Journal of Polymer Science Part A: Polymer Chemistry, Vol.54, No.18, 3019-3031, 2016
Peptide-Poly(tert-Butyl Methacrylate) Conjugate into Composite Micelles in Organic Solvents Versus Peptide-Poly(Methacrylic Acid) Conjugate into Spherical and Worm-Like Micelles in Water: Synthesis and Self-Assembly
Peptide-polymer conjugates are versatile class of biomaterials composed of a peptide block covalently linked with a synthetic polymer block. This report demonstrates the synthesis of peptide-poly(tert-butyl methacrylate) (Peptide-P t BMA) conjugates of varying molecular weights via a "grafting from" atom transfer radical polymerization (ATRP) technique using as-synthesized peptide-based initiator in toluene. Peptide-P t BMA conjugate is soluble in many organic solvents and undergoes self-assembly into micro/nanospheres in DMF/THF as observed from both FESEM and DLS results. The conjugate micro/nanospheres are nothing but the composite micelles formed by the secondary aggregation of primary micelles generated initially in these organic solvents. The hydrolysis of tert-butyl groups of Peptide-P t BMA conjugate leads to the formation of peptide-poly(methacrylic acid) (Peptide-PMA) conjugate. The circular dichroism (CD) analysis exhibits the presence of beta-sheet conformation of peptide moiety in synthesized conjugates. The formed Peptide-PMA conjugate is soluble in water and owing to its amphiphilic character, the conjugate molecules self-assemble into spherical micelles as well as worm-like micelles upon increasing the concentration of conjugate in water. However, the sodiumsalt of Peptide-PMA conjugates (Peptide-PMAS) self-assembles into only spherical swollen micelles in water at higher (pH = 10). The critical aggregation concentrations (CACs) of both Peptide-PMA and Peptide-PMAS micelles are measured by fluorescence spectroscopy. (C) 2016 Wiley Periodicals, Inc.