Solvent effect on the self-assembly of polyisobutylene-based glycopolymers

Investigation of polymeric conformations in different solvents is critical because block copolymer solution morphology is not only associated with the architecture but also with its characteristic features which depend upon the solvent polarity. A series of double hydrophobic diblock copolymers comprising polyisobutylene (PIB) segment and varying sugar pendant units have been prepared by a combination of living cationic and reversible addition-fragmentation chain transfer (RAFT) polymerizations. After the deprotection of the acetate from sugar pendants, the synthesized water-soluble amphiphilic block copolymers showed morphological transformations in both aqueous and organic media. A conformational transition due to a change in solvent polarity from polar protic to nonpolar was supported by 1H NMR spectroscopy. The dynamic light scattering (DLS) experiments demonstrated that the hydrodynamic diameters of aggregates varied with solvent polarity. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) evidenced the morphological changes from micellar to tubular orientation. Finally, the self-assembly behavior of PIB-based glycopolymers due to changes in solvent polarity is proposed.