Polymers computer programs

Novikov, V. U. Kozlov, G. V. Boronin, D. V. The fractal approach to numerical study of cross-linked polymers computer program elaboration. Material Science, 1999, 3, 25-28. 

A specialized computer program has been developed at PLASTEC to provide rapid access to data describing the influence of propints and expls on the behavior of polymers. Termed COMPAT for short — it is the only known central source of this type information, obtained from tests conducted at ARRADCOM and a wide assortment of data published in the open literature... 

A general methodology has been developed for the treatment of NMR data of polymer mixtures. The methodology is based on reaction probability models and computer optimization methods, resulting in a family of computer programs called MIXCO. The use of MIXCO programs enabled three components to be resolved from NMR tacticity data of fractionated polybutylene. 

NMR/Fractionation. The combination of NHR and fractionation is an excellent approach to study polymer mixtures.(17) If the components of the mixture are completely fractionated, then IIMR characterization is straightforward. If the components of the mixture are similar in structure such that separation is partial, then the computerized approach described above can be used to study the NMR/fractionation data and to deconvolute the consonants in each fraction. Thus far, three computer programs have been written to study MMR/fractionation data, two for polymer tacticity (MIXCO.CSX, MIXCO.C4X), and one for copolymer triad sequences (MIXCO.TRIADX). 

Size exclusion liquid chromatography M) has been widely used to characterize distributions of molecular weights in polymer specimens. This paper describes a package of computer programs for automatic data collection and data reduction in size exclusion liquid chromatography (2). The programs and the environment in which they operate are carefully tailored to emphasize the interaction between the user and his data rather than the Interaction between the user and the computer. The system we describe differs from that described by Koehler et al. (J) in that all functions are performed by a stand-alone system. 

The 300 MHz H NMR and 20 MHz 13C NMR spectra of poly(4-methyl-l-pentene) have been found to be more complex than the corresponding spectra of poly(3-methyl-l-butene) due to the presence of an additional isomer structure in the polymer. Investigation of the 20 MHz 13C NMR spectrum of the polymer has indicated that placement of units in different triad sequences is die cause of multiple methyl proton resonances which have been observed in the H NMR spectra of poly(3-methyl-l-butene) and poly(4-methyl-l-pentene). The use of a computer program for simulating and plotting spectra has enabled measurements of polymer composition to be made of poly(4-methyl-l-pentene) s prepared under a variety of synthesis conditions. 

Once a finite element formulation has been implemented in conjunction with a specific element type — either 1D, 2D or 3D — the task left is to numerically implement the technique and develop the computer program to solve for the unknown primary variables — in this case temperature. Equation (9.19) is a form that becomes very familiar to the person developing finite element models. In fact, for most problems that are governed by Poisson s equation, problems solving displacement fields in stress-strain problems and flow problems such as those encountered in polymer processing, the finite element equation system takes the form presented in eqn. (9.19). This equation is always re-written in the form... 

Despite the large number of analytical solutions available for the diffusion equation, their usefulness is restricted to simple geometries and constant diffusion coefficients. However, there are many cases of practical interest where the simplifying assumptions introduced when deriving analytical solutions are unacceptable. Such a case, for example, is the diffusion in polymer systems characterized by concentration-dependent diffusion coefficients.This chapter gives an overview of the most powerful numerical methods used at present for solutions of the diffusion equation. Indeed the application of these methods in practice needs the use of adequate computer programs (software). 

Automated polymer-based synthesis comes into its own when a stepwise polymerization is required with precise control over the addition of particular monomers in a specific sequence. This is almost a definition of peptide synthesis, Nature attaches each amino acid to a different polymer (transfer RNA) and uses a computer program (the genetic code) to assemble the polymers in the right order so that the amino acids can be joined together while bound to another polymer (a ribosome). No protection of any functional groups is necessary in this process. 

The calculations of the statistical characteristics of such polymers within the framework of the kinetic models different from the terminal one do not present any difficulties at all. So in the case of the penultimate model, Harwood [193-194] worked out a special computer program for calculating the dependencies of the sequences probabilities on conversion. Within the framework of this model, Eq. (5.2) can be integrated in terms of the elementary functions as it was done earlier [177] in order to calculate copolymer composition distribution in the case of the simplified (r 2 = Fj) penultimate model. In the framework of the latter the possibility of the existence of systems with two azeotropes was proved for the first time and the regions of the reactivity ratios of such systems [6] were determined. In a general version of the penultimate model (2.3-24) the azeotropic compositions x = 1/(1 + 0 ) are determined [6] by the positive roots 0 =0 of the following... 

A quarter of a century ago Behnken [224] as well as Tidwell and Mortimer [225] pointed out that the linearization transforms the error structure in the observed copolymer composition with the result that such errors after transformation have no longer zero mean and constant variances. It means that such transformed variables do not meet the requirements for the least-squares procedure. The only statistically accurate means of estimation of the reactivity ratios from the experimental data is based on the non-linear least-squares procedure. An effective computing program for this purpose has been published by Tidwell and Mortimer (TM) [225]. Their method is considered to be such a modification of the curve-fitting procedure where the sum of the squares of the difference between the observed and computed polymer compositions is minimized. 

In practice the lifetime distributions are usually obtained using a computer program such as the MELT [21] or CONTIN [22, 23] programs. The reliablity of these programs for measurring the o-PS lifetime distribution in polymers was shown by Cao et al [24]. A detailed description of these methods of data analysis is presented in Chapter 4. The advantage of the continuous lifetime analysis is that one can obtain free volume hole distributions rather that the average values obtained in the finite analysis. 

The current state-of-the-art is such that there are no reliable methods of predicting liquid-liquid equilibria of polymer-solvent systems. Thus, the recommended procedures and computer programs included in this Handbook treat only vapor-liquid equilibrium. A discussion of the correlation of LLE data is included in Chapter 2. 

Chapter 4 describes the polymer data bases. This chapter is organized into sections discussing the experimental methods available for measuring the thermodynamic data of polymer solutions with an overview of the advantages and disadvantages of each method. The next section, Data Reduction Methods, describes how the experimental measurements from these experiments can be used to calculate the activity coefficients that are necessary for phase equilibria calculations. Finally, a summary of all the systems that are available on the data diskettes is provided. A user can scan this section or use the computer program POLYDATA to find if data are available for a particular system. 

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