Polysulfone

Polysulfones are a family of thermoplastic polymers. These polymers are known for their toughness and stability at high temperatures. They contain the subunit aryl-SO2-aryl, the defining feature of which is the sulfone group. Polysulfones were introduced in 1965 by Union Carbide. Due to the high cost of raw materials and processing, polysulfones are used in specialty applications and often are a superior replacement for polycarbonates. Polysulfones are a family of thermoplastic polymers. These polymers are known for their toughness and stability at high temperatures. They contain the subunit aryl-SO2-aryl, the defining feature of which is the sulfone group. Polysulfones were introduced in 1965 by Union Carbide. Due to the high cost of raw materials and processing, polysulfones are used in specialty applications and often are a superior replacement for polycarbonates. In principle, any polymer containing a sulfonyl group could be called 'polysulfone'. However, the term 'polysulfone' is normally used for polyarylethersulfones (PAES), since only aromatic polysulfones are used in a technical context. Furthermore, since ether groups are always present in the industrially used polysulfones, PAES are also referred to as polyether sulfones (PES), poly(arylene sulfone)s or simply polysulfone (PSU). The three terms (and abbreviations) may therefore be synonyms. As a term for all polysulfones, 'poly(aryl ether sulfone)s (PAES)' is preferable because polysulfone (PSU), polyethersulfone (PES) and poly(arylene sulfone) (PAS) are additionally used as a name for individual polymers. These and some other PAES are listed in the chapter Industrially relevant polysulfones (below). The simplest polysulfone poly(phenylene sulfone) was known as early as 1960. It can be produced in a Friedel-Crafts reaction from benzenesulfonyl chloride: A r − S O 2 − C l ⟶ − [ − A r − S O 2 − ] n + H C l {displaystyle mathrm {Ar-SO_{2}-Cllongrightarrow -_{n}+HCl} } Since this polymer has a melting point of over 500 °C, it is on one side very heat resistant, on the other hand it is very difficult to process. In addition, its mechanical properties are rather poor. Therefore, thermoplastic (melt-processable) polysulfones were researched as an alternative. At that time it was already assumed that polyarylether sulphones (PAES) would be a suitable alternative. Appropriate synthetic routes to PAES were developed almost simultaneously, and yet independently, from 3M Corporation, Union Carbide Corporation in the United States, and ICI's Plastics Division in the United Kingdom. The polymers found at that time are still used today, but produced by a different synthesis process. The synthesis method used at that time followed an electrophilic synthesis. Not only para- but also ortho bonds were generated, which led to cross-linking in some cases and generally to worse mechanical properties. The syntheses consisted of an electrophilic aromatic substitution of an aryl ether with a sulfuryl chloride using a Friedel-Crafts catalyst (e. g. iron(III)chloride or antimony(V)chloride):