Poly(ethylene oxide-b-isoprene) diblock copolymer phase diagram
Poly(ethylene oxide-b-isoprene) diblock copolymer phase diagram
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DOI：
10.1021/ma001957p
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发表时间：
2001-04-24
期刊：
影响因子：
5.5
通讯作者：
Hadjichristidis, N
中科院分区：
文献类型：
--
作者：
Floudas, G;Vazaiou, B;Hadjichristidis, N
用小角x射线散射和神学方法研究了25种组成范围为0.05 < f(PEO) < 0.8的聚环氧乙烷-b-异戊二烯（PEO- pi）二嵌段共聚物的相态。此外，通过差示扫描量热法和压力-体积-温度测量获得了热学和热力学性质。其中20个双晶块表现出至少一个有序相变，2个表现出4个有序相。相图由熔体中的四个平衡相组成；层状（Lam），六边形填充圆柱体（Hex），球体填充在以体为中心的立方晶格（bcc）中，以及具有Ia(3)在硬空间群对称的双连续立方相，称为旋转相。后者在0.4 < f(PEO) < 0.45的范围内形成，这是迄今为止报道的最高的稳定陀螺相。相图中的高度不对称归因于PEO和PI的高度构象不对称（epsilon = 2.72）。在低温下，PEO结晶后，所有相恢复到结晶层状结构（L-c）。在0.66 < f(PEO) < 0.7的组成范围内，形成了另一个中间相，称为穿孔层（PL），这显然不是一个平衡相。发现热膨胀系数是有序微观结构的敏感探针。
The phase state of 25 poly(ethylene oxide-b-isoprene) (PEO-PI) diblock copolymers spanning the composition range 0.05 < f(PEO) < 0.8 has been studied using small-angle X-ray scattering and theology. In addition, the thermal and thermodynamic properties have been obtained from differential scanning calorimetry and pressure-volume-temperature measurements. Twenty of the diblocks exhibit at least one order-to-order transition, and two show four ordered phases. The phase diagram consists of four equilibrium phases in the melt; lamellar (Lam), hexagonally packed cylinders (Hex), spheres packed in a body centered cubic lattice (bcc) and a bicontinuous cubic phase with the Ia (3) over bard space group symmetry known as the gyroid phase. The latter is formed for the range of compositions 0.4 < f(PEO) < 0.45 which are the highest ever reported for a stable gyroid phase. The high asymmetry in the present phase diagram is attributed to the high conformational asymmetry of the PEO and PI (epsilon = 2.72). At low temperatures, upon PEO crystallization, all phases revert to the crystalline lamellar structure (L-c). Within the composition range 0.66 < f(PEO) < 0.7 another intermediate phase is formed known as perforated layers (PL) which is clearly not an equilibrium phase. The thermal expansion coefficient was found to be a sensitive probe of the ordered microstructures.