ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
Eunjoo Kim
Abstract Polystyrene- block -poly(2-vinyl pyridine) (PS- b -P2VP) block copolymer photonic gels are fabricated that exhibit controllable optical hysteresis in response to a cyclic pH sweep. The optical hysteresis is tuned by controlling the ion-pairing affinity between various anions and the protonated pyridinium ions on the P2VP block, which is highly dependent on the hydration energy of the ions, the dielectric constant of the solvent, and the ionic strength of the medium. The pH coercivity defining the magnitude of hysteresis of the photonic gels could be varied from 0.26 to 7.4. Photonic gel films with strong optical hysteresis can serve as wet photonic memory films where information can be cyclically recorded and erased at least 15 times and maintained for at least 96,h. The memory colors can be further tuned by selection of the copolymer molecular weight. [source]

Reactive Imprint Lithography: Combined Topographical Patterning and Chemical Surface Functionalization of Polystyrene- block -poly(tert -butyl acrylate) Films

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2010
Joost Duvigneau
Abstract Here, reactive imprint lithography (RIL) is introduced as a new, one-step lithographic tool for the fabrication of large-area topographically patterned, chemically activated polymer platforms. Films of polystyrene- block -poly(tert -butyl acrylate) (PS- b -PtBA) are imprinted with PDMS master stamps at temperatures above the corresponding glass transition and chemical deprotection temperatures to yield structured films with exposed carboxylic acid and anhydride groups. Faithful pattern transfer is confirmed by AFM analyses. Transmission-mode FTIR spectra shows a conversion of over 95% of the tert -butyl ester groups after RIL at 230,°C for 5 minutes and a significantly reduced conversion to anhydride compared to thermolysis of neat films with free surfaces in air or nitrogen. An enrichment of the surface layer in PS is detected by angle-resolved X-ray photoelectron spectroscopy (XPS). In order to demonstrate application potentials of the activated platforms, a 7,nm,±,1,nm thick NH2 -terminated PEG layer (grafting density of 0.9 chains nm,2) is covalently grafted to RIL-activated substrates. This layer reduces the non-specific adsorption (NSA) of bovine serum albumin by 95% to a residual mass coverage of 9.1,±,2.9,ng cm,2. As shown by these examples, RIL comprises an attractive complementary approach to produce bio-reactive polymer surfaces with topographic patterns in a one-step process. [source]

Self-Supporting, Double Stimuli-Responsive Porous Membranes From Polystyrene- block -poly(N,N -dimethylaminoethyl methacrylate) Diblock Copolymers

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Felix Schacher
Abstract Asymmetric membranes are prepared via the non-solvent-induced phase separation (NIPS) process from a polystyrene- block -poly(N,N -dimethylaminoethyl methacrylate) (PS- b -PDMAEMA) block copolymer. The polymer is prepared via sequential living anionic polymerization. Membrane surface and volume structures are characterized by scanning electron microscopy. Due to their asymmetric character, resulting in a thin separation layer with pores below 100,nm on top and a macroporous volume structure, the membranes are self-supporting. Furthermore, they exhibit a defect-free surface over several 100,µm2. Polystyrene serves as the membrane matrix, whereas the pH- and temperature-sensitive minority block, PDMAEMA, renders the material double stimuli-responsive. Therefore, in terms of water flux, the membranes are able to react on two independently applicable stimuli, pH and temperature. Compared to the conditions where the lowest water flux is obtained, low temperature and pH, activation of both triggers results in a seven-fold permeability increase. The pore size distribution and the separation properties of the obtained membranes were tested through the pH-dependent filtration of silica particles with sizes of 12,100,nm. [source]

