Polystyrene Rods Research Articles

Poly-β-(1→6)-N-acetyl-D-glucosamine mediates surface attachment, biofilm formation, and biocide resistance in Cutibacterium acnes.

The commensal skin bacterium Cutibacterium acnes plays a role in the pathogenesis of acne vulgaris and also causes opportunistic infections of implanted medical devices due to its ability to form biofilms on biomaterial surfaces. Poly-β-(1→6)-N-acetyl-D-glucosamine (PNAG) is an extracellular polysaccharide that mediates biofilm formation and biocide resistance in a wide range of bacterial pathogens. The objective of this study was to determine whether C. acnes produces PNAG, and whether PNAG contributes to C. acnes biofilm formation and biocide resistance in vitro. PNAG was detected on the surface of C. acnes cells by fluorescence confocal microscopy using the antigen-specific human IgG1 monoclonal antibody F598. PNAG was detected in C. acnes biofilms by measuring the ability of the PNAG-specific glycosidase dispersin B to inhibit biofilm formation and sensitize biofilms to biocide killing. Monoclonal antibody F598 bound to the surface of C. acnes cells. Dispersin B inhibited attachment of C. acnes cells to polystyrene rods, inhibited biofilm formation by C. acnes in glass and polypropylene tubes, and sensitized C. acnes biofilms to killing by benzoyl peroxide and tetracycline. C. acnes produces PNAG, and PNAG contributes to C. acnes biofilm formation and biocide resistance in vitro. PNAG may play a role in C. acnes skin colonization, biocide resistance, and virulence in vivo.

The recovery of fibres from non-textile items using a static charge

This study investigated a new method of fibre recovery from non-textile items using polystyrene rods which have a static charge. A range of natural and man-made fibres were used on a number of substrates, including weapons, paper and plastic bags. The average recovery rate from all substrates was 99.1%. The effect of humidity on fibre recovery was also studied and it was found to reduce the ability of the rods to recover fibres. However this is unlikely to be an issue if recovery takes place in a forensic laboratory. It was concluded that the rods would prove a beneficial addition to the forensic laboratory as a relatively quick method of fibre recovery from non textile items where the standard method of recovery using tape lifts cannot be used.

Weakly Segregated Smectic C Lamellar Clusters in Blends of Rods and Rod−Coil Block Copolymers

The morphology arising from the self-assembly of π-conjugated poly(diethylhexyloxy-p-phenylenevinylene) rod homopolymers (PPV) and poly(diethylhexyloxy-p-phenylenevinylene)−polystyrene (PPV−PS) rod−coil block copolymers is described. Two PPV−PS block copolymers, one with low rod volume fraction (∼17%) and the other with high volume fraction (∼50%), were synthesized by convergent anionic polymerization and atom transfer radical polymerization, respectively. In the first case, given the low volume fraction of the rod block, the pure asymmetrical rod−coil block copolymer formed an isotropic homogeneous phase. However, ordered clusters of alternating PS and PPV domains with characteristic length of the order of several micrometers appeared when PPV rod homopolymers were blended to the PS−PPV diblock. Furthermore, the long-range order of the clusters as well as their volume fraction could be greatly increased when the symmetric rod−coil PPV−PS was blended to PPV homopolymer. Tomographic reconstruction from transmission electron micrographs allowed demonstrating that the clusters were organized in lamellar phase with well-defined width for both the intercalated PS and PPV domains, while wide-angle X-ray scattering showed that within the PPV domains the PPV blocks and PPV homopolymer rods were closely packed. The study of the spacing widths of the PPV and PS domains showed that clusters are organized in a smectic C configuration with large tilt angles of the rods (54°) and stretching of the coil blocks which is typical of weakly segregated block copolymers organized in a lamellar phase. The stability of the rod-to-rod interaction peak at high temperatures (190 °C), well beyond the order−disorder transition temperature of the clusters (130 °C), suggests that the (i) aggregation of the rods is mediated by π−π interactions and (ii) the clusters are thermodynamically stable structures. The energetic driving force toward the formation of these clusters is discussed in the last part of this work.

