Glass Transition Of Polystyrene Research Articles

Investigating the role of solvents in modulating glass transition and dynamic mechanical characteristics of polystyrene film

This study investigates how different solvents impact the glass transition and dynamic mechanical properties of polystyrene (PS) films. Using FTIR spectroscopy, it analyzes solvent-induced variations in molecular vibrations, particularly in the phenyl ring region. Results show solvent-specific effects on the 750 cm-1 peak, associated with the "meta-substituted aromatic ring," influencing phenyl ring vibrations. DSC analysis highlights solvent effects on the glass transition temperature (Tg), revealing complexities in PS films prepared with chloroform, tetrahydrofuran (THF), and toluene. Varied Tg behavior suggests solvent-driven structural modifications and gradual solvent removal. Dynamic Mechanical Analysis (DMA) demonstrates solvent-dependent changes in storage modulus, loss modulus, and tan δ, indicating solvent polarity role in polymer chain dynamics. Toluene-induced plasticization reduces Tg and increases creep compliance, revealing PS film sensitivity to solvents. These findings stress solvent selection importance in tailoring thermal and mechanical properties of polymer films for specific applications.

Solubility of supercritical CO2 in polystyrene

Expanded polystyrene (ePS) plays an important role in the food packaging industry. However, the foaming process is environmentally unfriendly. A sustainable alternative is dissolving supercritical CO2 (scCO2) in the polystyrene (PS) matrix. Most studies so far were performed at temperatures above the PS glass transition temperature; however, a more general temperature window is desirable. In this work, the solubility of scCO2 in polystyrene was measured at 323 K, 343 K, 363 K and 383 K and pressure up to 130 bar using a magnetic suspension balance (MSB). It was concluded that the solubility of CO2 in PS decreases with temperature and increases with pressure. The Sanchez-Lacombe Equation of State was utilized to estimate the degree of swelling. The model developed was able to derive the experimentally determined solubilities after correction for the swelling. The interaction parameter, k12, turned out to be only a function of temperature. With these results the solubility and swelling of PS in scCO2 can be more accurately assessed for different temperatures and pressures.

Regulating polystyrene glass transition temperature by varying the hydration levels of aromatic ring/Li+ interaction.

Polymer properties can be altered via lithium ion doping, whereby adsorbed Li+ binds with H2O within the polymer chain. However, direct spectroscopic evidence of the tightness of Li+/H2O binding in the solid state is limited, and the impact of Li+ on polymer sidechain packing is rarely reported. Here, we investigate a polystyrene/H2O/LiCl system using solid-state NMR, from which we determined a dipolar coupling of 11.4 kHz between adsorbed Li+ and H2O protons. This coupling corroborates a model whereby Li+ interacts with the oxygen atom in H2O via charge affinity, which we believe is the main driving force of Li+ binding. We demonstrated the impact of hydrated Li+ on sidechain packing and dynamics in polystyrene using proton-detected solid-state NMR. Experimental data and density functional theory (DFT) simulations revealed that the addition of Li+ and the increase in the hydration levels of Li+, coupled with aromatic ring binding, change the energy barrier of sidechain packing and dynamics and, consequently, changes the glass transition temperature of polystyrene.

Study of microplastics with semicrystalline and amorphous structure identification by TGA and DSC.

The potential of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to identify, distinguish among the most relevant microplastics, and quantification, has been studied, including semicrystalline polymers (polypropylene (PP), polyamide (PA), high density polyethylene (HDPE), low density polyethylene (LDPE) and polyethylene terephthalate (PET)) and amorphous polymers (polystyrene (PS) and Polyvinyl Chloride (PVC)). The identification has been carried out by analyzing the decomposition, melting and glass transition temperatures. Both amorphous polymers (PVC and PS) can be properly identified by DSC using the glass transition temperature. Semicrystalline polymers, PA, PET, PP, HDPE and LDPE can be identified by using the melting temperature without the interference of other polymers, neither semicrystalline nor amorphous. The main limitation of the evaluated techniques is to distinguish between the semicrystalline polymer LDPE and the amorphous PS, as LDPE melting temperatures overlap with PS glass transition temperature, and this parameter would be useful only if one of these two polymers is present in the sample to be analyzed, since interference with other polymers (PA, PP, PET, LDPE, PVC and PS) do not exist. If both LDPE and PS are present in the sample, the best but not ideal option would be to analyze the decomposition temperature curves, since overlapping is weak in this case.

