Synthesis of allyl-bearing dendrimers with a resorcinarene core and their supramolecular complexes with fullerene C60

Dendritic branches of poly(arylether) with peripherial allyl chains have been attached to a resorcinarene core. Dendrimers of first, second, and third generation were synthesized. Viability to form supramolecular complexes with fullerene C60 was studied with three dendrimers of first, second, and third generation. All the compounds were characterized by 1H, 13C NMR, FTIR, UV-vis spectroscopy, MALDI-TOF, FAB+ mass spectra, and elemental analysis. Strong pi-pi, CH-pi, and n-pi interactions between the dendrimers and the fullerene C60 were detected in the supramolecular complexes by UV-vis, FTIR, and 13C CP-MAS NMR.     

Relationships between the generalized functional method and other methods of nonimaging optical design

The recently developed generalized functional method provides a means of designing nonimaging concentrators and luminaires for use with extended sources and receivers. We explore the mathematical relationships between optical designs produced using the generalized functional method and edge-ray, aplanatic, and simultaneous multiple surface (SMS) designs. Edge-ray and dual-surface aplanatic designs are shown to be special cases of generalized functional designs. In addition, it is shown that dual-surface SMS designs are closely related to generalized functional designs and that certain computational advantages accrue when the two design methods are combined. A number of examples are provided.     

Triethylsilyl Perfluoro-Tetraphenylborate, [Et(3)Si][F(20)-BPh(4)], a widely used Non-Existent Compound

The commonly used triethylsilyl per-fluoro-tetraphenylborate salt, [Et(3)Si(+)][F(20)-BPh(4) (-)], has been misidentified. As prepared, the cation is a hydride-bridged silane adduct [R(3)Si-H-SiR(3) (+)]. Under favorable circumstances it can be an effective source of the triethylsilylium ion Et(3)Si(+) but in the absence of a stabilizing base the potent electrophilicity of Et(3)Si(+) decomposes the "inert" F(20)-BPh(4) (-) counterion.     

Breakthroughs in computational modeling of cartilage regeneration in perfused bioreactors

We report about two specific breakthroughs, relevant to the mathematical modeling and numerical simulation of tissue growth in the context of cartilage tissue engineering in vitro. The proposed models are intended to form the building blocks of a bottom-up multiscale analysis of tissue growth, the idea being that a full microscale analysis of the construct, a 3-D partial differential equation (PDE) problem with internal moving boundaries, is computationally unaffordable. We propose to couple a PDE microscale model of a single functional tissue subunit with the information computed at the macroscale by 2-D-0-D models of reduced computational cost. Preliminary results demonstrate the effectiveness of the proposed models in describing the interplay among interstitial perfusion flow, nutrient delivery, and consumption and tissue growth in realistic scaffold geometries.     

Digital Detection of Single Virus Particles by Multi-Spot,Label-Free Imaging Biosensor on Anti-Reflective Glass

Rapid detection of whole virus particles in biological or environmental samples represents an unmet need for the containment of infectious diseases. Here, an optical device enabling the enumeration of single virion particles binding on antibody or aptamers immobilized on a surface with anti-reflective coating is described. In this regime, nanoparticles adhering to the sensor surface provide localized contributions to the reflected field that become detectable because of their mixing with the interfering waves in the reflection direction. Thus, these settings are exploited to realize a scan-free, label-free, micro-array-type digital assay on a disposable cartridge, in which the virion counting takes place in wide field-of-view imaging. With this approach we could quantify, by enumeration, different variants of SARS-CoV-2 virions interacting with antibodies and aptamers immobilized on different spots. For all tested variants, the aptamers showed larger affinity but lower specificity relative to the antibodies. It is found that the combination of different probes on the same surface enables increasing specificity of detection and dynamic range.     

The effect of interface characteristics on the morphology,rheology and thermal behavior of three‐component polymer alloys

Immiscible polymer blends are interesting multiphase host systems for fillers. Such systems exhibit, within a certain composition limits, either a separate dispersion of the two minor phases or a dispersion of encapsulated filler particles within the minor polymer phase. Both thermodynamic (e.g. interfacial tension) and kinetic (e.g. relative viscosity) considerations determine the morphology developed during the blending process. The effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB), or fibers (GF), was investigated. The system studied was based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semicrystalline highly polar copolymer. Modification of the interfacial properties was obtained through using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface. The compatibilizer was added in a procedure aimed to preserves the encapsulated EVOH/glass structure. Blends were prepared by melt extrusion compounding and specimens by injection molding. The morphology was characterized using scanning electron microscopy (SEM) and high resolution SEM (HRSEM), the shear viscosity by capillary rheometry and the thermal behavior using differential scanning calorimetry (DSC). The system studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfaces resulted in unique morphologies. The aminosilane glass surface treatment enhanced the encapsulation in the ternary [PP/EVOH]GB blends, resulting in an encapsulated morphology with no separtely dispersed EVOH particles. The addition of a MA‐g‐PP compatibilizer preserves the encapsulated morphology in the ternary blends with some finely dispersed EVOH particles and enhanced PP/EVOH interphase interactions. The viscosity of the binary and ternary blends was closely related to the blend's morphology and the level of shear rate. The treated glass surfaces showed increased viscosity compared to the cleaned glass surfaces in both GB and GF containing ternary blends. Both EVOH and glass serve as nucleating agents for the PP matrix, affecting its crystallization process but not its crystalline structure. The aminosilane glass surface treatment completely inhibited the EVOH crystallization process in the ternary blend. In summary, the structure of the multicomponent blends studied has a significant effect on their behavior as depicted by the rheological and thermal behavior. The structure‐performance relationships in the three‐component blends can be controlled and varied.     

