title: Structural and rheological characterizations of nanoparticles of environment-sensitive hydrophobic alginate in aqueous solution.
abstract: Amphiphilic polymers that form self-assembled structures in aqueous media have been investigated and used for the diagnosis and therapy of various diseases, including cancer. In our work, a series of environment-sensitive hydrophobic alginates (Ugi-Alg) with various weight-average molecular mass values (Mw~6.7×105-6.7×104g/mol) were synthesized via Ugi reaction. The structure of Ugi-Alg was characterized by1HNMR spectrometer. The electrostatic self-assembly of different molecular weight (Mw) and composition (M/G ratio) of Ugi-Alg chain under various Na+concentrations, was investigated by dynamic light scattering, electron spin resonance experiments, and transmission electron microscopy. Result showed that by comparing to other Ugi-Alg, the mid-Mw Ugi-Alg (Mw~2.8×105g/mol) could form stable and homogeneous nanoparticles in low Na+concentration solution. However, G/M values exerted no obvious effect on nanoparticles structure. Additionally, steady-shear flow, thixotropy and dynamical viscoelasticity tests were performed to characterize the rheological behavior of Ugi-Alg aqueous solutions as influenced by Mw and M/G ratio. All of the samples exhibited a non-Newtonian shear-thinning behavior above a critical shear rate (γ̇c2). The greater the Mw, the more sensitive the temperature-dependent behavior will be. The upward-downward rheograms showed that all of the systems evaluated in this study displayed a hysteresis loop, indicating a strong thixotropic behavior, and the thixotropic of mid-Mw Ugi-Alg was the strongest. The dynamical viscoelastic properties were characterized by oscillatory frequency sweep, revealing the gel-like viscoelastic behavior of mid-low Ugi-Alg and the fluid-like viscoelastic behavior of high-Mw Ugi-Alg.
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: 1479334044@qq.com.
authors: Kai
authors: K
authors: Chen
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: ljcfyh@263.net.
authors: Jiacheng
authors: J
authors: Li
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: hn136.163@163.com.
authors: Yuhong
authors: Y
authors: Feng
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: 6583161@qq.com.
authors: Furui
authors: F
authors: He
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: 1203701089@qq.com.
authors: Qingfeng
authors: Q
authors: Zhou
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: 1553137983@qq.com.
authors: Dunchao
authors: D
authors: Xiao
authors: College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China. Electronic address: 1014601375@qq.com.
authors: Yiyuan
authors: Y
authors: Tang
mesh_terms: D000464:Alginates / Q000737:chemistry*; D004777:Environment; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008970:Molecular Weight; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D066244:Proton Magnetic Resonance Spectroscopy; D012212:Rheology; D012996:Solutions; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D013696:Temperature; D014783:Viscosity
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D012996:Solutions; D020723:Glucuronic Acid
keywords: Dynamical viscoelasticity; Electrostatic self-assembly; Hydrophobic alginates; Nanoparticles; Steady-shear flow; Thixotropy