Calcium hydroxyapatite nanoparticles as a reinforcement filler in dental resin nanocomposite.

The current study focuses on the fabrication of calcium hydroxyapatite (Ca10(PO4)6(OH)2) (HA) in a nanorange having whiskers- and cubic-shaped uniform particle morphology. The synthesized HA particles hold a promising feature as reinforcement fillers in dental acrylic resin composite. They increase the efficacy of reinforcement by length and aspect ratio, uniformity, and monodispersity. Therefore, the acrylic resin was reinforced with the as-synthesized monodispersed HA filler particles (0.2-1 Wt%). The presence of filler particles in the composite had a noticeable effect on the tribological and mechanical properties of the dental material. The morphological effect of HA particles on these properties was also investigated, revealing that cubic-shaped particles showed better results than whiskers. The as-fabricated composite (0.4 Wt%) of the cubic-shaped filler particles showed maximum hardness and improved antiwear/antifriction properties. Particle loading played its part in determining the optimum condition, whereas particle size also influenced the reinforcement efficiency. The current study revealed that particle morphology, particle size, uniformity, etc., of HA fillers, greatly influenced the tribological and mechanical properties of the acrylic resin-based nanocomposite. Improvement in the tribological properties of HA particle-reinforced acrylic resin composites (HA-acrylic resin) followed the trend as AR < CmC < WC < CC.

A Tuneable, Photocurable, Poly(Caprolactone)-Based Resin for Tissue Engineering-Synthesis, Characterisation and Use in Stereolithography.

Stereolithography is a useful additive manufacturing technique for the production of scaffolds for tissue engineering. Here we present a tuneable, easy-to-manufacture, photocurable resin for use in stereolithography, based on the widely used biomaterial, poly(caprolactone) (PCL). PCL triol was methacrylated to varying degrees and mixed with photoinitiator to produce a photocurable prepolymer resin, which cured under UV light to produce a cytocompatible material. This study demonstrates that poly(caprolactone) methacrylate (PCLMA) can be produced with a range of mechanical properties and degradation rates. By increasing the degree of methacrylation (DM) of the prepolymer, the Young's modulus of the crosslinked PCLMA could be varied from 0.12-3.51 MPa. The accelerated degradation rate was also reduced from complete degradation in 17 days to non-significant degradation in 21 days. The additive manufacturing capabilities of the resin were demonstrated by the production of a variety of different 3D structures using micro-stereolithography. Here, ß-carotene was used as a novel, cytocompatible photoabsorber and enabled the production of complex geometries by giving control over cure depth. The PCLMA presented here offers an attractive, tuneable biomaterial for the production of tissue engineering scaffolds for a wide range of applications.

Formaldehyde-free self-polymerization of lignin-derived monomers for synthesis of renewable phenolic resin.

Most phenolic resins are synthesized with non-renewable petroleum-based phenol and formaldehyde, which have adverse effects on the environment and human health. To achieve green and sustainable production of phenolic resins, it is important to replace non-renewable toxic phenol and formaldehyde. Herein, a new strategy was proposed to completely replace phenol and formaldehyde, using lignin-derived monomers to synthesize renewable phenolic resins. Lithium aluminum hydride was utilized to reduce lignin-derived monomers, including vanillin, methyl vanillate, and syringaldehyde, to generate the corresponding vanillyl and syringic alcohol. With oxalic acid as the catalyst, vanillyl and syringic alcohol could be polymerized to phenolic resins without using formaldehyde. The structure of the phenolic resins based on lignin-derived monomers was analyzed by Fourier transform infrared spectroscopy and 13C and 31P nuclear magnetic resonance spectroscopy. Differential scanning calorimetry and thermogravimetric analysis were performed to characterize the thermal properties of the phenolic resins. The phenolic resins based on lignin-derived monomers exhibited excellent adhesion strength (6.14 MPa), glass transition temperature (Tg) (107-115 °C), and thermal stability, and its performance was similar to that of the commercial Novolak phenolic resin. This study presents a promising green and sustainable approach to synthesize renewable phenolic resins based on lignin-derived monomers without using formaldehyde.

