Parent Polystyrene Research Articles

Polystyrene Functionalized with Diarylacetonitrile for the Visualization of Mechanoradicals and Improved Thermal Stability.

The direct scission of polymer main chains leads to a decrease in the performance of the polymeric materials. Polystyrene-functionalized with diarylacetonitrile (DAAN) was prepared through a postpolymerization modification with 4-methoxymandelonitrile to generate mechanofluorescent polymers that enable the visualization of the scission of the polymer main chain. The polymeric mechanoradicals obtained from the homolytic cleavage of the polymer main chain in response to mechanical stress were observed using fluorescence and electron paramagnetic resonance spectroscopy. Moreover, a thermogravimetric analysis showed that the thermal stability of the polymers was greatly improved relative to the parent polystyrene, that is, the introduction of the DAAN moiety via postpolymerization modification endowed the original polymers with multiple functions in one step; specifically, the ability to visualize polymer main-chain scission and improved thermal stability.

Separation of parent homopolymers from poly(ethylene oxide) and polystyrene-based block copolymers by liquid chromatography under limiting conditions of desorption – 1. Determination of the suitable molar mass range and optimization of chromatographic conditions

We studied molar mass limits for the LC LCD separation of parent polystyrene (PS) and poly(ethylene oxide) (PEO) homopolymers from PEO/PS based block copolymers and we identified optimized chromatographic conditions. Time delays between barriers and sample injections were 0–2–3′10. Eluent was composed of dimethylformamide (DMF) 40wt.% and 1-chlorobutane (CLB) 60wt.%; Barrier 1 (B1), which retained block copolymer, was composed of 100wt.% CLB and Barrier 2 (B2), which retained PEO, was a mixture of DMF and CLB, which proportions were adjusted to studied block copolymers. With B2 composed of DMF 23wt.% and CLB 77wt.%, we obtained successful separation of PS23K-b-PEO35K-b-PS23K (56.5wt.% of PS, the subscripts indicate the molar mass in kgmol−1 of each polymer part in the block copolymer) from its parent homopolymers. With B2 adjusted to DMF 30wt.% and CLB 70wt.%, PS2.3K-b-PEO3.1K (42.6wt.% of PS) was also efficiently separated from its parent homopolymers.

Determining the Polydispersity in Chemical Composition and Monomer Sequence Distribution in Random Copolymers Prepared by Postpolymerization Modification of Homopolymers.

We report on establishing the polydispersity in chemical composition (PCC) and polydispersity in monomer sequence distribution (PMSD) in random copolymers of poly(styrene-co-4-bromostyrene) (PBrxS), where x = (0.385 ± 0.035) is the mole fraction of the 4-bromostyrene units (4-BrS), prepared by electrophilic substitution of bromine in the para-position of the phenyl ring of the parent polystyrene. Upon fixing the total number of repeating units, we tune the distribution of styrene and 4-BrS segments in PBrxS by carrying out the bromination reaction on polystyrene homopolymers in different solvents. While PBrxS with relatively random comonomer distribution is prepared in 1-chlorodecane, random-blocky sequences of 4-BrS in PBrxS are achieved by carrying out the bromination reaction in 1-chlorododecane. The PCC in both copolymers is established by fractionating both polymers using interaction chromatography (IC) and determining the chemical composition of the individual fractions by neutron activation analysis (NAA). The NAA data along with IC experiments reveal that the random-blocky sample possesses a narrowed PCC relative to a specimen with a more random comonomer sequence distribution. The full width at half-maximum (fwhm) in the chemical composition profile from IC is used to quantify PCC; the random mother sample possessed a 25% fwhm, while the random blocky mother sample has a fwhm equal to 8.7%. The change in the adsorption enthalpy per brominated segment due to adsorption is determined to be ≈1.5 times greater for the random-blocky than the relatively random sample, proving that more pronounced cooperative adsorption occurs in the case of the random-blocky sample relative to the random copolymer sample. Computer simulation employing the discontinuous molecular dynamic scheme further reveals that the distribution of comonomer sequences, that is, PMSD, in the random-blocky copolymer is narrower than that in the copolymer with a random distribution of both monomers.

