| Abstract
| - Temperature-dependent UV spectra of three isomeric, amorphous,ether-substitutedpolymethylsilanes, (RMeSi)n [R =(CH2)6OCH3,(CH2)5OC2H5, and(CH2)4OC3H7],show that, in the solidstate, the thermochromic pattern and transition temperature depend onthe nature of the ethersubstitutent. A discontinuous transition from 303 to 330 nm wasobserved for both methoxyhexyl andethoxypentyl polymers, whereas the propoxybutyl polymer merely showed agradually shifted absorption.As the oxygen atom is placed closer to the main chain, the glasstransition temperature and 29Si spin-lattice relaxation time decrease, consistent with enhanced side-chainmotions. Three symmetrical ether-substituted polysilanes, (R2Si)n[R = (CH2)6OCH3,(CH2)5OC2H5, and(CH2)4OC3H7],were also investigated.These polymers exist as hexagonal columnar mesophases above theirtransition temperatures; below thetransition temperature, they crystallized and exhibited a distinctthermochromism from 320 to 352 nm.
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