Polystyrene Chains Research Articles

Threading Polystyrene Stars: Impact of Star to POM‐POM and Barbwire Topology on Melt Rheological and Foaming Properties

AbstractPolymer topology highly impacts rheological melt and foaming properties. Grafting sidechains onto a linear polymer typically results in shear thinning and strain hardening in elongation flow. To study the influence of an increasing number of covalently connected polystyrene (PS) starsswith a linear PS chain (Mw,PS= 90 kg mol−1), low‐disperse branched polymers withsranging from one to four are synthesized. Each star contains approximately 12 sidechains with a length ofMw,a≈ 25 kg mol−1. Oscillatory shear measurements indicated that the zero‐shear viscosityη0scales withη0 ≈ atTref= 180 °C. Moreover, uniaxial elongation rheology allows determining the strain hardening factorSHF, which varies betweenSHF= 2–135, with increasings. Foaming experiments revealed that combining viscosity reduction with the improvement of stretchability promotes higher volume expansion ratios (VER= 3.21–10.41) and the formation of larger cells (D= 4.8–14.8 µm).

Nickel‐Catalyzed Reductive Homodimerization of Brominated Polystyrene Chains

AbstractA nickel‐based catalytic system leading to high yields (≈80%) of polymer chain coupling has been developed. The extent of coupling (Xc) is found to be relatively high (>75%) and consistent across a wide range of catalyst loadings (0.1 – 1.0 equivalent with respect to the chain end), comparing favorably with other chain‐end joining methods. A mechanistic cycle is proposed to occur with benzylic chain‐end radical intermediates, consistent with the addition of a nitroso radical trap substantially lowering coupling yields. The effect of the polymer chain end (Cl vs Br) and the halide associated with the nickel catalyst is also probed.

Polymer segmental dynamics near the interface of silica particles in the particle/polymer composites

We demonstrate an approach to examine the local segmental dynamics of a polymer near the interface of an inorganic filler by observing the rotational dynamics of the fluorescent probe at the chain ends of polymer brushes grafted onto the surface of the filler particles. Localization of the fluorescent probe was realized by designing and synthesizing fluorophore-tethered polystyrene (PS) brushes anchored on the surface of silica particles of controlled sizes. Fluorophore-functionalized telechelic PS with an azide functionality at the other chain end was achieved via a combination of atom transfer radical polymerization and post-polymerization modification. The azide-bearing PS chains were tethered to alkyne-functionalized particles via copper-catalyzed cycloaddition reaction. The molecular weight of the grafted polymer chains was controlled to be less than the critical entanglement molecular weight, and the chain density was controlled to be low enough so that the observed dynamics was not perturbed by the polymer brush conformation and brush-matrix polymer entanglement. The polymer dynamics near the surface of the particles at low concentrations was closely examined in the bulk film geometry by employing imaging rotational fluorescence correlation microscopy (irFCM). The observed polymer dynamics near the interface were not altered in the inorganic/polymer composite geometry when the surface did not have favorable interaction with the matrix polymer. The presented rational design of the chemical route and examination of local dynamics highlight a feasible approach to construct material systems with high complexities towards a deeper understanding of composite materials.

Poly(acrylic acid) block copolymers as stabilizers for dispersion polymerization

Dispersion polymerization stabilized with poly(acrylic acid) has been performed for decades to produce polymer particles whose surfaces are modified with pH-responsive poly(acrylic acid) moieties. To improve stabilizer efficiency, poly(acrylic acid) block copolymers, in which a poly(acrylic acid) chain is attached to the terminus of a polystyrene or PMMA chain, were used as stabilizers for the dispersion polymerization of styrene or MMA. Compared with the poly(acrylic acid) homopolymer, polystyrene-block-poly(acrylic acid) was found to improve the controllable ranges of particle size and the carboxylic-acid-group surface density of the resulting polystyrene particles. Furthermore, we also investigated the effect of heterogeneity between the polymer species of the particle core and the attached polystyrene or PMMA chains in the poly(acrylic acid) block copolymers. Finally, we also examined the applicability of polystyrene-block-poly(acrylic acid) as a stabilizer and surface modifier for the dispersion polymerization of various monomers.

