Hydroaminoalkylation for Amine Functionalization of Vinyl-Terminated Polyethylene Enables Direct Access to Responsive Functional Materials.

While functionalized polyethylenes (PEs) exhibit valuable characteristics, the constraints of existing synthetic approaches limit the variety of readily incorporated functionality. New methods to generate functionalized PEs are required to afford new applications of this common material. We report 100 % atom economic tantalum-catalyzed hydroaminoalkylation of vinyl-terminated polyethylene (VTPE) as a method to produce amine-terminated PE.

Impact of counterion valency on the rheology of sulfonated cellulose nanocrystal hydrogels.

A systematic rheological study on the influence of valency of different counterions on the properties of CNC hydrogels was carried out. Rheo-polarized microscopy was used to prove that preshear of 500 s for 1 min is adequate to completely breakdown agglomerates in the suspension. Furthermore, a rest period of 30 min is sufficient to recover the equilibrium structure of hydrogels.

Photocross-Linked Antimicrobial Amino-Siloxane Elastomers.

Mechanically robust bulk antimicrobial polymers are one way to address disease transmission via contaminated surfaces. Here, we demonstrate the visible light photo-oxidative cross-linking of amine-containing PDMS using a single-component, solvent-free system where amines have a dual role as antimicrobial functionalities and cross-linking sites. Rose Bengal, a xanthene dye used as a fluorescent stain, is thermally reacted with the polymer to give a solvent-free liquid siloxane that can generate reactive singlet oxygen upon aerobic green light irradiation, coupling the amine functionalities into imine cross-links.

Rheological Properties Related to Extrusion of Polyolefins.

Rheological properties related to the extrusion of polyolefins are the shear viscosity, the elongational viscosity, the slip velocity and their temperature- and pressure-dependencies. These properties are measured in the rheology lab mainly via a parallel-plate rheometer and a capillary rheometer. Then appropriate rheological models have to be used to account for all these properties.

Rheological characterization of CNC-CTAB network below and above critical micelle concentration (CMC).

The network of Cellulose Nanocrystal (CNC) suspension is explored below and above the critical micelle concentration (CMC), in the presence of cetyltrimethylammonium bromide (CTAB) with a positively charged head using TEM imaging and rheological characterization. CNC-CTAB gels show shear thinning behavior, complex relationship between strain amplitudes and CTAB concentration, diminishing thixotropic behavior as a function of CTAB and single and two yielding stress maxima as a function of CTAB, resulting from different microstructure below and above the critical Micelle Concentration (CMC) of CTAB. Comparing the flow curves of CNC-CTAB suspension/gel revealed the role played by CTAB content, CNC concentration and sonication energy in strengthening of the network.

Toward Biodegradable Electronics: Ionic Diodes Based on a Cellulose Nanocrystal-Agarose Hydrogel.

Bioderived cellulose nanocrystals (CNCs) are used to create light, flexible, biocompatible, and biodegradable electronic devices. Herein, surface modification of cellulose nanocrystals was employed to fabricate cationic and anionic CNCs. Subsequently, we demonstrated rectification behavior from a fixed junction between two agarose hydrogels doped with cationic and anionic cellulose nanocrystals.

Poisson-Boltzmann modeling and molecular dynamics simulations of polyelectrolyte gel diodes in the static regime.

We present molecular dynamics (MD) simulations of a model polyelectrolyte gel diode formed by a junction of two oppositely charged crosslinked polyelectrolyte networks, and compare the ion densities and electrostatic field to a corresponding continuum Poisson-Boltzmann (PB) model. At low electrostatic coupling strength (i.e.

Effect of Ionic Surfactants on the Viscoelastic Properties of Chiral Nematic Cellulose Nanocrystal Suspensions.

