Conformational, Dimensional, and Hydrodynamic Properties of Amylose Tris(n-butylcarbamate) in Tetrahydrofuran, Methanol, and Their Mixtures
Conformational, Dimensional, and Hydrodynamic Properties of Amylose Tris(n-butylcarbamate) in Tetrahydrofuran, Methanol, and Their Mixtures
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DOI：
10.1021/ma902200z
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发表时间：
2010-01-26
期刊：
影响因子：
5.5
通讯作者：
Norisuye, Takashi
中科院分区：
文献类型：
--
作者：
Terao, Ken;Murashima, Maiko;Norisuye, Takashi
在甲醇（MeOH）、四氢呋喃（THF）及其混合物中，在25℃（或20-25℃的红外条件下），通过光散射和小角度x射线散射、沉降平衡、粘度、红外吸收（IR）和旋光度，制备了12个重量-平均分子量为1.7 × 10(4)至1.7 × 10(6)的直链淀粉三（正丁基氨基甲酸酯）（ATBC）样品。对虫状链的均方旋转半径、粒子散射函数和特性粘度进行了分析，得到MeOH中h（每残基轮廓长度）= 0.32 nm, λ(-1)（库恩段长度）= 11 nm， THF中h = 0.26 nm, λ (-1) = 75 nm。λ (-1) = 75 nm表示的THF的高刚度很可能是由于ATBC的C=O和NH基团之间的分子内氢键在红外光谱中观察到其分裂的酰胺1带。此外，该溶剂中的h值明显小于不同溶剂中直链淀粉三酯的螺旋距（0.37-0.40 nm）和半挠性直链淀粉三酯（苯氨基甲酸酯）的螺旋距（0.32-0.42 nm） （λ (-1) = 15-24 nm），表明ATBC链在THF中形成轻缠绕螺旋。随着分子内氢键数的减少，即THF-MeOH混合溶剂中MeOH含量的增加，λ(-1)减小，h增大。这些关系成功地解释了两态模型，其中每个链由随机分布的半柔性（松散螺旋）和棒状（刚性螺旋）序列组成。棒状部分和半柔性部分的h值分别为0.25 ~ 0.26 nm和0.32 nm。
Twelve amylose tris(n-butylcarbamate) (ATBC) samples ranging in weight-average molecular weight from 1.7 x 10(4) to 1.7 x 10(6) have been prepared and studied by light and small-angle X-ray scattering, sedimentation equilibrium, viscosity, infrared absorption (IR), and optical rotation in methanol (MeOH), tetrahydrofuran (THF), and their mixtures at 25 degrees C(or 20-25 degrees C for IR). Data for mean-square radius of gyration, the particle scattering function, and the intrinsic viscosity are analyzed on the basis of the wormlike chain to yield h (contour length per residue) = 0.32 nm and lambda(-1) (Kuhn's segment length)= 11 nm in MeOH and h = 0.26 nm and lambda(-1) = 75 nm in THF. The high stiffness in THF indicated by lambda(-1) = 75 nm is most likely due to the intramolecular hydrogen bonding (between C=O and NH groups of ATBC observed its the splitting amide 1 band in the IR spectra. Furthermore, the h value in this solvent is considerably smaller than the helix pitches per residue of 0.37-0.40 nm for amylose triesters in the crystalline state and those of 0.32-0.42 nm for semiflexible amylose tris(phenylcarbamate) in various solvents (lambda(-1) = 15-24 nm), indicating that the ATBC chain forms a lightly wound helix in THF. As the number of intramolecular hydrogen bonds decreases, i.e., its the MeOH content increases in THF-MeOH mixed solvents lambda(-1) decreases while h increases. These relationships are successfully explained by a two-state model in which each chain consists of randomly distributed semiflexible (loosely helical),and rodlike (rigid helical) sequences. The resultant h Values for the rodlike and semiflexible portions are 0.25-0.26 and 0.32 nm, respectively.