No abstract

A general method for introducing various side chains onto a highly branched polysilaethylene (HBPSE) backbone is described. This method starts with a commercial oligomer mixture which has a highly branched structure, consisting of [H3SiCH2], [SiH2CH2], [SiH(CH2)2], and [Si(CH2)3] subunits combined to give an overall "SiH2CH2" average formula. Several alkyl-, aryl-, and allyl-substituted HBPSEs were prepared by first converting the parent HBPSE into a highly reactive bromo-substituted derivative which was then treated with organolithium reagents (RLi, R ) C4H9, C6H13, C8H17, C6H5, C6H4N(Me)2) or Grignard reagents (RMgBr, R ) Et, allyl). The parent HBPSE and its derivatives were characterized by means of NMR and IR spectroscopy, as well as elemental analysis, DSC, GPC, and VPO. It was shown that the allyl-substituted HBPSE can be used as a synthetic platform for attaching functional side chains via the hydrosilation reaction.

Introduction. Ring-opening polymerization of e-caprolactone can be achieved in a living manner using a variety of alkoxo complexes.1 In particular, aluminum,2 zinc,3 and rare-earth alkoxides4 have attracted much attention as versatile and highly active initiators, allowing the synthesis of block copolymers and end-group-functionalized poly(e-caprolactones). However, most of the highly Lewis acidic alkoxides, usually prepared in situ and therefore not isolated, cannot be considered to be struc-

A new series of poly(silylenemethylenes) of the type [Si(Me)(X)CH2]n, where X ) OR (R ) Et, CH2CF3, Ph, Ac), F, and R′ (R′ ) n-butyl, allyl), were obtained starting from the preformed [Si(Me)-(Cl)CH2]n polymer. The OR derivatives were obtained quantitatively from the [Si(Me)(Cl)CH2]n polymer by treatment with ROH/Et3N or NaOR. Reaction of the [Si(Me)(Cl)CH2]n polymer with the allyl Grignard reagent also gave 100% substitution, but the reaction with the n-butyl Grignard reagent was found to proceed only to the extent of ∼70%. The novel [Si(Me)(F)CH2]n polymer was obtained by the action of BF3‚Et2O on the [Si(Me)(OEt)CH2]n polymer. The atactic structures of these polymers were characterized by NMR spectroscopy, and their molecular weights and thermal properties were examined by GPC, DSC, and TGA. The [Si(Me)(OR)CH2]n polymers were found to vary widely in terms of their hydrolytic sensitivity and glass transition temperatures.

The poly(silylenemethylenes), [SiRRCH21,, constitute a relatively undeveloped class of inorganic polymers that are of potential interest as relatives of both the carbonbased polyolefinsl and such inorganic polymers as the polysilanes, polysiloxanes, and polyphosphazenes. Until quite recently, the only route that has been available for the preparation of high molecular weight, linear polymers of this type has involved the Pt-complexcatalyzed ring-opening polymerization of the corresponding substituted 1,3-disilacyclobutane monomers.This route works best for R and R = Me and Me, Ph substituents on Si.2 Of the polymers prepared by this route, only poly[(dimethylsilylene)methylenel has been well ~haracterized,~ and this is apparently an amorphous material with a relatively low Tg. Earlier attempts to introduce other functionality on Si by polymerization of the corresponding substituted disilacyclobutanes as well as by methyl-cleavage reactions on poly[(dimethylsilylene)methylenel resulted in low molecular weight material^.^^,^ The discovery made in our laboratory that polymerization and subsequent reduction of 1,3-dichloro-1,3-dimethyl-1,3-disilacy~lobutane~ and tetrachlorodisilacyclobutane6 gives high molecular weight poly(silapropy1ene) and poly(silaethylene), respectively, effectively opened up a new route to the preparation of substituted poly(silylenemethy1enes).Among the possible substituted poly(silylenemethy1enes) that would be of particular interest t o prepare are the alkoxy-substituted polymers, since these would apparently represent the first well-characterized linear polymers with alkoxy substituents on a backbone silicon atom. Such polymers may also have potential for use as sol-gel precursors to inorganidorganic network polymers and as functional polymers with novel physical properties. Moreover, to our knowledge, the only polymers known that have two alkoxy groups on the same backbone atom are the polyphosphazenes, some of which show such interesting properties as mesophase forma-tion7 as well as ionic conductivity when various Li salts are added. 8 We report here our investigations of synthetic routes for the preparation of alkoxy-substituted poly(sily1enemethylenes) as well as the preliminary characterization of some new members of this class of polymers, namely, [Si(OR)2CH21a and [Si(CH3)(0R)CH2In where R = CH2CF3 and CH2CH3.Generally speaking, there are two possible ways to synthesize alkoxy-substituted poly( silylenemethylenes). The first is the polymerization of the corresponding substituted monomers, and the second is the functionalization of a preformed polymer which has suitably reactive groups on the Si atoms.Based on our previous observation that the polymerization and subsequent reduction of tetrachlorodisilacyclobutane gives poly(silaethy1ene) with a degree of polymerization (DP) of 200,l functionalizing poly-[( dichlorosilylene)methylene] to obtain poly[(dialkoxysi-1ylene)methylenel was tried first. Unfortunately, all attempts to introduce ethoxy groups through reactions 0024-929719512...