PS Volume Fraction Research Articles

Influence of fiber types on the properties of the artificial cold-bonded lightweight aggregates

Abstract The cold-bonded pelletizing method is often employed in aggregate production since it uses less energy and helps reduce issues with gas emissions, contributing to economic and environmental benefits. In this study, fly ash was chosen as the raw material and used to partially replace cement in manufacturing artificial aggregate. Three types of fibers (polypropylene, polystyrene, and glass fiber) in different volume fractions were used to investigate their effect on the properties of the artificial cold-bonded lightweight aggregate. After the manufacturing process, aggregates were cured with a 28-day water curing. Their specific gravity, water absorption, density, impact value, and crushing value were tested to analyze the properties of the cold-bonded artificial aggregate. Results show that adding various volume fractions of PS, glass, and PP fibers during pelletization caused a more stable generation of aggregates with enhanced mechanical and physical properties.

Dynamics of High Molecular Weight Cylindrical and Lamellar Block Copolymers with X‐ray Photon Correlation Spectroscopy

AbstractThe structure and dynamics of polystyrene (PS)‐b‐poly(ethylene oxide) block copolymers (BCPs) are studied. The BCPs exhibit microphase‐separated cylindrical and lamellar morphologies. Structural dynamics are measured with X‐ray photon correlation spectroscopy in the small‐angle regime. Morphologies and domain sizes are evaluated using small‐angle X‐ray scattering (SAXS), scanning electron microscopy, and atomic force microscopy. Different solvent processing conditions are investigated. Grain sizes evaluated using SAXS are found to depend on processing only for the rubbery majority BCP. The structural relaxation times are examined as a function of PS volume fraction, temperature, morphology, and structural sizes. Well above the glass transition temperature (Tg) of PS, all samples exhibit stretched autocorrelation decays and diffusive dynamics. Near Tg of PS, the dynamics of all samples are anomalous with compressed autocorrelation decays and hyperdiffusive dynamics. This transition occurs at 153 °C or 1.13 Tg of PS. In the diffusive regime (at high temperature), structural relaxation times are dependent on the processing method. Near PS Tg (at low temperature), structural relaxation times scale with the PS volume fraction. Structural relaxation times do not correlate with grain size, indicating that the out‐of‐equilibrium state of PS dominates the structural dynamics of these strongly phase‐segregated BCPs.

Fabrication of Ordered Porous Polyimide Films Templated by (AB)m Type of Diblock Copolymer.

Ordered porous polyimide films were fabricated from (AB)m type of diblock copolymer polyimide-b-polystyrene (PI-b-PS). An increase in PS volume fraction (f VPS) is beneficial to decrease the relative dielectric constants and water contact angles of the obtained porous PI films: the relative dielectric constant decreases to 1.89 and water contact angle decreases to 43° when f VPS is 0.36, indicating porous PI films can be used as low-κ material and have good wettability. The solvent uptake of the porous PI films increases with increasing f VPS. A net-like morphology appears when f VPS reaches 0.36. The net-like porous PI film reaches equilibrium uptake of water within approximately 2.5 h, with a final equilibrium uptake ratio of 17.5%, and reaches equilibrium uptake of toluene within approximately 8 h, with a final equilibrium uptake ratio of 15.4%, displaying the highest and fastest solvent uptake compared with other microstructured porous PI films, which is ascribed to the specific characteristic of the interconnecting porous channels derived from the self-assembly of PI-b-PS with f VPS 0.36. Introducing thermally degradable segments to PI-based block copolymer is an effective method to prepare porous PI films and can enhance some of their properties.

A convenient and large-scale fabrication of ordered micron-sized porous polyimide film

Ordered micron-sized macroporous PI films were fabricated using PAA-b-PS with a specific volume fraction of PS, in which the synergistic effect of hydrogen bonds and π–π interactions of the main chain in PAA-b-PS plays a pivotal role.

