Nakagawa Daiki, Saiki Erika, Horikawa Yoshiki, Shikata Toshiyuki
Cellulose Research Unit, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
Division of Natural Resources and Eco-Materials, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
Molecules. 2024 Jan 17;29(2):466. doi: 10.3390/molecules29020466.
The viscoelastic behaviors of aqueous solutions of commercially available methyl cellulose (MC) samples with a degree of substitution of 1.8 and a wide range of weight average molar masses () were investigated over a wide concentration () range at some temperatures from -10 to 25 °C. The viscoelastic parameters useful to discuss the structure and dynamics of MC-forming particles in aqueous solutions were precisely determined, such as the zero-shear viscosity (), the steady-state compliance (), the average relaxation time (), and the activation energy (*) of . Because previously obtained scattering and intrinsic viscosity ([]) data revealed that the MC samples possess a rigid rod-like structure in dilute aqueous solutions over the entire range examined, the viscoelastic data obtained in this study were discussed in detail based on the concept of rigid rod particle suspension rheology. The obtained was proportional to the number density of sample molecules (ν = , where means the Avogadro's constant) over the range examined irrespective of . The reduced relaxation time (4(3 [])), where means the medium viscosity, was proportional to (), ; the average particle length depending on for each sample was determined in a previous study; and the reduced specific viscosity (( [])), where means the specific viscosity, was proportional to () in a range of < 3 × 10. These findings were typical characteristics of the rigid rod suspension rheology. Therefore, the MC samples behave as entangling rigid rod particles in the range from rheological points of view. A stepwise increase in * was clearly observed in a range higher than the [] value irrespective of . This observation proposes that contact or entanglement formation between particles formed by MC molecules results in an increase in *.
研究了市售的取代度为1.8且重均摩尔质量（）范围广泛的甲基纤维素（MC）样品水溶液在-10至25°C的某些温度下、较宽浓度（）范围内的粘弹性行为。精确测定了有助于讨论MC在水溶液中形成颗粒的结构和动力学的粘弹性参数，例如零剪切粘度（）、稳态柔量（）、平均弛豫时间（）以及的活化能（）。由于先前获得的散射和特性粘度（[]）数据表明，在所研究的整个范围内，MC样品在稀水溶液中具有刚性棒状结构，因此基于刚性棒状颗粒悬浮流变学的概念详细讨论了本研究中获得的粘弹性数据。在所研究的范围内，无论如何，所获得的与样品分子的数密度成正比（ν = ，其中表示阿伏伽德罗常数）。折合弛豫时间（4(3 [])），其中表示介质粘度，与（）成正比，；在先前的研究中确定了每个样品的平均颗粒长度取决于；并且折合比浓粘度（( [])），其中表示比浓粘度，在< 3×10的范围内与（）成正比。这些发现是刚性棒状悬浮流变学的典型特征。因此，从流变学角度来看，MC样品在范围内表现为缠结的刚性棒状颗粒。无论如何，在高于[]值的范围内都清楚地观察到的逐步增加。这一观察结果表明，由MC分子形成的颗粒之间的接触或缠结形成导致*增加。
