disclosed is a thermoreversible synthesis of a new type of material made by embedding a colloidal population within a thermo - reversibly gelled polymer . the polymer may be a physically cross - linked pva hydrogel . pva hydrogels are non - toxic , biocompatible , mechanically robust , and elastic . the present invention tgcca diffraction is similar to that of photo - polymerized pcca . the present invention tgcca can be irreversibly covalently cross - linked using glutaraldehyde . the cross - linked tgcca can be made responsive to chemical stimuli by functionalizing the hydrogel hydroxyl groups . the diffraction of carboxyl or amine functionalized tgcca was monitored as a function of the ph and determined diffraction wavelengths titrate with the pka of the functional group . it was also demonstrated that tgcca could be fabricated in arbitrarily large volumes and shapes . the present invention method fabricates inexpensive homogenously diffracting chemically modifiable tgcca .