Exploiting Self-assembly of Block Copolymers to Fabricate Nanocomposite Thin Films with Controlled Morphology at Nanoscale

As the advantageous properties of nanoparticles (NPs) often emerge only when appropriate coupling and exchange phenomena between the NPs can take place, the control of the inter-particle distance, regular ordering, and location of the nanoparticles onto solid supports is a critical issue. A robust method to control the spatial organization of NPs onto solid supports, based on the use of self-assembling di-block copolymers (BCPs) as structure-guiding material, is reported. Two different polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) BCPs, characterized by a different PS volume fraction, were used as matrices for the fabrication of nanocomposite thin films with cylindrical and lamellar morphologies controlled at the nanoscale. Selective inclusion of surface functionalized gold (Au) and zinc oxide (ZnO) NPs of appropriate size in the PS nanodomains was achieved from dispersions of the BCPs and NPs in a common solvent. The orientation of the BCPs cylinder and lamellar nanodomains in spin-coated thin films was controlled by solvent and thermal annealing protocols, coupled with techniques of surface neutralization.

Printed Thin Diblock Copolymer Films with Dense Magnetic Nanostructure

Thin hybrid films with dense magnetic structures for sensor applications are printed using diblock copolymer (DBC) templating magnetic nanoparticles (MNPs). To achieve a high-density magnetic structure, the printing ink is prepared by mixing polystyrene- block-poly(methyl methacrylate) (PS- b-PMMA) with a large PS volume fraction and PS selective MNPs. Solvent vapor annealing is applied to generate a parallel cylindrical film morphology (with respect to the substrate), in which the MNP-residing PS domains are well separated by the PMMA matrix, and thus, the formation of large MNP agglomerates is avoided. Moreover, the morphologies of the printed thin films are determined as a function of the MNP concentration with real and reciprocal space characterization techniques. The PS domains are found to be saturated with MNPs at 1 wt %, at which the structural order of the hybrid films reaches a maximum within the studied range of MNP concentration. As a beneficial aspect, the MNP loading improves the morphological order of the thin DBC films. The dense magnetic structure endows the thin films with a faster superparamagnetic responsive behavior, as compared to thick films where identical MNPs are used, but dispersed inside the minority domains of the DBC.

Janus particles with tunable shapes prepared by asymmetric bottlebrush block copolymers

Janus particles were prepared resulting from microphase separation between brush blocks with PS and PDMS side chains using asymmetric BBCPs. Through tuning the volume fraction of PS and the MW of the BBCP, the morphologies of Janus particles can be controlled.

Transition of liquid crystal anchoring at the microdomain interface observed for main-chain nematic polyester segments of block copolymers

The microdomain structures and liquid crystal (LC) orientations of ABA triblock copolymers comprising poly(styrene) (PS) A blocks and a main-chain LC polyester B block were examined via small-angle X-ray scattering and electron microscopy in the form of fibrous samples. The LC polyester blocks were segregated from the PS blocks to form a nematic LC in the lamellar microdomains of the copolymers, with the PS volume fraction (φ) ranging from 13 to 38%. As φ decreased, the nematic director was always positioned along the fiber axis, but the microdomain lamellae changed their direction from parallel to perpendicular with respect to the fiber axis and began to adopt a zigzag configuration. These lamellar orientations were attributed to the main-chain nematic LC segments lying along the microdomain interface but extending perpendicularly to the interface as the occupying interface area was reduced. The lamellar microdomains parallel to the nematic director increased the LC and PS lamellar thicknesses reversibly by 48 and 16%, respectively, at the same time as the isotropization of the nematic LC. Such changes in lamellar thickness suggest that both the PS and LC segments were elongated along the direction of the LC orientation.