H-BN Modification Using Several Hydroxylation and Grafting Methods and Their Incorporation into a PMMA/PA6 Polymer Blend

Hexagonal boron nitride (h-BN) has recently gained much attention due to its high thermal conductivity and low electrical conductivity. In this study, we proposed to evaluate the impact of the modification of h-BN for use in a polymethylmethacrylate/polyamide 6 (PMMA/PA6) polymer blend. Different methods to modify h-BN particles and improve their affinity with polymers were proposed. The modification was performed in two steps: (1) a hydroxylation step for which three different routes were used: calcination, acidic treatment, and ball milling using gallic acid; (2) a grafting step for which four different silane agents were used, carrying different molecular or macromolecular groups: the octadecyl group (Si-C18), propyl amine group (Si-NH2), polystyrene chain (Si-PS), and PMMA chain (Si-PMMA). The modified h-BN samples after hydroxylation and functionalization were characterized by FTIR and TGA. Py-GC/MS was also used to prove the successful graft with Si-C18 groups. Sedimentation tests and multiple light scattering were performed to assess the surface modification of h-BN. Granulometry and SEM observations were performed to evaluate the particle size distribution after hydroxylation. After the addition of Si-PMMA modified h-BN into a PMMA/PA6 co-continuous blend, the morphology of the polymer blend nanocomposites was characterized using SEM. The calculation of the wetting parameter based on the surface tension measurement using the liquid drop model showed that h-BN dispersed in the PA6 phase. Grafting PMMA chains onto hydroxylated h-BN particles combined with an adequate sequence mixing led to a successful localization of the grafted h-BN particles at the interface of the PMMA/PA6 blend.

A stable porous vessel for photocatalytic degradation of Azocarmine G dye

Porous nanocomposite of polystyrene (PS) is fabricated by non-solvent induced phase separation, and with the addition of ZnO nanomaterials through electrospinning, the different evaporation rates of solvent/non solvent mixture causes phase separation and improves the porosity of the fiber. The spherical particles of ZnO are uniformly distributed within the polymer chains, creating a networking effect that further restricts the motion of the PS chains and higher pores generation. The specific surface area and average pore size values were respectively 48 m2/g and 82.5 nm for the PS/ZnO with 3 wt% filler concentration, much higher than the neat polymer (23 m2/g and 61.1 nm). The PS/ZnO composite showed 95% degradation efficiency when irradiated with natural sunlight for Azocarmine G dye. This study addresses the correlation of porous structural characteristic with the sunlight driven photocatalysis as the porous sites provide active centers for the catalysis to take place. The porous structural integrity is maintained, and improved with ZnO addition and promising catalysis efficiency is achieved. Moreover, the ZnO imparts excellent antibacterial activity against S. aureus bacteria and the PS/ZnO fibers show good functional and structural stability.

Alcohol-Stable Perovskite Nanocrystals and Their In Situ Capsulation with Polystyrene.

In recent years, lead halide perovskite nanocrystals (PNCs) have presented potential scalable applications in all fields due to their outstanding properties. However, most commonly used PNCs capped with oleic acid (OA) and oleylamine (OAm) suffer from bad stability in polar solutions and thus require various surface protections with organic or inorganic materials. Encapsulation with highly hydrophobic polystyrene (PS) is one of the most efficient ways to protect PNCs; however, the presently used swelling-shrinking strategy faces several challenges, such as weak interaction between PS chains and the surface ligands in nonpolar media causing a low encapsulation efficiency, and serious aggregation of PS particles during the shrinkage process leading to very different particle sizes. Herein, alcohol-stable polyacrylic acid-capped CsPbBr3 PNCs (i.e., PAA-PNCs) are first synthesized and then in situ encapsulated with PS shells by polymerizing styrene monomer on the PNC surfaces in a polar organic solvent (e.g., ethanol). The in situ PS-encapsulated PAA-PNCs (i.e., PAA-PNCs@iPS) exhibit outstanding monodispersity, remarkable water, heat, and UV stability, high fluorescence activity, and color purity. The unique synthesis strategy and good performances of PAA-PNCs@iPS will boost the applications of PNCs in LEDs, biological imaging, and chemosensing.