Thermoplasmonic Patterning of Silver Nanocrystal/Polymer Composite Thin Films

AbstractThe lithographic patterning of polymer films is ubiquitous in manufacturing processes. In this work, the high photothermal conversion efficiency utilizes plasmonic nanoparticles to locally pattern polystyrene films. Silver nanocubes on polystyrene thin films are used as a heat source for photothermal lithographic patterning using a continuous‐wave, visible laser. Distinct states of the nanocomposite defined by their own far‐field optical properties and microscale topography are observed. At low intensities the nanocubes can be embedded into the polymer at a nanometer scale displacement precision and produce a notable shift in the distinct localized surface plasmon resonance, enabling two‐color optical patterning. Numerical modelling indicates the temperatures reached in the film surpass polystyrene's glass transition temperature (Tg, ≈90 °C). At higher laser intensities sufficient temperatures are reached to achieve pronounced polymer film displacement enabling direct‐write lithography. Temperature estimates highlight the role of collective contribution of nanoparticle heating in the process. The process can be controlled by selecting excitation wavelengths to tune the power absorbed by the nanocubes in accordance with their plasmonic absorption spectrum. The approach here outlines a general method of 2D optical patterning utilizing thermoplasmonics, which can be further expanded to other materials, applications, and potentially to subdiffraction length scales.

Exploration of Polymer Calorimetric Glass Transition Phenomenology by Two-Dimensional Correlation Analysis

Two-dimensional (2D) correlation analysis has been used to investigate the calorimetric glass transition of neat polystyrene (PS) and poly(methyl methacrylate) (PMMA) as well as their blends. The n...

Experimental study of substrate roughness on the local glass transition of polystyrene.

Numerous computer simulations have shown that local dynamics associated with the glass transition can be slower next to rough interfaces compared with smooth interfaces. Even though the impact of surface roughness has been frequently considered computationally and theoretically, almost no experimental studies exist investigating these effects. Using a hydrogen fluoride vapor treatment, we created silica substrates with an increase in roughness that left the surface chemistry unchanged. The local glass transition temperature Tg near silica substrates with an increase in roughness was measured using fluorescence, finding an increase in local Tg of 10 K with an increase in the root-mean-square roughness Rrms from 0.5 nm to 11 nm. Characterization of the substrate roughness needed to create an experimental change in local Tg was found to be quite large, leaving the mechanism for this observed behavior uncertain. We discuss possible causes associated with polymer chains being more readily able to make surface contacts and adsorb to roughened interfaces.

The potential of magnetic heating for fabricating Pickering-emulsion-based capsules

Pickering emulsions (particle-stabilized emulsions) have been widely explored due to their potential applications, one of which is using them as precursors for the formation of colloidal capsules that could be utilized in, among others, the pharmacy and food industries. Here, we present a novel approach to fabricating such colloidal capsules by using heating in the alternating magnetic field. When exposed to the alternating magnetic field, magnetic particles, owing to the hysteresis and/or relaxation losses, become sources of nano- and micro-heating that can significantly increase the temperature of the colloidal system. This temperature rise was evaluated in oil-in-oil Pickering emulsions stabilized by both magnetite and polystyrene particles. When a sample reached high enough temperature, particle fusion caused by glass transition of polystyrene was observed on surfaces of colloidal droplets. Oil droplets covered with shells of fused polystyrene particles were proved to be less susceptible to external stress, which can be evidence of the successful formation of capsules from Pickering emulsion droplets as templates.

Mechanism and quantitative study of specific heat change during glass transition of amorphous polystyrene and Pd<sub>40</sub>Ni<sub>10</sub>Cu<sub>30</sub>P<sub>20</sub>