Particle‐size‐dependent properties of sulfonated polystyrene nanoparticles

AbstractThe influence of sulfonation reaction time, temperature and the parent polystyrene (PS) particle size on the degree of sulfonation (DS), ion exchange capacity (IEC), morphology and glass transition temperature (Tg) of sulfonated polystyrene (SPS) particles was investigated. A longer reaction time (ca 2 h) at 40 °C and a smaller particle size resulted in SPS particles with a high DS. It was found that a larger PS particle size did not readily yield SPS particles with a high DS even with a longer reaction time. Contrary to the popular belief in the literature that a higher DS ensures a high IEC, we observed that the proportionality of IEC to DS is primarily controlled by the SPS particle size. Larger IEC values were obtained for larger particles rather than smaller ones despite their similar DS, owing to the presence of strong interactions between − SO3H groups within the particles in the latter case which restricts the availability of free H+ for ion exchange. The SPS particles displayed a core‐shell morphology in which the outer shell appeared because of sulfonation on the PS. The DS value and the SPS particle size significantly influenced the shell thickness and thereby the morphology of the SPS particles. Copyright © 2012 Society of Chemical Industry

Polymeric membranes composed of polystyrenes tethering amino acids for preferential CO2 separation over H2

Various N-tert-butoxycarbonyl (N-Boc) amino acids, such as glycine, valine, and serine, were combined to 4-chloromethylstyrene. The resulted monomers were readily polymerized to give polystyrenes tethering an amino acid by a conventional free radical polymerization technique. After deprotection of the N-Boc group with trifluoroacetic acid, the obtained polystyrene derivatives were soluble in ethanol and spin-coated on a commercial poly(ether sulfone) porous membrane to fabricate a composite membrane for CO2 separation over H2. The CO2 selective layer of synthesized PSt was ca. 200 nm thick, and the composite membranes showed preferential CO2 separation over H2, while parent polystyrene passed through H2 rather than CO2. Especially, the separation factor \( \alpha_{{{\text{CO}}_{ 2} /{\text{H}}_{ 2} }} \) was raised after alkaline treatment to form free primary amine on the terminus of graft chain. Serine tethered polystyrene showed the highest \( \alpha_{{{\text{CO}}_{ 2} /{\text{H}}_{ 2} }} \) (16) among them, which suggested the hydroxyl group would enhance the CO2 affinity of primary amine.

Rheological behavior of oligomeric ionomers

The rheological behavior of the alkali metal salts of oligomeric sulfonated polystyrene (PS) ionomers was characterized using dynamic and steady shear measurements. The starting PS had a weight average molecular weight of 4000g∕mol and a narrow molecular weight distribution (1.06). Two sulfonation levels were examined, 2.5 and 4.8mol%, which corresponded, respectively, to one and two sulfonate groups per chain on average. The ionomers exhibited nanophase separation of an ion-rich phase, and as a consequence, time-temperature superposition failed for all samples. Sulfonation increased the melt viscosity of the ionomers, as much as seven orders of magnitude. The zero shear viscosity scaled as cq∕a, where c was the concentration of the ionic groups, q was the charge of the cation, and a was the cation radius, and although the molecular weight of the parent polystyrene was much lower than the entanglement molecular weight, the ionomer melts exhibited strong elastic behavior. The flow activation energy of the ionomers was similar to that of high molecular weight PS and the calculated molecular weight between “entanglements” of the ionomers was the same as for PS.

General synthesis of hollow composite ellipsoids

A facile and general approach towards composite hollow ellipsoids has been proposed. The parent polystyrene (PS) hollow spheres are embedded in a matrix, for example, poly(vinyl alcohol), and stretched into the corresponding ellipsoids. The aspect ratio of the ellipsoids is tunable by stretching extent. Accordingly, sulfonated PS hollow ellipsoids are achieved by sulfonation of the PS hollow ellipsoids, which will facilitate an easy complexation with functional materials. Composite hollow ellipsoids, with varied composition ranging between polymer, metal and oxides, and inorganic materials, are synthesized against the polymer ellipsoids as templates. By controlling growth of the functional materials at specific sites, structure of the composite hollow ellipsoids is controlled such as surface-pillared, single-shelled and double-shelled. This approach avoids traditional removal of polymer templates, thus guarantees the shell integrity of the composite hollow ellipsoids.