Study on the mechanism of graft polymerization and sulfonation of proton exchange membranes for fuel cell

Poly (styrenesulfonic acid)-grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membrane (ETFE-PEM) applied for fuel cells was prepared by radiation induced-grafting using gamma-ray from 60Co source based on three steps (i) irradiation, (ii) polystyrene-graftedpoly(ethylene-alt-tetrafluoroethylene) (PS-g-ETFE), and (iii) sulfonation (ETFE-PEM). Mechanism of grafting and sulfonation of ETFE-PEM with grafting degree of 22% and sulfonation degree of 93% was revealed by solid 13C nuclear magnetic resonance (solid 13C NMR), Fourier transform infrared spectroscopy (FT-IR), and field emission scanning electron microscopy (FE-SEM). The obtained results indicated that the styrene was grafted on the matrix of ETFE polymer by the π bond-breaking reaction which could be attributed to free radicals and formed the polystyrene chain at the surfaces of crystalline phases. The styrene migrated deep into the membrane due to the concentration gradient. The grafting reactions occurred at sites of C-H and C-F in the ETFE backbone but dominantly at the C-F sites while the sulfonation took place at the para position of polystyrene. The signatures related to side (secondary) reactions and by-products were not observed in the spectra indicating that the graft polymerization and sulfonation are well-controlled.

ABC-Type, Bola-Form Giant Surfactants: Synthesis and Self-Assembly.

Due to the fast phase separation kinetics and small feature size, the self-assembly of giant molecules has attracted lots of attention. However, there is not much study on multicomponent giant surfactants. In this work, through a modular synthetic strategy, different polyhedral oligomeric silsesquioxane (POSS)-based molecular nanoparticles are installed with diverse functionalities (hydrophobic octavinyl POSS (VPOSS), hydrophilic dihydroxyl-functionalized POSS (DPOSS), and omniphobic perfluoroalkyl-chain-functionalized POSS (FPOSS)) on the ends of one polystyrene (PS) chain to build up a series of triblock bola-form giant surfactants denoted as XPOSS-PSn -FPOSS (X represents V or D). The target molecules are prepared by a combination of atom transfer radical polymerization (ATRP), esterification, as well as Cu(I)-catalyzed azide-alkyne cycloaddition(CuAAC) and thiol-ene "click" reactions. These macromolecules are thoroughly characterized by combined technologies including nuclear magnetic resonance(NMR), size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. It is revealed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) that VPOSS-PSn -FPOSS adopts a two-phase separation scenario where VPOSS and POSS are segregated in one phase. DPOSS-PSn -FPOSS with a third hydrophilic DPOSS shows a three-phase separation scenario, where highly ordered phase structures are difficult to develop owing to the competition of mutual phase separation processes and may be trapped in kinetically metastable states.

Silica/polystyrene bipod-like submicron colloids synthesized by seed-growth dispersion polymerisation as precursors for two-patch silica particles

We report the synthesis at the gram scale of spherical silica particles bearing two organic patches made of grafted polystyrene chains at their poles. The patchy character of the particles is evidenced by combining transmission electron microscopy analysis and electron energy-loss spectroscopy. The multi-stage synthesis is based on the fabrication of silica/polystyrene bipods by dispersion polymerisation followed by the selective dissolution of the polymeric nodules, and leads to about 70% pure batches. The morphological purity is increased up to 98% by flow cytometry experiments. The polyethylenimine used as a stabiliser in the polymerisation step seems to play an important role in the detection of patches since the latter proved unsuccessful for particles obtained in the presence of polyvinylpyrrolidone.

Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

Construction of Polymer-Decorated Fe3O4@Catechol-formaldehyde Resin Amphiphilic Janus Nanospheres for Catalytic Applications

