An elastomeric, healable, supramolecular polymer blend comprising a chain-folding polyimide and a telechelic polyurethane with pyrenyl end groups is compatibilized by aromatic π−π stacking between the π-electron-deficient diimide groups and the π-electron-rich pyrenyl units. This interpolymer interaction is the key to forming a tough, healable, elastomeric material. Variable-temperature FTIR analysis of the bulk material also conclusively demonstrates the presence of hydrogen bonding, which complements the π−π stacking interactions. Variable-temperature SAXS analysis shows that the healable polymeric blend has a nanophase-separated morphology and that the X-ray contrast between the two types of domain increases with increasing temperature, a feature that is repeatable over several heating and cooling cycles. A fractured sample of this material reproducibly regains more than 95% of the tensile modulus, 91% of the elongation to break, and 77% of the modulus of toughness of the pristine material.

A healable supramolecular polymer blend based on aromatic π-π stacking and hydrogen-bonding interactions

A recurring challenge in the field of nanocomposites is to control the spatial distribution of nanoparticles (NPs) in a polymer matrix. This issue is of critical importance since it is now well-established that a specific NP dispersion state is necessary to optimize a desired property of polymer nanocomposites (PNCs). This Perspective focuses on one particular approach to controlling NP spatial dispersion, and hence the properties of polymer-based nanocomposites: the use of polymer-grafted NPs. Novel developments over the past decade in synthesis techniques allow us to controllably functionalize NPs with polymer chains. This has ignited considerable interest in this field, leading to significant advances in creating nanocomposites with tunable physical properties. We begin by briefly outlining the various synthetic strategies for functionalizing NPs and then discuss various methods for controllably dispersing them in a polymer matrix. The consequences of having states with controlled NP dispersion on nano...

https://www.benicewiczgroup.com/UserFiles/benigroup/Documents/BB91.pdf

Nanocomposites with Polymer Grafted Nanoparticles

A device for accurately delivering aerosolized doses of a medicament disperses a measured amount of drug in a measured volume of carrier gas and transfers the resulting aerosol to a chamber prior to inhalation by a patient. The chamber is filled efficiently with the aerosol, and inhalation by the patient draws the aerosol dose into the lungs. This is followed by the inhalation of atmospheric air that will push the initial dose well into the lung interiors. The apparatus optimally includes a dose regulator, a counter, a clock, a dose memory and a signal to indicate when a dose is ready for inhalation. Optimal chamber designs are disclosed.

Method and device for delivering aerosolized medicaments

https://cyberleninka.org/article/n/397502.pdf

Melt rheology of organoclay and fumed silica nanocomposites

It is well recognized that nanocomposites formed by adding nanoparticles to polymers can have significantly enhanced properties relative to the native polymer. This review focuses on three aspects that are central to the outstanding problem of realizing these promised property improvements. First, we ask if there exist general strategies to control nanoparticle spatial distribution. This is an important question because it is commonly accepted that the nanoparticle dispersion state crucially affects property improvements. Because ideas on macroscale composites suggest that optimizing different properties requires different dispersion states, we next ask if we can predict a priori the particle dispersion and organization state that can optimize one (or more) properties of the resulting nanocomposite. Finally, we examine the role that particle shape plays in affecting dispersion and hence property control. This review focuses on recent advances concerning these underpinning points and how they affect measur...

Nanocomposites: Structure, Phase Behavior, and Properties

We explore filler reinforcement (i.e., increase of elastic modulus G‘ due to incorporation of fillers) and Payne effect (i.e., decrease of G‘ at large strain amplitudes) in terms of the matrix molecular weight, filler loading, and time scales used to probe the viscoelasticity of filled melts. Use of monodisperse non-cross-linked 1,4-polybutadiene (PBD) along with a silica filler allows illustration of different mechanisms of filler reinforcement in the elastic and liquid regimes. The greater filler reinforcement for matrices of higher molecular weight indicates the filler association through chain adsorption and bridging. The role of matrix-mediated filler−filler interactions is explicitly illustrated in terms of the increased elastic modulus in the terminal region due to replacement a fraction of the matrix chains with longer chains of the same kind. The Payne effect is seen to be time-dependent and comprised of an instantly recoverable and a slowly recovering component. Measuring G‘ at both high and low...