Cover Picture: Structural Modifications to Polystyrene via Self-Assembling Molecules (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2005
Mater.
Abstract The cover shows tensile failure of a sample of pure polystyrene (left), and a polystyrene sample with greater impact strength containing 1% by weight of dispersed nanoribbons (right), as reported in work by Stupp and co-workers on p.,487. The nanoribbons are formed by self-assembly of molecules known as dendron rodcoils (DRCs) in styrene monomer, resulting in the formation of a gel. This gel can then be polymerized thermally. We have previously reported that small quantities of self-assembling molecules known as dendron rodcoils (DRCs) can be used as supramolecular additives to modify the properties of polystyrene (PS). These molecules spontaneously assemble into supramolecular nanoribbons that can be incorporated into bulk PS in such a way that the orientation of the polymer is significantly enhanced when mechanically drawn above the glass-transition temperature. In the current study, we more closely evaluate the structural role of the DRC nanoribbons in PS by investigating the mechanical properties and deformation microstructures of polymers modified by self-assembly. In comparision to PS homopolymer, PS containing small amounts (,,1.0,wt.-%) of self-assembling DRC molecules exhibit greater Charpy impact strengths in double-notch four-point bending and significantly greater elongations to failure in uniaxial tension at 250,% prestrain. Although the DRC-modified polymer shows significantly smaller elongations to failure at 1000,% prestrain, both low- and high-prestrain specimens maintain tensile strengths that are comparable to those of the homopolymer. The improved toughness and ductility of DRC-modified PS appears to be related to the increased stress whitening and craze density that was observed near fracture surfaces. However, the mechanism by which the self-assembling DRC molecules toughen PS is different from that of conventional additives. These molecules assemble into supramolecular nanoribbons that enhance polymer orientation, which in turn modifies crazing patterns and improves impact strength and ductility. [source]

Self-Assembled Nanoscale Ring Arrays from a Polystyrene- b -polyferrocenylsilane- b -poly(2-vinylpyridine)Triblock Terpolymer Thin Film

ADVANCED MATERIALS, Issue 37 2009
Vivian P. Chuang
Hollow ring arrays with an outer and inner diameter of 33 and 11,nm, respectively, are formed from a thin film of poly-(styrene- b -ferrocenylethylmethylsilane- b -2-vinyl pyridine) (PS- b -PFS- b -P2VP) triblock terpolymer with a core/shell cylindrical morphology. The PS minority block forms a core surrounded by a PFS shell in a P2VP matrix; the core/shell structure is oriented perpendicularly to the film surface. The PS core and P2VP matrix blocks are partly removed using oxygen reactive ion etching, leaving ring patterns made from oxidized PFS. [source]

Fluorescent Polystyrene,Fe3O4 Composite Nanospheres for In Vivo Imaging and Hyperthermia

ADVANCED MATERIALS, Issue 21 2009
Donglu Shi
Quantum dots (QDs) are immobilized on the surfaces of magnetic Fe3O4 -composite nanospheres (MNSs, see figure). The QDs exhibit intense visible-light emission in fluorescence spectroscopy and successfully facilitate, for the first time, in vivo soft-tissue imaging in live mice. The Fe3O4 nanoparticles respond to an external magnetic field by increasing the temperature of the surrounding environment (i.e., hyperthermia), which can be used therapeutically. [source]

Highly Ordered Nanoporous Thin Films from Cleavable Polystyrene- block -poly(ethylene oxide),

ADVANCED MATERIALS, Issue 12 2007
M. Zhang
A cleavable trityl ether juncture is introduced between polystyrene (PS) and poly(ethylene oxide) (PEO), and thus highly ordered nanoporous thin films have been prepared from self-assembled PS- b -PEO diblock copolymers, via the removal of PEO from solvent-annealed PS- b -PEO thin films in a simple two or one-step process. When patterned substrates are used, addressable nanopore arrays with a high degree of lateral order and a well-defined lattice orientation can be readily produced (see figure). [source]

A Novel Microencapsulated Osmium Catalyst Using Cross-Linked Polystyrene as an Efficient Catalyst for Asymmetric Dihydroxylation of Olefins in Water

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005
Tasuku Ishida
Abstract A novel microencapsulated osmium catalyst (PSresin-MC Os) was developed using cross-linked polystyrene. The concept of this method may go beyond that of microencapsulation. The catalyst was successfully used in asymmetric dihydroxylation in water, and it was recovered quantitatively by simple filtration and reused several times without loss of activity. The shape of the catalyst was maintained even after several uses. Moreover, no leaching of the Os component was detected. [source]

Prediction of cooling time in injection molding by means of a simplified semianalytical equation

