Unconventional, amphiphilic polymers based on chiral poly(ethylene oxide) derivatives. 2. Ordering and assembly

The poly(ethylene oxide) derivatives 1-3 (Figure 1) are-in design-synthetic analogues of coiled-coil-forming peptides. A comparative optical rotatory dispersion (ORD) study and TEM measurements have been used to investigate the ordering and assembly processes that are involved in the aggregation of these amphiphilic polymers 1-3 in H2O. ORD measurements have shown that various ethylene oxide derivatives display an inversion of optical rotation upon complexation with KSCN, i.e. upon adoption of a helical conformation. This observation has led to the proposal that polymers 1-3 are helically ordered in H2O, since the methyl-substituted polymer 3 exhibits an inversion of optical rotation on going from apolar (THF) to polar (H2O) solvents; phase separation prohibits the detection of such an inversion for the isobutyl-substituted polymers 1 and 2. TEM studies on surfaces onto which polymers 1-3 were deposited from aqueous solutions revealed granular and threadlike aggregates. The formation of the threadlike higher structures requires a directionality in the assembly process. Such a directionality could be provided by the formation of coiled-coil tertiary structures. However, substantial evidence for the formation of coiled coils or other specific tertiary structures is lacking.