Interaction of polystyrene and fullerene C60 in benzene: Composition and molecular properties of the product

The molecular properties and composition of fullerene-containing polystyrenes prepared through evaporation of solvent from the combined solution of a polymer and C60 in benzene have been studied by viscometry, translational isothermal diffusion, GPC, UV spectroscopy, and electrooptical Kerr effect measurements. With this procedure of C60 introduction into the polymer, a partial depolymerization of the parent polystyrene takes place. It has been shown that the composites contain fullerene in two forms: a smaller part of C60 is bound to macromolecules, while a larger part of C60 is incorporated into the composition of low-molecularmass adducts—the products arising from the interaction of fullerene with fullerene-induced depolymerized polystyrene.

Novel fluorescent copolymers of styrene with benzazole chromophores

Novel green fluorescent copolymers of styrene and 2-[(5′- N-acryloyl)-2′-hydroxyphenyl]benzoxazole or 2-[(5′- N-acryloyl)-2′-hydroxyphenyl]benzothiazole were synthesized by radical polymerization. The copolymers were characterized by size exclusion chromatography, thermal analyses (DSC, TGA), UV–Vis and fluorescence spectrophotometry. The glass transition temperatures of the fluorescent copolymers were similar to that of the parent polystyrene and the average molecular weight was lower due to the chain transfer effect of the benzazole dyes. The maximum fluorescence emission wavelength of the copolymers in the solid state or in chloroform solution accessed by fluorescence spectrophotometry was also similar. The Stokes shift of the styrene–benzoxazole or –benzothiazole copolymers was similar to those presented by fluorochromes that exhibit an excited state intramolecular proton transfer mechanism.

Color center annealing in γ - irradiated polystyrene, under vacuum and air atmospheres

A primary effect of low doses of ionizing radiation on polystyrene is the production of absorption centers in the UV and Visible regions of the spectrum. There are two types of color centers: “annealable” and “permanent”. Annealable centers are most likely due to the formation of cyclohexadienyl, radicals in the polymer. These species have not only strong UV absorption bands (largely obscured by the parent polystyrene absorption) but also weak visible absorptions above 420nm. Post-irradiation annealing has been associated with diffusion of O 2 into the solid polymer sample. We now find that annealing can also occur in the absence of oxygen. These two annealing mechanisms can be understood in terms of colored free radicals, trapped within the irradiated solid matrix, which form colorless products upon reaction with O 2 or reaction with other (nearby) radicals. The rate of ambient temperature annealing in vacuum is drastically slower than in air. Annealing rates increase significantly with increasing temperature, particularly in vacuum where annealing times under ambient conditions are on the order of months or years, compared with several days at 80°C. In all cases, samples which were irradiated in vacuum and subsequently exposed to air, developed sharp annealing fronts. Front movement rates were found to be dose-dependent with an apparent saturation effect occuring at the high end of the dose range. Analyses of the front movements allowed estimates to be made of the oxygen consumed during the annealing process.

Factors Affecting the Location of the Peak Above TG in TSD Currents in Polystyrene

For polystyrene, independent measurements of dielectric relaxation time ?d determined from the TSD ? peak and of bulk conductivity a show that the relation ??d= ?0? holds. Space charge ? peaks are known to be hard to reproduce in TSD experiments. Factors such as electrode - sample contact, applied voltage, sample preparation and number of free charge carriers are examined separately and lead to consistent results. In polystyrene containing 1% sodium acetate segregation occurs at high temperature and the p peak resembles that of the parent polystyrene. When the salt is well dispersed this is no longer the case: the space charge peak is shifted to lower temperature when the number of free carriers increases.