Weight Polystyrene Research Articles

An integrated approach for plastic polymer degradation by the gut bacterial resident of superworm, Zophobas morio (Coleoptera:Tenebrionidae).

The potential of superworm to remove certain plastic polymers has recently been noted. In this study, aerobic bacterial strains were isolated from the gut of Zophobas morio larvae which were fed with polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS) polymers. Strains P2 (Leminorella), P6 (Bacillus), P9 (Bacillus), and P5 (Citrobacter) were associated with the highest PS (2.7%), PP (1.3%), PET (1.1%), and PE (0.42%) weight loss after 28days, respectively. Pretreatments including thermal treatment (80°C for 10days), weathering (4months in the free environment), and nitric and sulfuric acids (1 N, 10days) improved the degradation of PE (1.3%), PET (1.9%), PP (5.2%), and PS (8.3%) by the same strains, respectively. Further analyses on the PS degradation by Leminorella sp. P2 revealed acid pretreatment promoted the formation of the C = C, C = O, and O-H functional groups. Surface irregularities, as well as a 3.6-fold increase in surface roughness, were observed in the PS film subjected to biodegradation. The contact angle dropped from 98.4° to 42.2° following the biodegradation. Bacterial depolymerization was confirmed by the 8.7% and 3.4% reduction of Mn and Mw and the change in polydispersity from 1.65 to 1.75. The results suggest that Zophobas morio microbiota in combination with abiotic pretreatment can be considered for plastic waste management.

Revealing enhanced dilution effect of conjugated polymers in partially miscible blends

AbstractRecent experiments have shown that hole traps could be suppressed in polymer light‐emitting diodes under current stress by diluting the light‐emitting conjugated polymers within an “inert” large‐bandgap host material. However, it is unclear why there is an enhanced dilution effect in partially miscible blends rather than fully miscible blends, as intuition would suggest that better miscibility leads to better dilution. In this work, we propose a cascade analysis by combining multiple fluorescence microscopic techniques and all‐atom molecular dynamics simulations to study the solid‐to‐solid dilution of poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) in MEH‐PPV/polystyrene (PS) blends and MEH‐PPV/poly(vinylcarbazole) (PVK) blends. By varying the molecular weights of PS and PVK, we can regulate their miscibility with MEH‐PPV. The results corroborate that the dilution effect is enhanced in partially miscible blends rather than fully miscible ones. This is because, in partially miscible blends undergoing phase separation, the concentration of MEH‐PPV is notably decreased in the phase occupying the majority of the volume, leading to an overall greater dilution effect than in fully miscible blends. Moreover, MEH‐PPV could adopt the more extended conformation in the fully miscible blend, causing a shorter intermolecular distance to further undermine the dilution effect. These findings explain the seemingly counterintuitive more effective dilution effect observed in the recently reported partially miscible blends and provide guidance for further enhancing the performance of future generations of polymer light‐emitting diodes.

Core-Shell Double Gyroids Directed by Selective Solvation for ABC Triblock Terpolymers.

The formation of ABC triblock terpolymers through solution casting is still challenging. In this study, core-shell double gyroid network structures are fabricated via solution casting using poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) (F)-b-[poly(4-vinylpyridine) (P4VP) (P)]-b-[polystyrene (PS) (S)] (FPS) triblock terpolymers in N,N-dimethylformamide (DMF). Upon heat treatment, the polymer tends to form a sphere-in-lamellar structure at the F/S interface. Given the solubility properties of each component in DMF, it is anticipated that the effective volume fraction of F relative to P would increase in concentrated solutions and the effective volume fraction of S would decrease. The microphase-separated structure derived from the DMF solution consistently results in the formation of a network structure composed of a core-shell double gyroid, with F as the matrix, P as the shell, and S as the core, and their periodic lengths gradually increase to 110.8, 131.8, and 162.7nm as increase molecular weights of PS blocks to 13.8, 20.7, and 28.8kg mol-1. Based on the solubility properties of the polymer components highlighted in this study, the solvent selection strategy is broadly applicable to ABC triblock terpolymers featuring various polymer components, offering a more efficient avenue for fabricating core-shell double gyroid structures.

