Volume Of Polystyrene Research Articles

High-Resolution Nanoscale Solid-State Nuclear Magnetic Resonance Spectroscopy

We present a new method for high-resolution nanoscale magnetic resonance imaging (nano-MRI) that combines the high spin sensitivity of nanowire-based magnetic resonance detection with high-spectral-resolution nuclear magnetic resonance (NMR) spectroscopy. Using a new method that incorporates average Hamiltonian theory into optimal control pulse engineering, we demonstrate NMR pulses that achieve high-fidelity quantum control of nuclear spins in nanometer-scale ensembles. We apply this capability to perform dynamical decoupling experiments that achieve a factor of 500 reduction of the proton-spin resonance linewidth in a (50−nm)3 volume of polystyrene. We make use of the enhanced spin coherence times to perform Fourier-transform imaging of proton spins with a one-dimensional slice thickness below 2 nm.Received 20 July 2017Revised 10 January 2018DOI:https://doi.org/10.1103/PhysRevX.8.011030Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCompositionQuantum controlPhysical SystemsNanowiresTechniquesMagnetic resonance imagingNuclear magnetic resonanceCondensed Matter, Materials & Applied Physics

Dimethyl ether’s plasticizing effect on carbon dioxide solubility in polystyrene

The solubility of carbon dioxide (CO2) and dimethyl ether (DME) blends in polystyrene (PS) is studied as a function of the temperature and the pressure. The solubility was measured by means of the gravimetric method and a visualizing dilatometer which determined the swollen volume to compensate for the buoyancy change due to swelling. The solubility of the blend gases for the ternary PS/CO2/DME system is also predicted by the Simha-Somcynsky (SS) equation of state (EOS). The theoretical prediction of the blend solubility was in agreement with the experimental results. Adding DME to PS not only decreased the pressure required to dissolve CO2 in PS but the effects of plasticization were also observed. The remarkable plasticization effect due to the presence of DME increased the CO2 solubility via an increased free volume of PS.

Direct Visualization of Three-Dimensional Morphology in Hierarchically Self-Assembled Mixed Poly(tert-butyl acrylate)/Polystyrene Brush-Grafted Silica Nanoparticles

Three-dimensional (3D) morphology of hierarchically self-assembled mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brush-grafted 67 nm silica nanoparticles cast from chloroform on a carbon-coated transmission electron microscopy (TEM) grid was directly visualized using electron tomography (i.e., 3D TEM). The number-average molecular weights for PtBA and PS were 22.2 and 23.4 kDa, and their grafting densities were 0.51 and 0.34 chains/nm2, respectively. For a dense monolayer of mixed brush-grafted silica particles, a rippled phase structure was observed, and the monolayer consisted of protruded top portions from large nanoparticles and a bottom continuous film. In the top protruded part of large nanoparticles, isolated cylindrical PS microdomains were formed in the PtBA matrix due to the low PS volume fraction (i.e., 37%). The morphology in the lower continuous film was strongly influenced by interparticle interactions via mixed polymer brushes. As a result, bicontinuous nanostructures instead of i...

Viscoelastic behaviors of shell‐crosslinked core–shell nanoparticles suspended in polystyrene solutions

AbstractShell‐crosslinked core–shell nanoparticles (SCCSNs) were prepared via miniemulsion polymerization of styrene in the presence of silane‐modified inorganic silica. The polystyrene (PS) shell of 58.6% in weight fraction was crosslinked using divinylbenzene. SCCSNs were spherical with a diameter distribution from 32 to 98 nm determined by dynamic light scattering. Dynamic rheology of SCCSNs suspended in PS/toluene solution was compared with that of suspensions of naked silica. The critical strain for onset of rheological nonlinearity was independent of SCCSN concentration above a concentration threshold, which differs from the silica suspensions. Linear dynamic rheological investigation revealed that SCCSN suspensions with a PS volume fraction of 20% were fluid‐like at low particle concentrations while suspensions containing 4.2 vol% SCCSNs formed a gel‐like structure. On the contrary, the silica suspensions with 20.0 vol% PS underwent a fluid‐to‐solid‐like transition with increasing silica concentration. Reasons for the different rheological behaviors of the naked silica and SCCSN suspensions are discussed. Copyright © 2012 Society of Chemical Industry

