Liquid Crystalline Period Variations in Self-Assembled Block Copolypeptides-Surfactant Ionic Complexes

We investigate the complexation of ampholytic poly(N-isopropylacylamide)-block-poly-(L-glutamic acid)-block-poly(L-lysine) (PNiPAM-b-PLG-b-PLLys) triblock copolymers and PNiPAM-block-(PLG-co-PLLys) diblock copolymers with counter charged anionic and cationic surfactants. Both triblock and diblock copolymers are able to selectively form complexes through either L-glutamic acid-cationic surfactant or L-lySine-anionic surfactant ionic pairs, depending on the protonated or deprotonated states of the ampholytic peptide units. The complexes show ordering at multiple length scales: i) the block copolymer length scale (10(1) nm), ii) the liquid crystalline length scale (10(0) nm), and, iii) the peptidic secondary structures length scale (10(0) nm). We show that the liquid crystalline period can be tuned by varying the random/block copolypeptide architectures and the composition of the ampholytic amino acid species.