Application of Continuous Thermodynamics to The Stability of Polymer Systems. IV

Abstract

A method for establishing in the framework of continuous thermodynamics the stability criteria for multiple critical states of increasing order is presented. The method applies to a relatively general class of Gibbs free energy relations for polymer solutions: The function replacing the χ-term in the classic Flory-Huggins theory is permitted to depend on a finite number of moments of the polymer distribution so as to embrace most Gibbs free energy relations used in practice. In this way, determinant criteria for multiple critical states are formulated that are analogous in structure to those in traditional (discrete) thermodynamics. However, the dimension of the determinants is reduced from N (number of polymer species) to n (number of moments taken into account).     

APplication of Continuous Thermodynamics to the Stability of Polymer Systems. II

A determinant criterion for the critical state in solutions and mixtures of polydisperse polymers is established within the general framework of Gibbs theory. The treatment continues an earlier paper by considering more general Gibbs free energy relations: The function replacing the x-term in the classic Flory-Huggins equation is permitted to depend on a finite number of moments of the polymer distribution(s) so as to embrace most Gibbs free energy relations of practical use. The new criterion leads to a very large reduction of computer time and of needed storage capacity compared to the traditional Gibbs determinant criterion. Some relations known from the literature are shown to be special cases of the established new criterion.     

Application of Continuous Thermodynamics to Polymer Fractionation

Continuous thermodynamics was developed in recent years and applied successfully to the liquid-liquid equilibrium of poly disperse polymer solutions. Continuous thermodynamics is based on the direct use of continuous distribution functions in the thermodynamic equations. There is no need for a reduction to pseudocomponents. This paper presents the application of continuous thermodynamics to successive polymer fractionation procedures based on solubility differences. In this way, simple equations for the distribution function of the different polymer fractions are obtained. Furthermore, the other equations describing the fractionation possess a lucid structure favorable for computer simulations of the fractionation procedures.     

Polymer Compatibility by Continuous Thermodynamics

Abstract

By applying a continuous distribution function instead of the mole fractions, mass fractions, etc. of individual components, continuous thermodynamics permits a drastic reduction of the computational expense for calculating phase equilibria in complex multi-component systems such as petroleum fractions, shale oils, polymer solutions, and polymer mixtures. In this paper, continuous thermodynamics is applied to compatibility in mixtures of two polymers. If, e.g., the cloud-point curve is known, the shadow curve, the spinodal, the critical mixing point, and other interesting quantities may easily be calculated. Some examples are given to illustrate the method.     

Application of Continuous Kinetics to Polymer Degradation

Abstract

Degradation of polydisperse polymers is studied in the framework of continuous kinetics which is directly based on continuous distribution functions which depend on the molecular weight and the time. A firstorder formalism is presumed. A Schulz-Flory distribution (with time-dependent parameters) is assumed to be valid during the entire time of degradation. Thus, an essential simplification of the solution procedure of the continuous rate equation is achieved. As a proof of accuracy, the approximation solution and the exact solution are compared for the case of “random scission.” Furthermore, the developed method is shown to be suitable for describing the experimental data of dextran degradation caused by acid hydrolysis, by ultrasonic irradiation, and by enzymatic attack. The model parameters fitted to the experimental data allow the evaluation of the scission probability as a function of the molecular weight and of the location of the bond to be broken within the molecule.     

Capillary Thermodynamics of Nematic Polymer Interfaces

The Cahn‐Hoffman capillarity vector thermodynamics formalism for curved anisotropic interfaces is adapted to soft liquid crystalline polymer‐isotropic fluid interfaces. The Cahn‐Hoffman formalism in conjunction with the interfacial Landau‐de Gennes model is used to derive compact expressions for the capillary pressure, tangential Marangoni force, and interfacial torque. It is shown that the interfacial thermodynamics of nematic polymers can be analyzed in terms of three distinct modes: (i) area size change, (ii) area rotation, and (iii) tensor order parameter curvature. The formalism allows to clearly identify the nature and magnitude of these three contributions. Characteristic cases biaxial and uniaxial nematic ordering states are analyzed. Anisotropic liquid crystal surfaces display a number of novel interfacial effects: (a) capillary pressure even for flat surfaces, (b) tensor order parameter‐dependent renormalization of the tension coefficients due to anchoring energy, (c) tensor order parameter‐driven transitions between classical Laplace pressure and non‐classical behavior, (d) Laplace‐like capillary pressure due solely to orientation curvature, (e) generation of Marangoni forces through interfacial order and/or orientation gradients, and (f) surface torques generation.

Schematic of the geometry considered in this article.     

Polymer reactions. III. Structure of polypropylene hydroperoxide

Oxidation of polypropylene introduces hydroperoxide groups into the polymer. Infrared spectroscopy has determined that more than 90% of these groups are intramolecularly hydrogen bonded. The sequential lengths and sequence distributions of these neighboring hydroperoxides were estimated from the electronic spectra of the polyenes derived from the polypropylene hydroperoxide by two methods: (1) reduction, acetylation, and pyrolysis, and (2) reduction and dehydration. The results indicate that all the hydroperoxide groups are present in sequences of length two and greater. Intramolecular hydrogen abstraction during oxidation could account for the formation of these neighboring hydroperoxides.     