<sec>The nature of glass transition is one of the most interesting problems in modern condensed matter physics. There is a theory that shows that when the particle's diffusion motion probability <i>P</i> is less than <inline-formula><tex-math id="M2">\begin{document}$ {{\rm{e}}^{ - 2{{\rm{e}}^3}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20200331_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20200331_M2.png"/></alternatives></inline-formula>, the proportion of particles whose diffusion motion is frozen is not less than 1 + 2e<sup>3</sup>/ln<i>P</i>. Based on the modulus temperature formula of this theory and the experimental modulus-temperature curve of polystyrene in the literature, the free volume expansion coefficient of polystyrene is determined to be in a range of 0.00045－0.00052. </sec><sec>In this paper, we first quantitatively study the specific heat temperature relationship in the glass transition of polystyrene. Based on this theory, the specific heat-temperature formula in the glass transition region is derived. The material in the glass transition region is a mixture of rubber and glass, and this two-component (rubber and glass) system’s total specific heat is the product of the specific heat of the rubber and the percentage of rubber in the two-component system plus the product of the specific heat of the glass and the percentage of glass in the two-component system. Let <i>b</i> be the number of atoms in the main chain of the segment, then the proportion of rubber will be the <i>b</i>-th power of free volume fraction. This specific heat-temperature formula with polystyrene is tested. By substituting the obtained free volume expansion coefficient of the polystyrene into the specific heat-temperature formula, the resulting formula can accurately and quantitatively describe the specific heat-temperature relationship in the glass transition of polystyrene without fitting any parameters. </sec><sec>In this paper, we also study the change of motion in the glass transition of polystyrene. According to the analysis, the glass transition process of polystyrene is a process in which the diffusion movement of the main chain atoms is activated or frozen, which is consistent with the conclusions of relevant research on amorphous alloys. When the main chain atom is used as the molar unit of measurement, the specific heat change in the glass transition of polystyrene is 1.61<i>R</i> (<i>R</i> is the gas constant), which is consistent with the law, i.e. “the specific heat change in the glass transition of the amorphous alloy is about 1.5<i>R</i>”. These consistent conclusions predict that the glass transitions of amorphous alloys and glass transitions of polystyrene have the same essence. Based on this idea, the specific heat temperature formulas of the amorphous alloy Pd<sub>40</sub>Ni<sub>10</sub>Cu<sub>30</sub>P<sub>20</sub> and polystyrene are verified and prove to be consistent.</sec>

Fabrication of Damping Material over Broad Temperature Range: Blending Amorphous Styrene‐Butadiene‐Styrene Triblock Copolymer with Semi‐Crystalline Syndiotactic 1,2‐Polybutadiene

Broad‐temperature‐range (−85.4 to 96.2 °C) damping material was fabricated by blending amorphous styrene‐butadiene‐styrene triblock copolymer (SBS) with semicrystalline syndiotactic 1,2‐polybutadiene (s‐PB). According to dynamic mechanical thermal analysis (DMTA) analysis, SBS/s‐PB blends exhibited three consecutive damping peaks at −85.4, 2.7, and 96.2 °C. The peaks at −85.4 and 96.2 °C were associated with the glass transition of polybutadiene and polystyrene in SBS, and peak at 2.7 °C belonged to the glass transition of s‐PB. The analysis of rheological behavior and thermal properties showed that the mobility and thermal stability of SBS/s‐PB blends improved with the introduction of semi‐crystalline s‐PB. Moreover, regarding the results of DMTA, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) measurements, SBS and s‐PB were compatible in the macroscopic scale while they were immiscible in thermodynamic scale. Wide‐angle X‐ray diffraction (WAXD) results present the crystal structure of blends were unchanged. Besides, with the introduction of s‐PB in blends, 100% tensile modulus increased from 3.2 to 5.8 MPa and tear strength increased from 49.2 to 84.2 kN/m. The Kerner–Uemura–Takayanagi model was employed to compare with experimental data. Thus, broad‐temperature‐range damping material was fabricated by blending SBS with s‐PB and the material combined with good processability, thermal stability, and mechanical properties. J. VINYL ADDIT. TECHNOL., 26:336–347, 2020. © 2019 Society of Plastics Engineers

Nanoaperture fabrication via colloidal lithography for single molecule fluorescence analysis.

In single molecule fluorescence studies, background emission from labeled substrates often restricts their concentrations to non-physiological nanomolar values. One approach to address this challenge is the use of zero-mode waveguides (ZMWs), nanoscale holes in a thin metal film that physically and optically confine the observation volume allowing much higher concentrations of fluorescent substrates. Standard fabrication of ZMWs utilizes slow and costly E-beam nano-lithography. Herein, ZMWs are made using a self-assembled mask of polystyrene microspheres, enabling fabrication of thousands of ZMWs in parallel without sophisticated equipment. Polystyrene 1 μm dia. microbeads self-assemble on a glass slide into a hexagonal array, forming a mask for the deposition of metallic posts in the inter-bead interstices. The width of those interstices (and subsequent posts) is adjusted within 100–300 nm by partially fusing the beads at the polystyrene glass transition temperature. The beads are dissolved in toluene, aluminum or gold cladding is deposited around the posts, and those are dissolved, leaving behind an array ZMWs. Parameter optimization and the performance of the ZMWs are presented. By using colloidal self-assembly, typical laboratories can make use of sub-wavelength ZMW technology avoiding the availability and expense of sophisticated clean-room environments and equipment.

