Thermotropic and glass transition behaviors of n-alkyl β-D-glucosides
Thermotropic and glass transition behaviors of n-alkyl β-D-glucosides
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DOI：
10.1039/c3ra43187h
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发表时间：
2013-01-01
期刊：
影响因子：
3.9
通讯作者：
Osanai, Shuichi
中科院分区：
文献类型：
--
作者：
Ogawa, Shigesaburo;Asakura, Kouichi;Osanai, Shuichi
合成了不同烷基链长(n=1，2，3，…，12)的烷基β-D-葡萄糖苷(CnGlu)，并用差示扫描量热法(DSC)、偏光显微镜(POM)和X射线衍射仪(XRD)研究了疏水链长对其热致转变和玻璃化转变行为的影响。在结晶CnGlu(n>；=7)的加热过程中，观察到熔点(T-m)处的固体相与层状液晶(LC)相之间以及清点(T-c)处的LC相与各向同性液体(IL)之间的两个明显的转变。C6Glu的T-c在低于T-m的温度下呈单向性。当非晶烷基糖苷被快速冷却时，所有糖苷的玻璃化转变都被确定。在CnGlu(n>；=6)的情况下，形成了玻璃态LC相，该玻璃相具有片层状各向异性。由于氢键网络的减少，玻璃化转变温度(T-g)降低，直到链长达到C5，而进一步增加链长并不影响玻璃化转变温度(T-g)，与疏水链长(n>；=5)的个数无关。当CnGlu在T-m和T-g之间的室温下过冷时，X射线衍射测量表明，在生成的LC相中，作为亲水基团的葡萄糖部分没有结构上的差异。这表明了亲水性糖基之间的氢键对正构烷基β-D-葡萄糖苷玻璃化转变行为的重要性。
Alkyl beta-D-glucosides (CnGlu) with different alkyl chain lengths (n = 1, 2, 3,., 12) were prepared and the influence of the hydrophobic chain length on their thermotropic and glass transition behaviors was studied using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction analysis (XRD). In the heating process of crystalline CnGlu (n >= 7), two distinct transitions between the solid and the lamellar liquid crystalline (LC) phase at melting point (T-m) and between the LC phase and the isotropic liquid (IL) at the clearing point (T-c) were observed. T-c of C6Glu was observed monotropically at lower temperature than T-m. When the non-crystalline alkyl glucosides were rapidly cooled, the glass transition was ascertained for all glucosides. In the case of CnGlu (n >= 6) a glassy LC phase, the glass phase having anisotropy like lamellar phase, was formed. The glass transition temperature (T-g) lowered until the chain length reached C5 because of the reduction of the hydrogen bonding networks, while further increase of the chain length did not affect T-g irrespective of the of number of the hydrophobic chain length (n >= 5). When CnGlu was supercooled at room temperature, which is between T-m and T-g, XRD measurements showed that there was no structural difference in the glucose moiety working as a hydrophilic group in the resultant LC phase. It indicates the importance of the hydrogen bonding between the hydrophilic sugar moieties on the glass transition behavior of n-alkyl beta-D-glucosides.