The average properties of block copolymers formed via the one-prepolymer method and the two-prepolymer method

Full Paper: In this paper, a model is developed for determining the average properties of block copolymers formed via the one-prepolymer and the two-prepolymer methods. A knowledge of the average properties of reacting prepolymers, instead of their whole molecular weight distribution (MWD), is sufficient to calculate the desired average molecular weights of the resultant block copolymers. M̄_n, M̄_wand polydispersity index (PI) of the block copolymers formed via the one-prepolymer and two-prepolymer are studied in detail for comparison. The simulation results indicate that M̄_n,1p<M̄_n,2p and M̄_w,1p<M̄_bw,2p in the range 0≤α< 1, while M̄_n,1p = M̄_n,2p and M̄_w,1p = M̄_w,2p when α = 1. In addition, the conversion (α) does not significantly influence PI_2p, while PI_1p decrease linearly with increasing α. The results also show that PI_1p> PI_2p in the range 0 ≤ α<1. Finally, PI_1p and PI_2p approach the same value at α = 1. This indicates that the polydispersity of the block copolymers formed via the two-prepolymer method is usually narrower than that of the block copolymers formed via the one-prepolymer method. A schematic illustration of the block copolymerization of prepolymer A and prepolymer B (the two-prepolymer method).