Formation of Polymer and Nanoparticle Doped Polymer Minirods by Use of the Microsegmented Flow Principle

AbstractThe microsegmented flow principle was applied for the preparation of polymer minirods. A microfluidic assembly was used to form monomer segments separated by an immiscible perfluorinated aliphatic solvent. These segments were transformed into polymer rods by thermal polymerization. Uniform‐sized polystyrene rods with various diameters and lengths were prepared in this way. The microfluidic geometry and polymerization conditions were tuned to obtain polymer rods of various lengths and diameters. Metal nanoparticle doped polystyrene polymer rods were obtained by thermal polymerization of appropriate nanoparticle/monomer mixtures. After polymerization, the polystyrene rods were colored by an azo coupling reaction.

Micellar Aggregates of Amylose-block-polystyrene Rod−Coil Block Copolymers in Water and THF

Amylose-block-polystyrenes with various block copolymer compositions were investigated in water and in THF solution. Fluorescence correlation spectroscopy, dynamic light scattering (DLS), and asymmetric flow field-flow fractionation with multiangle light scattering detection indicate the presence of unimers, oligomers, and large micellar species in THF. Up to four different species were detectable by DLS with hydrodynamic radii ranging from a few nanometers to >10 μm, indicating that the system is not in a thermodynamic equilibrium state. Collapsed aggregates were monitored on a silicon surface by scanning force microscopy and transmission electron microscopy. In water, crew-cut micelles were obtained from the same block copolymers by a single solvent approach, using elevated temperature and pressure. These crew-cut aggregates are much more uniform than the respective star aggregates in THF, and their radii scale with Rh ∝ Ncore1/4, Rh ∝ Ncorona1/6 in solution and with R ∝ Ncore1/4, R ∝ Ncorona1/2 on a silicon surface.

The Role of Chain-Length Distribution in the Formation of Solid-State Structures of Polypeptide-Based Rod−Coil Block Copolymers

The structural details of thick polymer films made from poly(Z-l-lysine)−polystyrene rod−coil block copolymers, the polydispersity index being in the range ∼1.01−1.64, were investigated by small-angle X-ray scattering techniques. All films were found to have a hexagonal-in-zigzag lamellar morphology. The zigzag superstructure, a plane lamellar structure disrupted by kinks, results from the hexagonal packing of the polydisperse set of polypeptide α-helices, fractionated according to the length of helices. The data reveal a correlation between the molecular weight distribution of the polypeptide and the interface−curvature properties of the morphology.

Physical interactions at carbon nanotube-polymer interface

Mechanical properties of carbon nanotube (CNT) reinforced polystyrene rod and CNT reinforced epoxy thin film were studied and the CNT-polymer interface in these composites was examined. Transmission and scanning electron microscopy examinations of CNT/polystyrene (PS) and CNT/epoxy composite showed that these polymers adhered well to CNT at the nanometer scale. Molecular mechanics simulations and elasticity calculations were used to quantify some of the important interfacial characteristics that critically control the performance of a composite material. In the absence of chemical bonding between CNT and the matrix, it is found that the non-bond interactions, consist of electrostatic and van der Waals forces, result in CNT-polymer interfacial shear stress (at 0 K) of about 138 and 186 MPa, respectively, for CNT/epoxy and CNT/PS. The high interfacial shear stress calculated, about an order of magnitude higher than micro fiber reinforced composites, is believed attributed to intimate contact between the two solid phases at the molecular scale. Simulations and calculations also showed that local non-uniformity of CNT and mismatch of the coefficients of thermal expansions between CNT and polymer matrix also promote the stress transfer ability between the two.

New routes to the synthesis of amylose-block-polystyrene rod-coil block copolymers.

Hybrid block copolymers amylose-block-polystyrene were synthesized by covalent attachment of maltoheptaose derivatives to end-functionalized polystyrene and subsequent enzymatic grafting from polymerization. The maltoheptaose derivatives were attached by reductive amination or hydrosilation to amino- or SiH-terminated polystyrene (synthesized by anionic polymerization), respectively. The enzymatic polymerization could be started even though the primer-modified polystyrenes were insoluble in the medium of polymerization, i.e., citrate buffer. The polymerization kinetics show an interesting dependence on the molecular weight of polystyrene due to the micellar structure of the primer in water.