Investigating linear and nonlinear viscoelastic behavior using model silica-particle-filled polybutadiene

Measurements of average free volume hole sizes, 〈vf〉, and the fractional free volumes, fps, in vulcanized cis-polyisoprene (CPI), high-vinyl polybutadiene (HVBD), and their 50 : 50 blend were made via determination of orthopositronium annihilation lifetimes. The results are compared to corresponding data on the uncured materials. On crosslinking, 〈vf〉 decreases in the rubbery state but remains essentially unchanged in the glass. This is consistent with the expectation that the crosslinks greatly restrict the thermal expansion of the chains above the glass transition temperature (Tg) but have less influence on the packing density in the glass. Scaling relationships between 〈vf〉, fps, the thermal expansion coefficient αf = dfps/dt, and Tg are examined. We find that 〈vf〉g, the hole volume at Tg, and fps,g, the fractional free volume at Tg, each increase significantly with increasing Tg. This behavior is consistent with previous observations reported in the literature and has been interpreted as a manifestation of the kinetic character of the glass transition. High-Tg polymers need a larger free volume to pass into the liquid state. The change in expansion coefficient on passing from the glass to the liquid, Δαf = αf,l − αf,g, increases slowly with Tg, as predicted by free volume theory. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2754–2770, 1999

Positron annihilation lifetime studies of changes in free volume on cross-linking cis-polyisoprene, high-vinyl polybutadiene, and their miscible blends

Temperature and concentration effects on polar‐modified alkyllithium polymerizations and copolymerizations

The process described herein involves the preparation of block copolymers of the S-B-S type wherein S represents a block of polystyrene and B represents a block of polybutadiene. In order to have the initial polystyrene block soluble in the polymerization medium, cyclohexane and aromatic hydrocarbons have been used as the diluent or solvent in these polymerizations. The present process permits the use of hexane as diluent by having dissolved therein prior to polymerization a small amount of the S-B-S type of block copolymer being produced in the polymerization. Advantageously this solution used as the polymerization medium is prepared merely by washing the reactor used in a previous polymerization for production of the same type of S-B-S block copolymer with hexane to dissolve solid residues of S-B-S block copolymer deposited on the wall or agitator of the reactor. This hexane solution is then retained in the reactor to serve as the medium for the next polymerization batch. The dissolved S-B-S copolymer serves as a suspension agent for dispersion of the initial polystyrene block.

Process for the preparation of block copolymers

Thermoplastic elastomer blends of alpha-olefin polymers and copolymers, such as polypropylene, polyethylene, etc., having a melting point of at least 90° C. with hydrogenated butadiene medium and high vinyl polymers have good physical properties such as low brittle point, good impact resistance at low temperatures, minimum creep at high temperatures, and good elongation. The blends can be repeatedly processed and still maintain good physical properties. The amount of alpha-olefin polymer or copolymer in the blend may range from about 10 percent to about 60 percent with the amount of the hydrogenated polybutadiene correspondingly ranging from about 90 percent to about 40 percent based on the combined weight of the two components. The blends are mixed at temperatures at least as high as the melting point of the alpha-olefin polymer or copolymer. These blends have excellent ozone resistance and aging properties, as well as excellent paint adhesion.

Adel Farhan Halasa

Papers

Investigating linear and nonlinear viscoelastic behavior using model silica-particle-filled polybutadiene

Positron annihilation lifetime studies of changes in free volume on cross-linking cis-polyisoprene, high-vinyl polybutadiene, and their miscible blends

Temperature and concentration effects on polar‐modified alkyllithium polymerizations and copolymerizations

Process for the preparation of block copolymers

Thermoplastic elastomer blends of alpha-olefin polymers and hydrogenated medium and high vinyl butadiene polymers