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1.
Polystyrene (PS)/poly(ethylene oxide) (PEO) prototype brushes were prepared by alternating free‐radical copolymerization of methacryloyl‐terminated PS and α‐vinylbenzyl‐ω‐hydroxy or α‐vinylbenzyl‐ω‐perfluoroalkyl (Rf) PEO macromonomers with the addition of Lewis acid (SnCl4). It was found from their dilute‐solution properties that PS/PEO end‐capped with Rf (PBRf), and PS/PEO having OH groups at terminal ends (PBOH) prototype brushes formed a single molecule in benzene and aggregates in chloroform, respectively. However, the brush PBOH formed a single molecule in N,N‐dimethylformamide. Such aggregation behaviors seemed to be caused by the interaction between hydroxy groups of PEO chain ends. The brush PBOH was also converted into PBRf‐type brush by chemical modification, using corresponding acid chloride. The substitution of Rf groups was ~70% due to slipping of terminal hydroxy groups into PEO internal domains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 772–778, 2006  相似文献   

2.
Contact friction plays a critical role in all the major thermoforming processes for polymers. However, these effects are very difficult to measure in practice and, as a result, have received little scientific investigation. In this work, two independently developed test methods for the measurement of elevated temperature polymer‐to‐polymer contact friction are presented, and their results are compared in detail for the first time. One is based on a modified moving sled friction test, whereas the other uses a rotational rheometer. In each case, friction tests were conducted between two plug and two sheet materials. The results show that broadly similar coefficients of friction were obtained from the two test methods. The measured values were quite low (<0.3) at lower temperatures and typically were higher for polypropylene (PP) sheet than for polystyrene (PS). On approaching the glass transition temperature for PS (95°C) and the crystalline melting point for PP (165°C), the friction coefficients rose very sharply, and both test techniques became increasingly unreliable. It was concluded that despite their physical differences, both test techniques were able to capture the highly temperature sensitive nature of friction between polymer materials used in thermoforming. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers  相似文献   

3.
In this article, the particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring‐opening polymerization of laurolactam (LL) in the presence of polystyrene (PS) was investigated. Scanning electron microscopy (SEM) and Fourier Transform infrared Spectroscopy (FTIR) were used to analyze the morphology of the blends. The results show that the PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is 5 wt%. However, when the PS content is higher than 10 wt%, two particular phase morphologies appeared. Firstly, dispersed PS‐rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 and 15 wt%. Then the phase inversion occurred (the phase morphology of the PA12/PS blends changed from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) when PS content is 20 wt% or higher, which is unusual for polymer blends prepared via conventional methods such as mixing, hydrolytic polycondensation and so on. The formation of this particular phase morphology development was simply elucidated via a phase inversion mechanism. Furthermore, the stability of the phase morphology of the PA12/PS blends after annealing at 230°C was also investigated via SEM. POLYM. ENG. SCI., 52:1831–1838, 2012. © 2012 Society of Plastics Engineers  相似文献   

4.
In this article, a particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring-opening polymerization of Laurolactam (LL) in the presence of PS was investigated. SEM and FTIR were used to analyze the morphology of the blends. The results showed that PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is less than 5 wt %. When the PS content is higher than 10 wt %, two particular phase morphologies appeared. First, dispersed PS-rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 wt % and 15 wt %. Then, the phase inversion (the phase morphology of the PA12/PS blends changes from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) occurred when PS content is higher than 20 wt %, which is completely different from traditional polymer blends prepared by melt blending. The possible reason for the particular morphology development was illuminated through phase inversion mechanism. Furthermore, the stability of the phase morphologies of the PA12/PS blends was also investigated. SEM showed that the particular morphology is instability, and it will be changed upon annealing at 230°C for 30 min. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

5.
To obtain low polymeric polystyrene (PS), pyrolysis of high polymeric PS in solution was studied in the temperature range from 290 to 400°C by using additives or acid catalysts. The low polymeric PS targeted here was that with average molecular weight of 104. When the feed PS was pyrolyzed in tetralin by adding sulfur or diphenyl disulfide, the molecular weight of PS decreased greatly, even at lower temperatures, and the desired low polymeric PS was formed in a relatively large amount at the temperatures below 350°C. The degradation behavior was able to be explained in terms of a random polymer chain scission mechanism initiated by sulfur radicals formed from the additives. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2299–2305, 1998  相似文献   