The gelation of cellulose nanocrystal (CNC) suspensions is explored in the presence of two ionic surfactants, namely, sodium dodecyl sulfate (SDS) with a negatively charged head and cetyltrimethylammonium bromide (CTAB) with a positively charged head. The viscosity profile of pure CNC suspensions indicated that at concentrations greater than 5 wt %, they exhibit gel-like behavior, where the viscosity shows a single shear-thinning profile. However, at concentrations lower than 1 wt %, the suspension shows isotropic behavior and experiences a transition to chiral nematic biphasic domains at increasing CNC concentration.

Freeze-Thaw Gelation of Cellulose Nanocrystals.

Gels are attractive for applications in drug delivery, tissue engineering, and 3D printing. Here, physical colloidal gels were prepared by freeze-thaw (FT) cycling of cellulose nanocrystal (CNC) suspensions. The aggregation of CNCs was driven by the physical confinement of CNCs between growing ice crystal domains.

The sol-gel transition of ultra-low solid content TEMPO-cellulose nanofibril/mixed-linkage β-glucan bionanocomposite gels.

We present the preparation, morphological analysis, and rheological characterization of ultra-low solid content gels prepared by physically cross-linking TEMPO-oxidized cellulose nanofibrils (TEMPO-CNF) with the soluble plant-cell-wall polysaccharide, mixed-linkage β-glucan (MLG). Of particular note, gel formation was rapidly induced by very small amounts of MLG (e.g.

Molecular simulations of the piezoionic effect.

We present a molecular dynamics study of two polyelectrolyte gels with different degrees of ionization coupled in a slab geometry. Our simulations show that a pressure gradient emerges between the two gels that results in the buildup of a Nernst-Donnan potential. This methodology is reverse to experiments of the piezoionic or mechanoelectric effect, in which an electric potential gradient appears upon application of a pressure gradient to a hydrogel.

A stimulus-responsive, in situ-forming, nanoparticle-laden hydrogel for ocular drug delivery.

Most medications targeting optic neuropathies are administered as eye drops. However, their corneal penetration efficiencies are typically < 5%. There is a clear, unmet need for novel transcorneal drug delivery vehicles.

Antifouling Biomimetic Liquid-Infused Stainless Steel: Application to Dairy Industrial Processing.

Fouling is a widespread and costly issue, faced by all food-processing industries. Particularly, in the dairy sector, where thermal treatments are mandatory to ensure product safety, heat-induced fouling represents up to 80% of the total production costs. Significant environmental impacts, due the massive consumption of water and energy, are also to deplore.

Impact of aryloxy initiators on the living and immortal polymerization of lactide.

This report describes two different methodologies for the synthesis of aryl end-functionalized poly(lactide)s (PLAs) catalyzed by indium complexes. In the first method, a series of para-functionalized phenoxy-bridged dinuclear indium complexes [(NNO)InCl](μ-Cl)(μ-OPh) (R = OMe (1), Me (2), H (3), Br (4), NO (5)) were synthesized and fully characterized. The solution and solid state structures of these complexes reflect the electronic differences between these initiators.

Slip of polymer melts over micro/nano-patterned metallic surfaces.

The slip behavior of high-density polyethylenes (HDPEs) is studied over surfaces of different topology and surface energy. Laser ablation has been used to micro/nano-pattern the surface of dies in order to examine the effect of surface roughness on slip. In addition, fluoroalkyl silane-based coatings on smooth and patterned substrates were used to understand the effect of surface energy on slip.

Chemical, physical and morphological properties of bacterial biofilms affect survival of encased Campylobacter jejuni F38011 under aerobic stress.

Campylobacter jejuni is a microaerophilic pathogen and leading cause of human gastroenteritis. The presence of C. jejuni encased in biofilms found in meat and poultry processing facilities may be the major strategy for its survival and dissemination in aerobic environment.

The Role of Nitrogen Donors in Zinc Catalysts for Lactide Ring-Opening Polymerization.

