Modification of a Hyperbranched Hydridopolycarbosilane as a Route to New Polycarbosilanes

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.

Synthesis and characterization of a propargyl‐substituted polycarbosilane with high ceramic yield

“…These tetracarbosilicon, tricarbosilicon, dicarbosilicon, and monocarbosilicon units were further evidence of a branched structure. 3,6 In conclusion, the resultant polymers were confirmed as propargyl-substituted PCSs by means FTIR spectroscopy and NMR. On the basis of these findings, the molecular structure of PHPCS is given in Scheme 1.…”

Novel Processing of Unique Ceramic-Based Nuclear Materials and Fuels

“…AHPCS has a nominal structure of [Si( [48,[136][137][138], diagrammatically described as show in Fig. 32 [139].…”

Methylene-bridged carbosilanes and polycarbosilanes as precursors to silicon carbide—from ceramic composites to SiC nanomaterials

“…In addition to single-source CVD precursors to silicon carbide, 1 this research has led to the development of a commercial hyperbranched polycarbosilane precursor to SiC (AHPCS) [2][3][4] as well as linear polycarbosilanes of the type, [SiRR CH 2 ] n , that have been of fundamental interest as silicon analogs of important organic polymers, such as polyethylene 5 and polyvinylidene fluoride, 6 as well as for use in the study of the pyrolytic conversion of polycarbosilanes to SiC. 7 The synthesis of the hyperbranched polycarbosilane was originally carried out by coupling of the AB 3 -type monomer, ClMgCH 2 SiCl 3 , the Grignard reagent of ClCH 2 SiCl 3 , in ether solution, followed by reduction with LiAlH 4 .…”

“…10 Replacement of Cl by allyl ( CH 2 CH CH 2 ) groups, by using allylMgCl, yields a "[SiCl 2−x (allyl) x CH 2 ]", derivative with as high as 90% allyl substitution (x = 1.8). This highly allyl-substituted derivative (APCS) can be used to attach various types of side chains through hydrosilation reactions 3 leading, for example, to APCS-PEO side-chain polymers that, when doped with LiX salts, can serve as ionically conductive, Li + electrolyte media. 11 Partial substitution with allyl (on the order of 5-10%) prior to reduction of the remaining Cl groups to H with LiAlH 4 , yields an allylhydridopolycarbosilane (AHPCS) that exhibits high ceramic yield for conversion to a near stoichiometric, amorphous, SiC on pyrolysis to 1000 • C. 12 This relatively air-stable, liquid, polycarbosilane has been widely used as a precursor for SiC matrixes in SiC/SiC and C/SiC composites through polymer infiltration and pyrolysis and as part of a "molding compound" for the fabrication of particulate-reinforced SiC matrix composites and monoliths.…”