Janus particles are widely used as multifunctional materials for catalytic reactions due to their controllable asymmetry and stability efficiency of the interface structure. Herein, we propose a simple approach to design an amphiphilic “hairy” Janus nanocatalyst, which is composed of Fe3O4@catechol-formaldehyde resin (CFR) core–shell microspheres with different hydrophilic–hydrophobic polymer chains grafted on opposite sides of the microsphere and the catalytically active metal particles directly supported on the hydrophilic polymer chains. Amphiphilic Janus nanospheres (200–300 nm) with hydrophilic poly (N-isopropylacrylamide) (PNIPAM) and hydrophobic polystyrene (PSt) chains are synthesized by Pickering emulsion and mussel-inspired methods, followed by in situ reduction of Pd nanoparticles (Pd NPs) loaded onto the hydrophilic polymer chain side to form a Janus-structured Pd@PNIPAM-S-Fe3O4@CFR-S-PSt nanocatalyst. The amphiphilic Janus nanospheres have a good effect on the stability of the emulsion. Due to its special structural composition, the constructed Janus nanocatalyst exhibits excellent catalytic reduction performance for dyes and nitroaromatic compounds in both water and emulsion phases. Because of the existence of Fe3O4, the catalyst is easy to be separated and recovered, which augments the catalytic reaction cycle. In addition, the presence of temperature-sensitive PNIPAM polymer chains also enables the Janus nanocatalyst to display controllable temperature-responsive behaviors in stabilizing emulsions and emulsion catalysis. The as-prepared Janus nanomaterials with a variety of functions and properties possess potential for application in catalysis and biological and environmental areas.

Synthesis of zinc porphyrin complex for improving mechanical, UV-resistance, thermal stability and fire safety properties of polystyrene

Polystyrene (PS) is one of the most commonly used general plastics. Nonetheless, PS is greatly limited by its inherent disadvantages such as high flammability, low stability and brittleness. To address these issues, 5,10,15,20-tetrakis(4-bromophenyl) porphyrin (TBPP) and zinc 5,10,15,20-tetrakis(4-bromophenyl) porphyrin (Zn-TBPP) were synthesized as multifunctional additives for fabricating high-performance PS composites. Both TBPP and Zn-TBPP showed high thermal stability and excellent UV-absorption, which significantly enhanced the UV-resistance of PS without sacrificing mechanical property after 100 h UV-aging. The addition of 5 wt% Zn-TBPP led to the remarkable improvement of thermal stability of PS (41 °C and 79 °C increases in the thermal decomposition temperature at 5 wt% mass loss under N2 and air, respectively). Moreover, contributed from the strong π-π interaction between porphyrins and PS chains, the mechanical properties of PS were enhanced when 5 wt% Zn-TBPP was added into PS (11.1% increase in tensile strength and 96.6% increase in elongation at break). Furthermore, compared to TBPP/PS, Zn-TBPP/PS exhibited an improved flame retardant performance with 26.0%, 14.4% and 31.5% reduction of peak heat release rate, peak CO and CO2 production respectively, indicating the catalytic flame retardant effect from zinc element.

Synthesis and characterization of n-type semiconducting graft copolymers with polystyrene side chains

In this study, we synthesized and evaluated graft copolymers with polystyrene (PSt) as side chains on poly {[N,N´-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′ -bithiophene)} [P(NDI2OD-T2)], which is a typical n-type semiconducting polymer applied to in organic photovoltaics due to its intense optical absorption for the visible light, and high electron affinity. A well-controlled structure was confirmed by 1H-NMR analysis. It was found that enhanced electron mobilities in graft copolymer films were observed compared with the homopolymer. In order to clarify the role of PSt chains and the origins of the enhanced mobility, UV–vis absorption, electrochemical, morphological and thermal characteristics, and crystalline nature were investigated. As the results, it is suggested that the improved mobilities were attributed to the enhanced growth of π–π stacks, and increased crystallinity induced by PSt graft chains.

Engineering of polystyrene-supported artificial catalytic triad constructed by nanoprecipitation for efficient ester hydrolysis in water

To develop simple catalytic systems without well-defined tertiary structures is of paramount importance to perform bio-inspired chemistry but remains challenge. Here, we have developed a simple one-step strategy for preparing polystyrene-supported artificial catalytic triad (ACT) systems. Polymers containing ACTs and a polymer containing urea groups were designed and synthesized for the preparation of catalysts via nanoprecipitation. The coil-globule collapse of polystyrene chains created hydrophobic microenvironments. The catalytic performance could be regulated by altering polymer compositions. The hydrophobic microenvironments played important roles in the efficiency of polystyrene-supported artificial catalytic triads, arising from varied affinity for the hydrophobic substrates and/or regulating the local pKa of artificial catalytic triads. A postulated mechanism for ester hydrolysis over polystyrene-supported catalysts was presented. This strategy has potential applications for engineering other multifunctional, enzyme-inspired catalysts.