A facile one-step preparation of Ca10(PO4)6(OH)2/Li-BioMOFs resin nanocomposites with Glycyrrhiza glabra (licorice) root juice as green capping agent and mechanical properties study.

The Ca10(PO4)6(OH)2/Li-BioMOFs resin nanocomposites were prepared and introduced as a new dental resin nanocomposite. Ca10(PO4)6(OH)2/Li-BioMOFs resin nanocomposites were synthesized with individual mechanical properties in the presence of lecithin as a biostabilizer. The hydrothermal synthesis of hydroxyapatite (HAp) nanostructures occurred in the presence of Glycyrrhiza glabra (liquorice) root juice that acts not only as a green capping agent but also as a reductant compound with a high steric hindrance agent. Results showed that the mechanical properties of nano-Ca10(PO4)6(OH)2 structures with a concentration of 60 ppm Li-BioMOF were increased by ∼132.5 MPa and 11.5 GPa for the flexural and Young's modulus, respectively. Based on the optical absorption ultraviolet-visible spectrum, the HAp nanocrystallites had a direct bandgap energy of 4.2 eV. The structural, morphological, and mechanical properties of the as-prepared nanoparticles were characterized with the FT-IR (Fourier-transform infra-red), UV-Vis (ultraviolet visible) spectrums, X-ray diffraction, SEM (scanning electron microscopy), and TEM (transmission electron microscopy) images, and atomic force microscopy (AFM). It is suggested that HAp structures loaded on the Li-BioMOFs are as a suitable and novel substrate which can be considered as a promising biomaterial in dental resin nanocomposites significantly improved the strength and modulus.

Comparative study of photoinitiators for the synthesis and 3D printing of a light-curable, degradable polymer for custom-fit hard tissue implants.

Three-dimensional (3D) printing enhances the production of on-demand fabrication of patient-specific devices, as well as anatomically fitting implants with high complexity in a cost-effective manner. Additive systems that employ vat photopolymerisation such as stereolithography (SLA) and digital light projection are used widely in the field of biomedical science and engineering. However, additive manufacturing methods can be limited by the types of materials that can be used. In this study, we present an isosorbide-based formulation for a polymer resin yielding a range of elastic moduli between 1.7 and 3 GN mm-2 dependent on the photoinitiator system used as well as the amount of calcium phosphate filler added. The monomer was prepared and enhanced for 3D-printing using an SLA technique that delivered stable and optimized 3D-printed models. The resin discussed could potentially be used following major surgery for the correction of congenital defects, the removal of oral tumours and the reconstruction of the head and neck region. The surgeon is usually limited with devices available to restore both function and appearance and with the ever-increasing demand for low-priced and efficient facial implants, there is an urgent need to advance new manufacturing approaches and implants with a higher osseointegration performance.

Original synthesis of radiolabeling precursors for batch and on resin one-step/late-stage radiofluorination of peptides.

Radiolabeling of peptides with fluorine-18 is hurdled by their chemical sensitivity and complicated processes. Original triflyl-pyridine intermediates afforded ammonium precursors that were radiolabeled at low temperature. From that study, a generic tag has been designed to allow a simple one-step/late-stage radiolabelling of peptides. The strategy has been transposed to an automated "on-resin" radiolabelling.

Development of micropatterning polyimide films for enhanced antifouling and antibacterial properties.

A commercial biomedical Polyimide (PI) film was topographically and chemically modified by generating micrometric periodic arrays of lines using Direct Laser Interference Patterning (DLIP) in order to improve antifouling and antibacterial properties. DLIP patterning was performed with periods from 1 µm to 10 µm. The physical modification of the surface was characterized by SEM, AFM and contact angle measurements and, the chemical composition of the ablated surfaces was analyzed by ATR-IR and XPS spectroscopies. The antibacterial effects were evaluated through the effect on Pseudomonas aeruginosa colonies growth on the LB (Luria Bertani) broth. The results showed that the laser treatment change the topography and as a consequence the chemistry surface, also that the microstructured surfaces with periods below 2 µm, exhibited a significant bacterial (P. aeruginosa) adhesion decrease compared with non-structured surfaces or with surfaces with periods higher than 2 µm. The results suggest that periodic topography only confer antifouling properties and reduction of the biofilm formation when the microstructure presents periods ranging from 1 µm to 2 µm. On the other hand, the topography that confer strong antifouling superficial properties persists at long incubation times. In that way, polymer applications in the biosciences field can be improved by a surface topography modification using a simple, single-step laser-assisted ablation method.