Instabilities of PS/PMMA Bilayer Patterns with a Corrugated Surface and Interface

We study the patterns spontaneously formed by bilayer polymer films upon annealing. Specifically, polystyrene (PS) films were spin-cast on topographically patterned poly(methyl methacrylate) (PMMA) substrates and subsequently annealed at temperatures above the glass transition temperature of both polymers. The influence of the molecular weight and the volume of PS on the morphological evolution of the corrugated liquid–liquid interface was examined. When the PS formed isolated stripes both on the mesas and within the trenches of the PMMA pattern, capillary instability was observed for these nonaxisymmetric PS threads. The kinetics of the capillary breakup depended on the thread-to-matrix viscosity ratio, and was dictated by the more viscous component. In contrast, the characteristic wavelength of the breakup only slightly depended on some viscosity ratio, and reached a minimum at the viscosity ratio around 1. When the PS was thick enough to form a continuous layer, the instability of the film further depended on the molecular weight of the PS. For a molecular weight of 13 kg/mol, the PS dewetted from PMMA via a random nucleation and growth mechanism. However, for a molecular weight of 2000 kg/mol, localized nucleation on top of the PMMA mesas led to a mesh-like PS morphology, which eventually broke up due to capillary instability. Therefore, by controlling the molecular weight and the spin-cast volume of the top layer, the kinetics of morphological evolution and the resulting patterns can be controlled.

Flow activation volume of polystyrene/multiwall carbon nanotubes composites

We applied the rate theory of plastic deformation to evaluate the flow activation volume in polystyrene melts and in its composites with different concentrations of multiwall carbon nanotubes. The experiments consisted in the analysis of a perturbation induced to the melt by varying the shear rate of a monotonic test at a melt state with nearly constant viscosity. The variation consisted on the application of shear steps with lower shear rate during short-time intervals. The material’s response to the perturbation allows a flow activation volume to be evaluated. For the pure polymer, the flow activation volume compares to the volume of a tube confining the chains, confirming the validity of tube model. Addition of nanotubes to the melt affects the melt response in the high temperature flow region, resulting in the development of a plateau in G′(ω). This plateau is linked to interactions of chains with nanotubes. However, the flow activation volume was not affected by the addition of nanotubes, suggesting that tube model holds also for composites of polymer melts with carbon nanotubes.

Interphase development in a three-component polymer system with asymmetric mobility

We report a study on the interphase evolution in a system composed by three polymeric components with markedly different mobility distributed between two layers. One of the layers is a low-Tg blend containing a low molecular weight polystyrene (PS) as a plasticizer (low-M PS) and PS chains with much higher molecular weight (high-M PS). The counterpart is a high-Tg layer composed by polyphenylene oxide. The system was annealed at several temperatures between Tg of the polymer layers and the subsequent interphase development probed by optical sectioning with confocal Raman microspectroscopy. The profiles obtained revealed the existence of two diffusion fronts that advance in opposite directions, both showing a similar response with time and temperature. These fronts act as well-defined boundaries that structure the interphase into three well-defined regions with almost constant PS volume fraction. We discuss this particular phenomenology proposing a simple diffusion model that describes the main interphase features. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 627–633, 2010

Self-assembly of colloidal crystals from polystyrene emulsion at elevated temperature by dip-drawing method

The self-assembly of colloidal crystal arrays from polystyrene (PS) sphere emulsion at elevated temperature by dip-drawing method was investigated. The dependence of effective sphere transfer in the meniscus of emulsion on temperature was discussed. The results show that the assembled arrays formed at 50 °C have fewer defects than those at room temperature. The elevated emulsion temperature during the ordered arrangement of colloidal crystals causes quicker solvent evaporation, hence quicker sphere transfer. However, exceeding solvent flux and crystal growth induced by over high temperatures result in more fracture lines displayed in arrays. At 50 °C, the effective sphere transfer by the solvent flux to the array edge can also be enhanced by increasing the PS volume fraction of emulsion, which obviously reduces fracture lines on the surface of multilayer.