6.
Heat of mixing is introduced as a guide for phase stability predictions of polymer mixtures, and an appropriate equation is presented for it. The form of this equation is a combined function of temperature and mixture composition. The capability of the presented equation has been treated qualitatively and it has been shown that all types of exothermic, endothermic, and s‐shaped or sigmoidal heat of mixing curves can be produced. Utilizing the low molecular weight analogue calorimetry method, heat of mixing was measured at two temperatures, 27°C and 37°C for three polymer mixtures—poly(styrene)/poly(vinylchloride) (PS/PVC), poly(styrene)/ poly(methylmethacrylate) (PS/PMMA), and poly(styrene)/poly(vinylacetate) (PS/ PVAc) at an entire composition range. It has been shown that excellent agreement between the results of the calculations and the experimental heat of mixing data was achieved. Using the results of analogue calorimetric measurements for phase stability studies of polymer mixtures, it was found that often, acceptable predictions can be made by this method, but they are not always completely true.  相似文献   

7.
The chain conformations of cyclo-olefin polymer (COP) and polystyrene (PS) in less than 200-nm thick films on silicon wafers were investigated on the basis of the refractive index measured by multi-angle spectroscopic ellipsometry (MASE), and density measured by X-ray reflectometry (XRR). For both COP and PS, the density measured by XRR increases by decreasing the film thickness to below 50 nm. Densification may be caused by close packing of unentangled polymer chains in ultrathin films spincast from dilute solutions with polymer concentrations less than the overlap concentration (C*). For COP films, the refractive indices at incident angles of 45° and 70° measured by MASE agree well with those calculated by the Lorentz–Lorenz equation, indicating that densification of COP ultrathin films enhances their refractive indices. For PS films thinner than 50 nm, although the refractive index at an incident angle of 45° agrees with a calculation based on the Lorentz–Lorenz equation, one at 70° significantly deviates downward. A comparison of them with the results of quantum chemical calculation (QCC) suggested a plane-arrangement of benzene rings in PS ultrathin films, which was likely brought about by stacking of benzene rings and attractive interaction between π-electrons in the benzene rings and the substrate surface.  相似文献   

8.
Solvent‐free cyanoethylation of selected alcohols with acrylonitrile (AN) using a weakly basic polymer resin, Amberlyst A‐21 (AA‐21) was studied at 75°C. The conversion of primary alcohols, 1‐octadecanol, hexane‐1,6‐diol, pentaerythritol, but‐2‐yne‐1,4‐diol, N‐methyldiethanolamine, triethanolamine and diethanolamine is higher than secondary alcohols, isopropanol and glycerol in the presence of polymer resin. Of various alcohols, but‐2‐yne‐1,4‐diol gave the product in high conversion (87%) in cyanoethylation with a polymer resin/AN weight ratio of 0.04. The polymer resin showed recycling ability only in two cycles to produce cyanoethylated product from diethanolamine. In case of 1‐octadecanol, hexane‐1,6‐diol, and N‐methyldiethanolamine with AN under similar conditions, no recycling ability was observed. Thermally treated polymer resin at 75°C afforded the product in lower conversion (55%) whereas the same product was obtained in 69% when fresh polymer resin was used in cyanoethylation of 1‐octadecanol. No catalytic effect was observed for polymer resin treated at 100°C. Fourier transform infrared (FTIR) spectra showed CN stretching at 2248 cm?1 for the polymer resin collected after the reaction which was caused by the AN binding on polymer resin during the reaction. As per thermogravimetric curves, 5% weight loss was observed at 201°C for recovered resin and at 161°C for polymer resin treated at 100°C. Scanning electron microscope images confirmed the AN binding on polymer beads after catalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

