Random Copolymers Of Styrene Research Articles

AMPHIPHILIC BLOCK COPOLYMERS AS STABILIZERS OF SILICA AND SILICON NANOPARTICLES SYNTHESIZED IN PLASMA DISCHARGE UNDER ULTRASONIC CAVITATION

A range of tailor-made amphiphilic block copolymers of acrylic acid as a hydrophilic block and styrene as a hydrophobic block, as well as their homo- and random copolymers, were utilized for colloidal stabilization of silica and silicon nanoparticles in their hydrocarbon suspensions. Silicon-containing nanoparticles were synthesized in plasma discharge under intensive ultrasonic cavitation by decomposition of tetraethoxysilane. The influence of the molecular characteristics and architecture of the applied copolymers on the stabilization effect was examined. Random copolymers of styrene and acrylic acid were shown to provide poor stabilization effects, while diblock and triblock copolymers acted as effective suspension stabilizers. As a result of this study, the optimal molecular structure for diblock copolymers and the optimal molecular architecture for triblock copolymers were established. These findings allowed us to conduct a short reconnaissance study of the structure-dependent stabilization effects, opening prospective routes for tunable compatibilizers with stability varied as a function of composition.

Controlling self-assembling co-polymer coatings of hydrophilic polysaccharide substrates via co-polymer block length ratio

HypothesisThe degree of polymerization of amphiphilic di-block co-polymers, which can be varied with ease in computer simulations, provides a means to control self-assembling di-block co-polymer coatings on hydrophilic substrates. SimulationsWe examine self-assembly of linear amphiphilic di-block co-polymers on hydrophilic surface via dissipative particle dynamics simulations. The system models a glucose based polysaccharide surface on which random co-polymers of styrene and n-butyl acrylate, as the hydrophobic block, and starch, as the hydrophilic block, forms a film. Such setups are common in e.g. hygiene, pharmaceutical, and paper product applications. FindingsVariation of the block length ratio (35 monomers in total) reveals that all examined compositions readily coat the substrate. However, strongly asymmetric block co-polymers with short hydrophobic segments are best in wetting the surface, whereas approximately symmetric composition leads to most stable films with highest internal order and well-defined internal stratification. At intermediate asymmetries, isolated hydrophobic domains form. We map the sensitivity and stability of the assembly response for a large variety of interaction parameters. The reported response persists for a wide polymer mixing interactions range, providing general means to tune surface coating films and their internal structure, including compartmentalization.

Random Copolymers of Styrene with Pendant Fluorophore Moieties: Synthesis and Applications as Fluorescence Sensors for Nitroaromatics.

Five random copolymers comprising styrene and styrene with pendant fluorophore moieties, namely pyrene, naphthalene, phenanthrene, and triphenylamine, in molar ratios of 10:1, were synthesized and employed as fluorescent sensors. Their photophysical properties were investigated using absorption and emission spectral analyses in dichloromethane solution and in solid state. All copolymers possessed relative quantum yields up to 0.3 in solution and absolute quantum yields up to 0.93 in solid state, depending on their fluorophore components. Fluorescence studies showed that the emission of these copolymers is highly sensitive towards various nitroaromatic compounds, both in solution and in the vapor phase. The detection limits of these fluorophores for nitroaromatic compounds in dichloromethane solution proved to be in the range of 10−6 to 10−7 mol/L. The sensor materials for new hand-made sniffers based on these fluorophores were prepared by electrospinning and applied for the reliable detection of nitrobenzene vapors at 1 ppm in less than 5 min.

A Hidden Relaxation Process in Poly(2-vinylpyridine) Homopolymers, Copolymers, and Nanocomposites

In broadband dielectric spectroscopy experiments, we find that introducing an air gap between the top electrode and the polymer sample reduces DC conductivity substantially, allowing the study of low-frequency relaxations, whose signal would otherwise be hidden by the DC conductivity signal. An extra process slower than the α-relaxation process is observed in poly(2-vinylpyridine) (P2VP), consistent with some earlier reports. This “slower process” was studied in two heterogeneous systems to examine the interaction between the 2VP and other species to elucidate the mechanism behind the slower process signal. In a random copolymer of styrene and 2VP, the relaxation strength of the slower process relative to the α-process increases substantially at low 2VP mole fractions. Additionally, in a composite of P2VP and octa(aminophenyl) silsesquioxane (OAPS), the presence of OAPS increases both the strength and timescale of the slower process, leaving the α-relaxation process relatively unchanged. This suggests that the slower process could be caused by cooperative polymer relaxation coupled to the transport of heterogeneous components and impurities. Further studies are needed to probe the molecular-level mechanism of this slower process and its effect on interfacial properties.