Morphological Behavior of A2B Block Copolymers in Thin Films

Copolymer composed of two poly(2-vinylpyridine) blocks and one polystyrene block ((P2VP)2–PS) with a PS volume fraction (ΦPS) of 0.44 was synthesized, and their morphologies in bulk and thin films were compared to linear block copolymers (BCPs) having a similar ΦPS (PS-b-P2VP). For the symmetric diblock copolymer, a lamellar morphology was observed after thermal annealing, as was expected. However, (P2VP)2–PS in the bulk showed a hexagonally packed cylindrical microdomain morphology with PS forming the cylindrical microdomains in a P2VP matrix. In thin films, after solvent annealing in the vapors of a chloroform/ethanol mixture, the cylindrical microdomain morphology was retained and the microdomains were oriented parallel to the substrate surface. With the addition of ethanol into the annealing solvent, the morphology of (P2VP)2–PS was transformed from a bicontinuous morphology to one with cylindrical microdomains of PS oriented parallel to the substrate. The lamellar microdomain of the PS-b-P2VP copolym...

Nanopatterning via Self-Assembly of a Lamellar-Forming Polystyrene-block-Poly(dimethylsiloxane) Diblock Copolymer on Topographical Substrates Fabricated by Nanoimprint Lithography.

The self-assembly of a lamellar-forming polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer (DBCP) was studied herein for surface nanopatterning. The DBCP was synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane (D3). The number average molecular weight (Mn), polydispersity index (Mw/Mn) and PS volume fraction (φps) of the DBCP were MnPS = 23.0 kg mol−1, MnPDMS = 15.0 kg mol−1, Mw/Mn = 1.06 and φps = 0.6. Thin films of the DBCP were cast and solvent annealed on topographically patterned polyhedral oligomeric silsesquioxane (POSS) substrates. The lamellae repeat distance or pitch (λL) and the width of the PDMS features (dL) are ~35 nm and ~17 nm, respectively, as determined by SEM. The chemistry of the POSS substrates was tuned, and the effects on the self-assembly of the DBCP noted. The PDMS nanopatterns were used as etching mask in order to transfer the DBCP pattern to underlying silicon substrate by a complex plasma etch process yielding sub-15 nm silicon features.

Shape-Tunable Biphasic Janus Particles as pH-Responsive Switchable Surfactants

We report a simple and robust strategy to prepare pH-responsive biphasic Janus particles composed of polystyrene/poly(2-vinylpyridine) (PS/P2VP) homopolymers that are able to control the reversible formation, breakage, and switching of Pickering emulsions depending on their geometry- and pH-dependent hydrophilic–lipophilic balance. The chemical stability of these PS/P2VP Janus particles was tuned through the incorporation of cross-linkable benzophenone units along the backbone of the homopolymers. By employing these stabilized particles as emulsifiers for toluene and water, a facile transformation of emulsion types (i.e., from toluene-in-water to water-in-toluene emulsions) was achieved by adjusting the pH of the aqueous phase. More importantly, this pH-dependent switching behavior and associated stability of the emulsions could be actively controlled by adjusting the relative size ratio of PS to P2VP. When the PS volume fraction (ϕPS) was between 0.33 and 0.67, a wide range tuning of emulsion phase inclu...

Morphology and linear rheology of comb-like copolymer melts with high grafting density: Ⅰ. PVSt-g-(PS-b-PE) comb-like block copolymers

Comb-like block copolymers PVSt-g-(PS-b-PE) (PVSt: poly(4-(vinylpheneyl)-1-butene)) with high grafting density were successfully synthesized based on “Graft onto” strategy. The grafting density of PVSt-g-(PS-b-PE) was 35–39% (branch chain number per 100 repeating units of the backbone). By introducing PS block in the side chains, the total PS volume fraction in the copolymers could be adjusted to explore the influence of the volume fraction of total PS component (PVSt backbone + PS block) on morphology (at melt state) and linear rheological response of the copolymers. Compared to PSVS-g-PE copolymers with similar grafting density in the previous work (Macromolecules, 2015, 48, 7640), PVSt-g-(PS-b-PE) copolymers showed a microphase-separated structure at the melt state. The volume fraction of total PS in the comb-like block copolymers determined the type of morphology. When the volume fraction of PS changed from 11% to 55%, the microphase-separated structure changed from poor-order spherical structure to poor-order lamellar morphology, and all the samples of PVSt-g-(PS-b-PE) showed a typical rheological behavior of network-like structure. At the same time, the G′ curve and G″ curve were more away from each other at intermediate frequency with the increasing of PS content. The reason resulted from the formation of different microphase-separated structure types in the PVSt-g-(PS-b-PE).