Flattened chains dominate the adsorption dynamics of loosely adsorbed chains on modified planar substrates.

Herein, the adsorption of polystyrene (PS) on phenyl-modified SiO2-Si substrates was investigated. Different from those for PS adsorption on a neat SiO2-Si substrate, the growth rate (vads) in the linear regime and hads/Rg (hads, thickness of flattened and loosely adsorbed layers on the substrate; Rg, radius of gyration) declined with increasing molecular weight (Mw) of PS and the phenyl content on the modified substrates, while the thickness of the flattened layer (hflat) and its coverage increased with increasing phenyl content. The results indicated that the adsorption of loose chains was controlled by the adsorption of flattened chains, as it only occurred in the empty contact sites remaining after the adsorption of flattened chains. Before approaching quasi-equilibrium (t < tcross), the number of flattened chain contact sites increased due to an enthalpically favorable process and, correspondingly, their spatial positions dynamically changed, which perturbed the adsorption of loose chains. When the adsorption of flattened chains reached quasi-equilibrium (t > tcross), the adsorption of loose chains was determined by the empty contact sites. The coverage of flattened chains and time to reach quasi-equilibrium were increased with more phenyl groups on the substrate, enhancing π-π interfacial interactions and resulting in a decreased adsorption rate and fewer loosely adsorbed chains. Mw-dependent vads and hads/Rg differed on phenyl-modified substrates compared to the neat SiO2-Si substrate owing to fewer empty contact sites for loose chains. The study findings improve our understanding of the mechanism responsible for the formation and structure of the adsorbed layer on solid surfaces.

Insight into the effect of microplastics on photocatalytic degradation tetracycline by a dissolvable semiconductor-organic framework

The presence of microplastics (MPs) in large quantities in the aqueous environment significantly affects the degradation process of water pollution. Still, the interaction between MPs and pollutants during photocatalytic degradation has not been studied. Here, a soluble BiOCl-OH semiconductor-organic framework (BOCH-SOF) was prepared from xylitol, and the polystyrene (PS) MPs' effect on the photocatalytic degradation of tetracycline (TC) was investigated. It was found that the appropriate number of PS can promote TC degradation and also change degradation products and pathways. At the same time, the presence of TC can effectively enhance PS aging and reduce the molecular weight of PS. This indicates that BOCH-SOF produces a synergistic effect in treating the combined pollution of TC and PS. Through free radical analysis and density functional theory calculations, it was proposed that PS and TC can complement each other. A certain concentration and size of PS can promote the conversion of Bi(III) to Bi and enhance charge separation and radical generation; the TC can change the interfacial charge distribution and free radical depletion, extend the light absorption in the system, and the PS and TC work together to ultimately achieve the synergistic degradation of the TC and the aging PS. This paper provides an in-depth analysis of the mechanism of the effect of MPs on the photocatalytic degradation of antibiotics, which is significant in controlling the combined pollution of MPs and associated pollutants in the water environment.

Controlled formation of the β-phase in poly(9,9-dioctylfluorene) by blending with low-molecular-weight polystyrene

The poly(9,9-dioctylfluorene) (PFO) solid film exhibits various phases including disordered α-phase and well-ordered β-phase. Especially, the formation of the β-phase in PFO is crucial for enhancing its carrier transport properties. Recently, the β-phase conformation of the PFO chains was reported to be formed by blending PFO with polystyrene (PS). Here, the weight-average molecular weight (Mw) of PS was investigated to clarify the formation mechanism of the β-phase conformation in a PFO:PS blend film. The β-phase conformation was formed only when PFO was blended with low-Mw PS. The temperature for the formation of the β-phase in the PFO:PS blend film was likely to be reduced to near room temperature owing to the thermal properties of low-Mw PS. Furthermore, we demonstrated that the amount of conformational change and the content of β-phase of the PFO chains in the PFO:PS blend film can be controlled by adjusting the blending ratio of low-Mw PS.

