Synthesis and self-assembly of hydrophobically modified polybetaines

Date

2017-05

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Abstract

The reversible addition fragmentation chain-transfer polymerization (RAFT) was developed to synthesize hydrophobically modified polybetaines (HMPB) for the first time. In addition molecular dynamics simulation was used to study the self-assembly behaviors of HPMB. Chemical structures of monomers and polymers were characterized by FTIR and NMR. GPC was used to unravel the molecular weight and PDI of HMPB. The morphologies, aggregates sizes, and aggregates stabilities were characterized by TEM, DLS and zeta-potential. PDI of 1.214 was achieved with Mn of 70590 g/mol and Mw of 87080 g/mol, which indicated the success in controlling the molecular weight of HMPB for the first time. At low concentrations up to 0.3%, HMPB tended to aggregate into perfect or imperfect spherical structures. The discontinuously pH- and/or concentration-responsive self-assembly behaviors were observed; size changed from 70 nm to 230 nm. Isoelectric point was observed around pH of 1.8. The coarse-grained MARTINI force field works for studying self-assembly behavior of HMPB at different concentrations. According to the simulation results, the preference for circular shapes of construction units was explained by hydrophobic interactions. Electrostatic interactions were supposed to be the driving force behind the stimulation-responsive self-assembly behaviors of HMPB.

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Keywords

polybetaine, reversible addition fragmentation chain-transfer polymerization (RAFT), self-assembly, MARTINI- coarse-grained (CG) force field

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