The properties of nanostructured plastics are determined by complex relationships between the type and size of the nanoreinforcement, the interface, and the chemical interaction between the nanoreinforcement and the polymeric chain, along with macroscopic processing and microstructural effects. Recently, families of mono- and difunctionalized polyhedral oligomeric silsesquioxane (POSS) macromers bearing epoxide groups have been developed. This paper presents an investigation of the thermal and viscoelastic property enhancements in commonly used model epoxy resins reinforced with monofunctional POSS-epoxy macromers. The glass transitions of these POSS-epoxy nanocomposites were studied using differential scanning calorimetry. Small-strain stress relaxations under uniaxial deformation were examined to provide insight into the time-dependent viscoelastic behavior of these nanocomposites. The POSS-epoxy macromers utilized in this study were monofunctional and hence occupied chain terminus points within the network. Nevertheless, they were effective at hindering the molecular motion of the epoxy network junctions. Thus the glass transition temperature, Tg, was observed to increase with increasing weight fraction of the monofunctional POSS-epoxy. The viscoelastic response at temperatures below Tg was examined and was found to correlate to a stretched exponential relaxation function. Time-aging time-superposition was found to be applicable to the data under all test conditions and for all of the materials used in this study. Surprisingly, the instantaneous modulus was not observed to be affected by incorporation of the POSS nanoreinforcement. This suggests that while POSS cages influence polymer chain motions, including the motion of the molecular junctions, these nanoreinforcements did not participate in the overall deformation of the chains. Experiments performed under identical thermodynamic states, revealed that the molecular level reinforcement provided by the POSS cages also retarded the physical aging process in the glassy state. Therefore, the time required to reach structural equilibrium was longer for samples reinforced with POSS-epoxy than for those of the neat resins.

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A novel hybrid organic/inorganic triblock copolymer of polystyrene-butadiene-polystyrene (SBS) containing grafted polyhedral oligomeric silsesquioxane (POSS) molecules was synthesized by a hydrosilation method. The POSS molecules were designed to contain a single silane functional group, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block. Unlike typical free radical copolymerizations commonly used for many other POSS incorporations investigated, this synthesis method allows us to make a series of polymers with varying amounts of POSS without any change to the overall degree of polymerization or structure of the main SBS backbone. This gives us a unique opportunity to study the POSS behavior in the matrix and know that all differences are solely due to the POSS grafted to the soft continuous butadiene phase. X-ray diffraction revealed that the grafted POSS are very well dispersed in the matrix of the hybrid polymer, which is compared to the strong phase segregation observed in a POSS physical blend. Small-angle X-ray scattering indicates that although the cylindrical morphology attributed to the styrene component was not altered by the presence of POSS, attachment of POSS to the continuous phase (polybutadiene block) causes the packing of discrete phase (polystyrene blocks) to lack long-range features. Results of dynamic mechanical analysis showed that the POSS has sterically hindered the motion of the polybutadiene blocks. More interestingly, the presence of POSS in the soft segments also resulted in a tapered tan δ peak associated with the glass transition of polystyrene and a higher tensile strength when deformed at temperature near T g of polystyrene without affecting the elongational behavior of SBS at temperatures above Tg of polybutadiene.

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Introduction The novel coronavirus 2019 (COVID-19) pandemic in the United States (US) prompted widespread containment measures such as shelter-in-place (SIP) orders. The goal of our study was to determine whether there was a significant change in overall volume and proportion of emergency department (ED) encounters since SIP measures began. Methods This was a retrospective, observational, cross-sectional study using billing data from January 1, 2017–April 20, 2020. We received data from 141 EDs across 16 states, encompassing a convenience sample of 26,223,438 ED encounters. We used a generalized least squares regression approach to ascertain changes for overall ED encounters, hospital admissions, and New York University ED visit algorithm categories. Results ED encounters decreased significantly in the post-SIP period. Overall, there was a 39.6% decrease in ED encounters compared to expected volume in the pre-SIP period. Emergent encounters decreased by 35.8%, while non-emergent encounters decreased by 52.1%. Psychiatric encounters decreased by 30.2%. Encounters related to drugs and alcohol decreased the least, by 9.3% and 27.5%, respectively. Conclusion There was a significant overall reduction in ED utilization in the post-SIP period. There was a greater reduction in lower acuity encounters than higher acuity encounters. Of all subtypes of ED encounters, substance abuse- and alcohol-related encounters reduced the least, and injury-related encounters reduced the most.

A series of hybrid organic/inorganic triblock copolymers of polystyrene-butadiene-polystyrene (SBS) grafted with polyhedral oligomeric silsesquioxane (POSS) molecules with different chemical constituents were synthesized by a hydrosilation method. Four POSS macromers, R′R 7 Si 8 O 12 , were designed to contain a single silane functional group, R′, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block and seven identical organic groups, R. Small-angle X-ray scattering and rheological techniques were used to study the effect of sterically similar, yet electronically different, organic R groups, cyclopentyl (Cp), cyclohexyl (Cy), cyclohexenyl (Cye), and phenyl (Ph), on the morphology of SBS triblock copolymer and the order-disorder transition behavior. It was observed that POSS with phenyl moiety, when grafted to the polybutadiene (PB) phase, appears to show favorable interaction with the polystyrene (PS) phase; effectively, the Ph-POSS is plasticizing the SBS due to an effect whereby the Ph-POSS is at least partially solvated by the PS phase. This causes a significant decrease in the overall lamellae d spacing and the order-disorder transition temperature, T ODT , with increasing amounts of Ph-POSS attachment. As we change the POSS moiety to that of Cye, Cy, and Cp, the interaction between POSS-PS weakens, and the d spacing and T ODT become less dependent on the amounts of POSS attachment. At the highest POSS loadings investigated (20 wt %), there is a change to a perforated layer morphology, resulting in an increase of T ODT relative to the 10 wt % POSS-grafted copolymers for Cp, Cy, and Cye POSS moieties.