The effect of maleated compatibilizers on the structure and properties of EVOH/clay nanocomposites

The effect of compatibilizers on the blending torque, crystallization behavior, intercalation level, thermal stability and morphology of EVOH/treated clay systems was investigated. Maleic anhydride‐grafted ethylene vinyl acetate (EVA‐g‐MA) or maleic anhydride‐grafted linear low density polyethylene (LLDPE‐g‐MA) were used as compatibilizers of EVOH with clay, in various concentrations (1, 5 and 10 wt%). The blends were processed using Brabender Plastograph and characterized by XRD, SEM, DSC, DMTA and TGA. X‐ray diffraction shows advanced intercalation within the galleries when the compatibilizers were added. Unique results were obtained for the EVOH/clay/compatibilizer systems, owing to a high level of interaction developed in these systems, which plays a major role. Thermal analysis showed that with increasing compatibilizer content, lower crystallinity levels result, until at a certain content no crystallization has taken place. Significantly higher viscosity levels were obtained for the EVOH/clay blends compared to the neat polymer, as seen by a dramatic torque increase when processed in the Brabender machine. The DMTA spectra showed lower T_g values for the compatibilized nanocomposites compared to the neat EVOH and the uncompatibilized composites. Storage modulus was higher compared to the uncompatibilized EVOH/clay blend when EVA‐g‐MA compatibilizer was added (at all concentrations), and only at low contents of LLDPE‐g‐MA. TGA results show significant improvement of the blends thermal stability compared to the neat EVOH, and to the uncompatibilized blend, indicating an advanced intercalation.     

Highly filled thermoplastic composites. II: Effects of particle size distribution on some properties

The effect of irregularly shaped glass particle size and size distribution on the packing density and flexural mechanical properties of highly-filled composites with a rubbery thermoplastic matrix was studied. Increasing the particle's median size and size distribution width significantly increases the packing density of the composites. Compression molding causes the glass particles to fracture at a decreasing level with an increasing distribution width. Particle median size, rather than size distribution, affects the mechanical properties; The flexural modulus and strength increase and the ultimate deflection in flexure decreases with a decreasing median size. A “glass network” is formed in the compression molded composites because of the mechanical interlocking of particles. The nature of this continuous glass phase predominates the composites mechanical behavior. The particle's size and shape determine the nature of the glass network and, thus, have a dominating effect on the mechanical properties. The latter are significantly affected by the particle's surface properties. A specific silane treatment of the glass particles acts to reduce the particle/particle friction, resulting in a higher packing density. The treatment also acts as a cohesive liquid to increase the strength of the glass network, and to increase the particle/polymer adhesion, increasing the composites' strength and ductility.     

Polymer encapsulation of glass filler in ternary PP/PA-6/glass blends

The morphology and rheology of ternary isotactic polypropylene (PP)/polyamide-6 (PA-6)/glass blends is investigated and contrasted with the behavior of two-component (binary) PP/PA-6 blends. Injection molded samples of binary blends exhibit an interlayer slip morphology for both PP and PA-6 as the matrix and the blend shear viscosity is lower than expected from a rule of mixtures. The morphology of ternary blends is dependent on the choice of the matrix phase. In ternary blends with a PA-6 matrix, the PP domains and glass fibers are separately dispersed within the matrix. In ternary blends with a PP matrix, the PA-6 is mainly found surrounding (encapsulating) the glass fibers, and the extent of the interlayer slip morphology is reduced. Variations in glass surface treatment, blending time, and order of addition did not affect the rapid encapsulation of glass by the PA-6. A reduction in blending temperature, below the peak PA-6 melting temperature, hinders encapsulation.     

Short fiber reinforced thermoplastics. I. Rheological properties of glass fiber reinforced Noryl

An experimental study on the flow behavior of glass fiber reinforced Noryl (a commercial poly(phenyleneoxide)/polystyrene blend) using a capillary rheometer is described. The effect of fiber concentration on shear viscosity and die swell was studied at various temperatures. Breakage of glass fibers during flow through the rheometer is discussed; it was found that the average fiber length (about 230 μm) was not significiantly altered, except at the highest shear rate (575 s⁻¹) studied. The incorporation of short fibers into thermoplastic polymer melts increases their viscosity without changing the basic rheological character-shear rate dependency. No discernible viscosity changes were measured by incorporating 10 weight percent fibers, and upon further increase of fiber concentration from 20 to 30 weight percent no appreciable increase in viscosity was noted. It is shown that short glass fibers cause a large reduction in extrudate swell. The presence of voids and fiber orientation contribute to the decrease of the die swell, an effect greater than expected from volumetric considerations alone.