(629g) Synthesis of Hydrophobically Modified Polybetaines (HMPB) and Study of Their Self-Assembly By Molecular Dynamics Simulations

The presentation discusses reversible addition fragmentation chain-transfer (RAFT) polymerization of hydrophobically modified polybetaines (HMPB) and their self-assembly in aqueous solutions using a combination of experiments and molecular dynamics (MD) simulations. RAFT was used to synthesize HMPB for the first time and MD simulations were used to illustrate the self-assembled morphologies.

As a first step in the RAFT polymerization of HMPB, the desired enamine form of alkylaminocrotonate (monomer) was synthesized by thermal bulk reaction method. The synthesis was followed by purification of enamine alkylaminocrotonate, from the impurities of reactants and the imine form of alkylaminocrotonates, using silica gel chromatography. The monomer was characterized by FTIR and H-NMR. FTRP and C13-NMR, combining with GPC, were used to confirm polymer compositions and molecular weight distribution. Molecular weight of around 80,000 g/mol and a narrow molecular weight distribution of 1.214 was achieved.

The self-assembly behavior of RAFT-HMPB was investigated by both experimental characterization techniques and MD simulations. Both TEM characterization and MD simulations suggest that, at low concentration HMPB forms spherical aggregates. MD simulations show that at high concentrations, worm-like micelles are formed. The stability of these micelles was also investigated using MD simulations. Furthermore, DLS and zeta potential measurements indicated pH responsive behavior of HMPB aggregates. Concentration and pH responsive behavior of HMPB combined with its stability suggest that HMPB has potential for applications in drug delivery and enhanced oil recovery.