Evaluation of alternative models for the mechanism of chain‐growth copolymerization

A general method for discriminating between different models for chain‐growth copolymerization is described. The method is based on the non‐linear least‐squares analysis of variations in the copolymer compositions or sequence distributions with the compositions of the monomer feed mixture. It allows the best values for the reactivity ratios for each model to be evaluated, and their joint confidence regions to be delineated. The method is demonstrated by applications to the copolymerizations of styrene with acrylonitrile and maleic anhydride. Copyrigh

The heats of solution of alcohols in water

A new calorimeter has been developed and the enthalpy of solution of methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, and 2- methylpropan-2-ol, in water to low concentrations, measured between 5° and 35°. In all cases, the results can be adequately represented by a quadratic dependence of heat of solution on temperature. The results have been compared qualitatively with the data for the hydrocarbons

An investigation of microstructure of styrene-methacrylonitrile copolymers by FT-IR spectroscopy

The microstructure of styrene-methacrylonitrile copolymers has been investigated by FT-IR spectroscopy. The CN bond stretching frequency was shifted to a higher value with an increase in the methacrylonitrile (MAN) content in the copolymers. There was no linear relationship between the CN frequency and the diad fraction of MAN-MAN linkages in the copolymer chain, as reported previously for styrene-acrylonitrile copolymers. Different methods for the copolymer sample preparation can cause differences in the shifts in the CN frequency. This suggests that the polymer morphology plays an important role. A study of blends of poly(methacrylonitrile) (PMAN) with polystyrene has shown that the CN frequency is shifted to a higher value with an increase of the PMAN composition of the blends

The enthalpies of solution of hexa-1-ol and heptan-1-ol in water

The solubility of hexan-1-ol and heptan-1-ol in water has been measured over the temperature range 278-308 K. The free energy, enthalpy and heat capacity of solution of these alcohols has been calculated from this data and the enthalpy and heat capacity have also been obtained by direct calorimetric measurement. The thermodynamic function changes on solution of these two alcohols follow the pattern of the lower members of the homologous series. The results have been compared qualitatively with data for the other alcohols and for the hydrocarbons

Apparent molar volumes in dilute aqueous propanol solutions

Apparent molar volumes of propan-2-ol have been determined in dilute aqueous solution from 0° to 80°. Structural volume changes in propan-1-ol and propan-2-ol solutions are discussed and related to compressibilities

Bisphenol-a polysulfone as a temperature probe for the electron-beam irradiation of polymers

A procedure is described for determining the temperature of polymers during electron beam irradiation at high dose rates by measurement of the soluble fractions of samples after various doses of radiation. The soluble fraction data are analyzed to derive values of the crosslinking yield, G(X), at different times, which are compared with the G(X) values obtained for irradiation at various temperatures at lower dose rates, e.g., with 7-radiation, when the temperature is controlled and remains constant. The technique is demonstrated for bisphenol-A polysulfone, which is suggested as a standard reference that can be used to provide an estimation of the temperature rise in other polymers with similar dimensions during electron beam irradiation at high dose rates. Low dose-rate electron beam irradiation (3 Mrad/h) has been shown to give the same G values as “Co 7-irradiation (0.1 MGy/h) under the experimental conditions

Study of the Role of Charge-Transfer Complexes in Some Bulk-Phase Free-Radical Polymerizations

Literature copolymer composition data on the bulk polymerizations of maleic anhydride-styrene, acrylonitrile-styrene, and fumaronitrile-styrene have been considered in terms of the complex participation model. An assessment has been made in each case as to whether sequence information would be able to distinguish between the complex and penultimate polymerization models