Some Physical Properties of Cellulose Derivatives Prepared by Homogeneous Periodate Oxidation

根据新开发的均相高碘酸氧化法，我们首先制备了裂解程度较高的2，3-二元醇纤维素(DAC)，该纤维素膜清晰透明。研究了DAC的粘弹性能与纤维素的粘弹性。在-150ﾟC到150ﾟC的温度范围内，110 Hz的动态力学测量表明，DAC有两种弛豫过程，分别以-70ﾟC和111ﾟC为中心。-70ﾟC时的第一个过程与介电松弛有关，被认为是由于羟甲基的运动引起的，与纤维素中的过程类似。另一方面，葡萄糖环上C_2-C_3键的断裂导致该过程在112ﾟC左右发生，而类似区域的纤维素则未见类似过程的报道。这一过程归因于主链上的微布朗运动。从应力-伸长图的温度变化推算出DAC的玻璃化转变温度Tg约为80ﾟC，在Tg以上的DAC薄膜在112ﾟC时有明显的伸长率达200%。比较了Di-OAC和与Di-OAC具有相同侧链的相应纤维素衍生物(COAC)的动态力学性能。具有吡喃葡萄糖环的纤维素衍生物的特征是侧链存在微布朗运动，出现在不同于主链微布朗运动的区域。然而，研究表明，对于DIOAC来说，主链微布朗运动和侧链微布朗运动同时发生。根据这些结果，我们可以得出结论，所得到的二元醇纤维素衍生物的力学性能与普通的含葡萄糖环的纤维素衍生物有很大的不同。

In accordance with the newly developed homogeneous periodate oxidation procedure, we firstly prepared high cleavage level 2, 3- dialcohol cellulose(DAC)which gives off a clear and transparent film. Viscoelastic properties of DAC were investigated in relation to those of cellulose. Dynamic mechanical measurements for DAC at 110Hz over the temperature range from -150ﾟC to 150ﾟC revealed two kinds of relaxation processes, which were respectively centered around -70ﾟC and ll2ﾟC. The first process at -70ﾟC was related to dielectric relaxation, and was regarded to be, similar to the process in cellulose, due to the motion of methylol groups. On the other hand, the cleavage of C_2-C_3 bonds of the glucopyranose ring resulted in the process at around 112ﾟC, while no comparable process has been reported for cellulose in the similar region. This process was ascribed to the micro- Brownian motion along the main chain. From the temperature variation of the stress-elongation diagrams, the glass transition temperature Tg for DAC was estimated to be about 80ﾟC. The DAC film above Tg showed a marked elongation reaching 200% at 112ﾟC.We secondly prepared a, new dialcohol cellulose derivative(di-OAc)having oligo oxymeihylene ether groups in the side chain. Comparison of dynamic mechanical properties between di-OAc and the corresponding cellulose derivarive(COAc)with the same side chain as in di-OAc were made. Cellulose dirivatives with glucopyranose ring are known to be characterized by the presence of the micro Brownian motion in the side chain, which appears in the region different from the micro Brownian motion along the main chain. It was clarified, however, that for di-OAc the main chain and side chain micro- Brownian motion occur at the same time. From these results, we may conclude that the dialcohol cellulose derivative obtained here is quite different in the mechanical properties from ordinary cellulose derivatives having glucopyranose ring.