Poly(2-alkyl/aryl-2-oxazoline)-Imidazole Complexes as Thermal Latent Curing Agents for Epoxy Resins.

One-component epoxy resins (OCERs) with improved stability (shelf life) and controlled curing temperatures were prepared using epoxy resins and polyoxazoline-imidazole (POZ-Im) based thermal latent curing agents (TLCs). POZ homopolymers with molar masses of 1000, 2000, and 5000 g/mol were obtained via cationic ring-opening polymerization (CROP) of 2-ethyl-2-oxazoline, 2-propyl-2-oxazoline, 2-pentyl-2-oxazoline, and 2-phenyl-2-oxazoline. TLCs were prepared by physically entrapping imidazole, the curing agent, in the POZ matrix at the homopolymer/Im (HP/Im) ratios of 1:1 and 5:1 and characterized by FTIR and TGA.

Amphiphilic Polyoxazoline Copolymer-Imidazole Complexes as Tailorable Thermal Latent Curing Agents for One-Component Epoxy Resins.

One-component epoxy resins (OCERs) are proposed to overcome the energy inefficiency and processing difficulties of conventional two-component epoxy resins by employing latent curing agents, specifically thermal latent curing agents (TLCs). Despite recent progress, the need for TLCs with a simple preparation method for different curing agents, epoxy resins, and process conditions remains. Here, tailorable TLCs were prepared by forming complexes between imidazole (Im) and amphiphilic polyoxazoline copolymers with tunable structures and properties by a solvent evaporation method.

Decoding Polymer Architecture Effect on Ion Clustering, Chain Dynamics, and Ionic Conductivity in Polymer Electrolytes.

Poly(ethylene oxide) (PEO)-based polymer electrolytes are a promising class of materials for use in lithium-ion batteries due to their high ionic conductivity and flexibility. In this study, the effects of polymer architecture including linear, star, and hyperbranched and salt (lithiumbis(trifluoromethanesulfonyl)imide (LiTFSI)) concentration on the glass transition ( ), microstructure, phase diagram, free volume, and bulk viscosity, all of which play a significant role in determining the ionic conductivity of the electrolyte, have been systematically studied for PEO-based polymer electrolytes. The branching of PEO widens the liquid phase toward lower salt concentrations, suggesting decreased crystallization and improved ion coordination.

Pilot scale nanofiltration membrane fabrication containing ionic co-monomers and halloysite nanotubes for textile dye filtration.

Wastewater from the textile industry contains high concentrations of pollutants, so the wastewater must be treated before it is discharged. In addition, the reuse of treated wastewater should be considered from an environmental point of view, as large volumes of wastewater are produced. Since textile wastewater mainly contains dyestuffs, it must be treated effectively using environmentally friendly technologies.

Synthesis and Structure-Property Relationship of Amphiphilic Poly(2-ethyl--2-(alkyl/aryl)-2-oxazoline) Copolymers.

Poly(2-oxazoline)s (POZs) are widely investigated for their applications in various fields due to their unique properties. To exploit and combine different characteristics of the POZ family, 2-oxazoline monomers can be copolymerized to prepare tailor-made copolymers with the desired glass transition temperature ( ), melting temperature ( ), amphiphilicity, and functionality. Here, we report the synthesis and characterization of 2-oxazoline monomers and a range of POZ copolymers produced, thereof.

Triblock Superabsorbent Polymer Nanocomposites with Enhanced Water Retention Capacities and Rheological Characteristics.

Superabsorbent polymers (SAPs) are useful polymers in a wide range of application fields ranging from the hygiene industry to construction and agriculture. As versatility and high water absorption capacity are their important merits, SAPs usually suffer from low water retention capacity (fast release) and weak mechanical properties. To address these drawbacks, a set of new superabsorbent polymer-Halloysite nanotube (HNT) nanocomposites was synthesized via free radical polymerization of acrylamide, 2-acrylamido-2-methylpropane-1-sulfonic acid, and acrylic acid in the presence of vinyltrimethoxysilane (VTMS) as the crosslinker.

Synthesis and Morphological Control of VO Nanostructures via a One-Step Hydrothermal Method.

The morphology of nanostructures is a vital parameter to consider in components comprised of materials exhibiting specific functionalities. The number of process steps and the need for high temperatures can often be a limiting factor when targeting a specific morphology. Here, we demonstrate a repeatable synthesis of different morphologies of a highly crystalline monoclinic phase of vanadium dioxide (VO(M)) using a one-step hydrothermal method.

Halloysite nanotube blended nanocomposite ultrafiltration membranes for reactive dye removal.

In this paper, ultrafiltration (UF) flat sheet membranes were manufactured by introducing two diverse halloysite nanotubes (HNT) size (5 μm and 63 μm) and five different (0, 0.63, 1.88, 3.

Tuning Interaction Parameters of Thermoplastic Polyurethanes in a Binary Solvent To Achieve Precise Control over Microphase Separation.

Thermoplastic polyurethanes (TPUs) are designed using a large variety of basic building blocks but are only synthesized in a limited number of solvent systems. Understanding the behavior of the copolymers in a selected solvent system is of particular interest to tune the intricate balance of microphase separation/mixing, which is the key mechanism behind the structure formation in TPUs. Here, we present a computationally efficient approach for selecting TPU building blocks and solvents based on their Flory-Huggins interaction parameters for a precise control over the microphase separation/mixing.

