The effects of covalently incorporating a T-shaped photochromic spiropyran molecule with cholesterol- and biphenyl-substituted mesogens to a cyclic siloxane backbone on the liquid crystalline behavior of the resulting macromolecular siloxanes are reported. The siloxanes containing up to 20% spiropyran are liquid crystalline, whereas at higher compositions the products are amorphous. With increasing spiropyran content, the selective reflection band characteristic of the cholesteric mesophase shifted to lower wavelengths. The photochromic reaction leading to the blue merocyanine formation resulted in a narrowing of the reflection bandwidth. Steric effects imposed by cholesterol, biphenyl, and bulky spiropyran groups dominate the thermal decoloration kinetics of the merocyanine form. Aggregation of merocyanines was observed in nonpolar solvents, whereas in thin glassy films formed by shearing in the liquid crystalline state such an observation was not evident. In siloxanes bound only to spiropyran, an evidence of a shift in the thermal equilibrium toward merocyanine aggregate formation leading to molecular stacks was observed. Short spacer length of the leader group in spiropyran inhibited 100% attachment to the cyclic siloxane backbone, possibly due to steric effects. Longer spacer groups facilitated 100% attachment.