Precise preparation, microstructures, micromechanical behavior and morphology of well-defined PS-b-PS/Bd-b-PS triblock copolymers via RAFT seeded miniemulsion polymerization

Reversible addition-fragmentation transfer (RAFT) miniemulsion polymerization was one of the prominent controlled/“living” radical polymerization (CLRP) techniques with environmental friendly, energy saving and high efficient characteristics. The well-defined Polystyrene-block-Polystyrene/butadiene-block-Polystyrene (PS-b-PS/Bd-b-PS) triblock copolymers with uniform, tapered or gradient and pure polybutadiene compositions distribution in the middle block were precisely controllably prepared via RAFT seeded miniemulsion polymerization, in which number-average molecular weigh (Mn) t was from 60.00 ~ 82.00 kg/mol with narrow distribution and substantially the similar PS volume fraction about 0.64 ~ 0.65 and 0.80. The copolymers microstructures were characterized by gel permeation chromatography (GPC), fourier translation infrared spectroscopy (FT-IR) and hydrogen nuclear magnetic resonance spectroscopy (1H-NMR). The GPC traces indicated that type curves remained nearly symmetrical, unimodal molecular weight distribution in the whole PS-b-PS/Bd-b-PS triblock copolymers preparation. FT-IR and 1H-NMR results showed that microstructures of the copolymers were mainly 1, 4-trans butadiene with about 10% content of 1, 2-units. Microphase morphology, micromechanical behavior and thermal property of the copolymers were identified by transmission electron microscopy (TEM), tensile testing and differential scanning calorimetry (DSC). The fracture mechanisms of thin layer yielding and cavitation deformation were corresponding to the lamellar and cylindrical morphology in micromechanical behaviors, respectively. It was indicated that microphase morphologies, micromechanical properties and thermal properties were identical to their molecular microstructures, composition profiles distribution, toughening mechanisms and microphase separation strength.

FdddStructure in Polystyrene-block-polyisoprene Diblock Copolymer/Polystyrene Homopolymer Blends

We have induced Fddd structure in polystyrene-block-polyisoprene diblock copolymer (SI) which does not have Fddd phase by adding polystyrene (hPS) homopolymer. We prepared the SI/hPS blend samples in the range of 0.627 < ϕPI < 0.646 and investigated the phase boundary of Fddd phase by using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), where ϕPI is volume fraction of polyisoprene (PI) in SI/hPS. We found the Fddd phase as an equilibrium phase in the range of 0.631 ≤ ϕPI ≤ 0.641 and 26.6 < χN < 30.7, where χ and N are respectively the Flory–Huggins interaction parameter between PS and PI and polymerization index of the SI. The Fddd phase boundary in the SI/hPS is similar to that in the neat SI block copolymer since the effect of the addition of the hPS with the low molecular weight on the phase diagram corresponds to that of the same change of PS volume fraction in the neat block copolymer.