Study of Mechanical Properties of Micron Polystyrene-Toughened Epoxy Resin

Epoxy resin has a tight three-dimensional mesh structure after curing; due to this reason, the epoxy resin is brittle and not tough enough, which becomes the main reason for the destruction of the epoxy adhesive-steel/CFRP interface under fatigue loading of CFRP-reinforced steel structures. To prepare epoxy adhesives with good performance and suitable for CFRP-reinforced steel structures, the mechanical properties of epoxy adhesives are improved by adding polystyrene (PS) microspheres. In this work, five modified adhesives with PS weight fractions of 0 wt%, 1.25 wt%, 2.50 wt%, 3.75 wt% and 5 wt% are prepared by dispersion of PS particles through an ultrasonic cell crusher using a room-temperature curing process, and the tensile, flexural and impact properties of PS adhesives with different doping are investigated. Then, the microscopic morphology of the tensile section of the colloids is observed by scanning electron microscopy (SEM). The results show that the optimum dosing of PS is 2.5 wt%, and the tensile strength, tensile modulus of elasticity, flexural strength, flexural modulus and impact strength of the adhesive are increased by 77%, 147.7%, 71%, 35% and 22%, respectively, with this dosing. SEM analysis shows that PS particles produce large deformation to absorb energy when the matrix is fractured, and crack expansion needs to bypass or shear the PS particles, thus inhibiting crack expansion and achieving the purpose of toughening. Adhesion agglomeration of PS particles in the resin is the main reason for the decrease in the mechanical properties of adhesives.

Biodegradación de poliestireno con enterobacterias productoras de lacasa aisladas de un basurero municipal

In this work, the ability to biodegrade two samples of polystyrene (PS) was evaluated: crystal and expanded with three bacterial strains isolated from PS waste collected in the municipal dump of Chimalhuacán, Estado de Mexico. The biodegradation potential of the isolated strains was determined by means of substrate weight loss assays. All three bacterial strains were found to be able to biodegrade both types of PS. The study also aimed to determine if the isolated bacteria produce laccase. This enzyme belongs to the oxidoreductase family and is known to degrade polyethylene. Copper sulfate (CuSO4) was used as the inducer of laccase activity, and an increase in enzyme activity was observed with simultaneous loss of PS weight compared to the control assay without CuSO4. It was concluded that laccase directly participated in the biodegradation of this synthetic polymer. Enterobacter sp. UAMI-C3 proved to be the most efficient strain in the degradation of expanded PS with a weight decrease of 0.85% in 30 days with laccase activity at 9.8 x 10-3 U/mL.

Release of millions of micro(nano)plastic fragments from photooxidation of disposable plastic boxes

The widespread use of disposable plastic boxes is exacerbating the dangers of microplastics (MPs); however, little is known about the fragmentation behavior of MPs during aging. In this study, the dynamic evolution on the release of micro(nano)plastics and photoaging properties of two disposable plastic boxes (polypropylene (PP) and polystyrene (PS)) were investigated under light irradiation and mechanical abrasion. Results showed that the weight of PP and PS was decreased by 53 % and 100 %, respectively after 60 d of ultraviolet irradiation (UV60). Moreover, a large number of fragmented particles were produced from the combined light irradiation and abrasion, with 0.142 ± 0.006 and 0.141 ± 0.013 million micro(nano)plastics/mL particles from PP and PS boxes, respectively, and the nanometer range (<100 nm) accounted for 70.8 % and 46.8 %. The correlation model of the average size or alteration time versus carbonyl index (CI) was developed, which indicated that the fragmentation behavior was mainly related to the photooxidation, though mechanical abrasion also played a certain enhancing role. Additionally, PS was susceptible to the fragmentation and photooxidation compared to PP possibly since the phenyl ring of PS was more vulnerable to UV attack than the methyl of PP. The findings of this study clarify the dynamic fragmentation process of micro(nano)plastics of disposable plastic boxes and provide useful information to access environmental fate of MPs more holistically.