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2003
D. M. Zarkadas
Abstract A simplified semianalytical equation, used successfully in food freezing/chilling time prediction, is proposed as a potential simple alternative for cooling time prediction in injection molding of polymer parts, amorphous or semicrystalline. This equation is based on a convective boundary condition for the mold-part interface and requires information on the thermal contact resistance (TCR) or thermal contact conductance (TCC) at this interface, as well as information on the initial and final product temperatures, the mold surface temperature, and the thermal properties of the part. Eighty-five data points for four polymers, Polystyrene (PS), Polycarbonate (PC), Polypropylene (PP), and Polyethylene (PE) were generated with C-MOLDÔ, a commercial injection molding design software, and the performance of the proposed equation was tested. The % mean error and its standard deviation (SD) in cooling time prediction were, respectively, ,11.61 and 2.27 for PS, ,6.04 and 2.13 for PC, ,7.27 and 6.55 for PP, and ,8.88 and 2.93 for PE. It was also shown that the accuracy of the proposed equation is not affected significantly by the exact knowledge of the TCC, provided that the latter is not smaller than 1000,2000 W m,2 K,1. Since in this comparison all necessary temperatures were obtained from C-MOLDÔ, methods of using the proposed equation independently were tested. The use of the inlet melt temperature as the initial product temperature increased the % mean error by mostly 1.5% while its SD remained practically the same. By incorporating a literature based heat balance method in the proposed equation, it was possible to use it as a stand-alone predictor of polymer cooling time. The % mean error and its SD calculated this way were, respectively, ,9.44 and 0.97 for PS, ,9.44 and 0.83 for PC, ,14.22 and 5 for PP, and ,20.12 and 1.38 for PE. The proposed equation, at least in a preliminary stage, can be used successfully to predict the cooling time of the selected semicrystalline or amorphous polymers with the accuracy being higher for amorphous polymers. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 188,208, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10048 [source]

Analyzing the real advantages of bifunctional initiator over monofunctional initiator in free radical polymerization

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
Paula F. de M. P. B. Machado
Abstract Monofunctional initiators are extensively used in free radical polymerization. To enhance productivity, a higher temperature is usually used; however, this leads to lower molecular weights. Bifunctional initiators can increase the polymerization rate without decreasing the average molecular weight and this can be desirable. A bifunctional initiator is an important issue to be investigated, and it is of great interest to industries. The objective of this work is to study polymerization reactions with mono- and bi-functional initiators through comprehensive mathematical models. Polystyrene is considered as case study. This work collects and presents some experimental data available in literature for polymerization using two different types of bifunctional initiators. Model prediction showed good agreement with experimental data. It was observed that the initial initiator concentration has a huge impact on the efficiency of initiators with functionality bigger than one and high concentrations of bifunctional initiator make the system behave as if it were a system operating with monofunctional initiator. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Organic and aqueous compatible polystyrene,maleic anhydride copolymer ultra-fine fibrous membranes

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009
Corine Cécile
Abstract Polystyrene,maleic anhydride copolymer (PSMA, Mv= 700 kDa) was synthesized and efficiently processed into 400 to 600 nm diameter fibers via electrospinning from either 20 wt % dimethylformamide or 25 wt % dimethylsulfoxide solution. Crosslinking of PSMA was effective by adding glycerol and poly(vinyl alcohol) (PVA) (Mw = 31,50 kDa) in the dimethylformamide and dimethylsulfoxide solutions, respectively. The PSMA fibers containing glycerol at 29.4 mol% were auto-crosslinked whereas those with 12.9 mol% (2 wt %) glycerol and 15.4 mol% (0.75 wt %) PVA required heating to induce intermolecular esterification. Heat-induced crosslinking with glycerol was more effective in rendering the PSMA fibrous membranes insoluble in all solvents whereas that with PVA remained soluble in most solvents except for acetone and tetrahydrofuran. The crosslinked fibrous membranes had improved thermally stability and retained physical integrity upon exposure (2 hr at 40°C) to carbon disulfide, the solvent for Friedel-Craft reactions of the styrene moiety. Hydrolysis (0.01N NaOH) of the auto-crosslinked fibrous membrane significantly improved its hydrophilicity by reducing the water contact angles from 90.6° to 62.5° in a matter of seconds. These ultra-high specific surface PSMA fibrous membranes have shown superior organic and aqueous solvent compatibility to be used as highly reactive and easily retrievable supports for solid-phase synthesis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Effect of an anionic monomer on the pickering emulsion polymerization stabilized by titania hydrosol