9.
Arylamine polymers are among the most studied conducting polymers due to a whole range of interesting properties and applications. In this paper, we describe the synthesis of soluble and processable electroactive poly(triphenylamine-g-oligostyrene) by two polymerization methods in tandem. In the first step, oligostyrene macromonomers with well-defined molecular weight, polydispersity and chain-end functionality were obtained by radical-controlled polymerization (i.e., atom transfer radical polymerization, ATRP) of styrene. The styrene oligomerization was carried out using a new triphenylamine-based initiator, [4-(diphenylamino)benzyl 2-bromo-2-methylpropanoate], cuprous bromide as co-initiator and bipyridine as ligand, at 100 °C, in bulk. Using two feed molar ratios of components: [styrene]0:[initiator]0:[CuBr]0:[bipyridine]0, two macromonomers with M n = 9,900; M w/M n = 1.25 and M n = 3,460; M w/M n = 1.22, respectively, were synthesized. The presence of triphenylamine moiety at one end of the macromonomer allowed the chemical and electrochemical polymerization of macromonomers to polytriphenylamine brushes having short oligostyrene grafts in every structural unit. The oligostyrene substituents confer processability and good solubility in common organic solvent characteristics for polystyrene while preserving the optoelectronic properties of arylamine-conjugated main chain. The chemical oxidative polymerization of macromonomer was carried out using iron (III) chloride dissolved in nitrobenzene. The redox behavior of the initiator, macromonomer and graft polymer was investigated by cyclic voltammetry. In all cases, it was observed that the reversible oxido-reduction of arylamine sites was accompanied by irreversible oxidative electropolymerization by free-para positions of triphenylamine substituents and deposition of thin films on working electrode. The structures of the initiator, macromonomers and graft copolymers were determined by Fourier transform infrared, 1H and 13C NMR spectroscopy. The absorption and fluorescence spectroscopy have revealed absorption and emission maxima characteristics for triphenylamine group. DSC studies have confirmed glass transitions characteristics for styrene oligomers.  相似文献   

10.
Experimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐4‐12 ) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐6‐12 ). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (1H and 13C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.  相似文献   

11.
Polystyrene (PS) composites with a network of single‐walled carbon nanotubes (SWNTs) were fabricated by using monodispersed PS micospheres. First, PS spheres and surfactant‐dispersed SWNTs were mixed in water, then a hybrid cake was obtained by filtration via a microporous membrane and the SWNTs were filled within the spaces of packed polymer spheres. At this stage, the surfactants for dispersing SWNTs were totally removed from the composites by a thorough washing. Then the composite films with SWNT networks were obtained by compression molding at 160°C. Structure of the composites had been characterized by transmission electron microscopy and scanning electron microscopy. The present SWNT composites showed a low percolation threshold of electrical conductivities. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

12.
The solubility and diffusivity of supercritical carbon dioxide (sc‐CO2) in low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polypropylene (PP), ethylene‐ethylacrylate copolymer (EEA) and polystyrene (PS) were measured at temperatures from 150°C to 200°C and pressures up to 12 MPa by using the Magnetic Suspension Balance (MSB), a gravimetric technique for gas sorption measurements. The solubility of CO2 in each polymer was expressed by Henry's constant. The interaction parameter between CO2 and polymer could be obtained from the solubility data, and it was used to estimate the Pressure‐Volume‐Temperature relationship and the specific free volume of polymer/CO2 mixtures. The diffusion coefficients were also measured by the MSB for each polymer. The resulting diffusion coefficients were correlated with the estimated free volume of polymer/CO2 mixture. Combining Fujita's and Maeda and Paul's diffusion models, a model was newly developed in order to predict diffusion coefficients for the polymers studied. Polym. Eng. Sci. 44:1915–1924, 2004. © 2004 Society of Plastics Engineers.  相似文献   

13.
The solid‐state structure of syndiotactic polystyrene (s‐PS) after crystallization from the melt and the glassy state was examined by differential scanning calorimetry (DSC), density, and X‐ray diffraction analysis. It was possible to prepare semicrystalline s‐PS containing either the pure α‐ or the pure β‐crystalline form by melt crystallizing s‐PS from 280 or 330°C. The measurements confirmed the low density of both crystalline forms, which in the case of α‐crystalline form was smaller and in the case of β‐crystalline form was only slightly larger than the density of the glassy amorphous s‐PS. An endeavor to introduce the crystalline phase in s‐PS through cold crystallization at constant temperature above the glass transition resulted in a complex ordered phase. This ordered phase, depending on the crystallization temperature, contained the planar chain mesomorphic phase and the α‐crystalline phase with a low degree of perfection (cold crystallization in the range 120–175°C) or a mixture of the α‐ and β‐crystalline forms with a high degree of perfection (cold crystallization in the range 210–260°C). The combination of DSC and X‐ray measurements enabled us to resolve the complex ordered structure in semicrystalline s‐PS after cold crystallization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2705–2715, 2002  相似文献   