Is there a significant difference in microbiota between water and microplastic surfaces in winter? The possibility of spreading offshore into the ocean

Environmental problems caused by microplastics (MPs) are attracting global attention. The ecological risks of bacteria attached to MPs have not been studied in detail under low temperature conditions. Here, MPs in surface water were sampled in winter from the Changjiang (or Yangtze) River Estuary. The physical and chemical characteristics of the MPs were identified, and the diversity and species composition of bacteria on the surface water MPs were analyzed. Phenotypic prediction analysis was used to analyze the potential risk of bacteria in the biofilm on the surfaces of MPs. The main chemical composition in the MPs in the surface water were PP (polypropylene), PE (polyethylene), PS (polystyrene) and other light weight MPs. Sampling sites played a decisive role in the bacterial species composition. The potential plastic-degrading bacterium Acinetobacter and the potential pathogenic bacterium Pseudomonas showed significant differences across different sampling sites. Microbial communities on the surfaces of MPs in winter were not significantly different from planktonic bacteria in the water body. Phenotypic prediction results showed that bacteria on the surface of MPs had a marked capacity to form biofilms, but a low pathogenicity risk. Based on the results of biodiversity analysis and phenotypic prediction, the potential ecological risk of bacteria in biofilms on MP surfaces is lower at low temperatures. In addition, the numerical simulation results show that the possibility of bacteria attached to MPs from the Changjiang River entering the Pacific Ocean in winter is small. MPs attached bacteria in the Changjiang estuary have low ecological risk to the estuary and the Pacific Ocean in winter.

Conflicting Effects of Extreme Nanoconfinement on the Translational and Segmental Motion of Entangled Polymers

Physically confining polymers into nanoscale pores induces significant changes in their dynamics. Although different results on the effect of confinement on the dynamics of polymers have been reported, changes in the segmental mobility of polymers typically are correlated with changes in their chain mobility due to increased monomeric relaxation times. In this study, we show that translational and segmental dynamics of polymers confined in disordered packings of nanoparticles can exhibit completely opposite behavior. We monitor the capillary rise dynamics of entangled polystyrene (PS) in disordered packings of silica nanoparticles (NPs) of 7 and 27 nm diameter. The effective viscosity of PS in 27 nm $SiO_2$ NP packings, inferred based on the Lucas-Washburn equation, is significantly smaller than the bulk viscosity, and the extent of reduction in the translational motion due to confinement increases with the molecular weight of PS, reaching 4 orders of magnitude reduction for PS with a molecular weight of 4M g/mol. The glass transition temperature of entangled PS in the packings of 27 nm $SiO_2$ NPs, however, increases by 45 K, indicating significant slowdown of segmental motion. Interestingly, confinement of the polymers into packings made of 7 nm $SiO_2$ NPs results in molecular weight-independent effective viscosity. The segmental dynamics of PS in 7 nm $SiO_2$ NP packings are slowed down even further as evidenced by 65 K increase in glass transition temperature. These seemingly disparate effects are explained by the microscopic reptation-like transport controlling the translational motion and the physical confinement affecting the segmental dynamics under extreme nanoconfinement.

Conformational characteristics of regioselectively PEG/PS-grafted cellulosic bottlebrushes in solution: cross-sectional structure and main-chain stiffness

