Zhang Minghua, He Jianping, Deng Mingyu, Gong Peixin, Zhang Xi, Fan Minmin, Wang Ke
College of Polymer Science and Engineering, Sichuan University Chengdu 610065 China.
Jingkun Oilfield Chemistry Company Kunshan 215300 China.
RSC Adv. 2020 Aug 28;10(53):32050-32057. doi: 10.1039/d0ra04322b. eCollection 2020 Aug 26.
Three guar gum derivatives with hydrophobic unsaturated long-chains were successfully synthesized, including oleic guar gum (OGG), linoleic guar gum (LGG) and erucic guar gum (EGG). The guar gum derivatives were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Moreover, comparative studies on the rheological behaviours of guar gum (GG) and three guar gum derivatives were performed. Regardless of their hydrophobic side groups, all sample solutions showed the properties of non-Newtonian shear-thinning fluids, and their complex viscosities (*) increased significantly with increasing concentration. In contrast to GG, OGG or EGG, LGG exhibited the strongest shear-thinning property when the concentration is 1 wt%. It was found that the frequency-dependent viscous ('') and elastic modulus (') curves of GG and its derivatives aqueous solutions cross at a specific frequency. This crossover frequency decreases with increasing sample concentration, indicating that the viscoelasticity is highly dependent on polymer concentration. In addition, when the molar substitution (MS) of the repeating sugar units in the guar gum derivatives is less than 0.08, the LGG solution showed more obvious solid-like rheological properties than the OGG and EGG solutions at the same concentration.
成功合成了三种带有疏水不饱和长链的瓜尔胶衍生物，包括油酸瓜尔胶（OGG）、亚油酸瓜尔胶（LGG）和芥酸瓜尔胶（EGG）。通过傅里叶变换红外光谱（FTIR）和热重分析（TGA）对瓜尔胶衍生物进行了表征。此外，还对瓜尔胶（GG）和三种瓜尔胶衍生物的流变行为进行了对比研究。无论其疏水侧基如何，所有样品溶液均表现出非牛顿剪切变稀流体的特性，并且它们的复数粘度（*）随浓度增加而显著增加。与GG、OGG或EGG相比，当浓度为1 wt%时，LGG表现出最强的剪切变稀特性。发现GG及其衍生物水溶液的频率依赖性粘性（''）和弹性模量（'）曲线在特定频率处相交。该交叉频率随样品浓度增加而降低，表明粘弹性高度依赖于聚合物浓度。此外，当瓜尔胶衍生物中重复糖单元的摩尔取代度（MS）小于0.08时，在相同浓度下，LGG溶液比OGG和EGG溶液表现出更明显的类固体流变特性。
