ANIONIC-POLYMERIZATION OF DIETHYLCYCLOSIL OXANES - FORMATION OF LINEAR OLIGODIETHYLSILOXANES AND THEIR PHASE-TRANSITIONS

Anionic polymerization of hexaethylcyclotrisiloxane (D-3(e)) and octae thylcyclotetrasiloxane (D-4(e)) initiated by potassium silanolate has been studied. According to the GLC and GPC data, the polymerization of strained D-3(e) includes the stage of rapid polymerizatlon followed b y the stage of slower depolymerization. The polymerization of unstrain ed D-4(e) does not lead to the formation of a high-molecular poly(diet hylsiloxane). In both cases, short-chain linear oligo(diethylsiloxanes ) of the type KO-(D-e)(n)-K with n = 2 - 6 are formed in addition to t he cyclic D-n(e) oligomers. Under the equilibrium polymerization condi tions, active silanolate centers exhibit almost complete segregation i n the linear short-chain oligo(diethylsiloxanes) of the type KO-(D-e)( n)-K. The data obtained indicate that poly(diethylsiloxane) is a therm odynamic unstable system, in which macromolecules can form only under unequilibrium polymerization conditions. The phase transitions in olig o(diethylsiloxanes) with M = 3140 and 11800 were studied by DSC and X- ray diffraction.