SYNTHESIS OF POLY(SILYLENEMETHYLENE)S SYMMETRICALLY SUBSTITUTED WITH ALKYL SIDE-GROUPS CONTAINING 4-6 CARBON-ATOMS

New poly(silylenemethylene)s with long n-alkyl side chains, namely, po ly(di-n-butylsilylenemethylene) (PDBSM), poly(di-n-pentylsilylenemethy lene) (PDPeSM), and poly(di-n-hexylsilylenemethylene) (PDHSM), have be en prepared by means of catalytic ring-opening polymerization of the c orresponding tetraalkyl-substituted 1,3-disilacyclobutanes. Polymeriza tion yielded high molecular weight poly(silylenemethylene)s with a str ictly alternating SiR(2)/CH2 backbone structure. Longer polymerization times were necessary for 1,3-disilacyclobutanes substituted with long er n-alkyl chains than for the polymerization of monomers with methyl groups. High molecular weight fractions of the materials were characte rized by calorimetry with respect to their thermal behavior. Considera bly higher glass transition temperatures evidenced lower backbone flex ibility than for the analogous poly(di-n-alkylsiloxane)s. Surprisingly , all homologues including poly(di-n-propylsilylenemethylene) (PDPSM) displayed similar phase behavior, showing a small endotherm a few degr ees below isotropization, but no broad mesophases as observed in the c ase of the poly(di-n-alkylsiloxane)s.