摘要:

AbstractTetrahydropyranyl‐ (THP) and furanyl‐ (THF) protected polyhydroxystyrene (PHS) polymers have been investigated for their potential use in conjunction with onium salt acid precursors to yield high‐sensitivity resist systems. The synthesized polymers have high transmittance at 248 nm (the wavelength used in next‐generation excimer laser, KrF exposure tools). At 248 nm the transmittance for a 1‐μm thick film is ∼ 80% (Abs = 0.097 μm−1). The acid sensitivity of the acetal functionality at room temperature is high, requiring careful handling of all materials to prevent any premature deprotection of the hydroxy group. The highest lithographic sensitivities obtained so far with a system consisting of poly(p‐tetrahydropyranyl‐oxy‐styrene) base resin and 1 mol % of bis (p‐tert‐butyl phenyl) iodinium triflate (TBIT) was ∼ 2 mJ / cm2. High‐resolution line and space patterns (0.35 μm) were obtained with a system comprising PHS‐p‐THP and an acid precursor, using an excimer laser

ISSN:0021-8995    

DOI:10.1002/app.1991.070420401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA study has been made on the effect of mineral and organic acids on the radiation‐induced graft polymerization of styrene onto low‐density polyethylene films. Effects of different solvents and dose rate of irradiation on the grafting yield were also investigated. The influence of irradiation time and monomer concentration in the presence and absence of acid on the initial rate and grafting yield was studied. The dependence of the grafting rate on monomer concentration was found to be of the order 1.34 (in absence of acid), 0.61 (in presence of HCl), and 1.25 (in presence of oxalic acid). Such acid enhancement of the radiation grafting process is of practical importance from an economical point of v

ISSN:0021-8995    

DOI:10.1002/app.1991.070420402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIn this article, we use the technique of multistage emulsion polymerization to synthesize the LIPN PBA/PS/PMMA and use the gravimetric analysis method to study the apparent kinetics of the reaction process and to investigate the influence of the concentration of the initially emulsifying agent, the initiator, and the extent of the crosslinking on the distribution of the particle diameter and the dynamic mechanical properties of the products.

ISSN:0021-8995    

DOI:10.1002/app.1991.070420403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe thermal degradation of Nafion–H, Nafion–K, and the mixture of each of these with poly(methyl methacrylate) (PMMA) has been studied. A mechanism is proposed for the thermal degradation of Nafion–H that involves an initial cleavage of the carbon–sulfur bond leading to SO2and OH radical and a carbon‐based radical. This carbon‐based radical then undergoes further degradation. The addition of PMMA to Nafion–H inhibits further degradation of the Nafion carbon‐based radical and instead radical recombination reactions between PMMA fragments and this Nafion radical dominate the reaction scheme. The replacement of the hydrogen in Nafion–H with a potassium (i.e., Nafion–K) produces a much more robust material that does not degrade under conditions similar to those used for Nafion–H. Nafion–K has little effect on

ISSN:0021-8995    

DOI:10.1002/app.1991.070420404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractPolyurethane systems based on aliphatic diisocyanates were evaluated for suitability for use as underwater transducer encapsulants. A preliminary evaluation was performed to select the most promising urethane systems for further development. An investigation was then undertaken to determine the effect of compositional changes on the properties of these urethanes. The compositional parameters investigated were the soft‐segment molecular weight, the prepolymer isocyanate content, the composition of the cure formulation, and the cure stoichiometry. These urethanes were subjected to long‐term aging in seawater. It was found that this exposure did not significantly effect the physical or dynamic mechanical properties of the ureth

ISSN:0021-8995    

DOI:10.1002/app.1991.070420405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA highly porous and absorbable crosslinked polystyrene, prepared by the concentrated emulsion polymerization method, was used as host polymer for the preparation of conducting, large objects, polymer composites. The composites, whose conductivity can be as high as 0.80 S/cm, were prepared by (i) imbibing the host polymer with a pyrrole (or oxidant) solution, (ii) partially drying the imbibed host polymer, and (iii) imbibing again with an oxidant (or pyrrole) solution for polymerization to take place. The electrical conductivity of the composite and the penetration of polypyrrole in the host polymer are influenced by the polymerization conditions (i.e., the concentrations of oxidant and pyrrole and the nature of the solvents used for the oxidant and pyrrole), the order in which the two imbibing solutions are introduced, and the drying time used after the first imbibation. The mechanical properties of the host polymer are improved with the incorporation of polypyrrole. Scanning electron micrographs of the composites indicate that the polypyrrole coats uniformly as a film the inside of the porous host polymer.

