Synthesis and properties of poly(cis-1,4-dihydroxy-2,3-epoxybutane)

The cyclic acetone ketal of 1,4-dihydroxy-2,3-epoxybutane (DMTO) polymerizes with i-Bu₃Al-0.7 H₂O catalyst by a cationic mechanism at ?78°C to a moderate molecular weight (η_inh up to 0.7), atactic (based on ¹³C-NMR) polymer (PDMTO). At higher temperature and in bulk, up to 14% crosslinked polymer is obtained as a result of epoxide and ketal ring opening. Triethylaluminum is an effective catalyst at 0–50°C in bulk. Coordination catalysts were less effective but the results indicate that an effective one can be designed. PDMTO is readily hydrolyzed with aqueous HCl treatment to atactic, water-soluble poly(1,4-dihydroxy-2,3-epoxybutane) (PDHEB) with a T_g of 80°C. PDHEB is melt stable to 200°C and can be molded to give brittle, clear films that readily pick up 5–10% H₂O from the atmosphere to give properties like those of plasticized poly(vinyl chloride). PDHEB is degraded by electron beam radiation but can be crosslinked with glyoxal plus toluene sulfonic acid/The bis(trimethylsilyl) ether of cis-1,4-dihydroxy-2,3-epoxybutane was polymerized cationically with the i-Bu₃Al-0.7 H₂O catalyst at ?78°C to a fairly tactic, presumably racemic di-isotactic, amorphous polymer, with η_inh of 0.16. A mechanism is proposed for this stereoregular polymerization based on a complexation of the Si side group of the last chain unit with the propagating oxonium on.