Structural Analysis of Unimer Nanoparticles Composed of Hydrophobized Poly(amino acid)s

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• 作者：Phassamon Piyapakorn ; Takami Akagi ; Masahiro Hachisuka ; Tomoyuki Onishi ; Hideki Matsuoka ; Mitsuru Akashi
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：August 13, 2013
• 年：2013
• 卷：46
• 期：15
• 页码：6187-6194
• 全文大小：298K
• 年卷期：v.46,no.15(August 13, 2013)
• ISSN：1520-5835

文摘

Amphiphilic random copolymers of poly(纬-glutamic acid)-graft-l-phenylalanine (纬-PGA-Phe), with various lengths of 纬-PGA main chains (molecular weight of 70, 140, and 220 kDa) plus hydrophobic moieties of Phe groups (grafting degree 12鈥?0%), self-assembled in aqueous media to form nanoparticles (NPs). The aggregation number (N_agg) could be adjusted according to their molecular structures as well as the preparative methods/conditions. The 纬-PGA-Phe NPs were further characterized by means of dynamic and static light scattering, small-angle neutron scattering, as well as steady-state fluorescence measurements/quenching techniques. The single chain state had hydrophobic domains, and formed spherical structures, herein called unimer NPs, and were obtained using molecular weights of 纬-PGA higher than 140 kDa conjugated with Phe at 27鈥?2% due to the balance of hydrophobicity/hydrophilicity along the single polymer chain. The number of hydrophobic domains in one NP (N_domain), estimated by means of fluorescence quenching techniques and the rigidity of the inner particles detected by dipyrene fluorescence demonstrated that the N_domain and the rigidity were affected by the particle size and preparative methods. In addition, the effect of pH on the stability of the unimer NPs indicated a reduction of the N_domain upon the pH, supporting a loose packing due to hydrophobic association under alkaline conditions.