Synthesis and evaluation of acrylate resins suspending indole derivative structure in the side chain for marine antifouling.

A novel indole derivative (N-(1H-2-phenyl-indole-3-ylmethyl) acrylamide, NPI) synthesized by a Friedel-Crafts alkylation reaction was identified using IR spectroscopy, 1H NMR, 13C NMR and elemental analysis. The inhibitory effect of this novel indole derivative on bacteria and marine algae was studied. The results showed that the inhibition ratios of the indole derivative against Escherichia coli and Staphylococcus aureus were 95.93% and 94.91%, respectively, and the indole derivative possessed prominent inhibitory activity against Phaeodactylum tricornutum, Nitzschia Closterium and Skeletonema costatum. These findings indicate that the indole derivative has high biological activity. Subsequently, the indole derivative was introduced to acrylate resins by free-radical polymerization. The resulting acrylate resins were subjected to self-polishing, anti-algal and antifouling test, the results of which indicated that acrylate resins containing the synthesized indole derivative could exhibit significant antifouling properties because of the combination of the biofouling resistance of the indole derivative and the self-polishing properties of acrylate. This work provides an academic foundation for studying environmentally friendly and highly efficient antifouling coatings.

Attapulgite/hydrophilic molecularly imprinted monolithic resin composite for the selective recognition and sensitive determination of plant growth regulators in cucumbers.

In this study, through in-situ polymerization process, a novel composite of attapulgite/hydrophilic molecularly imprinted monolithic resin (AT/HMIMR) were prepared in pipette tips for extraction trace plant growth regulators in cucumbers. In the preparation procedure, fibrillar attapulgite nanoparticles were embedded to increase extraction capacity, polyethyleneglycol-6000 was employed as a dual-function porogen, that acted as both the structure-directing agent of the HMIMR and the attapulgite dispersant. N-(1-naphthyl) ethylenediamine dihydrochloride was used as a dummy template to accurate quantification on extraction procedures. Experimental parameters of AT/HMIMR for extracting plant growth regulators from cucumbers were optimized, and the results showed that the recoveries of ranged from 92.4% to 101.1% with relative standard deviations ≤ 6.5% (n = 3). Considering its microporous monolithic column structure, multiple adsorption mechanism, and specific selectivity, AT/HMIMR shows promise for applications that require specific recognition for the analytes in real complex samples.

Green protocol for the preparation of hydrophilic molecularly imprinted resin in water for the efficient selective extraction and determination of plant hormones from bean sprouts.

In this study, a novel and green synthesis of a new hydrophilic molecularly imprinted 3-aminophenol-hexamethylenetetramine (MIAPH) resin for the selective recognition and separation of plant hormones was developed. The MIAPH resin was obtained using 3-aminophenol as multifunctional monomer which introduced hydroxyl, amino, and imino groups simultaneously, and adenine was used as a dummy template for molecular imprinting. Meanwhile, hexamethylenetetramine released formaldehyde slowly through hydrolysis which was used as the cross-linking agent to avoid the direct and excessive use of toxic formaldehyde. The entire procedure was performed under mild conditions, and was facile, environmentally friendly and energy-efficient. The obtained MIAPH resin showed high specific recognition toward plant hormones and higher recoveries in bean sprouts compared to NIAPH, HLB, and C18. Various parameters affecting the extraction efficiency were optimized, and the calibration linearity of the MIAPH‒SPE‒HPLC method was determined from 0.07 to 2.86 mg kg-1 with a correlation coefficient (r) ≥ 0.9994 under the optimal conditions. Recoveries of spiked standards ranged from 90.2 to 99.1% for bean sprout with a relative standard deviation of ≤5.3%. Finally, the established MIAPH‒SPE‒HPLC method was successfully applied for the selective extraction and sensitive detection of plant hormones in a variety of complex vegetable matrices.

High Tg and Thermo-Oxidatively Stable Thermosetting Polyimides Derived from a Carborane-Containing Diamine.

To provide high-temperature polyimide matrix resins, novel carborane-containing thermosetting polyimides are presented. First, the low-viscosity carborane-containing imide oligomers are synthesized using newly designed 1-(3-amino-4-tolyl)-2-(4-aminophenyl)-o-carborane and aromatic dianhydride as monomers, 4-phenylethynyl phthalic anhydride as the end-capping reagent. Followed by thermal curing, the resulting polyimides show high Tg (≥500 °C) and above 92.1% char yield at 800 °C both in nitrogen and air atmosphere due to the incorporation of the bulky carborane cages. Aging studies, performed at 400 and 500 °C for 5 h in air on a carborane-containing polyimide and a carborane-free polyimide, show that the polyimide with carborane groups possesses excellent thermo-oxidative stability. Moreover, the novel polyimides exhibit constant and relatively low coefficient of thermal expansion values over a wide range of temperature, indicative of a remarkable dimensional stability. Thus, this study clearly demonstrates the viability of the incorporation of carborane cages to access polyimide thermosets with ultrahigh Tg and thermo-oxidative stability.

Green synthesis of hydrophilic protein-imprinted resin with specific recognition of bovine serum albumin in aqueous matrix.

The synthesis of biomacromolecule imprinted materials is a challenge with the bulkiness and instability of macromolecule, such as protein. A green strategy to prepare hydrophilic protein-imprinted resin (HPIR) was firstly developed using resorcinol and melamine as double functional monomers, hexamethylenetetramine instead of formaldehyde as crosslinker, water as solvent, and bovine serum albumin (BSA) as a dual-function template. BSA as dual-function template could not only act as template but also porogen in the preparation of HPIR. According to the adsorption experiments, the adsorption kinetics of BSA on HPIR obeyed pseudo-second-order adsorption kinetics and the equilibrium data were best described by Langmuir isotherm model. The adsorption capability was 44.3459 mg g-1 (25 °C), and the imprinted factor for binding BSA is 5.78. HPIR showed high adsorption capacity, fast mass transfer rate, and specific selectivity towards BSA in aqueous solvent. More importantly, HPIR can be applied to selectively adsorb target protein BSA in urine without the matrix interference of biological matrix, therefore, it is promising for HPIR to be applied to proteomics, diagnostics, and pharmaceutics.

Novel controllable hydrophilic thermo-responsive molecularly imprinted resin adsorbent prepared in water for selective recognition of alkaloids by thermal-assisted dispersive solid phase extraction.

A novel controllable hydrophilic thermo-responsive molecularly imprinted resin (T-MIR) with a switchable zipper-like architecture was synthesized in the aqueous phase and applied to the selective recognition and extraction of alkaloids by positive temperature regulation. In this synthesis process of T-MIR, 2-acrylamide-2- methylpropanesulfonic acid (AMPS) and acrylamide (AAm) were coupled as zipper-like thermo-responsive monomers, resorcinol, and melamine as hydrophilic monomers, formaldehyde as a cross-linker, and berberine chloride (BerbC) as the template. The resulting T-MIR achieved the controlled rebinding and release of BerbC from temperature stimuli (25-45 °C) and the adsorption process followed the Langmuir isotherm (R2>0.99856) and pseudo-second-order kinetic model (R2>0.98138). The highest theory adsorption ability (33.44 mg/g) and recognition ability (imprinting factor: 4.71) of T-MIR was activated between poly(AMPS) and poly(AAm) in the zipper-like architecture at 35 °C. T-MIR was then applied to the selective recognition alkaloids by dispersive solid phase extraction. The limit of detection and limit of quantitation of the method were less than 0.025 mg/L and 0.082 mg/mL, respectively. The recoveries of the proposed method at three spiked levels were 96.8-100.8%, with a relative standard deviation of less than 4.8%. In contrast to previous thermo-responsive materials, this switchable zipper-like hydrophilic T-MIR with good adsorption, specificity recognition, and excellent temperature controllable properties provides a unique alternative to the selective recognition and controlled rebind-release alkaloids by the temperature signal.

