We synthesized a series of polysilanes-[Si(CH3)(2)SiR2](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 solvatochromisin 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.