Thermoreversible Order−Order Transition of a Triblock Copolymer Containing a Mesogen‐Jacketed Liquid Crystalline Polymer with a Re‐Entrant Phase Behavior

Poly{2,5‐bis[(4‐butoxyphenyl)‐oxycarbonyl]styrene} (PBPCS) with a re‐entrant phase behavior is used to synthesize a new kind of ABC triblock copolymers (triBCPs), poly(dimethylsiloxane)‐b‐polystyrene‐b‐PBPCS (PDMS‐b‐PS‐b‐PBPCS, DSB). Two well‐defined triBCPs D120S100B50 and D120S100B120 with different molecular weights (MWs) and narrow MW distributions are synthesized by sequential atom transfer radical polymerization. The volume fractions of PDMS, PS, and PBPCS in D120S100B50 are 0.24, 0.26, and 0.50, respectively, while the values in D120S100B120 are 0.14, 0.16, and 0.70, respectively. At low temperatures, PBPCS is amorphous. Both samples form a core–shell hexagonally packed cylindrical (CSH) morphology. At high temperatures, PBPCS in the triBCPs can form a liquid crystalline (LC) phase, the transformation of which can induce an order−order transition (OOT) of D120S100B120. The nanostructure changes from a CSH structure to a three‐phase‐four‐layer lamellar structure, and the transition is thermoreversible. The sequence of the OOT is opposite to that of a coil−coil−coil triBCP. The unusual LC behavior of PBPCS plays an important role on the thermoreversible morphological transition of the triBCP. image

The change in the environment of the immiscible block stabilizes an unexpected HPC phase in a cured block copolymer/epoxy blend

A conventional SAXS study of ordered phases produced in cured block copolymer (BCP)/epoxy blends with different concentrations, led to the unexpected observation of an HPC (hexagonally-packed cylinders) phase for a blend containing a 55:45 volume ratio of both domains. The BCP was polystyrene (PS, Mn=28kDa)-b-poly(ethylene oxide) (PEO, Mn=11kDa), where PS is the “epoxy-phobic” block and PEO is the “epoxy-philic” block. The epoxy formulation was based on diglycidylether of bisphenol A (DGEBA) and 4,4′-methylenebis(2,6-diethylaniline) (MDEA). A fully cured blend containing 60wt% BCP, equivalent to 45% volume fraction of PS in the blend, exhibited an unexpected HPC morphology as supported by TEM images and SAXS spectra. The same techniques showed that a lamellar (L) phase was generated at low conversions in the same blend. The L to HPC transition was explained by the diffusion of epoxy–amine species out of the PS-rich phase with the increase in conversion. Order-order transitions in BCP/epoxy blends previously reported were explained by the partial phase separation of the miscible block from the epoxy solvent. These transitions go always in the sense of decreasing the interface curvature (e.g., from HPC to L). The transition reported in this study goes in the opposite sense (from L to HPC) and was generated by the change in environment of the immiscible block during polymerization.

Dinonylphenyl end-capped poly(ethylene glycol)-b-polystyrene: synthesis and its unusual crystalline and self-assembly behaviors

Block copolymers, dinonylphenyl end-capped polyethylene glycol-b-polystyrene (DNPE-PEO-b-PSs) were synthesized in a one-step atom transfer radical polymerization (ATRP) of styrene. The PEO block in the DNPE-PEO-b-PS samples (volume fraction of PS: 66.8–93.2 %) was found to be amorphous, which contrasts with DNPE-PEO precursor, traditional methoxide end-capped polyethylene glycol-b-polystyrene (PEO-b-PS) and dinonylphenyl end-capped poly-(ethylene glycol)-b-poly(fluorinated methyl methacrylate)(DNPE-PEO-b-PFMAs). Meanwhile, DNPE-PEO-b-PSs display an intriguing self-assembly behavior in solution. Block copolymer particles with mesoporous internal structures are directly formed by self-assembly of DNPE-PEO-b-PS in tetrahydrofuran/water solutions. It is proposed that DNPE end group has an important effect on the crystallization of the block copolymers as well as their self-assembly behaviors in solution.

