Self-assembly of linear-hyperbranched hybrid block polymers: crystallization-driven or solvent-driven?

Self-assembly of polyethylene-block-hyperbranched polyglycidol diblock polymers (PE1-b-hbPG(7)-OH8 and PE1-b-hbPG(26)-OH27) in selective or slightly selective or nonselective solvents of PE segments were investigated by microscopy (TEM, SEM and AFM). Study showed that both polymers can be assembled into a diamond-shaped lamellae driving by PE crystallization in toluene solvent, composed of PE single-crystal layer sandwiched between two hbPG layers tethered on the top and bottom basal surfaces. However, by adding the toluene solution of polymers to THF and MeOH, the morphology of the aggregate changed from lamellae to rod or sphere, indicating the change of driving force from the crystallization of PE block to the interaction parameter () between hbPG block and solvent. In addition, the degree of polymerization (DP) of hbPG segments affected the thickness of the lamellae (in toluene) and the shape and size of the rodlike or spherical aggregate (in mixed solvent), determined by the relative volume fractions of PE and hbPG chains in selective solvents.