RAFT solution copolymerization of styrene and 1,3-butadiene and its application as a tool for block copolymer preparation

For the first time, random copolymers of styrene (St) and 1,3-butadiene (Bd) (poly(Stn-r-Bdm), styrene butadiene rubber, SBR) were prepared via solution RAFT polymerization, that was further extended to produce poly[Xn-b-(Stm-r-Bdk)] block copolymers.

Surface PEGylation via Ultrasonic Spray Deposition for the Biofouling Mitigation of Biomedical Interfaces.

Air plasma and spray technology are common methods for surface modification. In this study, air plasma is used to generate hydroxyl groups on various material surfaces. Then random copolymers of styrene and ethylene glycol methacrylate (PS-r-PEGMA) are spray-coated to achieve coating densities ranging between 0.1 and 0.6 mg/cm2. PS50-r-PEGMA50 led to the best overall antifouling properties, while a coating density of 0.3 mg/cm2 was enough to significantly reduce biofouling. This surface modification technique enabled efficient modification of a wide range of materials and biofouling reduction by at least 75% on polymeric surfaces (polystyrene, polyvinylidene fluoride, poly(tetrafluoroethylene), polydimethylsiloxane), metallic surfaces (steel, titanium alloy), or ceramic surface (glass). Applied to the modification of well plate used for blood-typing, this antifouling modification permitted to greatly increase the signal sensitivity (×4).

Synthesis of Boratrane-pendant Random Copolymers by Side-chain Modification

Random copolymers bearing triethanolamine borate (TEAB) groups in the side chains were investigated as the first example of boratrane-containing polymers. The title polymers were synthesized via two steps of polymer reactions from random copolymers of styrene and glycidyl methacrylate. The obtained polymers exhibited superior thermal properties compared to the precursor polymers owing to the rigid cage structures of TEAB. The pendant TEAB groups were relatively stable to hydrolysis, but were quantitatively hydrolyzed in the presence of fluoride anions.

Rationalizing the Composition Dependence of Glass Transition Temperatures in Amorphous Polymer/POSS Composites.

We report that the fractions of "bonded" or "unbonded" monomers at a filler interface dictate the composition dependence of the glass transition temperatures (Tg) of polyhedral oligomeric silsesquioxane (POSS)-containing nanocomposites. Tg is arguably the single most important material property; however, predicting Tg in nanocomposites is often challenging because of confounding interfacial effects. To this end, we design a model nanocomposite to systematically study Tg of nanocomposites by leveraging the "all-interfacial" nature of ultrasmall POSS fillers loaded into random copolymers of styrene and 2-vinylpyridine (2VP). The amine-functionalized POSS forms hydrogen bonds only with 2VP, which behaves as a "bonded" monomer. The influence of copolymer composition and POSS loading on the Tg of this model composite is successfully explained by a Fox equation framework. This model also captures the Tg increase of other POSS-based polymer composites and potentially directs the future design of nanocomposite materials with tailored Tg.

Bi-continuous positively-charged PVDF membranes formed by a dual-bath procedure with bacteria killing/release ability