Nanosilicate embedded agarose hydrogels with improved bioactivity.

This paper reports the synthesis of nanocomposite agarose hydrogels with improved bioactivity with the incorporation of anisotropic 2D nanosilicates (Laponite) to promote cell binding, growth and proliferation. Rheological measurements showed that the incorporation of nanosilicates slightly increased the gelation temperature (T). The use of higher nanosilicate content at the constant agarose concentration improved the mechanical properties of the gels.

Design of Pt-Supported 1D and 3D Multilayer Graphene-Based Structural Composite Electrodes with Controlled Morphology by Core-Shell Electrospinning/Electrospraying.

Platinum (Pt)-decorated graphene-based carbon composite electrodes with controlled dimensionality were successfully fabricated via core-shell electrospinning/electrospraying techniques. In this process, multilayer graphene sheets were converted into the three different forms, fiber, sphere, and foam, by tailoring the polymer concentration, molecular weight of polymer, and applied voltage. As polymer concentration increased, continuous fibers were produced, whereas decreasing polymer concentration caused the formation of graphene-based foam.

Single Additive Enables 3D Printing of Highly Loaded Iron Oxide Suspensions.

A single additive, a grafted copolymer, is designed to ensure the stability of suspensions of highly loaded iron oxide nanoparticles (IOPs) and to facilitate three-dimensional (3D) printing of these suspensions in the filament form. This poly (ethylene glycol)-grafted copolymer of N-[3(dimethylamino)propyl]methacrylamide and acrylic acid harnesses both electrostatic and steric repulsion to realize an optimum formulation for 3D printing. When used at 1.

Dynamic glass transition of the rigid amorphous fraction in polyurethane-urea/SiO nanocomposites.

We report molecular dynamics in the rigid amorphous fraction (RAF) of the polymer bound at the interfaces with nanoparticles in polymer nanocomposites and calculate the glass transition temperature, T, for this bound layer of polymer. We follow the '3-phase-model' for semicrystalline polymers where the polymer matrix consists of the crystalline fraction (CF), the mobile amorphous fraction (MAF) and the RAF. While the amorphous polymer bound by crystallites is completely rigid, neither contributing to the glass transition, nor displaying molecular dynamics, the amorphous polymer bound at the interfaces with filler displays decelerated dynamics, as compared to the bulk polymer.

Poly(carboxylate ether)-based superplasticizer achieves workability retention in calcium aluminate cement.

Calcium aluminate cement (CAC) suffers from loss of workability in less than an hour (~15 minutes) after first touch of water. Current superplasticizers that are utilized to modify the viscosity of cement admixtures are designed to target ordinary Portland cement (OPC). The high affinity between these superplasticizers and cement particles were found to be detrimental in CAC systems.

Molecular basis for solvent dependent morphologies observed on electrosprayed surfaces.

We study the causes of the observed tunable hydrophobicity of poly(styrene-co-perfluoroalkyl ethylacrylate) electrosprayed in THF, DMF, and THF:DMF (1:1) solvents. Under the assumption that equilibrium morphologies in the solvent significantly affect the patterns observed on electrosprayed surfaces, we use atomistic and coarse-grained simulations supported by dynamic light scattering (DLS) experiments to focus on the parameters that affect the resulting morphology of superhydrophobic electrosprayed beads. The differing equilibrium chain size distributions in these solvents examined by DLS are corroborated by chain dimensions obtained via molecular dynamics simulations.

Dual scale roughness driven perfectly hydrophobic surfaces prepared by electrospraying a polymer in good solvent-poor solvent systems.

We demonstrated a facile method to produce perfectly hydrophobic surfaces (advancing and receding angles both 180°) via electrospraying. When a copolymer of styrene and a perfluoroacrylate monomer was electrosprayed in good solvents, surfaces composed of micrometer size beads were formed and fairly low threshold water sliding angles could be achieved. Addition of high boiling point poor solvents to the solutions resulted nanoscale roughness on the beads due to a possible phase separation that occurs in a predominantly poor solvent environment.

MWCNTs/P(St-co-GMA) composite nanofibers of engineered interface chemistry for epoxy matrix nanocomposites.

Strengthened nanofiber-reinforced epoxy matrix composites are demonstrated by engineering composite electrospun fibers of multi-walled carbon nanotubes (MWCNTs) and reactive P(St-co-GMA). MWCNTs are incorporated into surface-modified, reactive P(St-co-GMA) nanofibers by electrospinning; functionalization of these MWCNT/P(St-co-GMA) composite nanofibers with epoxide moieties facilitates bonding at the interface of the cross-linked fibers and the epoxy matrix, effectively reinforcing and toughening the epoxy resin. Rheological properties are determined and thermodynamic stabilization is demonstrated for MWCNTs in the P(St-co-GMA)-DMF polymer solution.

Engineering chemistry of electrospun nanofibers and interfaces in nanocomposites for superior mechanical properties.

The novelty of this work is based on designing the chemistry of the electrospun nanofibers, so that the resultant composites substantially benefit from cross-linking between the nanofibers and the polymer matrix. Specifically, the solution of in-house synthesized copolymers polystyrene-co-glycidyl methacrylate P(St-co-GMA) is electrospun to produce mats of surface reactive nano-to-submicron scale fibers that are accompanied later by spraying over the ethylenediamine (EDA) as a supplementary cross-linking agent for epoxy. The P(St-co-GMA)/EDA fiber mats are then embedded into an epoxy resin.