Not only does the choice of solvent influence the solution viscosity, but the different degrees of chain transfer activity associated with different solvents affects the molecular weight of the polymer formed. The peroxide initiator reactivity is also influenced by the solvent, the initiator half-life being affected by certain solvents.
The boiling point of the solvent has a major influence on the reaction conditions since its presence during the polymerisation dictates the maximum reaction temperature which can be utilised. In turn the reaction temperature will influence the choice and quantities of initiator and modifier used to achieve the desired molecular weight and degree of conversion. Thus solvent combinations are often used to allow the polymerisation to be carried out at a suitable reaction temperature. Often where low boiling solvents are required in the final polymer solution, they are added after polymerisation has been carried out in another solvent.