The invention provides a process for polymerizing a polymer comprising monomeric units derived from styrene and 1,3-butadiene, said process comprising: A) adding less than 60 weight percent of the total amount of the butadiene used in the polymerization, to a reactor comprising the total amount of styrene used in the polymerization and solvent; B) adding at least one initiator to the reactor, and allowing the reaction to proceed for a time t; C) adding the remaining amount of butadiene to the reactor in two or more separate additions; and wherein for each butadiene addition, the amount of subsequent butadiene added is less than, or equal to, the amount of butadiene added in the immediately prior addition; and wherein for each butadiene addition, the butadiene is added over a time, tnc, and after each addition, the reaction is allowed to proceed for a time, tnr, wherein n is the number of the butadiene addition, and for each addition, n is independently greater than, or equal to, 1.