Control of micellar size and critical micelle concentration for nonamphiphilic poly(vinyl phenol)-block-polystyrene diblock copolymers

Control of micellar size and cmc was studied for nonamphiphilic poly(vinyl phenol)-block-polystyrene diblock copolymers (PVPh-b-PSt) in the micellization by 1,4-butanediamine (BDA). The micellization was explored for the copolymers with Mn(PSt blocks) = 20 K, 35 K, 75 K, and 125 K, holding the PVPh block length constant (Mn(PVPh blocks) = 10 K), in order to investigate effect of the PSt block length on the size of micelles. Dynamic light scattering demonstrated that the copolymers with longer PSt blocks formed larger micelles, although the copolymers had a slight difference in the unimer size. The copolymers had the transition from the unimers to the micelles at the same BDA concentration, indicating that the cmc of the copolymers was independent of the PSt block length. The PVPh block length had effects not only on the micellar size but also on the cmc. The copolymers with longer PVPh blocks showed the transition at lower BDA concentration. When the copolymers had almost the same unit ratios of VPh to St, the copolymer with larger molecular weight formed larger micelles at lower BDA concentration. The size of micelles and the cmc were also manipulated by the mixed ratio of the copolymers with different block length.