Synthesis and self-assembly of a linear coil-coil-rod ABC triblock copolymer

An interesting order-order transition between two different complex nanostructures was observed in a new liquid crystalline linear coil-coil-rod ABC triblock copolymer (triBCP). First, the ABC triBCP, poly(dimethylsiloxane)-bpolystyrene-b-poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PDMS-b-PS-b-PMPCS), was synthesized through sequential atom transfer radical polymerization. The degrees of polymerization of PDMS, PS, and PMPCS blocks are 58, 159, and 106, and the corresponding volume fractions of PDMS, PS, and PMPCS are 0.09, 0.29, and 0.62, respectively. The phase behaviors of the PDMS-b-PS diblock copolymer precursor and the final triblock copolymer were studied by smallangle X-ray scattering, one-dimensional wide-angle X-ray scattering, and transmission electron microscopy experiments. The PDMS-b-PS precursor self-assembles into hexagonally packed cylinders with a relatively small periodic size after thermal annealing. When the triblock copolymer is annealed at a relatively low temperature (120 °C) at which the PMPCS block is in the amorphous state, the triBCP forms core-shell hexagonally packed cylinders (CSH) with a relativly large periodic size. After the triBCP is annealed above 140 °C at which the PMPCS block transforms to the liquid crystalline (LC) phase, the nanophase-separated structure transforms to a three-phase four-layer lamellar structure (LAM-3P4L). Thus, accompanied with the transition of the PMPCS blocks from the amorphous state to the LC phase, the order-order transition from CSH to LAM-3P4L occurs in the PDMS-b-PS-b-PMPCS ABC triBCP.

Co-Assembly of A–B Diblock Copolymers with B′-type Nanoparticles in Thin Films: Effect of Copolymer Composition and Nanoparticle Shape

The coassembly of A–B diblock copolymers with B′-type nanoparticles (i.e., nanoparticles that are slightly incompatible with the B domain) leads to hierarchical structures, where the block copolymer phase separates first and the nanoparticles create close-packed arrays within the B domains due to a slower, secondary phase separation process. Here we report the results of a comprehensive study, which focused on two aspects: the influence of the nanoparticle shape (spherical vs rod-like) and the effect of the volume composition of the blocks. Three polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymers featuring similar molecular weights but differing in PS volume fraction were mixed with spherical and rod-shaped poly(ethylene oxide)- (PEO-) capped CdS nanoparticles at different filling fractions and cast as thin films. Our results highlight the mutual influence between the block copolymer and the nanoparticles on the resulting morphology, demonstrating the ability to control the film morphology by the filling fraction of the nanoparticles and their tendency to localize at the film surface, and by confinement-induced nanoparticle aggregation. Most importantly, the results reveal the influence of the nanoparticle shape on the structure of the film.

Diffusion Behavior of Polystyrene/Poly(2,6-dimethyl-1,4-phenylene oxide) (PS/PPO) Nanoparticles Mixture: Diffusion Mechanism for Liquid PS and Glassy PPO

We investigated the diffusion behavior of polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) (PS/PPO) nanoparticles mixture prepared by the nanoprecipitation method. The diffusion experiments of liquid PS into the glassy PPO matrix (l-PS/g-PPO) were conducted by annealing the PS/PPO mixture at temperatures between the glass transition temperatures (Tgs) of the PS and PPO components. By tracing the Tg evolution of the PS-rich domain behind the diffusion front, we obtained the master curve of PS volume fraction during diffusion by time–temperature superposition (TTS) and studied the diffusion mechanism of the l-PS/g-PPO system based on the core–shell model. As there is ongoing debate on the diffusion mechanism for the liquid/glassy polymers interdiffusion, herein we confirm that the diffusion behavior of PS/PPO nanoparticles mixture follows the characteristics of the Fickean mechanism rather than the case II mechanism. Both of the shift factors (aT) and the diffusion coefficients in the initial (Dinitial) obey the Arrhenius equation, which yield almost the same apparent activation energy (Edf) (about 153.6 kJ/mol). As the PS/PPO nanoparticles mixture is a limited liquid supply system, both of the calorimetric and rheological measurements reveal the departure in the time scaling laws, which corresponds to the change of PS chain dynamics from the reptation type to the Rouse type during the diffusion process.