Influence of Ionic Complexes on Phase Behavior of Polystyrene-b-poly(methyl methacrylate) Copolymers

The influence of ionic complexes on phase behavior of PS-b-PMMA copolymers over a wide range of molecular weights and PS volume fractions was investigated by small-angle X-ray scattering (SAXS), grazing incidence small-angle X-ray scattering (GISAXS), transmission electron microscopy (TEM), and neutron reflectivity (NR). The disorder-to-order transition (DOT) in both symmetric and asymmetric copolymers indicates that the overall Flory−Huggins segmental interaction parameter, χeff, between polystyrene (PS) and poly(methyl methacrylate) (PMMA) blocks with lithium−PMMA complexes is increased compared to that of the neat copolymers. This enhanced χeff further results in an order-to-order transition (OOT), from spheres to cylinders, and an increase in the ordering and spacing of microdomains. Moreover, transitional metal ionic complexes, such as copper−PMMA complexes, are found to have the similar influence on phase behavior of PS-b-PMMA copolymers. The formation of ionic complexes in the copolymers not only offers a parameter to tune the degree of microphase separation of PS-b-PMMA copolymers but also provides a way to fabricate multifunctional materials.

Thermodynamic analysis of phase separation in an epoxy/polystyrene mixture

The phase separation process of an epoxy prepolymer based on diglycidyl ether of bisphenol A (DGEBA) with a thermoplastic polystyrene (PS) was thermodynamically studied in the frame of the Flory–Huggins theory. The thermodynamic treatment was carried out in two steps: first analysing the phase separation in cloud point conditions, and second analysing the advance of the phase separation for two compositions of 2 and 10% in volume of PS. The effect of the polydispersity of thermoplastic on phase separation was also studied. The polydispersity of PS produces a displacement of the threshold temperature to lower thermoplastic volume fraction (between 2 and 3%) and higher temperature value and the fact that the shadow curve and coexistence curves do not superimpose with the cloud point curve. Theoretical calculations of molecular weight distributions of PS at different degrees of phase separation were realized and different average molecular properties were obtained in each separated phase.

Polystyrene thin films in CO(2).

In air, or vacuum environments, liquid polystyrene (PS) thin films (thickness, h<100 nm ) supported by SiOx /Si substrates are structurally metastable or unstable, depending on film thickness. They rupture and eventually form droplets on the SiOx /Si substrates (dewet) due to the influence of destabilizing long-ranged van der Waals dispersion forces. We used scanning force microscopy to examine the structural stability of liquid PS films in the thickness range 5 nm<h<100 nm in liquid and in supercritical carbon dioxide ( CO2 ) environments. All films in this thickness range were metastable; holes developed throughout the films and over time these holes grew, impinged, and eventually formed droplets. The rate of destabilization is controlled by three factors: film thickness, temperature, and CO2 pressure (which dictates CO2 volume fraction in the films). Calculations of the effective interface potentials suggest that the energy barrier for nucleation and growth of holes in CO2 is larger than that in air, and in the limit of vanishingly low PS volume fraction the films should be stable.

Dynamics of Polymers in Organosilicate Nanocomposites

Dynamic secondary ion mass spectrometry (DSIMS) measurements were performed to measure the effects of functionlized organosilicate clay (Cloisite 6A) on the tracer diffusion coefficient, D, in polystyrene (PS) and poly(methyl methacrylate) (PMMA) matrices. The results indicate that D is unaffected by the addition of 5% (by volume) of PS and is reduced by a factor of 3 with the addition of the same volume fraction in a PMMA matrix. The same ratio was also obtained for the extrapolated zero shear rate viscosity of PS and PMMA melt-mixed composites with the same volume fraction of clay. DSIMS was also used to measure the mobility of the clay platelets, which was found to be much lower than the polymer chains in both matrices. Examination of the sample morphology with scanning force and transmission electron microscopy indicated that in contrast to melt mixing, spin casting produced a large degree of exfoliation in both PS and PMMA matrices. Hence the difference in the dynamics in the presence of clay was ascribed to preferential interactions between the PMMA polymer and the platelet surface, rather than the extent of exfoliation.

Improvement of Mechanical and Thermal Properties of Elastomeric Polystyrene-block-poly (ethylene-co-but-1-ene)-block-polystyrene Triblock Copolymer upon Ordering of Spherical Microdomains on BCC Superlattice

We report the improvement of mechanical and thermal properties of an elastomeric polystyrene-block-poly (ethylene-co-but-1-ene)-block-polystyrene triblock copolymer upon ordering of spherical microdomains on the body-centered cubic (bcc) superlattice. The sample has a minor polystyrene (PS) composition (the volume of PS, φPS =0.084), and therefore forms glassy spherical microdomains being embedded in rubbery poly (ethylene-co-but-1-ene) matrix. The microdomain structures were analyzed by small-angle X-ray scattering technique and transmission electron microscopy. The mechanical properties were examined by dynamic viscoelastic measurements and tensile stress-strain tests. Upon annealing at 130°C for 10h, regularity of the bcc superlattice was improved as compared to a sample annealing at 150°C for 10h. Accordingly, the tensile modulus increased significantly, which can be ascribed to ordering of the glassy PS spheres on the bcc superlattice. Moreover, the thermal resistance was also improved. Namely, a decrease in the tensile modulus above Tg of PS was less remarkable in the film annealed at 130°C for 10h than at 150°C for 10h.

Structure of Waterborne Organic Composite Coatings

The mechanical properties and structure of composite films made of high-Tg polystyrene (PS) nodules dispersed in a low-Tg poly(butyl acrylate) (PBuA) matrix were studied by means of dynamic mechanical spectrometry and small-angle neutron scattering. At temperatures between the Tg of PS and PBuA, the mechanical properties depend drastically on the spatial distribution of the glassy PS domains. For films cast from mixtures of PS and PBuA latexes, an aggregation of PS particles into dense clusters dispersed in the PBuA matrix was observed. As a consequence, a large density of contacts between PS particles in the dry films ensured a strong mechanical reinforcement above a percolation threshold of 30% PS volume fraction. Extensive coalescence of PS particles occurred at their contacts upon annealing the films above the Tg of PS, leading to further mechanical reinforcement. For films cast from core−shell particles, the aggregation phenomenon was prevented, depending on the coverage of the PS core by the PBuA shell. An efficient core encapsulation in the core−shell morphology led to poor contact between PS cores, the elastic moduli were then close to that of the PBuA matrix, and the PS coalescence upon annealing was prevented.

Morphology of Model Graft Copolymers with Randomly Placed Trifunctional and Tetrafunctional Branch Points

The morphologies of two series of model graft copolymers were studied using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Both series of materials have monodisperse polybutadiene (PB) backbones and monodisperse polystyrene (PS) graft blocks. In one series there are on average five trifunctional junction points randomly distributed along the PB backbone. Each junction point grafts one PS block to the backbone. In the other series there are on average four tetrafunctional junction points randomly distributed along the PB backbone. Each junction point grafts two PS blocks to the backbone. A range of overall PB and PS volume fractions was investigated for both series. These materials simulate a controlled and known degree of architectural disorder. Current theory cannot rigorously predict the morphological behavior for these complex molecular architectures. However, it is found that an approximate extension of existing theory utilizing the constituting block copolymer (fundam...

Positronium Diffusion in Polystyrene at Low Temperatures

Diffusion of ortho-positronium (o-Ps) in polystyrene (PS) at low temperatures (20-300K) was studied by means of the positron annihilation lifetime technique. 2,2'-Dinitrobiphenyl was added to PS as a Ps quencher, and the diffusion coefficients were determined from the measured Ps quenching rate constants, assuming that the reaction between Ps and the quencher is entirely diffusion-controlled. The determined diffusion coefficient increases with increasing temperature, and is significantly influenced by such structural relaxation of PS as δ and β transitions. The estimated diffusion length of o-Ps, 1.5 2.5 nm. is only a few times larger than the Ps cavity size, indicating that the effect of the Ps diffusion on the Ps lifetime distribution is almost insignificant in PS at low temperatures. The size distributions of free volume in pure PS were obtained from the lifetime distributions of o-Ps without taking an effect of the diffusivity of o-Ps into consideration. Peculiar broadening of the size distribution of free volume for PS, which is induced by an inhomogeneous local structure. is observed at the transition temperatures, T δ and T β .

Small angle neutron scattering studies of composite latex film structure

The mechanical properties and structure of composite films made of high T g polystyrene (PS) nodules dispersed in a low T g polybutylacrylate (PBuA) matrix were studied by means of dynamic mechanical spectrometry and small angle neutron scattering. For films cast from mixtures of PS and PBuA latexes, film mechanical reinforcement was obtained above a percolation threshold of about 30% PS volume fraction. A segregation of PS particles into dense clusters in the PBuA continuous matrix, reminiscent of a phase separation, was observed. For films cast from core-shell particles, this segregation phenomenon may be prevented, depending on the coverage of the PS core by the PBuA shell. An efficient core encapsulation in the core-shell morphology leads to poor contact between PS cores, and the elastic moduli are then close to that of the PBuA matrix. Upon annealing the films above the T g of PS, extensive coalescence of PS particles occurred when large contacts were already present in the dry film at room temperature, and a percolating network of coalesced PS domains provides large elastic moduli at temperatures between the T g of PBuA and PS. The coalescence was prevented when PS particles were taken apart by the PBuA shell.

Ultrasonic measurement of relaxation behavior in polystyrene

We report measurements of the temperature and pressure dependence of ultrasonic modulus and specific volume in polystyrene between 50 and 280°C and applied pressures up to 775 bar. The volumetric glass transition temperature is found to vary linearly with pressure. Furthermore, it coincides with the temperature at which the velocity of sound and the attenuation in the material show pronounced change from solid-like to liquid-like behavior. The storage and loss moduli are analyzed within the Havriliak-Negami model and very good agreement is found over the entire temperature and pressure ranges. Using the Vogel-Tammann-Fulcher equation for the relaxation time, the Kauzmann temperature Tk and the fragility parameter D of polystyrene were determined from fits to the data. Tk is also a linear function of pressure, but D is constant over the whole pressure range. The value of D allows us to classify polystyrene among the fragile-glass formers. © 1996 John Wiley & Sons, Inc.

Ultrasonic measurement of relaxation behavior in polystyrene

We report measurements of the temperature and pressure dependence of ultrasonic modulus and specific volume in polystyrene between 50 and 280°C and applied pressures up to 775 bar. The volumetric glass transition temperature is found to vary linearly with pressure. Furthermore, it coincides with the temperature at which the velocity of sound and the attenuation in the material show pronounced change from solid-like to liquid-like behavior. The storage and loss moduli are analyzed within the Havriliak-Negami model and very good agreement is found over the entire temperature and pressure ranges. Using the Vogel-Tammann-Fulcher equation for the relaxation time, the Kauzmann temperature Tk and the fragility parameter D of polystyrene were determined from fits to the data. Tk is also a linear function of pressure, but D is constant over the whole pressure range. The value of D allows us to classify polystyrene among the fragile-glass formers. © 1996 John Wiley & Sons, Inc.

Molecular weight‐dependence of free volume in polystyrene studied by positron annihilation measurements

AbstractPositron annihilation lifetime measurements are reported for four monodisperse polystyrenes with molar mass M = 4,000, 9,200, 25,000, and 400,000. The temperature dependences of orthopositronium (o‐Ps) lifetime (τ3) and intensity (I3) were measured from 5°C to Tg + 30°C for each sample. From these data, the free volume hole size, 〈vf(τ3)〉, and fractional free volume hps=CI3〈vf(τ3)〉 were calculated. The temperature dependences of τ3, 〈vf(τ3)〉 and hps show a discrete change in slope at an effective glass transition temperature, Tg,ps, which is measurably below the conventional bulk Tg. This suggests that τ3 is sensitive to large holes which retain their liquid‐like mobility in the glassy state. Good agreement was found for T &gt; hg,ps between hps and the theoretical free volume fraction hth deduced from experimental P‐V‐T data for polystyrene using the statistical mechanical theory of Simha and Somcynsky. Below Tg,ps, deviations between hps and hth are observed, hps falling increasingly below hth as temperature decreases. Whereas hps and hth depend strongly on M in the melt, each essentially independent of M in the glass. A free volume quantity, computed from the bulk volume, which is in good numerical agreement with the Simha‐Somcynsky h‐function in the melt, gives improved agreement with hps in the glassy state. © 1994 John Wiley &amp; Sons, Inc.