Polyetherimide substrates for future high density optical data storage

Polyetherimide (PEI) substrate for next‐generation high density optical data storage is fabricated and characterized. Cover‐layer incident or first‐surface recording configurations do not require optical properties of the substrate, which are the prerequisite conditions for the conventional material of polycarbonate (PC). Instead of the optical properties, good mechanical properties with a sufficient transcribability are required. Even though PEI has higher glass transition temperature than that of PC, a microscopic transcribability of PEI is comparable with PC by laminating a thermal insulation layer on the backside of a stamper to retard the heat flow. A macroscopic warpage of PEI substrate is smaller than that of PC substrates, which reduces tilt and servo burden. The lowest critical speed coupled with the flutter of PEI substrate is larger than that of PC substrate because of the mechanical properties of PEI. POLYM. ENG. SCI., 48:97–101, 2008. © 2007 Society of Plastics Engineers     

Polymers for information storage systems

Summary Various multiethylene glycol dimethacrylates were polymerized by UV light in the presence of 2,2-dimethoxy-2-phenyl-acetophenone as a photoinitiator. The ensuing highly crosslinked polydimethacrylates were characterized by thermomechanical analysis and swelling studies. The crosslinked structure was investigated and kinetic aspects of the reactions were analyzed.     

Edge-decorated graphene nanoribbons by scandium as hydrogen storage media

On the basis of density functional theory calculations, we show that edge-decorated graphene nanoribbons (GNRs) by scandium can bind multiple hydrogen molecules in a quasi-molecular fashion. The average adsorption energy of H(2) on Sc ranges from 0.17 to 0.23 eV, ideally suited to hydrogen storage. For the narrowest GNR with either armchair or zigzag edges, the predicted weight percentage of H(2) is >9 wt%, exceeding the gravimetric target value set by the Department of Energy (DOE). The bonding energy between Sc and the GNR is significantly greater than the cohesive energy of bulk Sc so that clustering of Sc will not occur once Sc is bonded with carbon atoms at the edge of GNRs. Moreover, the adsorption energy of H(2) can be modestly tuned (either enhanced or reduced) by applying an external electric field.     

石蜡乳状液储热技术研究进展与应用前景

石蜡乳状液是一种新型的相变储热及潜热输送介质,不仅具有较高的潜热值,而且能保持能良好的流动性,在输送过程中能大大节约泵耗.结合研究成果,介绍了石蜡乳状液储热机理及研究进展,评述了该相变材料在工业余热利用、电锅炉及供暖领域中的应用.     

A first-principles study of alkali-metal-decorated graphyne as oxygen-tolerant hydrogen storage media

One serious problem encountered in hydrogen storage based on metal-decorated porous materials is the oxidation of metal atoms as it is irreversible due to strong oxygen-binding and blocks the adsorption of molecular hydrogen. We study the adsorption of molecular oxygen on graphyne decorated with alkali (AM) and alkali earth metals (AEM) using first-principles calculations. For comparison, we also calculate the adsorption characteristics of metal atoms and subsequent molecular oxygen in pristine and boron-doped graphene. We find that the binding energy of molecular oxygen on AM–graphyne complexes, especially Li–graphyne complex, is much smaller than that on AM in graphene or comparable to that in boron-doped graphene. We show that the binding strength of molecular oxygen is mainly affected by the center of empty p- or d-band of AM or AEM on adsorbents and by the work-function of metal-adsorbent complexes. We investigate the effect of biaxial tensile strain as a means of controlling the binding strength of molecular oxygen.     

气体水合物在空调蓄冷中的应用研究进展

介绍了国内外近几年气体水合物蓄冷技术应用研究进展.从节能与环保角度出发,分析了气体水合物作为新型蓄冷工质在空调蓄冷中应用的必要性.从气体水合物相平衡热力学、结晶动力学、数值模拟以及蓄冷装置等方面阐述了气体水合物在空调蓄冷中应用的可行性,为气体水合物蓄冷技术尽快走向实用化提出了研究重点.     

Polymers as Catalysts

Polymers have been widely used as catalysts or catalyst supports and the various applications can be categorised conveniently into four groups (a) catalysis by soluble linear polymers, (b) catalysis by ion exchange resins, (c) polymer-supported ‘homogeneous’ metal complex catalysts and (d) polymer-supported phase transfer catalysts. A brief review of each of these is given, with citation of some of the more recent and important examples which illustrate some of the basic principles involved.     