14.
A novel oscillatory pressure sintering (OPS) process is reported to prepare high‐quality ceramics. The oscillatory pressure was applied at three stages (initial, intermediate, and final) during sintering process of zirconia ceramics for the first time. The microstructure of the samples prepared by OPS develops in a more homogeneous manner, leading to a higher final density, a smaller average grain size, and a narrower distribution of grain sizes compared with the samples prepared by conventional pressureless sintering (PS) and hot‐pressing (HP) processes. Remarkably, the OPS samples was obtained at relatively lower heating temperature and less soaking time for 1300°C and 0.5 hours than the samples prepared by other two techniques at 1450°C and 1 hour. The current results suggest that OPS is an effective technique for preparing high‐quality zirconia ceramics with low heating temperature and short sintering time, thus, it obviously reduces cost.  相似文献   

15.
Durairaj Baskaran 《Polymer》2003,44(8):2213-2220
Hyperbranched polymers were synthesized using anionic self-condensing vinyl polymerization (ASCVP) by forming ‘inimer’ (initiator within a monomer) in situ from divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIPB) using anionic initiators in THF at −40 °C. The reaction of equimolar amounts of DVB and nBuLi results in the formation of hyperbranched poly(divinylbenzene) through self-condensing vinyl polymerization (SCVP). The hyperbranched polymers were invariably contaminated with small amount of gel (<15%). No gelation was observed when using DIBP with anionic initiators. The presence of monomer-polymer equilibrium in the SCVP of DIPB restricts the growth of hyperbranched poly(DIPB). The inimer synthesized from DIPB at 35 °C undergoes intermolecular self-condensation to different extent depending on the nature of anionic initiator at −40 °C. The molecular weight of the hyperbranched polymers was higher when DPHLi was used as initiator. A small amount of styrene ([styrene]/[Li+]=1) was used to promote the chain growth by inducing cross-over reaction with styrene, and subsequent reaction of styryl anion with isopropenyl groups of inimer/hyperbranched oligomer. The hyperbranched polymers were soluble in organic solvents and exhibited broad molecular weight distribution (2<Mw/Mn<17).  相似文献   

16.
Positive temperature coefficient to resistivity (PTCR) characteristics of polystyrene (PS)/Ni‐powder (40 wt%) composites in the presence of multiwall carbon nanotubes (MWCNTs) has been investigated with reference to PS/carbon black (CB) composites. The PS/CB (10 wt%) composites showed a sudden rise in resistivity (PTC trip) at ≈110°C, above the glass transition temperature (Tg) of PS (Tg ≈95°C). Interestingly, the PTC trip temperature of PS/Ni‐powder (40 wt%)/MWCNT (0.75 phr) composites appeared at ≈90°C (below Tg of PS), indicating better dimensional stability of the composites at PTC trip temperature. The PTC trip temperature of the composites below the Tg of matrix polymer (PS) has been explained in terms of higher coefficient of thermal expansion (CTE) value of PS than Ni that led to a disruption in continuous network structure of Ni even below the Tg of PS. The dielectric study of PS/Ni‐powder (40 wt%)/MWCNT (0.75 phr) composites indicated possible use of the PTC composites as dielectric material. Dynamic mechanical analysis (DMA) and thermogravimetric analysis studies revealed higher storage modulus and improved thermal stability of PS/Ni‐powder (40 wt%)/MWCNT (0.75 phr) composites than the PS/CB (10 wt%) composites. POLYM. COMPOS., 33:1977–1986, 2012. © 2012 Society of Plastics Engineers  相似文献   