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2009
Xiaomei Song
Abstract Polystyrene (PS) nanocomposite particles with high titania content are prepared by Pickering emulsion polymerization. A self-made titania hydrosol modified by an anionic monomer sodium styrene sulfonate (NaSS) is used as a stabilizer and photocatalyst. The stability of the emulsion system is greatly improved by the electrostatic interaction between negatively charged NaSS and positively charged titania nanoparticles. The nanocomposite spheres with the diameter of around 120 nm are highly charged, indicating titania-rich surfaces of latex particles. It is also proven by the field-emission transmission electron microscope and field-emission scanning electron microscope images. The well-defined core-shell structure of the obtained PS/titania composite particles is confirmed by the formation of fragile hollow titania nanospheres after thermogravimetric analysis tests. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5728,5736, 2009 [source]

Synthesis of PS and PDMAEMA mixed polymer brushes on the surface of layered silicate and their application in pickering suspension polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007
Yongfang Yang
Abstract An ammonium free radical initiator was ion exchanged onto the surface of clay layers. Polystyrene (PS) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) mixed polymer brushes on the surface of clay layers were prepared by in situ free radical polymerization. PS colloid particles armored by clay layers with mixed polymer brushes were prepared by Pickering suspension polymerization. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the colloid particles. Clay layers on the surface of PS colloid particles can be observed. Because of the cationic nature of the PDMAEMA brushes the colloid particles have positive zeta potentials at low pH values. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface of the colloid particles. N1s binding energy of PDMAEMA chains on the surface of clay layers was detected by XPS. The two peaks of the N1s binding energy indicate two different nitrogen environments on the surface of clay layers. The peak with a lower binding energy is characteristic of neutral nitrogen on PDMAEMA chains, and the peak with a higher binding energy is attributed to protonated nitrogen on PDMAEMA chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5759,5769, 2007 [source]

PS/PMMA mixed polymer brushes on the surface of clay layers: Preparation and application in polymer blends

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007
Jian Zhang
Abstract Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X-ray diffraction, and high-resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo-PMMA chains and PMMA brushes on the surface of clay layers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5329,5338, 2007 [source]

Construction of a polymer skeleton that is cut in half by ionizing radiation

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2005
Takashi Shimizu
Abstract Polystyrene with a benzyl ester of carboxylic acid at the center of a polymer skeleton was synthesized by living radical polymerization. The initiator used had two functional groups for 2,2,6,6-tetramethylpiperidinoxyl (TEMPO)-mediated living radical polymerization on the benzyl and the carboxylic sides of the benzyl ester. Introduction of the benzyl ester changed the polystyrene from a crosslink type to a scission type polymer on ,-irradiation. Irradiation of the polymer resulted in a binary change of the molecular weight because of the dissociative capture of secondary electrons by the benzyl ester, as: The binary change of the molecular weight suggests that the polymer can be used as a new type of radiation resist with high sensitivity and spatial resolution to ionizing and high resistivity to plasma etching. The number of scissions per 100 eV radiation energy absorbed was 0.29, which was about one fourth of the yield of secondary electrons. The low efficiency was because of the recombination of polymer radicals generated by the dissociative electron attachment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1068,1075, 2005 [source]

Synthesis of Polystyrene- block -Poly(methyl methacrylate) with Fluorene at the Junction: Sequential Anionic and Controlled Radical Polymerization from a Single Carbon