The synthesis of functional Janus nanosheets as compatibilizers for the immiscible polyamide 6 /polystyrene (PA6/PS): Formation of the nanosilica monolayer at the interface

The non-spherical Janus nanosheets (JNSs) have been large-scale synthesized by grafting polystyrene (PS) chains and epoxy group on the opposite sides of JNS, denoted as epoxy-silica-PS JNS. The functional JNSs are employed as compatibilizer in the immiscible polyamide 6 (PA6)/polystyrene (PS) blend. In the melt-blending process, the JNS with epoxy group can react with carboxyl (amino)-capped PA6 and in-situ form the PA6-silica-PS JNS. Owing to the amphiphilicity and Pickering effect, the JNSs can be exclusively located at the polymeric interface and assemble into the nanosilica monolayer at 0.5 wt% loading. With increasing the JNSs loading, the size of dispersed PS phase is decreased gradually and the JNSs still maintain the single layer structure at the interface. The dynamic moduli of the blends have been effectively improved for the JNSs at the interface. This report provides an extended application of Janus nanosheets to stabilize and functionalize the polymeric interface.

Self-Assembly of Nanocrystals into Ring-like Superstructures: When Shape, Size, and Material Do Not Matter.

This manuscript describes a universal method for the spontaneous self-assembly of nanostructures ranging from 2-4 nm spherical particles to ∼440 nm long anisotropic nanorods into ring-like superstructures. The nanostructures composed of Au, Pt, and Pd as surface materials were synthesized in an aqueous cetyltrimethyl ammonium bromide (CTAB) solution. The ligand exchange technique with 4-mercaptophenol was applied to replace CTAB from the surface of nanostructures with a functional thiol. The esterification reaction was carried out to covalently attach carboxy-terminated long-chain polystyrene (PS) molecules to the surface of nanostructures. The high grafting density of PS chains around nanocrystals made them highly soluble in a wide range of organic solvents. When a drop of nanostructure solution in a volatile nonpolar solvent was dried on a solid surface, the nanostructures spontaneously arranged themselves in the form of ring-like assemblies. The condensation of microscopic water droplets from the atmosphere on the surface of an evaporating solvent creates templates for the self-assembly of nanostructures into rings. We demonstrate that this self-assembly method is highly universal and can be extended to various nanostructures regardless of their shapes, sizes, and surface materials.

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.

Solvent-Induced Assembly of One-Patch Silica Nanoparticles into Robust Clusters, Wormlike Chains and Bilayers.

We report the synthesis and solvent-induced assembly of one-patch silica nanoparticles in the size range of 100–150 nm. They consisted, as a first approximation, of silica half-spheres of which the truncated face was itself concave and carried in its center a polymeric patch made of grafted polystyrene chains. The multistage synthesis led to 98% pure batches and allowed a fine control of the patch-to-particle size ratio from 0.69 to 1.54. The self-assembly was performed in equivolume mixtures of tetrahydrofuran and ethanol, making the polymeric patches sticky and ready to coalesce together. The assembly kinetics was monitored by collecting samples over time and analyzing statistically their TEM images. Small clusters, such as dimers, trimers, and tetramers, were formed initially and then evolved in part into micelles. Accordingly to previous simulation studies, more or less branched wormlike chains and planar bilayers were observed in the long term, when the patch-to-particle size ratio was high enough. We focused also on the experimental conditions that could allow preparing small clusters in a good morphology yield.

Deep-Learning Based Estimation of Dielectrophoretic Force.

The ability to accurately quantify dielectrophoretic (DEP) force is critical in the development of high-efficiency microfluidic systems. This is the first reported work that combines a textile electrode-based DEP sensing system with deep learning in order to estimate the DEP forces invoked on microparticles. We demonstrate how our deep learning model can process micrographs of pearl chains of polystyrene (PS) microbeads to estimate the DEP forces experienced. Numerous images obtained from our experiments at varying input voltages were preprocessed and used to train three deep convolutional neural networks, namely AlexNet, MobileNetV2, and VGG19. The performances of all the models was tested for their validation accuracies. Models were also tested with adversarial images to evaluate performance in terms of classification accuracy and resilience as a result of noise, image blur, and contrast changes. The results indicated that our method is robust under unfavorable real-world settings, demonstrating that it can be used for the direct estimation of dielectrophoretic force in point-of-care settings.