When looking at what affects SVA, one of the main things that come up first is the solvent that is used, and what nanostructure is wanted to be obtained. For example, if a hierarchical structure is desired, a solvent that has a vapor that can selectively mobilize the amorphous polymer chains of a semi-crystalline polymer is ideal because it can also keep the integrity of the crystals, allowing for the secondary structure to form.
Looking more at BCP itself, they make ordered nanostructures because of thermodynamic differences between different blocks of the polymer. The sample morphology at equilibrium can be predicted using the molar mass of the blocks, the degree of polymerization of the chains (N), and the Flory-Huggins interaction parameter (χ) which is a magnitude of exactly how incompatible the different blocks are. These factors, along with the composition of the BCP, allow microphase separation of chains and the rearrangement into the desired product. The composition provides an especially important part of the process as knowing the ordering, such as alternating AB monomers, gives light on how to section the polymer in the desired manner.
Along with this, the selection of a specific type of block polymer is important for the process and its effectiveness. The main thing to consider is the original structure of the block at room temperature, as well as, temperatures in which each block will begin to change phase. Knowing these temperatures is critical in determining when each will begin to react and take in solvent and at what rate this will happen, which is critical in pushing to a desired morphology of the given block polymer through annealing.
Other factors that affect SVA are parameters such as vapor pressure, solvent concertation in the film, and evaporation rate of the solvent. Each of these factors contributes to the volatility and imprecision at times of this method, not possessing a set mechanism for the construction of structures that are desired, such as nanocylinders. Getting perfect success of the desired morphology of a polymer has yet to be achieved with these plethoras of factors dictating formation.