Polymers as Materials

Abstract

The chemistry and technology of polymers has developed rapidly during the last three decades; it concerns itself with materials consisting essentially of the elements C, H, N, and O, and being therefore conventionally classified as organic polymers. However, in many instances other elements such as B, Si, P, S, F, and CI are present in certain proportions and have a more or less important influence on the ultimate properties of the products. Together with the large family of metallic compounds and ceramic systems, organic polymers represent useful and increasingly important engineering materials in the construction of buildings, vehicles, engines, applicanes, textiles, packaging, printing and writing materials, plastics, rubber goods and household articles of all kinds.     

Amino-p-benzoquinone Adducts and Polymers as Adhesion Promoters for Steel

Phenolic and quinonoid compounds are widely studied in biological sciences because of their ability to chelate heavy metals like iron and copper and recently have found new applications in synthetic macromolecules. Amino-p-benzoquinone polymers, poly[(2,5-hexamethylenediamino)-1,4-benzoquinone] and poly{[2,5-(2,2′-bistrifluoromethyl)-4,4′-biphenylenediamino]1,4-benzoquinone} were synthesized and evaluated as adhesion promoters for steel/epoxy joints. An improvement in the torsional shear strength of these joints was observed when these polymers were used as adhesion promoters. The durability of the adhesive bond was also improved after boiling water treatment, relative to untreated and silane-treated joints. The improvement in adhesion could be attributed to the formation of a chelate between the polyaminoquinone (PAQ) and the iron surface and a chemical reaction between the PAQ and the epoxy resin. A low molecular weight model compound, bis[2,5-(4-methylanilido)]-1,4-benzoquinone, was also used to study coupling between the epoxy adhesive and the steel surface. Electron spin resonance (ESR), atomic absorption spectroscopy and infrared spectroscopy were used to document the epoxy-coupling agent reaction and the chelate formation.     

Review: Polymers,Surface-Modified Polymers,and Self Assembled Monolayers as Surface-Modifying Agents for Biomaterials

Biocompatibility and nontoxicity of biomaterials are of utmost importance when foreign bodies come in contact with a biological system. Irrespective of the nature of material, nonspecific protein adsorption is the first process observed at surface–biological system interfaces followed by cellular processes. Nonspecific protein adsorption leads to deleterious cellular processes such as biofouling and finally immunological host response. Hence, surface modification becomes mandatory for preventing undesirable implant failure and inflammatory responses. Various polymers, surface-modified polymers and surfaces withself assembled monolayers, have been tested to tune surface properties for a given application. Surface functional groups and surface structures of polymers and copolymers regulate surface hydrophobicity, nonspecific protein adsorption, biomaterial stability, and antifouling property, etc. Self assembled monolayers are formed by covalent linkage with more controlled surface structure and smoothness. Mixed and hybrid self assembled monolayers containing both hydrophilic and hydrophobic groups result in moderate wettability. Further, we have discussed different methods of surface modification using polymers, modified polymers, and self assembled monolayers for improved surface biocompatibility and nonfouling properties.     

维生素E作为聚合物抗氧剂的研究与应用现状

综述了维生素E在聚合物中的抗氧机理、产品特点、应用性能及市场消费情况,简要分析了维生素E作为聚合物抗氧剂的国内外现状。     

Triolein-phosphatidylcholine-cholesterol emulsions as substrates for lipoprotein and hepatic lipases

Lipolysis of emulsified glycerol tri[9,10-³H]oleate by lipoprotein lipase purified from bovine milk (E.C. 3.1.1.34) and by hepatic lipase purified from rat liver perfusate was studied as a function of the phosphatidylcholine molecular species and the cholesterol content of the emulsions. Overall, the activities of the two enzymes were similar on a molar basis. Lipoprotein lipase initial lipolysis rates also were comparable for emulsions made with egg phosphatidylcholine or with saturated (dimyristoyl, dipalmitoyl and distearoyl) phosphatidylcholines when cholesterol was low. Increasing the cholesterol content of the emulsion from 2–3 mole percent to 7–14 mole percent reduced triolein lipolysis by lipoprotein lipase in emulsions made with saturated phosphatidylcholines. Rat hepatic lipase was more sensitive to increased cholesterol in emulsions made with saturated phosphatidylcholines than was lipoprotein lipase. The ability to maintain triolein lipolysis during longer incubations differed strikingly among the emulsions and for the two enzymes. Lymph chylomicrons were better substrates for both enzymes than any of the emulsions.     

