Assessment of the performance of nonfouling polymer hydrogels utilizing citizen scientists

To facilitate longer duration space travel, flight crew sickness and disease transmission amongst the crew must be eliminated. High contact surfaces within space vehicles provide an opportunity for bacterial adhesion, which can lead to biofilm formation or disease transmission. This study evaluates the performance of several nonfouling polymers using citizen science, to identify the best performing chemistry for future applications as bacteria resistant coatings. The specific polymer chemistries tested were zwitterionic sulfobetaine methacrylate (SBMA), and polyampholytes composed of [2-(acryloyloxy)ethyl] trimethylammonium chloride and 2-carboxyethyl acrylate (TMA/CAA), or TMA and 3-sulfopropyl methacrylate (TMA/SA). Each polymer chemistry is known to exhibit bacteria resistance, and this study provides a direct side-by-side comparison between the chemistries using a citizen science approach. Nearly 100 citizen scientists returned results comparing the performance of these polymers over repeat exposure to bacteria and 30 total days of growth. The results demonstrate that TMA/CAA polyampholyte hydrogels show the best long-term resistance to bacteria adhesion.

Synthesis and characterization of novel thermo- and salt-sensitive amphoteric terpolymers based on acrylamide derivatives

A novel linear amphoteric terpolymers based on neutral monomer — N-isopropylacrylamide (NIPAM), ani- onic monomer — 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), and cationic mono- mer — (3-acrylamidopropyl) trimethylammonium chloride (APTAC) were synthesized by free-radical polymerization in aqueous solution and characterized by methods of 1H NMR and FTIR spectroscopy, TGA, GPC, Dynamic light scattering (DLS) and zeta-potential. The thermal and salt sensitivity of amphoteric ternary polymers of various compositions, particularly, [NIPAM]:[AMPS]:[APTAC] = 90:2.5:7.5; 90:5:5; 90:7.5:2.5 mol.% were studied in aqueous and aqueous-salt solutions in the temperature range from 25 to 60 C and at the NaCl ionic strength  interval from 10–3 to 1M. It was found that due to hydrophobic/hydrophilic balance, the temperature dependent conformational and phase change of macromolecular chains becomes sensitive to salt addition and allows the fine-tuning of the phase transition. In aqueous and aqueous-salt solutions, the average hydrodynamic size of amphoteric terpolymers is varied from 8 to 300 nm exhibiting bimodal distribution at room temperature. The number average (Mn) and weight average (Mw) molecular weights, polydispersity index (PDI), and zeta-potentials of amphoteric terpolymers in aqueous solu- tions were determined

Establishment of Silane/GO Multistage Hybrid Interface Layer to Improve Interfacial and Mechanical Properties of Carbon Fiber Reinforced Poly (phthalazinone ether ketone) Thermoplastic Composites

This study focused on the faint interface bonding between carbon fiber (CF) and poly(phthalazinone ether ketone) (PPEK) thermoplastic, a multistage hybrid interface layer was constructed via the condensation reaction of N-[3-(Trimethoxysilyl)propyl]-N,N,N-trimethylammonium chloride (KHN+) and the electrostatic adsorption of graphene oxide (GO). The influence of the contents of GO (0.2 wt%, 0.4 wt%, 0.6 wt%) on the interfacial properties of composites was explored. FTIR, Raman spectra, XPS tests indicated the successful preparation of CF-KHN+-GO reinforcements. The multistage hybrid interface layer significantly increased fiber surface roughness without surface microstructure destruction. Simultaneously, polarity and wettability are remarkably improved as evidenced by the dynamic contact angle experiment. The interlaminar shear strength (ILSS) and flexural strength of the CF/PPEK composites with 0.4 wt% GO (CF-KHN+-4GO) were 74.57 and 1508 MPa, which was 25.2% and 23.5% higher than that of untreated CF/PPEK composite, respectively. Dynamic mechanical analysis proved that CF/GO/PPEK composites have excellent high-temperature mechanical properties. This study furnishes an unsophisticated and valid strategy to build an interface transition layer with a strong binding force, which would offer a new train of thought in preparing high-performing structural composites.