Synthesis of Amylose-block-polystyrene Rod−Coil Block Copolymers

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSynthesis of Amylose-block-polystyrene Rod−Coil Block CopolymersKatja Loos and Reimund StadlerView Author Information Makromolekulare Chemie II, Universität Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany Cite this: Macromolecules 1997, 30, 24, 7641–7643Publication Date (Web):December 1, 1997Publication History Received10 July 1997Revised19 September 1997Published online1 December 1997Published inissue 1 December 1997https://doi.org/10.1021/ma971022hCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2738Altmetric-Citations72LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (77 KB) Get e-AlertsSUBJECTS:Aromatic compounds,Copolymers,Gel permeation chromatography,Hydrocarbons,Polymers Get e-Alerts

A polystyrene absorbed-dose-rate calorimeter

A simple portable calorimeter was constructed by embedding a calibrated thermistor on the axis of a polystyrene rod. This instrument was positioned on the axis of a cylindrical array of 60 Co rods. The duration of the measurements was ∼ 70 s. Absorbed dose rates of ∼ 70 Gy/min were measured to a daily precision of several tenths of a percent standard deviation. The results are in good agreement with earlier measurements made with a graphite calorimeter. An absorbed dose of 620 kGy resulted in no detectable change is thermistor sensitivity. The specific heat capacity of the polystyrene presumably increased ∼ 0.0024%/kGy. The use of a chart recorder was not necessary.

Polystyrene degradation during combustion

AbstractA novel driven‐rod, radiant pyrolysis technique has been used to study steady‐state linear regression of vertically mounted polystyrene rods degrading under high‐flux, nonflaming conditions that simulate those of combustion. With this technique a reliable, reproducible temperature‐depth profile (identical for combustion and radiant pyrolysis) for polystyrene has been obtained and used to successfully calculate the observed mass loss rate. Residues and volatiles have been analyzed. Mechanistic treatment of these results indicates that degradation of polystyrene under these rapid‐heating conditions is similar to that under more conventional slow‐heating conditions in the absence of oxygen. Oxidation is unimportant in the condensed‐phase degradation of polystyrene in this configuration. This radiant pyrolysis technique has also been used to obtain the heat of gasification of polystyrene.

Recovery of compressive strain in atactic polystyrene

Atactic polystyrene rods were compressed in an Instron universal testing machine to about 35% strain and then annealed near the glass transition temperature, T g, (100° C) in a thermal mechanical analyser. The change of length during annealing was recorded and the compressive strain was found to recover obeying second-order kinetics at least during the later part of recovery. The activation enthalpy obtained from the temperature dependence of the second-order rate constant varied from 126 to 260 kcal mol−1 as the annealing temperature decreased from 112 to 94° C. These activation enthalpies are attributed to the diffusion of positive or negative defects or configurations which annihilate during recovery. While these activation enthalpies agree with the findings of Andrews on retraction of hot-stretched filaments, they differ considerably from the spectrum obtained by Kimmel and Uhlmann using the data from Andrews' work. The reason for such differences is discussed.

Transport and solution of gases and vapors in styrene-butadiene block copolymers: Absorption and desorption of n-hexane vapor

Abstract The integral absorption and desorption of n-hexane vapor by styrene-butadiene block copolymers were studied as a function of film thickness and vapor pressure at 25°C by use of a weighing method. The morphologies of the samples were (1) polystyrene rods dispersed in a polybutadiene matrix and (2) a series of alternating lamellae of styrene and butadiene components. For both copolymer samples (1) and (2), reduced solvent weight uptake plots for films of differing thicknesses did not give a single curve ½ when plotted against the Fickian variable, t½/X, where t is time and × is film thickness, though the individual absorption and desorption curves appeared to have a Fickian shape. In certain concentration regions, the two-stage type of non-Fickian behavior was observed with copolymer film having a type (2) morphology. As expected, absorption and desorption processes in homopolybutadiene films were purely Fickian. From these results it was concluded that the segmental motions in the polybutadiene phase in the styrene-butadiene copolymers are more restricted than those in the homopolybutadiene. The initial slopes of both the reduced absorption and desorption curves increased with increasing × and appeared to approach limiting values at the limit of infinite X. Mutual diffusion coefficients D of the copoly-mer systems were calculated by assuming that absorption and desorption processes for a hypothetical film of infinite × are purely Fickian. The values of D extrapolated to zero concentration of penetrant for the copolymers were lower than the extrapolated D value for homopolybutadiene. A comparison of the equilibrium solubilities of n-hexane in the copolymers and homopolybutadiene suggests that partial mixing of component block chains occurs at the interface between the polystyrene and polybutadiene domains.

