The development of diblock copolymers as structure directing agents for phase selective additives to generate thin films is discussed. Different systems ranging from pure organic [(poly(alpha-methyl styrene-block-4-hydroxystyrene) and poly(alpha styrene-block- isoprene) with photoactive crosslinkers] to an organic-inorganic [poly(isoprene-block- ethylene oxide) with 3-glycidyloxypropyltrimethoxysilane and aluminum-tri-sec-butoxide] to a non-oxide high temperature system [poly(isoprene-block-dimethylamino ethylmethacrylate) with a polyureamethylvinylsilazane additive] are explored. Characterization is accomplished through a variety of techniques (atomic force microscopy, scanning electron microscopy, grazing incidence small angle x-ray scattering, nuclear magnetic resonance, and Rutherford backscattering) and supplemented by quantitative analysis (radial and bond orientation distribution functions, Voronoi diagrams, and GISAXS simulations). Hybrid organic-inorganic mesoporous monolayer thin films are used as templates to structure silicon at the 30 nm length scale through a transient laser induced melt and capillarity driven pore filling process.