Cellulosic bottlebrushes with polystyrene (PS) and poly(ethylene glycol) (PEG) side chains at the O-6 and O-2,3 positions, respectively (PEG-PS-cellulose), were synthesized and characterized in diluted solution to reveal the second structure of heterografted bottlebrushes. The regioselectivity and degree of substitution were evaluated by 1H- and 13C-nuclear magnetic resonance spectroscopy and size-exclusion chromatography (SEC). The cross-sectional structure of PEG-PS-cellulose was evaluated from the cross-sectional radius of gyration determined by the small angle X-ray scattering technique as a function of the molecular weight of the PS side chain. As a result, PEG-PS-cellulose was found to show a core-shell-corona structure, in which PEG and PS side chains formed a homogeneous shell layer surrounding the cellulosic core and the outer segments of PS chains formed an outer corona layer. The stiffness parameter (λ−1) of the main chain was analyzed by the SEC–multiangle light scattering technique along with the Kratky-Porod wormlike chain model. In comparison with a previously reported cellulosic bottlebrush with a PS side chain at the O-6 position, it is suggested that the observed increase in λ−1 with increasing molecular weight of PS is mainly derived from the interaction among PS side chains located in an outer layer, while the PEG side chains at the O-2,3 position effectively suppressed the internal rotation of the cellulosic main chain. Cellulosic bottlebrush regioselectively possessing poly(ethylene glycol) (PEG) and polystyrene (PS) side chains (PEG-PS-cellulose) was synthesized, and its secondary structure in dilute solution was investigated with SAXS and SEC-MALS. The relationship between the cross-sectional mean squared radius of gyration (〈Sc2〉) and molecular weight of PS chain (MWPS) showed that PEG-PS-cellulose has a core-shell-corona structure in cross section. The dependency of main-chain stiffness (λ−1) on MWPS was discussed on the basis of the interactions of the PS and PEG side chains as well as the restricted rotation of the cellulosic main chain.

Smaller Is Not Always Better: Large-Size Hollow Polydopamine Particles Act as an Efficient Sun Protection Factor Booster for Sunscreens.

Ultraviolet (UV) radiation from the sun is the most harmful factor for human skin, causing sunburn, melasma, freckles, blemishes, and skin cancer. Sunscreens play a key role in blocking UV absorption on the skin. This study focused on the synthesis of hollow polydopamine (h-PDA), whose structure mimics the naturally occurring melanin in humans, for use as an active ingredient in sunscreens by means of a hard-template-based method. The reactions involve a spontaneous polymerization of a dopamine monomer in the presence of tris(hydroxymethyl)aminomethane (Tris) as a catalyst onto a polystyrene (PS) core template. Different sizes of the PS core (about 280 and 450 nm) and weight ratios of PS/DA were applied to elucidate the effect of the hollow diameter and thickness of the shell on the morphology and absorbance of the synthesized h-PDA. From UV absorption results, it was observed that the synthesized h-PDA particles with a larger core diameter (about 450 nm) and a thin shell thickness (about 57 nm) presented high UV absorption. We found that the structure of the synthesized h-PDA is mainly composed of a mixture of 5,6-dihydroxyindole and indole-5,6-quinone precursors covalently linked together. After blending the h-PDA particles with the base cream, the formulation containing h-PDA with a large void diameter of about 450 nm showed the highest sun protection factor (SPF) of up to 7.43, which is related to % booster of 234.7%. In addition, the h-PDA particles exhibited biocompatibility and cellular uptake in keratinocyte HaCaT cells after 24 h of incubation, indicating the potential to mimic natural melanin in preventing UV-induced DNA damage, which could be safely used as an alternative sunscreen.

Response of the yellow mealworm (Tenebrio molitor) gut microbiome to diet shifts during polystyrene and polyethylene biodegradation

Plastic biodegradation by mealworm is regarded as an emerging strategy for plastic disposal. In this study, the polystyrene (PS) and low density polyethylene (LDPE) degradation efficiency by yellow mealworms (Tenebrio molitor larvae) supplemented with bran and the effects of plastics on the gut core microbiome were explored to construct a circular and continuous reactor for plastic biodegradation in the future. The gut microbiome was also investigated with dietary shift to explore the relationship between specific diets and gut microbes. The bran plus plastic (7:1 ratio, w/w) co-diet contributed to the mealworm survival and growth. The formation of −C˭O−/−C−O− groups in the plastic-fed mealworms frass represented the oxidation process of plastic biodegradation in the mealworm gut. The changes in molecular weights (Mw, Mn and Mz) of residual PS and LDPE in mealworms frass compared with that of PS and PE feedstock confirmed the plastic depolymerization and biodegradation. Lactobacillus and Mucispirillum were significantly associated with PE + bran diet compared to bran diet and PE diet, representing the response of mealworm gut microbiome to the bran and plastic mixture was distinguished from either bran or plastics alone. The gut microbiome changed substantially with the diet shift, indicating that microbial community assembly was a stochastic process and diverse plastic-degrading bacteria might occur in the mealworm gut.