• Original positively-charged copolymers are synthesized. • Positively charged membranes are formed by dual-bath procedure. • Bacteria killing occurs upon contact with the membrane’s surface. • Membranes can be regenerated by washing with saline solution. • Membranes can kill while rejecting bacteria. This work reports the synthesis of a unique positively-charged copolymer obtained from the reaction between iodomethane and a random copolymer of styrene and 4-vinylpyridine. This copolymer, referred to as qP(S- r -4-VP), was fully characterized by 1 H NMR, FT-IR, XPS and GPC, and then mixed with poly(vinylidene fluoride) (PVDF) to form porous membranes able to kill bacteria upon contact. Membranes were prepared by a dual-bath procedure using methanol (10 min) and water (24 h). They exhibited typical bi-continuous structure with large pores (mean pore flow diameter: 0.2–0.45 µm) that decreased with the copolymer content, and large porosity (77%-80%). The presence of the copolymer on the membrane surface was ascertained by FT-IR. All membranes exhibited a high water contact angle in air (>140°), but hydration capacity was enhanced with the copolymer content in the membrane (from 10 mg/cm 3 for the virgin membrane up to 225 mg/cm 3 for modified membranes). The surface charge of the membrane increased with the copolymer content. Q3 membrane (containing 3 wt% copolymer) was selected as the best membrane able to kill various bacteria including Escherichia coli , Stenotrophomonas maltophilia and Staphylococcus epidermidis . Besides, washing with a saline solution of sodium citrate or sodium hexametaphosphate disturbed electrostatic and hydrophobic interactions between dead bacteria and membrane surface, making bacterial release possible. Membrane regeneration properties were also demonstrated from multiple killing/release cycles. Finally, it was shown that membranes were able to kill bacteria during a dead-end filtration process, while achieving 100% rejection. The material and membrane presented in the frame of this work could be of interest to decrease the pathogenicity of a feed during separation

Machine learning glass transition temperature of styrenic random copolymers

For styrenic random copolymers, the glass transition temperature, Tg, is an important thermophysical parameter, which is sometimes difficult to measure and determine by experiments. Approaches based on data-driven modeling provide alternative methods to predict Tg in a fast and robust way. The Gaussian process regression (GPR) model is investigated to present the statistical relationship between important quantum chemical descriptors and glass transition temperature for styrenic random copolymers. 48 samples with Tg that have been measured experimentally are explored, which range from 246 K to 426 K. The modeling approach demonstrates high accuracy and stability, and provides a novel and promising tool for efficient and low-cost estimations of copolymer Tg values.

The effect of macromolecular structure on the rheology and surface properties of amphiphilic random polystyrene-r-poly(meth)acrylate copolymers prepared by RDRP.

In this work rheological and surface properties of various random copolymers of styrene and sodium (meth)acrylate, prepared using reversible deactivation radical polymerization (RDRP), were studied. It is shown that the properties of these polymers in water solution, relevant for several applications, are affected by their chemical structure and molecular weight. Cryo-TEM images of their concentrated water solutions do not show the presence of nano-objects as micelles, however the existence of some aggregates seems to be confirmed by fluorescence measurements using pyrene as a hydrophobic probe and by surface tension measurements. Moreover, interesting results are displayed about the viscosity as well as the surface tension of these water polymer solutions, due probably to different interactions at the molecular level as suggested by fluorescence measurements.

Abrasive wear behaviour of SBR/HIPS (%35–55) polymer blends

Styrene Butadiene Rubber (SBR), being the most widely produced synthetic rubber, is a random copolymer of styrene and butadiene. The physical properties of SBR are related to the amount of styrene in copolymer chains and styrene/butadiene ratios in the copolymer. SBR is used in many areas such as tires, conveyor belts, mats, shoe soles, and heels, while Polystyrene, due to its brittle nature, its usage is limited. This study examines the abrasive wear behavior of SBR and High-Impact Polystyrene (HIP) polymer blends. For the experiments, SBR /HIPS polymer blends were prepared by adding HIPS at different ratios (35%–55%) to SBR. Using emery paper of 240 G and 500 G, wear tests were carried out on a pin-on disc wear test apparatus under the load value of 5 N, for sliding distances ranging from 25 to 100 m and at a sliding speed of 1 m s−1. Density and hardness measurements of the samples were carried out. The worn surfaces of the pin were examined using an optical microscope. It is clearly shown that the wear coefficients of polymer blends are dependent on both abrasive nature and the ratio of blends.

Synthesis and Characterization of Tunable, pH-Responsive Nanoparticle-Microgel Composites for Surface-Enhanced Raman Scattering Detection.

