[Introduction] Block copolymers have attracted wide attention due to their specific chemical property and widely applications. Many of the multi-stimuli responsive polymers are block copolymers. Among the various stimuli, thermo-responsiveness has been focused on. Recently, our group showed carboxylated poly-l-lysine (PLLSA) shows lower critical solution temperature (LCST). On the other hand, poly-sulfobetaine (PSPB) has been reported to exhibit upper critical solution temperature (UCST) behavior in water and inhibit protein aggregation. In order to get the polymer with all these properties, we prepared a diblock copolymer of PLLSA and poly-SPB. [Experimental] The diblock copolymers were synthesized by a three-step reversible addition fragmentation chain transfer (RAFT) polymerization. First, PLLSA was obtained by substituting different degree of substitution of succinic anhydride (SA) to PLL. The addition of the RAFT agent to PLLSA was followed. The formed macro-chain transfer agent can be used to control the degree of polymerization of SPB. The diblock copolymers were obtained after dialysis and freeze dry. All the diblock copolymers were characterized by NMR. UV-Vis spectroscopy and dynamic light scattering (DLS) were employed to analyze the dual-thermo-responsive property. [Results and Discussion] From the NMR spectroscopy, the characteristic peak of the two blocks was clearly seen (Fig1a). From the graph we can clearly see the diblock copolymer solutions showed turbid at lower and higher temperature, indicating the dual-thermo-responsive property (Fig1b). Furthermore, the DLS result showed the diblock copolymers showed aggregation at low and high temperature (Fig1c). [Conclusion] The diblock copolymers were successfully prepared by RAFT polymerization. And the diblock copolymers exhibited dual-thermo-responsive property.

Synthesis and characterize of the dual-thermo- responsive diblock copolymer

2019 Spring National Meeting

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