Despite advances in nanomaterials synthesis, the bottom-up preparation of nanopatterned films as templates for spatially confined surface reactions and nucleation of crystalline inorganics remains a challenge. I developed an approach to fabricating nanoscale thin film surface structures with periodicities on the order of 20 to 50 nm and with the capacity to localize reactions with small molecules and nanoparticles. A block copolymer (BCP) of polystyrene-block-poly[(allyl glycidyl ether)-co-(ethylene oxide)] (PS-b-P(AGE-co-EO)) is used to prepare periodically-ordered, reactive thin films. As proof-of-principle demonstrations of the versatility of the chemical functionalization, a small organic molecule, an amino acid, and ultrasmall silica nanoparticles are selectively attached via thiol-ene click chemistry to the exposed P(AGE-co-EO) domains of the BCP thin film. My approach employing click chemistry on the spatially confined reactive surfaces of a BCP thin film overcomes the solvent incompatibilities typically encountered when synthetic polymers are functionalized with water-soluble molecules. Moreover, this post-assembly functionalization of a reactive thin film surface preserves the original patterning, reduces the amount of required reactant, and leads to short reaction times. The small molecule functionalized area can subsequently template the confined crystallization of copper (I) oxide (Cu2O) and zinc oxide (ZnO) with high fidelity, from aqueous solutions at low temperatures (below 60 °C) with periodicities on the order of 50 nm. The demonstrated method provides a versatile materials platform to control the growth of nanostructured crystalline materials via the introduction of a plethora of surface functional groups. The resulting organic substrates can be used to template the growth and control the crystal orientation and texturing of multiple different crystalline inorganic materials on surfaces nanostructured via BCP self-assembly. The demonstrated approach is expected to provide a new materials platform in applications including sensing, catalysis, pattern recognition, or microelectronics.