Separation of Protactinium Employing Sulfur-Based Extraction Chromatographic Resins.

Protactinium-230 ( t1/2 = 17.4 d) is the parent isotope of 230U ( t1/2 = 20.8 d), a radionuclide of interest for targeted alpha therapy (TAT). Column chromatographic methods have been developed to separate no-carrier-added 230Pa from proton irradiated thorium targets and accompanying fission products. Results reported within demonstrate the use of novel sulfur bearing chromatographic extraction resins for the selective separation of protactinium. The recovery yield of 230Pa was 93 ± 4% employing a R3P═S type commercially available resin and 88 ± 4% employing a DGTA (diglycothioamide) containing custom synthesized extraction chromatographic resin. The radiochemical purity of the recovered 230Pa was measured via high purity germanium γ-ray spectroscopy to be >99.5% with the remaining radioactive contaminant being 95Nb due to its similar chemistry to protactinium. Measured equilibrium distribution coefficients for protactinium, thorium, uranium, niobium, radium, and actinium on both the R3P═S type and the DGTA resin in hydrochloric acid media are reported, to the best of our knowledge, for the first time.

Synthesis and Characterization of a Novel Microporous Dihydroxyl-Functionalized Triptycene-Diamine-Based Polyimide for Natural Gas Membrane Separation.

An intrinsically microporous polyimide is synthesized in m-cresol by a one-pot high-temperature condensation reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and newly designed 2,6 (7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH). The 6FDA-DAT1-OH polyimide is thermally stable up to 440 °C, shows excellent solubility in polar solvents, and has moderately high Brunauer-Teller-Emmett (BET) surface area of 160 m2 g-1 , as determined by nitrogen adsorption at -196 °C. Hydroxyl functionalization applied to the rigid 3D triptycene-based diamine building block results in a polyimide that exhibits moderate pure-gas CO2 permeability of 70 Barrer combined with high CO2 /CH4 selectivity of 50. Mixed-gas permeation studies demonstrate excellent plasticization resistance of 6FDA-DAT1-OH with impressive performance as potential membrane material for natural gas sweetening with a CO2 permeability of 50 Barrer and CO2 /CH4 selectivity of 40 at a typical natural gas well partial pressure of 10 atm.

Development of a novel resin-based dental material with dual biocidal modes and sustained release of Ag+ ions based on photocurable core-shell AgBr/cationic polymer nanocomposites.

Research on the incorporation of cutting-edge nano-antibacterial agent for designing dental materials with potent and long-lasting antibacterial property is demanding and provoking work. In this study, a novel resin-based dental material containing photocurable core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) was designed and developed. The shell of polymerizable cationic polymer not only provided non-releasing antibacterial capability for dental resins, but also had the potential to polymerize with other methacrylate monomers and prevented nanoparticles from aggregating in the resin matrix. As a result, incorporation of AgBr/BHPVP nanocomposites did not adversely affect the flexural strength and modulus but greatly increased the Vicker's hardness of resin disks. By continuing to release Ag+ ions without the impact of anaerobic environment, resins containing AgBr/BHPVP nanoparticles are particularly suitable to combat anaerobic cariogenic bacteria. By reason of the combined bactericidal effect of the contact-killing cationic polymers and the releasing-killing Ag+ ions, AgBr/BHPVP-containing resin disks had potent bactericidal activity against S. mutans. The long-lasting antibacterial activity was also achieved through the sustained release of Ag+ ions due to the core-shell structure of the nanocomposites. The results of macrophage cytotoxicity showed that the cell viability of dental resins loading less than 1.0 wt% AgBr/BHPVP was close to that of neat resins. The AgBr/BHPVP-containing dental resin with dual bactericidal capability and long term antimicrobial effect is a promising material aimed at preventing second caries and prolonging the longevity of resin composite restorations.

Exploring the potential of high resolution mass spectrometry for the investigation of lignin-derived phenol substitutes in phenolic resin syntheses.

