Shrinkage and recyclability of poly(1,2-ethylene- bis(dimethylsiloxane))

摘要

Non-shrinking polymers are desirable as encapsulants for strain-free packaging for electronics. Ring-opening polymerizations of cyclic monomers such as lactams, cyclic ethers, and cyclic oligosiloxanes have proven an effective strategy for reducing shrinkage. In this report the authors examined the loss of volume during the ring-opening polymerization of neat 2,2,5,5-tetramethyl- l-oxa-2,5-disilacyclopentane to give poly(1,2-ethylene- bis(dimethyl-siloxane)). Monomer 1 is under sufficient strain (8--12 kcal/mole) to permit its facile base-catalyzed polymerization to afford high molecular polymer. Monomer 1 was prepared by hydrolyzing and condensing either 1,2-bis(chlorodimethylsilyl)ethane or 1,m2-bis(dimethyle thoxysilyl)ethane to give a low molecular weight oligomer. Pyrolysis of this oligomer with potassium hydroxide at 280 C afforded the cyclic monomer in good yield (60--70%). The ease with which the oligomer can be converted to monomer also led the authors to investigate the potential for recycling the high molecular weight polymer.