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2009
Nathan D. Contrella
Abstract Polystyrene- block -poly(methyl methacrylate) (PS- b -PMMA) has been synthesized by sequential anionic and reverse atom transfer radical polymerization (ATRP) or a variation of nitroxide mediated polymerization (NMP) from a single initiating site, specifically the 9-carbon on 2,7-dibromofluorene or fluorene. The addition of the second arm (PS) relied on thermal decomposition of 2,2,-azoisobutyronitrile (AIBN) to generate radicals, abstracting the 9-H on the polymer-bound fluorene species to form the initiating radical. Styrene was not present in the reaction mixture when AIBN was decomposed, preventing competition between addition across the monomeric alkene and hydrogen abstraction from the fluorene. After 1,h, styrene was introduced and mediation of the subsequent radical polymerization was achieved by the presence of CuCl2/ligand or TEMPO. Characterization of the diblock copolymers by gel permeation chromatography (GPC) revealed substantial shifts in number average molecular weight () values compared to the anionically prepared PMMA macroinitiator, while polydispersity indices (PDI's) remained relatively low (typically,<,1.5). Characterization by UV detection with GPC (at 310,nm) verified that the diblock polymer is chromophore-bound, which was further verified by UV-vis spectroscopy of the isolated diblock. [source]

Synthesis of Well-Defined Telechelic Macrophotoinitiator of Polystyrene by Combination of ATRP and Click Chemistry

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19 2009
Mustafa Degirmenci
Abstract A new well-defined telechelic macrophotoinitiator of polystyrene was synthesized by combination of ATRP and click chemistry. The ATRP of styrene by means of 2-oxo-1,2-diphenylethyl-2-bromopropanoate (PI-Br) initiator with CuBr/2,2,-bipyridine yields polystyrene with photoactive benzoin (PI) and bromine (Br) group (PI-PSt-Br). Subsequently, PI-PSt-Br was converted to PI-PSt-N3 by simple nucleophilic substitution reaction. Alkyne functionalized benzoin (PI-alkyne) was synthesized by using benzoin photoinitiator and propargyl bromide. Then the coupling reaction between PI-PSt-N3 and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that low-polydispersity polystyrene with desired photoinitiator functionality at both end of the chain, PI-PSt-PI, was obtained. [source]

Heteroarm Star Polystyrene- block -Poly(4-vinylpyridine): Multiple Morphologies in Dilute Solutions

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2008
Chia-Hung Lin
Abstract Synthesis and solution morphologies of four new heteroarm star polystyrene- block -poly(4-vinylpyridine) were studied. As the water content increased, a morphological transformation of heteroarm PS4 -P4VP4 from spheres to cylinders, vesicles, and large compound vesicles was observed. The morphology of PS4 -P4VP4 in the solvent mixture of DMF/water or 1,4-dioxane/water was spherical, but changed to large compound micelles in THF/water. As the P4VP molar ratio decreased, the morphology changed from spherical mixed with cylindrical to vesicles, giant vesicles, and then to LCMs. The present study demonstrated the formation of multiple morphologies through manipulating solvent polarity and block ratio in dilute solution. [source]

Two-Dimensional Chromatography of Complex Polymers, 7 , Detailed Study of Polystyrene- block -Polyisoprene Diblock Copolymers Prepared by Sequential Anionic Polymerization and Coupling Chemistry

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19 2008
Valentina Mass
Abstract Two-dimensional chromatographic methods were developed using LC-CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS- b -PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D-LC analysis provides information on the purity of the reaction products, the presence of by-products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D-LC is discussed. [source]

Immobilization of Candida antarctica lipase B on Polystyrene Nanoparticles

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2010
Nemanja Mileti
Abstract Polystyrene (PS) nanoparticles were prepared via a nanoprecipitation process. The influence of the pH of the buffer solution used during the immobilization process on the loading of Candida antarctica lipase B (Cal-B) and on the hydrolytic activity (hydrolysis of p -nitrophenyl acetate) of the immobilized Cal-B was studied. The pH of the buffer solution has no influence on enzyme loading, while immobilized enzyme activity is very dependent on the pH of adsorption. Cal-B immobilized on PS nanoparticles in buffer solution pH 6.8 performed higher hydrolytic activity than crude enzyme powder and Novozyme 435. [source]

Selective Guest Uptake from Solvent Mixtures in the Clathrate Phase of Syndiotactic Polystyrene

