【作者】 贾晓辉；

【导师】 沈青；

【作者基本信息】 东华大学 ， 仿生材料， 2008， 硕士

【摘要】 本文在考察纤维素醚（羟丙基纤维素）HPC和羟丙基甲基纤维素（HPMC）溶液性质及溶液─凝胶动力学转变过程的基础上,以HPMC为原料,通过热引发的方法制备了一种新型的水凝胶,并对其智能响应行为进行了研究。首先使用乌氏粘度计测试了HPC和HPMC在不同溶剂中的粘度,通过传统的特性粘数的求算方法计算出各稀溶液体系的特性粘数,根据得到的特性粘数对稀溶液的性质进行研究发现:在强极性溶剂DMF中,由于较强的氢键作用的存在,分子线团呈卷紧状。氯离子的加入则会破坏氢键作用,导致分子线团松散。同时氯离子的存在会产生静电排斥作用,大分子之间的近程相互作用力减弱。根据经验公式,用特性粘数估算出各溶液体系的临界交叠浓度。分子量对于临界交叠浓度有十分显著的影响,溶剂的影响则不是很明显。离子的加入会引起临界交叠浓度一定的降低,这可能是由于离子的静电排斥作用导致的大分子无规线团松散变大,从而使得临界交叠浓度减小。用旋转粘度计研究了HPMC浓溶液的流变性质,结果表明:分子量对于HPMC溶液的流变性质有着显著的影响,高分子量的样品具有更明显的假塑性流体的性质,取代度对流变性质的影响不是特别显著。给出的数学模型表明,对HPMC的四种样品,流体行为指数与浓度之间均存在着一致的指数关系:n=k*exp（-C/t₀）+b。用动态流变仪对HPMC水溶液的热凝胶过程进行跟踪测试,通过分析体系粘弹性力学行为的变化考察HPMC热凝胶的可逆过程。研究结果表明:HPMC凝胶动力学分为预凝胶和凝胶两个阶段进行,凝胶化和去凝胶化过程并不完全相同,疏水聚集体和网络结构的解体要发生在低于其形成时的温度下。HPMC的两个取代基团对热凝胶过程的影响效果是相反的,羟丙基和水分子之间的氢键作用对预凝胶阶段的开始起着阻碍作用,而甲氧基则对凝胶阶段的大分子的疏水结合起促进作用。甲氧基含量高且羟丙基含量低的HF系列样品易于形成热凝胶。分子量的高低对于凝胶过程不起决定性的影响作用,不同取代度的样品分子量的影响不同。对HF系列,甲氧基取代基团的影响占主导,高分子量的样品易于成凝胶,而HK系列中,羟丙基的阻碍作用占主导,因此分子量的影响趋势相反。以不同分子量和取代度的HPMC样品通过热引发的方法制备了水凝胶,并对凝胶的溶胀动力学进行了研究,结果表明:HPMC热引发制备的水凝胶具有较好的溶胀吸水性能,其溶胀过程分三个阶段进行,符合Schott二级溶胀动力学方程,即水凝胶的溶胀度随时间的变化符合规律:t/SR=A+Bt。研究了HPMC水凝胶的环境智能响应行为,结果表明:HPMC水凝胶的平衡溶胀度随温度的增加而减小。温度对两个系列的凝胶的影响敏感程度不同,对HK系列而言,平衡溶胀度与温度成二次关系,而对HF系列则成一次的线性关系。HPMC水凝胶的溶胀行为受溶剂影响显著,在强极性溶剂中,氢键作用加强,溶胀度增加。弱极性溶剂中溶胀性能则迅速下降。在水中溶胀平衡的水凝胶置于弱极性溶剂中会发生消溶胀行为。pH值的改变对凝胶溶胀性能的影响不是特别显著,但是由于盐离子的加入而产生的盐析作用,溶胀吸水性能有不同程度的下降。分子参数对凝胶溶胀行为的影响研究结果表明:羟丙基含量高、甲氧基含量低的HK系列凝胶由于大分子和水分子之间更多的氢键作用,吸水溶胀性能明显高于HF系列凝胶。分子量的影响要受到取代度的干扰,HK系列的凝胶平衡溶胀度随分子量增加而增加,而HF系列则呈现相反的影响趋势。更多还原