The synthesis of microgels with pH-tunable swelling leads to adjustable and pH-responsive substrates for surface-enhanced Raman scattering (SERS)-active nanoparticles (NPs). Sterically stabilized and cross-linked latexes were synthesized from random copolymers of styrene (S) and 2-vinylpyridine (2VP). The pH-dependent latex-to-microgel transition and swellability were tuned based on their hydrophobic-to-hydrophilic content established by the S/2VP ratio. The electrostatic loading of polystyrene/poly(2-vinylpyridine) microgels [PSxP2VPy (M)] with anions such as tetrachloroaurate (AuCl4–) and borate-capped Ag NPs was quantified. The PSxP2VPy (M) can load ∼0.3 equiv of AuCl4– and the subsequent photoreduction results in Au NP-loaded PSxP2VPy (M) with NPs located throughout the structure. Loading PSxP2VPy (M) with borate-capped Ag NPs produces PSxP2VPy (M) with NPs located on the surface of the microgels, where the Ag content is set by S/2VP. The pH-responsive SERS activity is also reported for these Ag NP-loaded microgels. Analytical enhancement factors for dissolved crystal violet are high (i.e., 109 to 1010) and are set by S/2VP. The Ag NP-loaded microgels with ∼80 wt % 2VP exhibited the most stable pH dependent response.

Chemical modification of a random copolymer of styrene, isoprene, and butadiene, prepared by anionic polymerization in solution

A promising ternary copolymer of styrene, isoprene, and butadiene, synthesized by anionic polymerization in solution, was subjected to chemical postpolymerization modification using the following branching and endcapping agents: tin and silicon tetrachlorides, N-methylpyrrolidone, and Michler’s ketone. The combined method of chemical modification of the copolymer performed in the two-stream mode (branching and endcapping), with the subsequent mixing of the streams, is the most efficient.

Mixing Thermodynamics of Ternary Block–Random Copolymers Containing a Polyethylene Block

The mixing interactions among polyolefins and other hydrocarbon polymers are of strong fundamental and practical interest, especially in mixtures involving the simplest member of the family, polyethylene (E). The present work examines the interaction energy densities between E and random copolymers of styrene and hydrogenated isoprene (SrhI), and between E and random copolymers of vinylcyclohexane and hydrogenated isoprene (VCHrhI), by measuring the order–disorder transition temperatures of near-symmetric E–SrhI and E–VCHrhI diblock–random copolymers. The E–SrhI case is of special interest, since the solubility parameters δ fall in the order δS > δE > δhI; if regular mixing were obeyed, zero interaction energy between E and SrhI could be obtained for a suitable SrhI composition. However, large positive deviations from regular mixing are observed in the E–SrhI system, while smaller but significant negative deviations are observed in the E–VCHrhI system. Notwithstanding these irregularities, a ternary mixing model (“copolymer equation”), using independently determined values of the three component interaction energy densities, provides a good representation (within ≈15%) of the experimental interaction energies.

Preparation of Styrene–Maleic Anhydride Random Copolymer by Stabilizer-Free Dispersion Polymerization

In this paper, random copolymer of styrene (St) and maleic anhydride (MAH) were prepared by stabilizer-free dispersion polymerization, with dicumyl peroxide (DCP) as initiator and ethyl butyrate as solvent at 120°C. The microsphere morphology and sequential structure of the copolymers were characterized by SEM and 13C-NMR, respectively. When the molar feed ratio of MAH to St (MAH/St) was 20/80, the overall MAH content in the copolymer was about 26% (molar) from the 13C-NMR spectrum, and the three St-centred triads SSS, MSS+SSM, and MSM were about 41%, 44%, and 15%, respectively. The variation of sequential structure of the copolymer on the changes of the polymerization time is marginal. When the feed ratio of MAH/St was less than 15/85, it was observed that the obtained copolymer could be partially dissolved in the solvent. The molecular weight of the soluble fraction was smaller than that of the precipitation part. The effects of feed ratios of MAH to St, the initiator concentrations, and monomer concentrations on polymerization yields and compositions of the copolymer were investigated in detail. The results showed that a stable dispersion of SMA random copolymer particles was formed when the feed ratio MAH/St≥20/80.

Why Ionic Amphiphilic “Block” Copolymer Can Be Non-surface Active? Comparison of Homopolymer, Block and Random Copolymers of Poly(styrenesulfonate)

Abstract Ionic amphiphilic diblock copolymers, such as polystyrene-b-poly(styrenesulfonate), show non-surface activity when some requirements are satisfied. The main origin of this unique property has been thought to be an image charge repulsion at the air/water interface. In this study, surface activity/non-activity was examined for random copolymers in addition to homopolymers. Random copolymers of styrene and styrenesulfonate were found to be surface active, while the poly(styrenesulfonate) homopolymer was slightly surface active. This observation cannot be interpreted by image charge repulsion alone since these are all polyanions and the block copolymer is mostly hydrophobic. Stable polymer micelle formation in the block copolymer system is also an essential origin of non-surface activity.