Radiolytic synthesis of gold nanoparticles in HEMA-based hydrogels: Potentialities for imaging nanocomposites

This article reports on the radiolytic synthesis of nanocomposites containing gold nanoparticles (AuNPs) within two types of hydrogels based on 2-hydroxyethyl methacrylate (HEMA): (i) plain networks with various contents in ethylene glycol dimethacrylate (EGDMA), as a cross-linker and (ii) stimuli-responsive (SR) networks prepared from these monomers copolymerized with [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT) to confer pH-switchable swelling. Hydrogels were prepared by photopolymerization with well-defined composition and a high degree of monomer conversion using two experimental procedures, as xerogels or in aqueous solution. Besides MADQUAT, acrylic acid (AA) or N-isopropylacrylamide have been tested as copolymers, yielding pHor temperature-sensitive hydrogels, respectively. Isothermal swelling in water was affected by monomer composition. Electron beam (EB) irradiation at doses up to 100 kGy of poly(HEMA) xerogels and water-swollen networks prepared with 0.5 wt% of EGDMA had a moderate impact on swelling characteristics and thermomechanical properties of the plain materials, whereas small amounts of extractables were formed. Poly(HEMA)-based nanocomposites containing AuNPs were successfully obtained by EB irradiation of samples swollen by aqueous solutions of Au(III). The effects of dose and cross-linking density on the formation of AuNPs were monitored by UV-visible spectroscopy. Irradiation at well-defined temperatures of the Au(III)-loaded SR hydrogels induced the formation of nanoparticles with size-dependent features, whereas the efficiency of Au(III) reduction at 10 kGy was not significantly affected by the network structure. EB-induced reduction of Au(III) in poly(HEMA) hydrogels using a lead mask to generate well-defined patterns yielded coloured and long-lasting images in the zones where the nanocomposite was formed.

CO2 Capture by Reduced Graphene Oxide Monoliths with Incorporated CeO2 Grafted with Functionalized Polymer Brushes

The monolithic materials of reduced graphene oxide (rGO) can be used successfully in CO2 adsorption. Here, the incorporation of CeO2 particles with and without polymer brushes grafted from the particles showed that the structural properties could be changed, affecting the adsorption of CO2. Polymer brushes of (1) poly(acrylic acid) (PAA), (2) poly(vinyl caprolactam) (PVCL) and (3) poly[(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC) were grafted from CeO2 via reversible addition−fragmentation chain transfer (RAFT) polymerization. The preparation of monoliths of rGO with different modified CeO2 particles led to different thermal properties (TGA), structural changes (BET isotherms) and CO2 adsorption. The responsive character of the CeO2@polymer was proven by the DLS and UV results. The responsive character of the particles incorporated into the rGO monolith affected not only the adsorption capacity but also the microstructure and values of the surface volume of the pores of the monolith. Monoliths with porosity values for better adsorption were affected by the responsive character of the polymer.

Aggregation of Gold Nanoparticles in Presence of the Thermoresponsive Cationic Diblock Copolymer PNIPAAM48-b-PAMPTMA6

The adsorption of the thermoresponsive positively charged copolymer poly(N-isopropylacrylamide)-block-poly(3-acrylamidopropyl)trimethylammonium chloride, PNIPAAM48-b-PAMPTMA6(+), onto negatively charged gold nanoparticles can provide stability to the nanoparticles and make the emerging structure tunable by temperature. In this work, we characterize the nanocomposite formed by gold nanoparticles and copolymer chains and study the influence of the copolymer on the expected aggregation process that undergoes those nanoparticles at high ionic strength. We also determine the lower critical solution temperature (LCST) of the copolymer (around 42 °C) and evaluate the influence of the temperature on the nanocomposite. For those purposes, we use dynamic light scattering, UV-vis spectroscopy and transmission electron microscopy. At the working PNIPAAM48-b-PAMPTMA6(+) concentration, we observe the existence of copolymer structures that trap the gold nanoparticles and avoid the formation of nanoparticles aggregates. Finally, we discuss how these structures can be useful in catalysis and nanoparticles recovery.