【Abstract】 A new-style hydrogel were prepared by hydroxypropyl methyl cellulose in thermal induced way, after reviewing the solution property of cellulose ethers （hydroxypropyl cellulose HPC and hydroxypropyl methyl cellulose HPMC） and process of sol-gel transition of HPMC. The intelligent responding behaviors of this hydrogel were studied as well.The viscosity of HPC and HPMC solutions with different solvents were tested by Ubbelohde viscosity meter, and its intrinsic viscosity were calculated by a traditional way. Subsequent investigations about properties of dilute solution were carried out with intrinsic viscosity and the following findings can be concluded: first, in the solvents with strong polarity such as DMF, molecular chains show a curly state because of the presence of stronger hydrogen bond. Addition of Cl" will lead to weaken of hydrogen bond and molecular chains become more relaxed. At the same time, the reciprocity of short range between macromolecules declined due to the static repulsion of Cl^-. Critical overlap concentration （C^*） of different solution systems were estimated from experiential formula by intrinsic viscosity. The influence of molecular weight on C^* is remarkable, while solvent property has a weak effect. Fall of C^* can be observed after adding ions, as a result of the relaxation of molecular chains led by the static repulsion between ions.Rheological property of HPMC solutions were studied by rotary viscosity meter. The flow behavior is much more influenced by molecular weight than degree of substitution. Critical overlap concentration can be concluded from the rheological test. By fitting the curves of studied solutions, a mathematical model was established which show there is a coincident function relationship between flow behavior index and concentration: n=k^*exp（-C/t₀）+b.Thermoreversible gelation process of HPMC samples were reviewed on dynamic rheometer by analyzing the change of visco-elastic mechanical behavior. This process can be divided in two stages: pre-gel stage and gel stage. The hydrophobic association in heating process is not the same as the disassociation in cooling. Thermal gelation behavior is strongly influenced by the degree of substitution. More methoxy content and lower hydroxypropyl content is easier to form a gel at lower temperature. But the effect of molecular weight is different for two sample series. The sample with higher molecular weight gels easily for HF series whose thermal behavior is mostly controlled by methoxy groups while there is an opposite trend for HK series because of the predominant inhibition of hydroxypropyl groups.HPMC hydrogel were prepared by thermal induced way using different MW and DS samples and its swelling kinetics were researched at the same time. It was found that HPMC hydrogel has a good absorbency. Its swelling behavior processed in three steps and was accordant with Schott mode, namely, the relationship between the swelling ration and times follow the equation as: t/SR=A+Bt.Intellective responsive behavior of HPMC hydrogel has been investigated: equilibrium swelling ration decrease with the increase of temperature. The sensitivity of effect of temperature on equilibrium swelling ratio is different. Relationship between ESR and temperature for HK series display a square relation, while show linearity for HF series. Swelling behavior of HPMC hydrogel were also greatly influenced by solvents. Swelling ratio increase in strong polarity solvents because of the enhancement of hydrogen bond, while descend rapidly in weak polarity solvents. It is not very obvious for the effect of change of pH on swelling ability, but there are different reductions of absorbency due to salt-out action brought by the addition of ions from acid or base.The results of research about effect of MW and DS on swelling behavior are as following: owing to more hydrogen bond action between macromolecules, HK hydrogel which has higher hydroxypropyl and lower methoxy content get a better swelling ability than HF series. Equilibrium swelling ratio of HK series hydrogel increases with the augment of MW, while a contrast influencing trend can be observed for HF series hydrogel.更多还原