The electronic effects of nitrogen donors in zinc catalysts for ring-opening polymerization of cyclic esters were investigated. Alkyl and benzyloxy zinc complexes supported by tridentate diamino- and aminoimino phenolate ligands were synthesized, and their solid-state and solution structures characterized. The solution-state structures showed that the alkyl complexes are mononuclear, while the alkoxy complexes are dimeric with the ligands coordinated with different denticities depending on the nature of the ligand donors.

Hydrothermal Gelation of Aqueous Cellulose Nanocrystal Suspensions.

We report the facile preparation of gels from the hydrothermal treatment of suspensions of cellulose nanocrystals (CNCs). The properties of the hydrogels have been investigated by rheology, electron microscopy, and spectroscopy with respect to variation in the temperature, time, and CNC concentration used in preparation. Desulfation of the CNCs at high temperature appears to be responsible for the gelation of the CNCs, giving highly porous networks.

Effect of Extreme Wettability on Platelet Adhesion on Metallic Implants: From Superhydrophilicity to Superhydrophobicity.

In order to design antithrombotic implants, the effect of extreme wettability (superhydrophilicity to superhydrophobicity) on the biocompatibility of the metallic substrates (stainless steel and titanium) was investigated. The wettability of the surface was altered by chemical treatments and laser ablation methods. The chemical treatments generated different functionality groups and chemical composition as evident from XPS analysis.

Enhanced Barrier Performance of Engineered Paper by Atomic Layer Deposited Al2O3 Thin Films.

Surface modification of cellulosic paper is demonstrated by employing plasma assisted atomic layer deposition. Al2O3 thin films are deposited on paper substrates, prepared with different fiber sizes, to improve their barrier properties. Thus, a hydrophobic paper is created with low gas permeability by combining the control of fiber size (and structure) with atomic layer deposition of Al2O3 films.

Slip mechanisms in complex fluid flows.

The classical no-slip boundary condition of fluid mechanics is not always a valid assumption for the flow of several classes of complex fluids including polymer melts, their blends, polymer solutions, microgels, glasses, suspensions and pastes. In fact, it appears that slip effect in these systems is the rule and not the exemption. The occurrence of slip complicates the analysis of rheological data, although it provides new opportunities to understand their behavior in restricted environments delineating additional molecular mechanisms i.

Star-shaped PHB-PLA block copolymers: immortal polymerization with dinuclear indium catalysts.

The first example of a one-component precursor to star-shaped polyesters, and its utilization in the synthesis of previously unknown star-shaped poly(hydroxybutyrate)-poly(lactic acid) block copolymers, is reported. A series of such mono- and bis-benzyl alkoxy-bridged complexes were synthesized, fully characterized, and their solvent dependent solution structures and reactivity were examined. These complexes were highly active catalysts for the controlled polymerization of β-butyrolactone to form poly(hydroxybutyrate) at room temperature.

Contact angle hysteresis of non-flattened-top micro/nanostructures.

A two-dimensional (2D) thermodynamic model is proposed to predict the contact angle (CA) and contact angle hysteresis (CAH) of different types of surface geometries, particularly those with asperities having nonflattened tops. The model is evaluated by micro/nano sinusoidal and parabolic patterns fabricated by laser ablation. These microstructures are analyzed thermodynamically through the use of the Gibbs free energy to obtain the equilibrium contact angle (CA) and contact angle hysteresis (CAH).

Femtosecond laser irradiation of metallic surfaces: effects of laser parameters on superhydrophobicity.

This work studies in detail the effect of femtosecond laser irradiation process parameters (fluence and scanning speed) on the hydrophobicity of the resulting micro/nano-patterned morphologies on stainless steel. Depending on the laser parameters, four distinctly different nano-patterns were produced, namely nano-rippled, parabolic-pillared, elongated sinusoidal-pillared and triple roughness nano-structures. All of the produced structures were classified according to a newly defined parameter, the laser intensity factor (LIF); by increasing the LIF, the ablation rate and periodicity of the asperities increase.