ISSN:0021-8995    

DOI:10.1002/app.1991.070420406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractOxoalkyl acrylates of long‐chain 7‐oxo alcohols were synthesized as intermediate monomers for the preparation of poly[n‐alkyl (oxy) ‐n‐hexyl acrylates] for the first time. These polymers have wide applications as fluidity improvers (pour point depressants) for petroleum crude oils. Characterization of all the intermediate monomers was done by IR,1H‐NMR, and MS, and that of polymers by IR,1H‐NMR, and GPC. These polymers were systematically investigated for their efficacy as pour point depressants on three types of high waxy Bombay High (Indian) crudes. In addition to establishing the pour points, relevant rheological parameters of the untreated and the additive‐treated crude oils were determined in the laboratory with a rotational viscometer. Results of the crude oils that were pre‐ and posttreated with these new polymers have shown enhanced activity of flow properties as compared to the crudes that were treated with poly(n‐alkyl acry

ISSN:0021-8995    

DOI:10.1002/app.1991.070420407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe increase in the viscosity of an aqueous solution or gel of hydroxypropylmethylcellulose (HPMC) in the presence of an anionic surfactant is attributed to a two‐step process: (a) the surfactant undergoes ion–dipole interaction with the ethereal oxygen in HPMC, in the absence or presence of water, and (b) hydrocarbon moieties in the now pendant surfactant molecules undergo hydrophobic bonding, in the presence of water, resulting in an apparent increase in the molecular weight of the HPMC. DSC of dry blends and dried gels or films confirmed HPMC–sodium lauryl sulfate interaction. Work‐to‐break measurements on films cast from aqueous solutions of HPMC, in the absence or presence of anionic surfactants, indicated an apparent increase in the molecular weight of HPMC in the presence of su

ISSN:0021-8995    

DOI:10.1002/app.1991.070420408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractEffects of several processing parameters on the properties of poly[4‐ (terephthaloylamino) benzoic acid hydrazide] semipermeable membranes were investigated. The membranes were prepared using a polymer phase inversion method that consisted of the following sequence of steps: casting of thin, neutralized polymer solution layers on suitable solid support; thermal treatment of the obtained layers to form viscous liquid protomembranes; coagulation of the protomembranes into solid semipermeable membranes; and, when that was additionally desired, posttreatment of the obtained membranes in order to further affect their final separation properties. The processing parameters investigated included temperature and time of exposure to thermal treatment during the preparation of protomembranes, nature of the employed medium, time of exposure, and temperature of the posttreatment of coagulated membranes. In addition, particular attention was devoted to the effect of polymer molecular weight on the properties of the membranes, and for that purpose a series of five polymer samples with molecular weights that ranged from about 17,000 to about 64,500 was prepared using the previously described viscometrical method to monitor the polymer forming polycondensation reactions. The results obtained showed that membrane performance was very much influenced by all of the examined processing variables and that products with considerably different properties could be obtained from the same polymer sample by using different processing parameters. Thus, the use of higher temperatures and longer exposure times in the protomembrane forming thermal treatment step gave higher rejection and lower permeability of the finished membranes, although there seems to exist limiting “ceiling conditions” above which this trend rather abruptly ceases to continue any further. It appears that these conditions correspond to the onset of irreversible changes, either in the polymer chemical structure or in the membrane supermolecular organization. Posttreatment of the prepared membranes was found essential for useful properties in the single‐stage separation applications, which require high membrane selectivity. Of the investigated possibilities, annealing in boiling deionized water was crucial, while exposure to concentrated acids was also important in the case of HCl but rather deleterious in the case of H2SO4. Most significantly, the membrane properties clearly depended on the polymer molecular weight, and it was found that there was a critical polymer molecular weight above which this dependence ceased to be important for practical purposes. It is suggested that this may be a general phenomenon, characteristic for all membrane forming polymer materials, and a possible explanation of its nature is tentatively

ISSN:0021-8995    

DOI:10.1002/app.1991.070420409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractPolystyrene is not normally shear‐modifiable. Addition of small amounts of plasticizer (butyl benzyl phthalate) result in changes in melt viscosity and elasticity during extrusion. Fiber spinning experiments are shown to provide useful indications of the rheological state of polymers that are sensitive to shear history. Here, the density, modulus and work to rupture of lightly plasticized polystyrene is shown to vary with extrusion history of the materia

ISSN:0021-8995    

DOI:10.1002/app.1991.070420410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY