Temperature-dependent UV spectra of three isomeric, amorphous, ether-substituted polymethylsilanes, (RMeSi)(n) [R = (CH2)(6)OCH3, (CH2)(5)OC2H5, and (CH2)(4)OC3H7], show that, in the solid state, the thermochromic pattern and transition temperature depend on the nature of the ether substitutent. A discontinuous transition from 303 to 330 nm was observed for both methoxyhexyl and ethoxypentyl polymers, whereas the propoxybutyl polymer merely showed a gradually shifted absorption. As the oxygen atom is placed closer to the main chain, the glass transition temperature and Si-29 spin-lattice relaxation time decrease, consistent with enhanced side-chain motions. Three symmetrical ether-substituted polysilanes, (R2Si)(n) [R = (CH2)(6)OCH3, (CH2)(5)OC2H5, and (CH2)(4)OC3H7], were also investigated. These polymers exist as hexagonal columnar mesophases above their transition temperatures; below the transition temperature, they crystallized and exhibited a distinct thermochromism from 320 to 352 nm.