Attenuation Characteristics of Circular Dielectric Waveguide at Millimeter Wavelengths

Experiments were done to determine the practicality of using circular dielectric waveguide for a low-loss transmission line at millimeter wavelengths. The lowest order mode on a circular dielectric guide will propagate regardless of how small the guide diameter is. Thus it is possible to make the attenuation factor of a circular dielectric guide arbitrarily small by reducing its diameter. Loss measurements for several different diameters of polystyrene and Teflon rods were made at 72.70 GHz. The measurements were made by directly probing long sections of dielectric guide and plotting the average power as a function of length on an X-Y plotter. Dielectric constants were measured from the standing wave patterns of polystyrene Teflon, and fused quartz rods at 71.0 GHz. Teflon rods exhibited attenuation factors from 0.8 dB/m to 2.2 dB/m depending on the diameter. This is an improvement over silver waveguide at this frequency. Polystyrene rods were found to have attenuation factors ranging from 3.9 dB/m to 12.5 dB/m, again depending on the diameter of the rod. The measured dielectric constants are consistent with previously published data. The various attenuation factors are related to the intrinsic loss tangent of the dielectric using the theory of the HE/sub 11/ mode. Values of tan delta derived from measurements of different rods are consistent indicating that the experimental results are valid. The problem of radiation from dielectric rods is discussed. The experimental results are not conclusive but it appears likely that radiation loss is negligible.

Diffusion and solution of gases and vapors in styrene‐butadiene block copolymers

AbstractThe diffusion, solution, and permeation behavior of a series of inert gases (helium, argon, nitrogen, krypton, and xenon) in S‐B block copolymer films was studied by transient permeability measurements and by the equilibrium desorption method. The morphologies of most of the samples used in the measurements were (a) polystyrene rods dispersed in a polybutadiene matrix and (b) alternating lamellae of styrene and butadiene components. It was indicated, as far as the kinetic nature at lower temperatures is concerned, that the diffusion and permeation processes of gases, except for helium, are governed primarily by behavior in the polybutadiene matrix. At lower temperatures, it was shown that the transient method counts only the mobile penetrant in the polybutadiene matrix, while the equilibrium method counts less diffusive species in the polystyrene domains as well. The diffusion behavior in the copolymer films was compared with that in homopolybutadiene and discussed in terms of two impedance factors: the tortuosity and the chain immobilization factors. From the homopolymer‐block copolymer comparison along with results obtained from diffusion experiments using n‐hexane as the penetrant, it was indicated that segmental motions in the polybutadiene phase in the copolymers are restricted relative to motions in homopolybutadiene. Also, from data on gas sorption in samples of various styrene contents, involving both S‐B block copolymers and binary mixtures with homopolystyrene, it was suggested that the partial mixing of component block chains occurs at the interface between the domains, resulting in rather diffuse domain boundaries.

Correlation between morphology and stress—strain properties of three block copolymers i. stress-softening effect

The stress-softening effect, which comes out when SBS three block copolymers are stretched, is taken into consideration and the conclusion is reached that it is due to a disruption of the polystyrene continuous phase, according to the hypothesis of other authors. This conclusion is supported by two kinds of experiments performed on samples having a well known and simple morphology. First of all by stress-strain measurements on specimens previously swollen: it can be seen that the stress-softening effect disappears as soon as the structure of the material is completely modified by the treatment. Secondly by the direct observation at the electron microscope of the structure after the deformation. This shows how the original continuous and regular polystyrene rods of the “single crystal” assume a string of pearl structure which finally is irreversibly disrupted.