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004
Yukihiro Uda
Abstract Summary: Selective absorption uptake during the guest-exchange processes in the , form of syndiotactic polystyrene (sPS) was confirmed by IR spectroscopy. When films of the , form were immersed in hexane/decane or chloroform/decane mixtures, decane molecules were incorporated preferentially in the , form. Sorbate uptake by the , form was greatly accelerated when the sorbate was mixed with a solvent penetrable to the amorphous region of sPS. Concentration changes in a , -form film during sorption processes: sorption of a chloroform(D)/decane(H) mixture (1:1 molar ratio). [source]

Partially Sulfonated Polystyrene and Poly(2,6-dimethyl-1,4-phenylene oxide) Blend Membranes for Fuel Cells

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2004
Bokyung Kim
Abstract Summary: Based on Flory,Huggins parameters (,), the miscibility and the effect of morphological change on proton conductivity and methanol permeability of partially sulfonated polystyrene (SPS) and partially sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), having an identical ion exchange capacity, were investigated. When 50 wt.-% of SPPO was blended, both the proton conductivity and methanol permeability had the highest values, which resulted from the change of amorphous domains and the hydrogen bonding between the two ionomers. The proton conductivities, water uptake and methanol permeability for the SPPO/SPS blend membranes studied here. The membranes with 50 wt.-% SPPO clearly showed the greatest increase in these properties. [source]

Glass Transition of Low-Dimensional Polystyrene

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2004
Qing Jiang
Abstract Summary: A unified model is developed for the finite size-effect on the glass-transition temperature of polymers, Tg(D), where D denotes the diameter of particles or thickness of films. In terms of this model, Tg depends on both the size and interface conditions. The predicted results are consistent with the experimental evidence for polystyrene (PS) particles and films with different interface situations. Tg(D) function of free-standing PS films. [source]

An Experimental Study on the Free-Radical Copolymerization Kinetics with Crosslinking of Styrene and Divinylbenzene in Supercritical Carbon Dioxide

MACROMOLECULAR REACTION ENGINEERING, Issue 1 2009
Pedro R. García-Morán
Abstract A study on the effect of process conditions and composition of the reacting mixture on the kinetics and particle properties in the copolymerization of styrene and divinylbenzene in supercritical carbon dioxide is presented. Polystyrene -block- polydimethylsiloxane and Krytox 257 FSL (Dupont) were used as stabilizers, and their performance compared. A 38 mL, high-pressure view cell, equipped with one frontal and two lateral sapphire windows, was used as the reacting vessel. The polymer product was characterized for total monomer conversion, gel content, molecular weight averages of the sol fraction and particle size distribution. Acceptable polymerization rates and partially-agglomerated spherical particles were produced under the conditions tested. [source]

Thermally-Induced Phase Transitions in the Uniaxially-Oriented , Form of Syndiotactic Polystyrene

MACROMOLECULAR SYMPOSIA, Issue 1 2006
E. Bhoje Gowd
Abstract The empty , (,e) form of uniaxially-oriented syndiotactic polystyrene (sPS) samples were obtained by extracting the solvent molecules from the , form of sPS and solvent complex in acetone and methanol. Temperature dependence of the X-ray fiber diagrams starting from the uniaxially-oriented ,e and , form has been measured successfully at various temperatures for the first time. The transition behavior was traced clearly by separating the equatorial and layer line reflections. The ,e form transformed to the , form via an intermediate form. The intermediate form is speculated to take disordered structure due to the empty cavities present in the ,e form. Calorimetric studies showed an endotherm followed by an exotherm during this phase transition, which is consistant with such a speculation. On the other hand the , form transformed to the , form directly without passing through the intermediate form or ,e form. During the , to , phase transition the solvent molecules evaporate through the columnar structure in a broad range of temperature, allowing the transition to occur smoothly. [source]

Use of the Surfmer 11-(Methacryloyloxy) undecanylsulfate MET as a Comonomer in Polystyrene and Poly(methyl methacrylate)

