The Effect of PEO Length on the Self-Assembly of Poly(ethylene oxide)−Tetrapeptide Conjugates Prepared by “Click” Chemistry

Two series of poly(ethylene oxide)−tetrapeptide conjugates have been prepared using a “Click” reaction between an alkyne-modified tetra(phenylalanine) or tetra(valine) and various azide-terminated poly(ethylene oxide) (PEO) oligomers. Three different PEO precursors were used to prepare these conjugates, with number-average molecular weights of 350, 1200, and 1800 Da. Assembly of mPEO−F4−OEt and mPEO−V4−OEt conjugates was achieved by dialysis of a THF solution of the conjugate against water or by direct aqueous rehydration of a thin film. The PEO length has a profound effect on the outcome of the self-assembly, with the F4 conjugates giving rise to nanotubes, fibers, and wormlike micelles, respectively, as the length of the PEO block is increased. For the V4 series, the propensity to form β-sheets dominates, and hence, the self-assembled structures are reminiscent of those formed by peptides alone, even at the longer PEO lengths. Thus, this systematic study demonstrates that the self-assembly of PEO−peptides depends on both the nature of the peptides and the relative PEO block length.