Heparinized Polymers as Thromboresistant Biomaterials

A major research field of recent development concerns the synthesis and evaluation of thromboresistant polymers for use in heart valves, artificial hearts, ventricular assist devices, and external devices such as heart-lung and kidney machines. Although a wide variety of plastics and elastomers is available, none is completely satisfactory for long-term use in contact with blood.     

Ferrocenylenesilylene Polymers as Coatings for Tapered Optical-Fiber Gas Sensors

In this paper we report the use of ferrocenylenesilylene polymers as coatings for tapered optical-fiber sensors. The principle of operation of this device is based upon environmentally induced changes in the refractive index of the polymer layer which change the power transmitted through the tapered fiber. The results for two sensor arrays fabricated using the ferrocenylenesilylene polymer [( ⁵-C₅H₄)Fe( ⁵-C₅H₄)MePhSi] _m and copolymer {[( ⁵-C₅H₄)Fe( ⁵-C₅H₄)SiPhMe] _n [( ⁵-C₅H₄)Fe( ⁵-C₅H₄)Me₂Si] _m are presented. We also show that the sensitivity of this device is a function of the taper beat length.     

Methyl-branched octanoic acids as substrates for lipase-catalyzed reactions

Hydrolyses of racemic methyl-branched octanoic acid thiolesters are described using six commercial lipases as catalysts. Branching at positions 2, 4 and 5 greatly reduced activity; branching at the 3-position virtually eliminated activity. The reactivities of the racemic branched thiolesters relative to the unbranched ester were very similar for each lipase preparation examined. In reactions involving configurationally pure 2-methyloctanoic acids, the S-enantiomer reacted faster both in esterification of aliphatic alcohols and in hydrolyses of aliphatic alcohol esters with all of the lipases examined. Stereobiases in hydrolyses of the octanoic acid esters branched at other positions were low and variable. In sharp contrast to the hydrolyses of the thiolesters of 2-methyloctanoic acid, two aryl esters of 2-methyloctanoic acid catalyzed byR. miehei lipase hydrolyzed with a bias for the R-configuration. A view of the ester-enzyme complex is offered, to explain the relative rates of reaction of the racemic esters. Reference to a brand or firm name does not constitute endorsement by the U.S. Department of Agriculture over others of a similar nature not mentioned.     

Polymers for information storage systems. II. Polymerization kinetics for preparation of highly crosslinked polydimethacrylates

Polymers of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate were prepared by photoinitiated polymerizations in the presence of 2,2-dimethoxy-2-phenyl-acetophenone at 27°C. The reactions led to highly crosslinked polymeric networks. The volume shrinkage observed during polymerization was a function of the number of ethylene glycol units in the dimethacrylate monomer. The kinetic rate constants of polymerization, as determined from the photopolymerization characteristics using a dilatometric technique, were again dependent on the number of ethylene glycol units in the monomer. The importance of these results on the crosslinked structure of the prepared networks is discussed.     

Birefringence–An important property of plastic substrates for magneto-optical storage disks

Birefringence is an important substrate property for optical data storage media. The basic definitions of birefringence and its relation to the chemical nature of polycarbonate are outlined. The polarizability of the monomer unit, expressed in the rheo-optical constant and the degree of remaining polymer chain orientation, determines the level of birefringence in polycarbonate disk substrates. Based on this theory, the theory of blending materials with positive and negative rheo-optical constants Is developed, and the current work with polycarbonate/polystyrene blends is reviewed. The biggest disadvantage of the reviewed system Js that only binary systems with low LCST (lower critical solution temperature) (<240°C) can be formulated. Finally, we report on successful development work of a single-phase blend of a modified polycarbonate with a special styrene-acrylonitrile copolymer. The experimental results are compared with the theoretical expectations, and the implications on the injection molding of disk substrates are discussed.     

Polymers in mixed solvents: linear representation of viscosity data as a function of molecular weight

In this paper the corrected Stockmayer-Fixman-Burchard equation recently proposed¹³ is applied to the case of polymers dissolved in mixed solvents. A linear plot for viscosity over a very broad range of molecular weights is observed. The unperturbed dimensions of polymers obtained in mixed solvents are related to the thermodynamic properties of the solvent mixtures.