Polymer-Polymer Interfacial Perturbation on the Glass Transition of Supported Low Molecular Weight Polystyrene Thin Films.

Clarifying interfacial perturbation on polymer relaxation is important for polymer material development. Herein we investigated polymer-polymer interfacial perturbation on low molecular weight (MW) polystyrene (PS) thin film (15-180 nm) glass transition by depositing various polymers atop PS films. Overall, rubbery topcoats induced Tg depression of PS thin film (below 60 nm), whileglassy topcoats induced Tg elevation of PS thin film (below 30 nm). Importantly, for the rubbery topcoat, Tg perturbation strength is largely dependent on the Tg difference between interfacial polymers and a larger Tg difference would induce stronger perturbation, while for the glassy topcoat this dependence is inconspicuous. Meanwhile, the interfacial perturbation length during PS glass transition by rubbery topcoats is estimated to be around 8 nm, while it is considered to be about 3.5 nm for glassy topcoats. The different interfacial perturbation length induced by disparate topcoats was accounted for by their different perturbation strength on adjacent PS molecules and disparate interfacial roughness. The results can promote the understanding of polymer interfacial perturbation and benefit the design and development of polymer-based materials.

Glass transition at the polystyrene/polyethylene glycol interface observed via contact angle measurements

We investigated the possibility of detecting the interfacial glass transition of a polymer with static contact angle measurements of a liquid polyethylene glycol on the polymer surface. The observed contact angle θ reflects the deviation from an equilibrium state at low temperatures, and the temperature dependence of cos θ changes discontinuously at the interfacial glass transition temperature Tg, manifesting a change in the interfacial entropy. This outcome was demonstrated experimentally for a liquid of polyethylene glycol (PEG) on an atactic polystyrene (PS) surface. The evaluated Tg was ca. 362 K. This value is lower than a calorimetric Tg for a bulk PS. This difference reflects molecular interactions at the interface, indicating that the Tg obtained from the contact angle measurement is sensitive to the dynamics near the polymer/liquid interface. The possibility of detecting the interfacial glass transition of polystyrene with contact angle measurements of a liquid polyethylene glycol on the polymer surface was investigated. The observed contact angle reflects the deviation from an equilibrium state at low temperatures, exhibiting a discontinuous change in the temperature dependence of the interfacial tension. The evaluated Tg was ca. 362 K, which is lower than a calorimetric Tg for a bulk polystyrene. The interfacial glass transition appears to be detected when the polymer/liquid interactions affect the wetting process.

Stability of Polymer:PCBM Thin Films under Competitive Illumination and Thermal Stress

AbstractThe combined effects of illumination and thermal annealing on the morphological stability and photodimerization in polymer/fullerene thin films are examined. While illumination is known to cause fullerene dimerization and thermal stress their dedimerization, the operation of solar cells involves exposure to both. The competitive outcome of these factors with blends of phenyl‐C61‐butyric acid methyl ester (PCBM) and polystyrene (PS), supported on PEDOT:PSS is quantified. UV–vis spectroscopy is employed to quantify dimerization, time‐resolved neutron reflectivity to resolve the vertical composition stratification, and atomic force microscopy for demixing and coarsening in thin films. At the conventional thermal stress test temperature of 85 °C (and even up to the PS glass transition), photodimerization dominates, resulting in relative morphological stability. Prior illumination is found to result in improved stability upon high temperature annealing, compatible with the need for dedimerization to occur prior to structural relaxation. Modeling of the PCBM surface segregation data suggests that only PCBM monomers are able to diffuse and that illumination provides an effective means to control dimer population, and thus immobile fullerene fraction, in the timescales probed. The results provide a framework for understanding of the stability of organic solar cells under operating conditions.

Effect of bimodal molecular weight distribution on glass transition of confined polystyrene

We study the effect of bimodal molecular weight distribution on glass transition of polystyrene (PS) under one-dimensional confinement by employing hot-stage spectroscopic ellipsometry. The bulk PS is found to have an exceptionally low glass transition temperature (Tg) of around 61 °C. This intriguing finding is attributed to the presence of a sizable fraction of very low molecular weight components (∼3000 g/mol). A further suppression of Tg compared to the already reduced bulk value is observed upon reduction of the film thickness. We also observe that glass transition width of the bulk PS is broader than its monodisperse counterpart which is further broadened upon confinement.

