New hyperbranched polymers (1P-3P) from propargyloxysilanes (1-3) are described. The propargyloxysilanes were prepared from readily available reagents in 53-61% yields. The polymerizations were clean, one-pot hydrosilylation processes catalyzed by Pt/C that were typically complete within 3 h. The polymers contained pendant acetylenic groups that underwent thermally induced crosslinking reactions. Heating the polymers to 1300 degreesC in flowing nitrogen resulted in weight losses ranging from 33 to 66%. Methyl substitution resulted in lower thermal stability. Further modification of the polymers was demonstrated by the reaction of 1P and 2P with phenylethynyldimethylsilane in the presence of a Pt catalyst.