【作者】 邹时英；

【导师】 江波；

【作者基本信息】 四川大学 ， 高分子化学与物理， 2003， 硕士

【摘要】 瓜尔胶虽是目前已知的水溶性最好的天然高分子化合物之一，但却有溶解速度慢，水不溶物含量高，粘度不易控制等缺点，这使得它难以满足工业应用的要求，因此需要进行改性，如酯化、醚化等，以扩大它的应用范围。本文利用环氧丙烷与瓜尔胶的反应，制备了羟丙基瓜尔胶；用分光光度法和核磁共振测定了羟丙基瓜尔胶的取代度，考察了羟丙基在瓜尔胶上连接方式；并利用Brookfield DV-Ⅲ流变仪考查了羟丙基的引入对瓜尔胶水溶液流变性的影响。羟丙基和1，2—丙二醇都能和浓硫酸发生反应，产物和茚三酮生成的紫色化合物在586nm处的吸光度与羟丙基或1，2—丙二醇的浓度在一定范围内成正比，由此建立了分光光度法测量羟丙基瓜尔胶摩尔取代度的方法。在羟丙基瓜尔胶的¹H NMR谱图中，半乳糖和甘露糖H-1的共振信号处于最低场，而—CH₃氢的化学位移最小，三种氢原子峰都能和其它氢原子峰相分离，利用它们的峰面积之比也可以测定羟丙基瓜尔胶的摩尔取代度。光度法与核磁共振测定的结果相一致。将瓜尔胶和羟丙基瓜尔胶的¹³C NMR谱图进行了比较，发现谱图中碳原子峰的位置完全一样，且强度基本未发生变化，从而推测羟丙基是以长链方式与瓜尔胶相连接，而不是在糖单元上均匀分布。结合¹³C NMR的灵敏度，可以估计出羟丙基的最小链长。此外，从瓜尔胶及羟丙基瓜尔胶溶液的表观粘度—剪切速率变化的曲线上可以看出，瓜尔胶和羟丙基瓜尔胶溶液都呈假塑性，同时，羟轻丙基瓜尔胶的制备及表征丙基瓜尔胶溶液的粘度较瓜尔胶有很大程度的降低且降低的程度随摩尔取代度的增大而增大。更多还原

【Abstract】 Guar gum, a water-soluble natural polymer, is often chemically modified to improve its physical and chemical properties. Pure and modified guar gums are widely used as thickeners or protective colloids in the food, textile, petroleum and mining industries. In this work, hydroxypropyl guar gum is prepared and characterized. The preparation is based on the reaction of guar gum with propylene oxide. The characterization is focused on the determination of molar substitution and the connection between guar gum and hydroxypropyl chain. Spectrometry and 1H NMR are used to determine molar substitution, and the results determined by the two methods are in good agreement. 13C NMR is used to assume the connection between guar gum and Hydroxypropyl and the length of polyoxypropyl chain. The effects of introduction of hydroxypropyl group are evident from rheological parameters such as r\0 and E. The n0 and E of hydroxypropyl guar gum are smaller for a given concentration than those of guar gum, and the decreases are morepronounced with the increasing of molar substitution. The introduction of hydrophobia hydroxypropyl group in guar gum is quite favorable for its practical application.更多还原