Kinetic Equations for Describing the Liquid-Glass Transition in Polymers

We present a theoretical approach based on nonequilibrium thermodynamics and used to describe the kinetics of the transition from the liquid to the glassy state (glass transition). In the framework of this approach, we construct kinetic equations describing the time and temperature evolution of the structural parameter. We discuss modifications of the equations required for taking the nonexponential, nonlinear character of the relaxation in the vitrification region into account. To describe the formation of polymer glasses, we present modified expressions for the system relaxation time. We compare the obtained results with experimental data, measurements of the polystyrene glass transition for different cooling rates using the method of differential scanning calorimetry. We discuss prospects for developing a method for describing the polymer glass transition.

Glass Transition and Molecular Dynamics in Polystyrene Nanospheres by Fast Scanning Calorimetry

We employ fast scanning calorimetry (FSC) to characterize the glass transition of polystyrene (PS) nanospheres. We observe suppression of the glass transition temperature (Tg) in comparison to bulk PS, both in terms of limiting fictive temperature (Tf) and temperature range of vitrification. At the same time, the polymer molecular mobility is found to be independent of the nanospheres diameter and bulk-like. Importantly, apart from the fact that this result has been obtained on the same samples and experiments and at comparable time scales, in all cases, a perturbation of the entropy is induced. Hence, to understand these results, the conceptual difference between vitrification kinetics and molecular mobility is highlighted. The main consequence of the outcome of the present study is that arguments beyond those based on the modification of the molecular mobility must be accounted for to explain Tg suppression in polymer glasses subjected to nanoscale confinement.

Glass transition of polystyrene (PS) studied by Raman spectroscopic investigation of its phenyl functional groups

In polymeric materials the glass transition (GT) is a well-known and very important relaxation process related to movements of functional groups in the polymeric chain. In this work, we show the potential of Raman spectroscopy for exploring the GT process in the polymer polystyrene. We collected Raman spectra during a step-by-step heating process of the sample, which allowed us to collect signatures of the GT process from peak parameters of specific vibrational modes, and to verify the GT temperature. Results of the latter were in accordance with published values obtained via other methods. We identified the aromatic ring vibrational modes of the phenyl functional groups to be those which, due to steric hindrance, suffer the largest influence during the GT process. This confirms that Raman spectroscopy can be used as a complementary technique to perform GT investigations in polymeric materials due to its sensitivity to small intermolecular changes affecting vibrational properties of relevant functional side groups.

On the possibility of modeling of polymers glass transition in a wide range of cooling and heating rates

The presented work continues the investigation of the problems connected with modeling of the kinetics of polymers glass transition in a wide range of temperature change rates. In our previous work Tropin et al. (2015) , an attempt to model a big set of heat capacity curves of polystyrene glass transition has been made, and the inability of the common methods to do this within a single set of parameters has been demonstrated. To go a step further, in this work we proceed with the common and several novel methods of modeling. To normalize the models with each other, a fit of the 10K/min cooling/heating DSC curves of polystyrene is made, and the literature model parameters readjusted. Further, the modeling of the reduced heat capacity curves at the cooling and heating rates in a wide range of q=10−6–106K/s with a logarithmic step is performed. The comparison of Tg(q) behavior with lately measured data for polystyrene is made. It is shown, that the methods need some modifications to qualitatively describe details of the glass transition kinetics in a wide range of q. Some of the possibilities to advance the models are discussed.

Determination of electronic properties of nanostructures using reflection electron energy loss spectroscopy: Nano-metalized polymer as case study

In this work, Au was deposited with nominal effective thickness of 0.8nm on polystyrene (PS) at room temperature. According to previous study, using XPS peak shape analysis [S. Hajati, V. Zaporojtchenko, F. Faupel, S. Tougaard, Surf. Sci. 601 (2007) 3261–3267], Au nanoparticles (Au-NPs) of sizes 5.5nm were formed corresponding to such effective thickness (0.8nm). Then the sample was annealed to 200°C, which is far above the glass transition of PS. At this temperature, the Au-NPs were diffused within the depth 0.5nm–6.5nm as found using nondestructive XPS peak shape analysis. Electrons with primary energy 500eV were used because the electronic properties will then be probed in utmost surface (∼1 IMFP range of depths that is 1.8nm for PS). By using QUEELS software, theoretical and experimental electron inelastic cross section, energy loss function, electron inelastic mean free path and surface excitation parameters were obtained for the sample. The information obtained here, does not rely on any previously known information on the sample. This means that the method, applied here, is suitable for the determination of the electronic properties of new and unknown composite nanostructures.