Side Chain Effect on Thermochromism and Solvatochromism of End-Grafted Polysilane [Si(CH₃)₂SiR₂]_n (R = C₂H₅, n-C₄H₉, n-C₆H₁₃, n-C₈H₁₇, n-C₁₀H₂₁)

Abstract

We synthesized a series of polysilanes -[Si(CH 3)2SiR2]n-[R ) C2H5, n-C4H9, n-C6H13, n-C8H17, n-C10H21] end-grafted on a quartz surface by utilizing the anionic polymerization of the corresponding source materials. We first confirmed that these symmetrically alkyl-substituted polysilanes exhibited reversible thermochromism in isooctane solution. When the polysilanes were end-grafted on the quartz surface, they also exhibited reversible thermochromism in a vacuum and reversible solvatochromism as the ratio of the isooctane/ethanol cosolvent was varied. In all of these experiments, we observed the transition between two clearly distinguishable phases. No side chain effect was observed for the peak wavelengths of the absorption band. However, the side chain effect appeared at a critical temperature and a critical cosolvent ratio for the transitions. The packing force between the alkyl chains in the highly ordered structure of the polysilane plays a dominant role in these transitions. We also discuss the difference in the transition behavior in solution, in the solid state, and in the end-grafted state.

Evaluation of Global Conformation of Polydialkylsilane Using Correlation between Persistence Length and Excitonic Absorption

“…One of the most unique physical phenomena of PSis is thermochromism, which has been observed under various conditions; such as dilute solution, cast film, and even isolated single chain tethered on the substrates . Depending on their alkyl side chains, the thermochromism of the PSis involves either gradual or abrupt bathocromic shift in the λ max with decrease in temperature .…”

Polysilanes on surfaces

“…74 The masked disilene-based tethering method for PSi on surfaces led to the first observation of unique chromisms such as solvent-free thermochromism and solvatochromism in poor solvents. 76…”

Core Phase Transition of Radiation-Modified Polysilane Micelles as Revealed from Their Thermochromism

“…This result is explained by local concentration of PMPrS chains within the core. 13 In the solid core, PMPrS chains contact with each other and therefore the local concentration of the PMPrS chains is high. The conformational transition of PMPrS chains requires large thermal energy because of the restriction of the chain motion.…”