Enhancing response time of micro-patterned thermoresponsive hydrogels by incorporation of pores

Micro-patterned hydrogels have received increasing attention in various research fields that need a fine structure and advanced functions compared to bulk hydrogels. For enhancing their performance, control of the size and distribution of pores in hydrogels is crucial. In particular, for the application of thermoresponsive hydrogels to a soft actuator, the characteristics of pores play an important role in enhancing the response time. We formed a porous structure in micro-patterns of polydiethylacrylamide (PDEAM), a thermoresponsive hydrogel, and analyzed the effect of pore size on the response time of the patterned hydrogels. Micro-patterned thermoresponsive hydrogels are fabricated by photo-crosslinking PDEAM copolymerized with benzophenone photo-crosslinker and polystyrene (PS) as a porogen. Pores sufficiently smaller than patterned objects, between a few micrometers to a few tens of micrometers, are successfully formed by controlling the content and molecular weight of PS. As the size and number of pores increase, the response time is improved, and the response time for swelling and deswelling is improved by up to 52 and 43% by blending PDEAM with 50 vol% of low molecular weight PS (5 kg/mol). This simple way to form a sub-millimeter scale hydrogel structure with controlled pores can be utilized in the emerging research fields, including 3D cell scaffolds, targeted drug delivery, and soft robotics.

Preparation and characterization of nanofibrous metal-organic frameworks as efficient catalysts for the synthesis of cyclic carbonates in solvent-free conditions.

Environmental concerns, particularly global warming, represent serious threats to public health globally. Metal-organic frameworks (MOFs) are innovative materials with prominent features such as ultrahigh surface area, high porosity and tunable cavities, which make them unique materials both in adsorption of carbon dioxide and catalysis. The design of new nanocomposites by using metal-organic frameworks as building materials has received broad attention recently. Here, nanocrystals of two unique MOF structures (UiO-66 and ZIF-67) were incorporated into electrospun polyvinyl alcohol (PVA) and polystyrene (PS) fibers (noted as MOFibers) by an ex situ method, to transform non-toxic, abundant, economical and renewable CO2 gas to cyclic carbonates in a solvent-free medium. In order to improve the composites' performance, different electrospinning parameters, including applied voltage, flow rate, collection distance, PVA and PS weight fraction in solution, and MOF weight fraction relative to the polymer, were intensively investigated. The synthesized samples were characterized by multiple techniques, such as FTIR, XRD, SEM, UV-vis and TGA, as well as N2 and CO2 adsorption measurement. It was found that all of the composites show properties combining the advantages of MOFs and polymers, such as thermal, chemical, and mechanical stability, structural flexibility, lightweight, adsorption performance and catalytic properties. Additionally, all systems were environment-friendly and the PVA/MOF fibers were easily separated and recycled for consecutive cycles.

Biodegradation and disintegration of expanded polystyrene by land snails Achatina fulica

