked silicone rubber without EB irradiation and EB crosslinking agent.