Spirocycles versus Networks: Polycondensations of Ge(OEt)₄ with Various Aliphatic α,ω-Diols

Abstract

Ge(OEt)4 was heated with various α,ω-alkanediols beginning with 1,2-ethanediol up to 1,16-hexadecanediol, whereby a nearly quantitative polycondensation with elimination of EtOH took place. All polycondensation products proved to be insoluble and infusible gels with the exception of the six-numbered spirocycle derived from 1,3-propanediol. A soluble spirocycle was also obtained from cis-1,4-butenediol, whereas an insoluble, infusible gel was formed by trans-1,4-butanediol. When Ge(OEt)4 was polycondensed with monodisperse oligo(ethylene glycol)s soluble syrupy mixtures of spirocycles were obtained in all cases. These results were explained on the basis of different conformational properties of alkane or ethylene oxide chains and on the basis of our theory of thermodynamically controlled polycondensations featuring a decisive role of ring−ring equilibria. The soluble spirocyclic Ge−oligoethylene oxides proved to be useful initiators for the ring-opening polymerization of ε-caprolactone.