Despite increasing evidence of widespread plastic pollution in soil, it remains largely unknown about the fate of plastic influenced by soil animals. In this study, ingestion and biodegradation capability of expanded polystyrene (PS) foam was investigated in a globally distributed soil invertebrate, Achatina fulica. After 4-week exposure, 18.5 ± 2.9 mg polystyrene was ingested per snail, and egested microplastics (1.343 ± 0.625 mm) in feces with significant mass loss of mean 30.7%. Gel permeation chromatography analysis indicated a significant increase in weight-average molecular weight (Mw) and number-average molecular weight (Mn) of feces-residual PS, indicating limited extent depolymerization. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance confirmed the formation of functional groups of oxidized intermediates. Suppression of gut microbes with oxytetracycline did not affect the depolymerization, indicating the independence of gut microbes. High-throughput sequencing analysis revealed significant shifts in the gut microbiome after ingestion of PS, with an increase of family Enterobacteriaceae, Sphingobacteriaceae, and Aeromonadaceae, suggesting that gut microorganisms were associated with PS biodegradation. These findings suggest that plastic litter can be disintegrated into microplastics and partially biodegraded by A. fulica, which highlights the significance of soil animals for the fate of plastic and its biodegradation in soil environments.

Spatial structures formation of surface-modified nanoparticles in polymer nanocomposite thin films

The spatial structures of polystyrene (PS) nanocomposite thin films containing oleic acid-modified nanoparticles were investigated. A layer of the nanoparticles was formed at the surface of the thin film under all conditions in this work. Aggregates of the nanoparticles were formed simultaneously in the film when the concentration of the nanoparticles was relatively high. The effects of the evaporation rate and the molecular weight of PS on the spatial structures of the nanoparticles in the thin films were discussed using the ratio of the time constants for phase separation (diffusion) of the nanoparticles, gravitational sedimentation of the aggregates and drying. As the ratio of the diffusion time to the drying time increased, the thickness of the nanoparticle layer and the diameter of the nanoparticle aggregates decreased, and then reached a constant value. When the ratio of the sedimentation time to the drying time was high, the relatively small aggregates were dispersed throughout the thin film since the effect of gravitational sedimentation was small.

Low-Frequency Vibrational Motions of Polystyrene in Carbon Tetrachloride: Comparison with Model Monomer and Dependence on Concentration and Molecular Weight

In this study, the low-frequency vibrational dynamics of polystyrene (PS) in CCl4 was investigated by femtosecond Raman-induced Kerr effect spectroscopy. Ethylbenzene (EBz) was also investigated as a model monomer of the polymer to elucidate the unique dynamical features of PS in solution. The broadened low-frequency spectrum of the PS/CCl4 in the frequency region below 150 cm-1 is significantly different from that of the EBz/CCl4. Difference spectra between the PS or EBz solutions and neat CCl4, normalized to an internal vibrational mode of CCl4, clearly show a much lower spectral intensity for the PS/CCl4 than the EBz/CCl4 in the low-frequency region below ca. 20 cm-1. This indicates that translational motions are suppressed in the PS/CCl4 compared to the EBz/CCl4. Moreover, the high-frequency motion at ca. 70 cm-1, mainly due to phenyl ring librations, occurs at higher frequency in PS (78 cm-1) than EBz (65 cm-1). In addition, the results of concentration-dependent experiments show that the first moment (M1) of the low-frequency difference spectra of both PS/CCl4 and EBz/CCl4 is almost independent of the concentration. The molecular weight dependence of the low-frequency spectrum in the PS/CCl4 shows that the M1 value of the low-frequency spectral band of PS shifts to higher frequencies when the molecular weight of PS increases up to Mw = ∼1000, which corresponds approximately to the decamer, and then remains constant upon further increasing the molecular weight.

Phase-equilibrium measurement of a carbon dioxide/toluene/polystyrene ternary system using laser turbidimetry

The phase behavior of a carbon dioxide (CO2)/toluene (Tol)/polystyrene (PS) ternary system was measured. The measurements were performed using a synthetic method combined with a reflected light intensity measurement. The bubble points were determined by visual observation, and the cloud points were determined from the change in the reflected light intensity. The phase boundaries were measured at temperatures ranging from 313.2 K to 373.2 K and CO2 weight fractions ranging from 0.10 to 0.41. The homogeneous phase area decreased when the molecular weight of PS and/or the ratio of PS to Tol increased. It was found that the phase behavior of ternary systems, especially the liquid-liquid phase separation behavior, was altered by a change in the mutual solubility between the three components.