J. Idris Jones

Abstract One facet of materials science which has been the subject of intensive research over the last decade is the development of new ther mally stable polymers. The main stimulus has come from the need to meet the demands of modern technological advances and, in particular, the increasingly stringent environmental requirements of the space program. Much effort has been expended on the synthesis and evaluation of the thermal stability of new organic, organometallic, and inorganic polymers; highly fluorinated polymers; coordination polymers; and pyrolytic polymers. The goal has been to extend the useful upper temperature limits a t which polymers maintain their desirable properties to at least 300°C, with an ultimate objective of 500°C o r above. The protection of spacecraft and missiles against the intense heat encountered on “reentry” has focused attention on the ablative properties of plastics, and many studies have been devoted to the protective mechanism and performance of various materials, notably reinforced plastics. The investment in this area of research has been very substantial but although significant advances have been made in some directions, as in the field or organic polymers, success has been elusive in others. The synthesis of more thermally stable elastomers still presents a formidable challenge. As fallout from this largely government-sponsored research program, some new polymers have been developed to the stage where they represent technologically useful high-temperature materials.

J. L. Hales, J. I. Jones and A. S. Lindsey, J. Chem. Soc., 1954, 3145 DOI: 10.1039/JR9540003145

Abstract Tar base fractions commonly described as “commercial β‐picoline” are mixtures containing β‐ and γ‐picoline and 2 : 6‐lutidine in variable, if usually roughly equal proportions. Many methods for the separation of one or more of the individual components have been proposed yet few are suitable for commercial exploitation. In the present paper it is shown that by azeotropic fractional distillation the three bases may be readily separated in purities of 95‐98% and with little loss, if acetic or propionic acids are used as azeotropic‐formers, and it is possible to recover for re‐use the acids from the separate base‐acid azeotropes with the aid of a suitable hydrocarbon entrainer. It is also shown that the hydrochlorides of the bases differ very markedly in physical properties and can be easily separated. Pure specimens of the three bases were obtained by fractional freezing of 95‐88% pure materials : 2 : 6‐lutidine, b.p. 144°, f.p. −5·97°; β‐picoline b.p. 1447middot;0°, f.p. −177middot;77°; γ‐picoline b.p. 145·37°, f.p. + 47middot;3°.