MACROMOLECULAR SYMPOSIA, Issue 1 2004
P.C. Hartmann
Abstract The polymerizable surfactant sodium 11-(methacryloyloxy) undecanylsulfate (MET) has been synthesized with high purity, and its thermal stability and phase transitions have been studied by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. MET has been copolymerized in solution with methylmethacrylate (MMA) or styrene (S), initiated by azo-bis-isobutyronitrile (AIBN). The copolymers thus obtained have been studied by Gel Permeation Chromatography (GPC), Transmission Electron Microscopy (TEM), and DSC. Due to the incompatibility between the polar head of the MET units and the non polar S or MMA units, MET units organize in the amorphous polymer matrix and arrange in lamellar structures. [source]

Reactively and physically compatibilized immiscible polymer blends: stability of the copolymer at the interface

MACROMOLECULAR SYMPOSIA, Issue 1 2003
Charef Harrats
Abstract This paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene-maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence. In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co-continuous two-phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes. [source]

Molecular Simulation Via Connectivity-altering Monte Carlo and Scale-jumping Methods: Application to Amorphous Polystyrene

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7-8 2008
Tim Mulder
Abstract Well-equilibrated atactic-polystyrene (aPS) samples are obtained through the end-bridging Monte Carlo (EBMC) algorithm. A coarse-grained (CG) description of aPS is used; monomers are represented by two CG beads. The algorithm produces correct polymer conformations on all length scales, beyond the size of the CG beads. The code is very efficient, even though the acceptance of 0.001,0.005% is approximately 10,100 times lower than in the original EB code for PE. Systems of aPS of the order of 5000 monomers (50 chains of 100 monomers on average) can be equilibrated on all length scales within a week, in a single-processor run. The computer code is also adequate for simulations of other polymers that have the same regularity in their sequence of chemical groups and that are modeled at the same or at a coarser level of description. [source]

Origin of Bends in Unperturbed Vinyl Polymers: An Illustration with Polystyrene

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007
Yergou B. Tatek
Abstract Previous experimental works have shown that dendronized vinyl polymers exhibit bends when adsorbed onto a surface. Two different mechanisms are believed to be responsible for the formation of these bends. These mechanisms are the temperature dependent random fluctuations of torsional bond states on one hand, and the intramolecular interactions due to the randomness in the stereochemical sequence of side chains on the other hand. Investigation of the amplitude and scope of the above mechanisms has been made by studying the conformational space of PS chains via RIS based Monte Carlo sampling. It was found that at low temperature bend formation is due to tacticity, whereas it was thermally driven at high temperature. The existence of a transition temperature between these two bend formation modes was demonstrated. It was also shown that for atactic chains, the maximum of bend formation occurs at Pm,,,0.7. [source]

Structural and mechanical properties of polystyrene nanocomposites with 1D titanate nanostructures prepared by an extrusion process

POLYMER COMPOSITES, Issue 9 2009
Polona Umek
Polystyrene (PS) nanocomposites with titanate nanotubes and titanate nanoribbons were prepared by an extrusion process at 180°C. Nanocomposites with 1 wt% of nanofillers and pure PS that had also been exposed to the extrusion process were comparatively examined with scanning electron microscopy (SEM), electron dispersive X-ray spectrometry (EDS) mapping, solid state proton nuclear magnetic resonance measurements (1H NMR), tensile tests, and shear creep measurements. SEM images and EDS mapping analysis show that titanate nanoribbons homogeneously distribute at a micrometer length-scale in the PS matrix during the extrusion process. This is not the case for titanate nanotubes, which show a stronger tendency to form clusters. Solid state 1H NMR studies, however, proved that the nanocomposites are inhomogeneous at a nanometric scale where structural components with highly mobile PS molecules coexist with domains of rigid PS molecules. Differences in the 1H spin-lattice relaxation at and above the glass transition temperature Tg = 373 K suggest that nanofillers affect the thermodynamic properties of nanocomposite domains. Only a slight increase in mechanical tensile properties was observed in the case of the nanocomposite containing 1 wt% of titanate nanoribbons (TiNRs) probably reflecting a weak interaction between the polymer matrix and the nanofiller. Nevertheless, our results prove that the use of functionalized TiNRs may, in combination with the extrusion process, represent a very promising starting point for the preparation of TiNR nanocomposites at the industrial level. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]