Thermodynamic Aspects of Polymer Mixtures

There have been a great many studies on polymer mixtures both from a scientific and an engineering viewpoint and they have been reviewed by many authors^1–3 and in many books.^4–6 However, it is only recently that polymer mixtures have been shown to be analyzable by thermodynamics. One of the many reasons for this situation is that polymer mixtures had previously been believed to be incompatible with each other due to the small entropy of mixing for long polymer chains and positive energy of mixing usually observed between polymers. However, due to rapid progress in experimental techniques used to study the state of polymer mixtures such as small angle neutron scattering (SANS),⁷ small angle X-ray scattering (SAXS),⁸ pulsed nuclear magnetic resonance (NMR),^9,10 Fourier transform infrared absorption (FT-IR),¹¹ thermal analysis.¹² excimer fluorescence,¹³ etc., quite a few polymer mixtures showing compatibility in molecular or segmental scale have been found. Moreover, some polymer mixtures have been shown to exhibit lower critical solution temperature (LCST)-or upper critical solution temperature (UCST)-type phase diagrams for liquid/liquid equilibrium and melting point depression for liquid/crystalline polymer mixtures. Therefore, it becomes quite natural to treat these problems thermodynamically as extensions of polymer solution theories or theories for metallically.^2,14,15     

Photochemical reduction of n-tosylsulfilimines with thiolate anion

The reaction between N-tosyldiarylsulfilimines and p-toluenethiolate anion did not take place in the dark even upon heating up to 62° but proceeded smoothly upon irradiation with visible light in DMF at room temperature, affording S-N bond cleavage products.     

Simultaneous determinationof cyanide and thiocyanate by the pyridine/barbituric acid method after diffusion through a microporous membrane

A flow-injection system for the simultaneous determinationof cyanide and thiocyanate is described. A microporous tubular PTFE membrane module with an outer casing was constructed and included inthe system. Cyanide and thiocyanate diffuse thourgh the membrane wall from the phosphoric acid donor stream to a phosphate or carbonate buffer acceptor stream. Percentage transference of cyanide and thiocyanate were 68% and 59%, respectively, at pH 6.0. At pH 8.1, the percentage transference of cyanide was only 19%. The transferred cyanide and thiocyanate are determined by a pyridine/barbituric acid method. Thiocyanate reacts slowly with chloramine-T at pH 8.1, so that cyanide can be determined without interference from thiocyanate. Total cyanide and thiocyanate are determined at pH 6.0. The detection limits (S/N = 3) are 0.3 μM cyanide and 0.2 μM thiocyanate at pH 6.0, and 5 μM cyanide at pH 8.1. A mechanism for the transference thourgh the membrane is discussed. Bromine interferes with the determination of cyanide and thiocyanate at both pH 6.0 and 8.1. Hexacyanoferrate(II) and hexacyanoferrate(III) interfere at pH 8.1, but not at pH 6.0. Cyanate, oxaloacetate, oxalate, tartrate, albumin, globulin and lysozyme do not interfere.     

Synthetic studies toward marine toxic polyethers (4) synthesis of segment -A of okadaic acid via anti-selectivity by heteroconjugate addition

Segment-A of okadaic acid was synthesized in an optically active form by coupling the lithium acetylide (segment-A₂) and the previously prepared segment-A₁. The key step was the preparation of $\text{anti}$-diastereoisomer for C-12/13 asymmetric center by means of heteroconjugate addition involving Mitsunobu inversion of $\text{syn}$-isomer or direct formation of $\text{anti}$-isomer by beta-chelation effect.     

Aberrations compensation in holographic high order diffracted wave imaging

This study extends the analysis of image formation and aberrations in holography to that of high order diffracted waves to find a method for compensating the aberrations. The proposed method is able to eliminate all aberrations simultaneously by utilizing special conditions. Experimental results are also presented to support the method.     

Effect of the composition ratio of copolymerized poly(carbonate) glycol on the microphase‐separated structures and mechanical properties of polyurethane elastomers

Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C₆) and tetramethylene (C₄) units between carbonate groups in various composition ratios (C₄/C₆ = 0/100, 50/50, 70/30, and 90/10), and the number‐average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass‐transition temperature of the soft segment in the PUEs and the glass‐transition temperature of the original glycol polymer decreased and the melting point of the hard‐segment domain increased with an increasing C₄ composition ratio. The microphase separation of the poly(carbonate) glycol‐based PUEs likely became stronger with an increasing C₄ composition ratio. Young's modulus of these PUEs increased with an increasing C₄ composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C₄ composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase‐separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase‐separated structure and mechanical properties of the PUEs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4448–4458, 2004     

Analytical and computational solution of adaptive inventory processes

H. Scarf (Ann. Math. Statist.30 (2) (1959)) has discussed a technique for the computation of optimal inventory level in the case where the demand distribution contains an unknown statistical parameter. It was assumed that initially the parameter could be described by a priori distribution, which would be subsequently revised on the basis of additional demand information. By assuming that the demand distribution of a cumulative observed demand is a sufficient statistic for the unknown parameter, it was shown that the optimal inventory levels could be obtained by the recursive computation of a sequence of function of two variables. He also showed (N.R.L.A.7 (8) (1960)) that if the demand distributions are gamme distributions and if the holding and penalty costs are linear, then the sequence of function of two variables may be solved by a related set of equations requiring tabulation of functions of only one variable. The main part of the argument presented in this paper is that an analytical consideration and numerical examples of equation requiring tabulation of function of only one variable given by H. Scarf were given with special choices of the factors, and were compared with solution when demand distribution is assumed exactly known and unknown.     

Equilibrium analysis of reactions of metal-pyridylazoresorcinolato chelates with quaternary ammonium ion, nonionic surfactant and polyethylene glycol in aqueous solution by capillary zone electrophoresis.

The resolutions of metal-4-(2-pyridylazo)resorcinol chelates by capillary zone electrophoresis (CZE) were investigated in the presence of some interacting reagents; also, equilibrium reactions between the chelates and the interacting reagents were analyzed in an aqueous solution. Among nine metal chelates formed in aqueous solution, the chelates of VV, FeII, CoIII, NiII, and CuII were resolved and detected by CZE, while other chelates were decomposed during electrophoretic migration. The electrophoretic mobility of the chelates of FeII, NiII, and CuII increased with increasing pH of the migrating solution; also, the acid-dissociation constants of these three chelates were determined by analyzing the mobility change. The ion-association constants of the five anionic chelates and pyridylazoresorcinolate ion with quaternary ammonium ions were also determined by analyzing the mobility change. The binding behavior of the ligand and its chelates with nonionic surfactant micelle, as well as with polyethylene glycol, were investigated, and their binding constants were determined through the mobility change. When Brij 35 was used as a nonionic surfactant interacting with the anionic chelates, the FeII chelate decomposed at Brij 35 concentrations over 6.67 mM. The equilibrium constants and the reactivity were compared with each other.     

Real time optical correlator with a Bil2SiO20 crystal

In this paper we propose a new design of a joint transform correlator in which two transform lenses are used to minimize the influence of their aberration, and a magnification lens is used to make the optics compact. Experimental results show the correlator can be used to recognize characters and/or halL tone images in real time.