Structural Design and Application of Azo-based Supramolecular Polymer Systems

This article presents a brief overview of recent advances in azo-containing supramolecular systems. In literature, it has been shown that azo supramolecular polymers and their composite materials exhibit fast and intelligent responses to various external stimuli,such as temperature, p H change, redox reagents, ligands, coupling reagents, etc. In applications, these systems are widely used for molecular motors, shape memory, liquid crystal, solar thermal energy storage, signal transmission, intelligent encryption, and other purposes. Furthermore, these systems can function as key components for device upgrade processing. However, the design and rules of azo supramolecular polymers are still not supported by an exact theory. Information about the relationship between the spatial structure and behavior is lacking, and new supramolecular materials cannot be designed by adding functional moieties to known azo polymers.Based on the current research status, this review mainly summarizes the structural design principles as well as structures and applications of known azo supramolecules; meanwhile, it highlights the emerging development fields, recent advances, and prospects in fabricating self-assembling intelligent supramolecular systems with azo supramolecular polymers as responsive units. The goal of this review is to bring new inspiration to researchers who want to optimize the chemical structure, steric conformation, electrostatic environment, and specific molecular functionalization.     

Thermodynamics of ionic solid solutions: III. An addendum

In two earlier papers (C.A. 117:259320(1;121:19411y) the activity coefficients of the salts in binary solid solutions at 25‡C for 38 salt pairs, in which the members of each pair differ with respect to only one kind of ion, were determined. While the activity data are correct, the conclusions regarding deviations from ideality for eight of these pairs, namely those in which there are two moles of replaceable ion per mole of salt, require modification in order to be consistent with ideal entropies of mixing. By changing the formulation of the component salts to one-half of what is usual, the inconsistencies disappear. This half-mole approach, applied to the salt pairs CU_1/2(NH₄/K)SO₄-3H₂O, Mg_1/2NH₄(SO₄/ CrO₄)-3H₂O, Mg_1/2NH₄(SeO₄/SO₄)-3H₄O, Mg_1/2NH₄(SeO₄/CrO₄)-3H₄O, Mg_1/2 (K/NH₄)SeO₄-3H₂O, (NH₄/K)(SO₄)_1/2, and Ba_1/2(ClO₃/BrO₃)-1/2 H₂O shows that these solid solutions exhibit positive, not negative, deviations from ideality at 25‡C. Only the system Pb_1/2(C1/Br) still deviates negatively.     

刺激响应聚合物在金纳米粒子催化体系中的应用

刺激响应聚合物是近几年来研究的热点之一,这类聚合物能够感受外界刺激而发生响应,产生物理或化学性质的变化。金纳米粒子由于量子效应,具有良好的催化性质,因此有广阔的应用前景。但是在实际的应用中却常常面临易于团聚的问题,因此时常需要将其负载于载体之上。将刺激响应聚合物引入金纳米粒子催化体系之中,一方面可以发挥普通载体所能起到的分散作用,防止金纳米粒子团聚,另一方面也可实现可控催化,可以通过外界条件的改变来调控金纳米粒子的催化性能。本文综述了该体系近期的研究进展,从体系的构建方式、刺激响应类型等方面进行了论述,并对该体系的研究与应用进行了总结与展望。     

Monolayer properties of fatty acids : III. Thermodynamics of mixing

The thermodynamic properties of mixed fatty acids have been studied in the region of the surface vapor pressure. Using myristic acid as a common component various saturated and unsaturated fatty acid mixtures have been compared with regard to their tendency to be miscible or immiscible. Deviations from expected ideal behavior have allowed estimation of activity coefficients. Measurement of surface heats of vaporization has led to the determination of solubility parameters for each fatty acid. Applying regular solution theory or using activity coefficients allows independent estimation of , the partial molar enthalpy of mixing, and the two approaches are in good agreement. Therefore, it is possible to predict mixing tendencies for any combination of fatty acids used in this study.     

含醇溶液的热力学研究Ⅲ.超额体积

根据先前提出的含醇溶液形成的热力学模型，利用充上和释放两个组分间引力 势能的方法，建立了一个含醇溶液超额体积方程．该方程有清晰的物理意义，不仅 能描述各种各样含醇溶液的超额体积随组成的变化规律，而且还能显示自缔合、交 叉缔合和组分间的van der Waals引力对超额体积的贡献．     

Polymer additive analysis by pyrolysis-gas chromatography. III. Lubricants

Lubricants are widely used in thermoplastic polymers to increase the overall rate of processing or to improve surface release properties. Because of the low level of lubricants normally used in a polymer, it may not be possible to analyze the additive directly by common spectroscopic or thermal chemical techniques. However, lubricants as well as other additives in the polymer can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) after extraction. In this work, several lubricants have been studied to demonstrate that Py-GC is a viable tool to investigate lubricants. The advantages of using Py-GC in the analysis of lubricant have also been discussed.     

聚合物胶乳的立体稳定性

本文首先叙述了影响聚合物胶乳稳定性的各种效应,然后着重介绍了立体稳定的基本原理。     

Liquid-Liquid Equilibrium of Polydisperse Copolymer Solutions. Multivariate Distribution Functions in Continuous Thermodynamics

In addition to the usual polydispersity with respect to molar mass, copolymers show chemical polydispersity. Thus, the species present may not be adequately characterized by a single variable, and a divariate distribution function has to be applied for describing the composition of the copolymer. In continuous thermodynamics, such continuous distribution functions are used directly (without splitting into pseudocomponents) for describing the composition of complex multicomponent systems. Whereas until now usually only one distribution variable has been used in continuous thermodynamics, consideration of copolymers requires an extension to divariate distribution functions. Continuous thermodynamics is generalized to divariate distribution functions in this paper. The liquid-liquid equilibrium of copolymer solutions is considered as a specific example.