Routine Creatinine Determination: An Equilibrium Technique Involving Reusable Cation Exchange Membranes

A specific creatinine method is described. Serum samples of 400 μ1 are diluted with hydrochloric acid. At a pH of approx. 3, positively charged creatininium ions are isolated from other Jaffe-chromogens by adsorption to cation-exchange resin membranes fixed to polystyrene rods. After adsorption the resin membranes are washed with distilled water, and bound creatinine is released into tubes containing alkaline picrate. Finally, the resin membranes are regenerated using lithium chloride solution. The membranes can be used through several hundreds of cycles. In routine conditions the day-today coefficient of variation has been estimated to be 4.4%. Reference values: males 70–125 μmol/l, females 50–105 μmol/l.

Low-density inhomogeneity corrections for 22-MV x-ray therapy.

The intent of this paper is to present a status report on the examination of correction factors to be used with 22 MV x rays in low-density inhomo-geneities. The problem arose in an attempt to deal with lung in betatron dose distributions. Some interesting values, which will be described, were obtained when electronic equilibrium had not been established before the beam entered the lung. The experimental data were obtained as follows. A phantom was constructed, using Lucite as the tissue-equivalent material and cork as the low-density material simulating lung. LiF capsules were spaced at l-cm intervals along a polystyrene rod on the central axis of the betatron beam and within the cork around the central axis, so that one capsule would not be in the shadow of another. Experiments were performed, varying the thickness of the cork and the thickness of Lucite overlying the cork. The results were compared with values obtained in a solid phantom. All values were adjusted to account for the non-tissue density of the Lucite and polystyrene. The experiment was repeated, with no buildup, with 60Co radiation to obtain data for later comparison with calculated data. The calculated data were obtained in two ways. The first was derived from Batho's method for 60Co (1) as shown in Figure 1, A. The correction of the dose at a point P, at a distance A from the lung-tissue interface, where the thickness of the lung is B and the thickness of the tissue overlying the lung is C is [TAR(A)/TAR(A + B)]0.65 (1). The density of the lung was assumed to be 0.35 and the exponent represents (I-density of B). In Batho's work the effect of the tissue overlying the lung was neglected and values within the lung were not calculated. We found that if this formula was used with 22 MV x-ray data, a situation was approximated which assumed no tissue overlying the lung, and consequently, if the lung thickness was less than 4-cm tissue-equivalent, a correction factor <1 would appear up to some depth below the lung-tissue interface. To duplicate the experimental conditions, an exponent of 0.79 was used, 0.21 being the measured density of the cork. An allowance for the tissue overlying the cork, C, was introduced into Bathe's expression which then became [TAR (A + C)/TAR(A + B + C)]0.79. The corrected per cent depth-dose values, within and below the cork, were then calculated by this exponent method. The second calculation method (Fig. 1, B) assumed the lung-simulating material divided into an air portion and a tissue-equivalent portion and the correction to be the ratio formed as follows [TAR (A + 0.21 B + C)jTAR(A + B + C)].

Measurements of Wavelengths and Attenuation in Dielectric Waveguides for Lower Modes

The wavelength of a wave guided by a dielectric rod has been measured for the TEon, TMon, HEln, and EHln, modes for n = 1 and 2. The measurements were made on polystyrene, lucite, textolite, and paraffin rods, as well as on plastic tubes filled with Nujol and dioxane. The measurements agree very well with the solutions of the characteristic equation. The solution of the characteristic equation corresponding to the second radial mode and the angular mode of order one has two branches, both of which are found experimentally. Measurements are made of the attenuation in a dielectric rod due to losses in the dielectric and due to bending of the dielectric guide.

Effect of Orientation on the Mechanical Properties of Polystyrene

Abstract Extruded polystyrene rod was first annealed, and then stretched hot to elongations as high as 12,000 per cent. Tests were made in tension, flexure, and torsion at temperatures ranging from 0 to 80 C. Tests included creep and relaxation as well as tests at strain and load rates ranging as high as 1.0 in/in/min and 10,000 lb per min to determine the effect of orientation upon these mechanical properties. Tensile and flexural strengths increased two to threefold, depending upon rate and temperature; torsional strength decreased; and modulus of elasticity increased moderately. Fracture changed from a sharp break to a fibrous separation. Birefringence measurements revealed marked orientation of the material, but low-angle x-ray diffraction studies revealed no “crystalline” structure.