BACKGROUND: Poly(olefin sulfone)s have been shown to form helical regions and to display main-chain liquid-crystalline behaviour in the bulk when they possess long side-chains. It is believed that increasing the tacticity of the backbone could enhance their liquid-crystalline behaviour. This study aims to produce tactic poly(olefin sulfone)s by stereospecific ring-opening polymerisation. RESULTS: Tactic polythiranes were successfully obtained from a racemic mixture of thirane monomers using a series of chiral catalyst systems. The isotactic placement (P-i) was determined using C-13 NMR analysis of carbons in or near the backbone. The polysulfides were oxidised by peracetic acid to their corresponding polysulfones. Powder X-ray diffraction studies showed that the isotactic polysulfones formed more ordered structures than their atactic analogues, an effect attributed to a tightening of the helical pitch. CONCLUSIONS: Tactic poly(1-hexene sulfone)s have been prepared for the first time by stereoselective ringopening polymerisation. (C) 2007 Society of Chemical Industry.