17.
Phase diagrams including tie lines for nine ternary solvent–polymer–polymer systems have been obtained using size exclusion chromatography. The systems studied were toluene–polystyrene (PS)–isoprene rubber (IR), toluene–PS–butadiene rubber (BR), cyclohexane–PS–BR, tetrahydrofuran(THF)–PS–poly(methyl methacrylate) (PMMA), and THF–PS–poly(butyl methacrylate) (PBMA) at temperatures between 30 and 75°C. The results indicate PS-PMMA is less compatible than PS-PBMA in the presence of THF. Also, the combination of trans- and 3,4–IR-PS is less compatible than cis–IR-PS in the presence of toluene. The original Flory–Huggins model for ternary systems has been modified to account for the concentration dependence of the interaction parameters. The modified Flory–Huggins model consists of two interaction parameters per binary. Using this model, six parameters have been regressed for each of the experimental systems studied. Although the parameters are not physically meaningful, the model and the parameters obtained using it are useful for correlating the experimental phase diagrams. The results obtained using the modified six parameter model are shown to be superior to those obtained using the original three parameter model. © 1993 John Wiley & Sons, Inc.  相似文献   

18.
In this study, aromatic sulfonated poly(sulfone‐pyridine‐amide) (S‐PSPA) has been prepared via polycondensation of sulfonated monomer 1‐(4‐thiocarbamoylaminophenyl‐sulfonylphenyl)thiourea and 2,6‐pyridinedicarboxylic acid at high temperature. Mechanically robust and thermally stable hybrid membranes were prepared using non‐functional and functional multiwalled carbon nanotube (MWCNT) i.e., S‐PS/S‐PSPA/MWCNT‐NF and S‐PS/S‐PSPA/MWCNT via solution blending. Field emission scanning electron microscopy exhibited porous membrane structure for 0.1–0.5 wt% nanotube loading, whereas well‐aligned functional MWCNT were observed in 1 wt% loaded sample. Increasing the functional nanotube content from 0.1 to 1 wt% increased tensile strength of functional S‐PS/S‐PSPA/MWCNT hybrids from 62.19 to 65.29 MPa compared with non‐functional hybrid (53.34 MPa) and neat S‐PS/S‐PSPA. 10% decomposition temperature of S‐PS/S‐PSPA/MWCNT 0.1–1 was in the range 491–502°C, while S‐PS/S‐PSPA/MWCNT‐NF showed relatively lower thermal stability (T10 489°C). Glass transition temperature of functional S‐PS/S‐PSPA/MWCNT was also higher (201–243°C) relative to S‐PS/S‐PSPA/MWCNT‐NF (194°C). Furthermore, functional MWCNT‐based membranes had higher ion exchange capacity (IEC) 3.2–3.6 mmol/g and lower activation energies (95–36 kJ/mol). Novel functional membranes also revealed high proton conductivity 1.68–2.55 S/cm in a wide range of humidity at 80°C higher than that of perfluorinated Nafion® membrane (1.1 ×10?1 S/cm) at 80°C (94% RH). POLYM. ENG. SCI., 55:1776–1786, 2015. © 2014 Society of Plastics Engineers  相似文献   

19.
Vinylbenzyl-terminated polystyrene (PS) macromonomers were prepared by the direct reaction of living PS anions with p-chloro-methylstyrene (CMS). The propagation rate constant (k p) was obtained from free-radical polymerization of PS macromonomers in the presence of 1-buten-3-ol as a degradative chain transfer agent by using gel permeation chromatography (GPC) analysis. In this condition, the polymer radicals were terminated by a unimoiecular mechanism. Subsequently, we studied the radical propagation step of vinylbenzyl-terminated diblock poly[styrene (S)-b-isoprene (I)] and poly[S-b-2-vinylpyridine (2VP)] macromonomers in benzene. The vinylbenzyl groups at the terminal ends of diblock macromonomers apparently take the concentrated state in micelles. These results are discussed from the point of view of polymer-polymer reactions.  相似文献   

20.
The grafted homopolymer and comb‐shaped copolymer of polyacrylamide were prepared by combining the self‐assembly of initiator and water‐borne surface‐initiated atom transfer radical polymerization (SI‐ATRP). The structures, composition, properties, and surface morphology of the modified PET films were characterized by FTIR/ATR, X‐ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electronic microscopy (SEM). The results show that the surface of PET films was covered by equable grafting polymer layer after grafted polyacrylamide (PAM). The amount of grafting polymer increased linearly with the polymerization time added. The GPC date show that the polymerization in the water‐borne medium at lower temperature (50°C) shows better “living” and control. After modified by comb‐shaped copolymer brushes, the modified PET film was completely covered with the second polymer layer (PAM) and water contact angle decreased to 13.6°. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

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