Development of Poly-NIsopropylacrylamide Surfaces for the Selection of Swine Sperm

The reproductive efficiency of pig farms is directly correlated with the fertility of the boars. The aim of this work was to develop polymeric materials that can be used as a platform to select a subpopulation of sperm with better cell physiological parameters. Polymeric hydrogels composed of Poly-N-isopropylacrylamide with different positive charges given by copolymerization with (3-acrylamidopropyl) trimethylammonium chloride (APTA, 5-10-15%), were synthesized. Subsequently, the interaction between the sperm cells and the polymeric surfaces was analyzed in TALP medium. Release of the spermatozoa from the polymeric surfaces was induced by changing to Ca2+ free media. Sperm motility, cell viability, plasma membrane and acrosome integrity were evaluated. The results indicated that a higher percentage of swine sperm attached to PNIPAM co-15% APTA hydrogels (62.86±3.33%). Ninety seven percent (97.19±1.45 %) of the sperm released from the PNIPAM co-15%APTA surfaces were viable (p<0.05 vs unbound population and raw semen), with acceptable motility (58.89±1.28%) and with intact plasma and acrosomal membranes (69±1.2% and 98.5±0.65% respectively). These results indicate that hydrogels can be used to select boar sperm with high viability and mobility for use in assisted reproductive techniques.

Cationic Lignin Polymers as Flocculant for Municipal Wastewater

The radical polymerization of acid-washed and unwashed softwood kraft lignin with [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was attempted to investigate the production of lignin-based flocculants for simulated wastewater. The incorporation of METAC onto lignin resulted in a cationic charge density (2.3–3.3 meq/g), increased water solubility (89–96% in neutral pH), and increased molecular weight (70,000–210,000 g/mol) of lignin. The lignin–METAC polymers generated from acid-washed lignin had higher molecular weights than those generated from unwashed lignin. The lignin–METAC polymers showed lower resistance to thermal decomposition than unmodified lignin due to the inclusion of PolyMETAC. The unmodified acid-washed lignin samples did not significantly affect the COD of the wastewater, while the unmodified unwashed lignin samples contributed to the COD, implying that unmodified lignin was not suitable for wastewater treatment. The flocculation of wastewater with lignin–METAC led to the chemical oxygen demand (COD) reduction of 17–23% and total organic carbon (TOC) drop of 51–60%. The lignin–METAC polymer with the highest molecular weight (produced from acid-washed lignin) reached the highest COD removal, while lignin–METAC polymer with the highest charge density (produced from unwashed lignin) reached the highest TOC removal. Focused beam reflectance measurement (FBRM) studies revealed that the lignin–METAC polymer produced from acid-washed lignin with a high molecular weight generated larger and more flocs in wastewater than the lignin–METAC polymer produced from unwashed lignin. The comparison of theoretical and experimental dosages required for neutralizing the charges of wastewater demonstrated that charge neutralization was the main flocculation mechanism, although a bridging mechanism was also involved for component removals from wastewater. The use of 1 mg/L of alum along with 65 mg/L lignin–METAC in a dual coagulation–flocculation system led to higher average phosphorous (42%) and COD (44%) removals than the singular flocculation system only using 65 mg/L of lignin–METAC (with phosphorous removals of 3.4% and COD removals of 18.7%). However, lignin–METAC flocculant slightly increased the ammonia–nitrogen content in both singular flocculation and dual coagulation–flocculation systems due to the residual ammonia content of lignin–METAC. The coagulation–flocculation system determined that the use of lignin–METAC (65 mg/L) could reduce the alum dosage significantly while maintaining a similar organic content reduction of 44% for wastewater.

Synthesis and characterization of high molecular weight amphoteric terpolymer based on acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt and (3-acrylamidopropyl)trimethylammonium chloride for oil recovery

High molecular weight amphoteric terpolymer based on a nonionic monomer, acrylamide (AAm), an anionic monomer, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), and a cationic monomer, (3-acrylamidopropyl) trimethylammonium chloride (APTAC), was prepared using free-radical copolymerization in an aqueous solution and characterized by 1H NMR, FTIR, GPC, DLS, zeta potential and viscometry. The polymer was shown to be viscosifying, and therefore can be utilized as a polymer flooding agent in the high salinity and temperature conditions of oil reservoirs. Injection of 0.25 wt.% of amphoteric terpolymer, dissolved in 200-300 g∙L-1 brine, into high and low permeability sand pack models demonstrated that the oil recovery factor (ORF) increases by up to 23-28% in comparison with saline water flooding. This is explained by an increase in the viscosity of brine solution due to disruption of intra- and interionic contacts between oppositely charged AMPS and APTAC moieties, demonstrating the antipolyelectrolyte effect. In high saline water, the anions and cations of salts screen the electrostatic attraction between positively and negatively charged macroions, resulting in expansion of the macromolecule. This phenomenon leads to an increase in the viscosifying effect on the brine solution, thus decreasing the mobility factor (M), which is defined as the ratio of displacing phase mobility (water) to displaced phase mobility (oil).