THE GYROID - A NEW EQUILIBRIUM MORPHOLOGY IN WEAKLY SEGREGATED DIBLOCK COPOLYMERS
THE GYROID - A NEW EQUILIBRIUM MORPHOLOGY IN WEAKLY SEGREGATED DIBLOCK COPOLYMERS
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DOI：
10.1021/ma00093a006
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发表时间：
1994-07-18
期刊：
影响因子：
5.5
通讯作者：
FETTERS, LJ
中科院分区：
文献类型：
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作者：
HAJDUK, DA;HARPER, PE;FETTERS, LJ
我们报告了在中间到弱分离的二嵌段共聚物熔体中发现的一种新的平衡微畴形态。聚苯乙烯-聚异戊二烯（SI）二嵌段共聚物由37 wt %苯乙烯和总M(w) = 27 400组成，在低于有序-无序转变（ODT）约50℃的退火温度下，观察到从片层形貌（在低退火温度下处于平衡状态）转变为新的形貌。观察到这种转变是热可逆的。通过小角x射线散射（SAXS）和透射电子显微镜（TEM）对新结构的形貌进行了研究，发现新结构具有显著的三维长程有序性，属于立方空间群Ia3d，具有双连续立方结构。通过对模型结构的计算机模拟和与显微镜结果的比较，我们提出了基于Schoen发现的三周期G最小曲面（gyroid）的新形态模型；在各种微相分离的表面活性剂-水体系中也观察到类似的形貌。用该双嵌段与各种短链均聚物共混，研究了相图上i3d稳定区域的组成范围；结果表明，在较宽的少数组分体积分数范围内，Ia3d相是稳定的。
We report the identification of a new equilibrium microdomain morphology in an intermediate to weakly segregated diblock copolymer melt. A polystyrene-polyisoprene (SI) diblock copolymer consisting of 37 wt % styrene and of total M(w) = 27 400 was observed to transform from the lamellar morphology (in equilibrium at low annealing temperatures) to a new morphology at annealing temperatures approximately 50-degrees-C below the order-disorder transition (ODT). The transformation was observed to be thermoreversible. investigation of the new morphology via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) revealed the new structure to have remarkable three-dimensional long-range order, to belong to the cubic space group Ia3d, and to possess a bicontinuous cubic microstructure. From computer simulations of model structures and comparison with microscopy results, we propose models for the new morphology based on the triply periodic G minimal surface (gyroid) discovered by Schoen;1 similar morphologies have been observed in a variety of microphase-separated surfactant-water systems. Blends of this diblock with various short-chain homopolymers were used to investigate the compositional extent of the region of Ia3d stability on the phase diagram; the results indicate that the Ia3d phase is stable over a wide range of minority component volume fractions.