A novel shortened electrospun nanofiber modified with a ‘concentrated’ polymer brush

We report the fabrication of shortened electrospun polymer fibers with a well-defined concentrated polymer brush. We first prepared electrospun nanofibers from a random copolymer of styrene and 4-vinylbenzyl 2-bromopropionate, with number-average molecular weight Mn=105 200 and weight-average molecular weight Mw=296 700 (Mw/Mn=2.82). The fibers had a diameter of 593±74 nm and contained initiating sites for surface-initiated atom transfer radical polymerization (SI-ATRP). Then, SI-ATRP of hydrophilic styrene sodium sulfonate (SSNa) was carried out in the presence of a free initiator and the hydrophobic fibers. Gel permeation chromatography confirmed that Mn and Mw/Mn values were almost the same for free polymers and graft polymers. Mn agreed well with the theoretical prediction, and Mw/Mn was relatively low (<1.3) in all the examined cases, indicating that this polymerization proceeded in a living manner. Using the values of the graft amount measured by Fourier transform infrared spectroscopy, the surface area, and Mn, we calculated the graft density σ as 0.22 chains nm−2. This value was nearly equal to the density obtained on silicon wafers (σ=0.24 chains nm−2), which is categorized into the concentrated brush regime. Finally, we mechanically cut the fibers with a concentrated poly(SSNa) brush by a homogenizer. With increasing cutting time, the fiber length became shorter and more homogenous (11±17 μm after 3 h). The shortened fibers exhibited excellent water dispersibility owing to the hydrophilic poly(SSNa) brush layer.

A novel shortened electrospun nanofiber modified with a ‘concentrated’ polymer brush

We report the fabrication of shortened electrospun polymer fibers with a well-defined concentrated polymer brush. We first prepared electrospun nanofibers from a random copolymer of styrene and 4-vinylbenzyl 2-bromopropionate, with number-average molecular weight Mn=105 200 and weight-average molecular weight Mw=296 700 (Mw/Mn=2.82). The fibers had a diameter of 593±74 nm and contained initiating sites for surface-initiated atom transfer radical polymerization (SI-ATRP). Then, SI-ATRP of hydrophilic styrene sodium sulfonate (SSNa) was carried out in the presence of a free initiator and the hydrophobic fibers. Gel permeation chromatography confirmed that Mn and Mw/Mn values were almost the same for free polymers and graft polymers. Mn agreed well with the theoretical prediction, and Mw/Mn was relatively low (<1.3) in all the examined cases, indicating that this polymerization proceeded in a living manner. Using the values of the graft amount measured by Fourier transform infrared spectroscopy, the surface area, and Mn, we calculated the graft density σ as 0.22 chains nm−2. This value was nearly equal to the density obtained on silicon wafers (σ=0.24 chains nm−2), which is categorized into the concentrated brush regime. Finally, we mechanically cut the fibers with a concentrated poly(SSNa) brush by a homogenizer. With increasing cutting time, the fiber length became shorter and more homogenous (11±17 μm after 3 h). The shortened fibers exhibited excellent water dispersibility owing to the hydrophilic poly(SSNa) brush layer.

Organization and properties of a novel amphiphilic crown-ether dye in monolayers at the air/water interface

The novel amphiphilic benzodiaza-15-crown-5-styryl dye (BI68) forms stable insoluble monolayers at the air/water interface (collapse pressure 47 mN/m) and on aqueous subphases containing alkali metal or heavy metal salts (collapse pressures in the range of 38–45 mN/m, respectively). The organization of the dye monolayer depends on chromophore association and interactions with salts in the subphase as observed by measuring surface pressure–area and surface potential–area isotherms, reflection spectra and by Brewster angle microscopy observations. Immiscibility was found in two-component monolayers of BI68 and random copolymers of styrene with methacrylic acid and with N-vinylpyrrolidone, respectively.