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首页> 外文期刊>Journal of Applied Polymer Science >Thermotropic Mesomorphism fo Selected (2-hydroxypropyl)cellulose Derivatives
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Thermotropic Mesomorphism fo Selected (2-hydroxypropyl)cellulose Derivatives

机译：（2-羟丙基）纤维素衍生物的热致同构

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摘要

The thermotropic measomorphism of some cellulose derivatives (CD) based on the (2-hydroxypropyl)cellulose (HPC) was investigated. Three types of derivatives: two esters (PPC, HxPC) and cyanoethyl derivative (CEPC) were prepared. The X-ray diffraction patterns of CDs were compared with the differential scanning calorimetry, thermooptical, and mechanical measurements within a broad range of hte temperature. Two relaxation processes #alpha#_(#alpha#) and #alpha#_m, observed in the solid state of HPC, are also exhibited by all CDs, however, at lower temperatures. The #alpha#_m relaxations, which indicate the transition from frozen anisotropic phase to mobile liquid crystalline (LC)-phase, are shifted towards the lower temperatures with a corresponding increase in the d-spacing of the poly(saccharide) main chains of CDs (as seen in the X-ray measurements). The transition temperature to isotropic phase T_ni as well as glass transition temeprature T_g (#alpha#_(#alpha#)-relaxation) of the investigated CDs depend on the invteractions between the lipophilic side chains and the hydrophilic poly(saccharide) main chains of CDs. These interactions are determined by the length and polarity of the lipophilic side chains. The observed changes in the transition temperature to isotropic phase T_ni for CDs is consistent with the assumption that LC-organization of the poly(saccharide) main chains is stabilized by the lipophilic side-chains system. A significant increase in the length of the lipophilic side chains leads to nonlinear conformation, thus reducing teh influence of van der Vaals forces, and consequently lowering T_ni. The polymer with high polarity lipophilic side chains (CEPC) exhibits higher T_ni in comparison to the ester derivative PPC with the same length of the side chaihs but having lower polarity. The stabilization effect of the lipophilic side-chains system on the LC-organization of the poly(saccharide) mian chains is determined by the dynamci balance between length adn polarity of the li;ophilic sise-chains system.
机译：研究了基于（2-羟丙基）纤维素（HPC）的一些纤维素衍生物（CD）的热致同构。制备了三种类型的衍生物：两种酯（PPC，HxPC）和氰乙基衍生物（CEPC）。 CD的X射线衍射图谱与差示扫描量热法，热光学和机械测量值在很宽的温度范围内进行了比较。在HPC固态下观察到的两个弛豫过程#alpha #_（＃alpha＃）和＃alpha＃_m也显示在所有CD上，但是温度较低。 ＃alpha＃_m弛豫表示从冻结的各向异性相到移动液晶（LC）相的过渡，随着CD的多糖主链d间距的相应增加，移向更低的温度（如X射线测量所见）。研究的CD的各向同性相T_ni的转变温度以及玻璃化转变温度T_g（#alpha #_（＃alpha＃）-松弛）取决于亲脂性侧链与亲水性多糖主链之间的相互作用CD。这些相互作用是由亲脂性侧链的长度和极性决定的。 CD观察到的向各向同性相T_ni的转变温度的变化与以下假设相符：多糖亲链侧链系统稳定了多糖主链的LC组织。亲脂性侧链长度的显着增加导致非线性构象，从而降低了范德华力的影响，因此降低了T_ni。与具有相同侧链长度但具有较低极性的酯衍生物PPC相比，具有高极性亲脂性侧链（CEPC）的聚合物表现出更高的T_ni。亲脂性侧链系统对多糖棉链的LC-组织的稳定作用取决于亲脂性sise链的长度和极性之间的动态平衡。

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