Michael M. Coleman

Concerning the Application of FT-IR to the Study of Coal: A Critical Assessment of Band Assignments and the Application of Spectral Analysis Programs

The problems associated with the application of FT-IR to the characterization of coal structure are critically discussed. The controversies concerning band assignments are considered and it is concluded that the strong 1600 cm−1 band can be assigned to an aromatic ring stretching mode that in most coals is intensity enhanced by the presence of phenolic groups. The application of computer routines to the determination of OH and CH groups is considered. Established criteria for curve fitting are applied to the problem. Qualitative identification of functional groups is achieved, but consistent quantitative measurements will require a determination of the relationship between the extinction coefficients of resolved bands.

Hydrogen bonded polymer blends

Abstract Since the publication of our monograph, Specific Interactions and the Miscibility of Polymer Blends in 1991, there have been a number of significant advances in the field of hydrogen bonded polymer blends. This paper is essentially a progress report and we review both theoretical and experimental developments that have occurred over the last three or so years.

A practical guide to polymer miscibility

In this paper a general guide to polymer miscibility is presented. The view taken here is that in many polymer systems mixing can be predicted on the basis of a simple balance between unfavourable ‘physical forces’, described in terms of non-hydrogen bonded solubility parameters, and favourable specific interactions. In essence, the closer the values of the two solubility parameters and the greater the relative strength of the potential intermolecular interactions present between the polymeric components of the blend, the greater the probability of miscibility. This is discussed in terms of critical values of the interaction parameter, χCrit, and the upper limits of the non-hydrogen bonded solubility parameter difference, Δδ. It is then demonstrated that this approach can be applied to the prediction of trends in miscibility for a wide range of binary polymer blend systems.

Concerning the miscibility of poly(vinyl phenol) blends: FTi.r. study

Abstract The results of a Fourier transform infrared study of poly(vinyl phenol) (PVPh) blends containing a number of chemically and structurally dissimilar polymers are presented. These polymers include the polyesters poly(e-caprolactone) and poly(⊤-propiolactone); poly(vinyl alkyl ethers) where the alkyl groups are methyl, ethyl and isobutyl respectively; poly(ethylene oxide) and poly(vinyl pyrrolidone). All of these PVPh blends, with the exception of that containing poly(vinyl isobutyl ether), exhibit infrared spectral features consistent with a significant degree of mixing. Intermolecular hydrogen bonding interactions involving the PVPh hydroxyl group and either the carbonyl or ether oxygen moieties of the other polymers in the blend are identified. The relative strengths of these intermolecular interactions are discussed together with ramifications pertinent to the overall subject of polymer miscibility.

Further studies of coal oxidation

The low-temperature oxidation of coal has been investigated by Fourier transform infrared spectroscopy (FT-i.r.). Samples were oxidized at 140 and 60 °C for intervals of a few hours to days. These FT-i.r. results were correlated to changes in the thermoplastic properties of the coal measured by a Gieseler plastometer. The loss of Gieseler fluidity as a function of oxidation time corresponds to loss of aliphatic CH groups. Curve-resolving methods were used to distinguish between various C = 0 functional groups. At both oxidation temperatures there was an overall increase in carbonyl and carboxyl groups, but in different relative proportions depending on the oxidation temperatures.

FTi.r. studies of polymer blends containing the poly(hydroxy ether of bisphenol A) and poly(ε-caprolactone)

Abstract Fourier transform infra-red (FTi.r.) studies of the polymer blend system poly(hydroxy ether of bisphenol A) (phenoxy)-poly(e-caprolactone) (PCL) are presented. These two polymers are miscible in the amorphous state and information concerning the presence and nature of intermolecular interactions between the two polymers has been gained. Specifically, direct evidence has been obtained for a hydrogen bonding interaction between the PCL carbonyl group and the phenoxy hydroxyl group. Significantly, the relative strength of this interaction is found to be weaker than the corresponding intermolecular hydrogen bonding interaction in pure phenoxy. In contrast, a cursoryFTi.r. study of phenoxy-poly(ethylene oxide) blends reveals that the intermolecular interaction occuring between these two polymeric components is stronger than that occuring in pure phenoxy. In addition, PCL is a crystallizable polymer and studies performed on the PCL-phenoxy blends at room temperature have led to further information on the state of order of PCL in these blends. The ramifications of these results are discussed.

Fourier Transform Infrared study of mineral matter in coal. A novel method for quantitative mineralogical analysis

Abstract A novel method for the quantitative determination of mineral matter in coal is reported. The low-temperature ash of coal is analysed by means of absorbance spectral subtraction of individual components. The spectra of individual minerals, stored in digital form on computer memory, are multiplied by appropriate weighting factors and subtracted from the spectrum of the low-temperature ash, so that the characteristic bands of the mineral are removed. Provided that the weight of each mineral in the infrared beam is known then the weight fractions can be determined from the weighting factors. Successive subtraction starting with the most strongly absorbing components reveals the minor or less strongly absorbing species, which could not previously be determined by infrared spectroscopy. The analysis of several mixtures and of the low-temperature ash of various coal samples is reported.

Low Temperature Air Oxidation of Caking Coals: Fourier Transform Infrared Studies

Fourier transform infrared spectroscopy has been used to characterize the oxidation of a coking coal. The results demonstrate that the most important initial products of oxidation are carbonyl and carboxylic acid groups. Bands associated with carbon-oxygen single bonds, as in ethers or phenols, do not become prominent until the later stages of the oxidative process. Upon reaction with potassium in tetrahydrofuran a number of changes in the spectrum of both the oxidized and unoxidized coal become apparent. This reagent cannot be considered specific for cleavage of ether bonds, but can also lead to products usually associated with air oxidation.

Studies of the phase behaviour of poly(vinyl phenol)-poly(n-alkyl methacrylate) blends

Abstract The results of theoretical and experimental studies of poly(4-vinyl phenol) (PVPh) blends with a series of poly(n-alkyl methacrylates) are presented. PVPh is miscible with poly(methyl methacrylate), poly(ethyl methacrylate) and poly(n-propyl methacrylate) over the entire composition range at temperatures between ambient and 200°C. In contrast, PVPh—poly(n-butyl methacrylate) blends phase separate at temperatures below 200°C. Quantitative analyses of the fraction of hydrogen bonded carbonyl groups were obtained by FT i.r. spectroscopy for all the PVPh blends—poly(n-alkyl methacrylates) as a function of composition and temperature. The data obtained from the miscible blend systems was employed to determine values of the equilibrium constant describing inter-association, K A , and the enthalpy of hydrogen bond formation, h A . Theoretical fractions of hydrogen bonded carbonyl groups and spinodal phase diagrams were calculated using a recently reported association model. The results compare very favourably to experiment.

Studies of the degradation of acrylonitrile/acrylamide copolymers as a function of composition and temperature

Abstract The degradation of acrylonitrile/acrylamide copolymers as a function of composition at 160 and 200°C under reduced pressure has been studied by Fourier transform IR spectroscopy. The results are somewhat surprising and indicate that above a certain threshold of comonomer concentration the fraction of available nitrile groups that undergo reaction is limited and falls within a remarkably narrow range. From a consideration of the copolymer and stereochemical sequence distribution, the stereochemistry of ring formation and intermolecular crosslinking. we have concluded that a “step-ladder” model for the degraded product is applicable. Additionally, we have concluded that the distribution of tactic placements in the copolymer chains is a factor limiting the degree of cyclization of the available nitrile groups. A computer program has been developed for calculating the extent of reaction of the acrylonitrile units based upon the above model and the results are in good agreement with the experimental observations.