Chemical degradation is an efficient method to obtain bio-oils and other compounds from lignin. Lignin bio-oils are potential substitutes for the phenol component of phenol formaldehyde (PF) resins. Here, we developed an analytical method based on high resolution mass spectrometry that provided structural information for the synthesized lignin-derived resins and supported the prediction of their properties. Different model resins based on typical lignin degradation products were analyzed by electrospray ionization in negative ionization mode. Utilizing enhanced mass defect filter techniques provided detailed structural information of the lignin-based model resins and readily complemented the analytical data from differential scanning calorimetry and thermogravimetric analysis. Relative reactivity and chemical diversity of the phenol substitutes were significant determinants of the outcome of the PF resin synthesis and thus controlled the areas of application of the resulting polymers. Graphical abstract ᅟ.

One pot synthesis of chitosan grafted quaternized resin for the removal of nitrate and phosphate from aqueous solution.

The present study deals with the synthesis of chitosan quaternized resin for efficient removal of nitrate and phosphate from aqueous solution. The resin was characterized with FTIR, SEM with EDX and XRD. Batch method was carried out to optimize various parameters such as contact time, initial concentration of nitrate and phosphate, dosage, pH, co-anions and temperature on the adsorption capacity of the adsorbent. The adsorption process illustrated that the Freundlich isotherm and the pseudo-second order are the best fitted models for the sorption of both anions. The respective negative values of ΔH° and ΔG° revealed that the adsorption of both the anions were exothermic and spontaneous. The removal efficiency of nitrate and phosphate on chitosan quaternized resin were 78% and 90% respectively with 0.1g of adsorbent and the initial concentration as 100mg/L. Nitrate and phosphate anions adsorbed effectively on chitosan quaternized resin by replacing Cl- ions from quaternary site through electrostatic attraction as well as ion-exchange mechanism. Hydrogen bonding also played important role in adsorption process. Even after 7th regeneration cycle the adsorbent retained its adsorption capacity as 23.7mg/g and 30.4mg/g for both nitrate and phosphate respectively.

Adsorption performance of salicylic acid on a novel resin with distinctive double pore structure.

Two approaches were used to synthesize two resins with different pore structures. In one way, the CH2Cl groups in macroporous chloromethylated polystyrene resin were transformed to methylene bridges, and achieved a hypercrosslinked resin with plentiful micropores (denoted GQ-06). In the other way, 50% of the CH2Cl groups in chloromethylated polystyrene resin was used to produce micropores, while the residual 50% of the CH2Cl groups was reacted with 2-aminopyridine, and prepared another resin with double pore structure of hypercrosslinked resin and macroporous resin (denoted GQ-11). The adsorption of salicylic acid (SA) on GQ-11 was investigated using GQ-06 as the reference adsorbent. The effect of pH on the adsorption of SA on GQ-06 was consistent with the dissociation curve of SA. The maximum adsorption capacity of SA on GQ-11 was observed at the solution pH of 2.64. The greater adsorption rate of SA on GQ-11 than that of GQ-06 was attributed to its double pore structure. The multifunctional adsorption mechanism of anion exchange and hydrophobic interaction resulted in the larger equilibrium capacity of SA on GQ-11 than that of GQ-06. GQ-06 and GQ-11 could be regenerated by absolute alcohol and 80% of alcohol -0.5mol/L of sodium hydroxide aqueous solution, respectively.

A Cocatalytic Effect between Meldrum's Acid and Benzoxazine Compounds in Preparation of High Performance Thermosetting Resins.

In this work, a cocatalytic effect between Meldrum's acid (MA) and benzoxazine (Bz) compounds has been explored to build up a self-promoting curing system. Consequently, the MA/Bz reactive blend exhibits a relatively low reaction temperature compared to the required temperatures for the cross-linking reactions of the pure MA and Bz components. This feature is attractive for energy-saving processing issues. Moreover, the thermosetting resins based on the MA/Bz reactive blends have been prepared. The MA component can generate additional free volume in the resulting resins, so as to trap air in the resin matrix and consequently to bring low dielectric constants to the resins. The MA-containing agent is an effective modifier for benzoxazine resins to reduce their dielectric constants.