Microphase separation of carbohydrate-based star-block copolymers with sub-10 nm periodicity
Microphase separation of carbohydrate-based star-block copolymers with sub-10 nm periodicity
复制标题
DOI：
10.1039/c8py01745j
复制
发表时间：
2019-03-07
影响因子：
4.6
通讯作者：
Satoh, Toshifumi
中科院分区：
文献类型：
--
作者：
Isono, Takuya;Kawakami, Nao;Satoh, Toshifumi
具有高Flory-Huggins相互作用参数（chi）和低聚合度(N)的嵌段共聚物（bcp）正被研究用于创建周期低于10 nm的微相分离结构(d)。然而，较低的N值也会导致不良的性能。在本文中，我们证明了使用星块结构是在不降低分子量的情况下实现亚10 nm d微相分离的有效方法。因此，由聚（epsilon-己内酯）（PCL）和麦糖三糖（MT）组成的三臂、四臂和六臂星形嵌段共聚物，即（PCL-b-MT）(x) (x分别= 3、4和6)，具有相当的臂长和MT体积分数，通过epsilon-己内酯开环聚合、链端修饰和点击反应三步合成。小角度x射线散射实验表明，（PCL-b-MT）(x)微相分离成6 ~ 8 nm的六边形密排柱状结构。（PCL-b-MT） x的d值和形貌与相应臂单元即线性二嵌段共聚物（PCL-b-MT）的d值和形貌基本相同。换句话说，即使通过增加臂数来增加BCP的总分子量，d值也可以固定在10 nm以下。此外，与PCL-b-MT相比，（PCL-b-MT）(x)在薄膜状态下具有更高的有序-无序转变温度和更好的纳米结构质量。总体而言，获得了d值小于10 nm的有序微相分离结构，而bcp的总分子量大于10 000 g mol（-1）。
Block copolymers (BCPs) with a high Flory-Huggins interaction parameter (chi) and a low degree of polymerization (N) are being investigated to create microphase-separated structures with sub-10 nm periodicity (d). However, the lowered N value also leads to undesirable properties. In this paper, we demonstrate that the use of a star-block architecture is an effective way to achieve microphase separation with sub-10 nm d without reducing the molecular weight. Thus, three-, four-, and six-armed star-block copolymers consisting of poly(epsilon-caprolactone) (PCL) and maltotriose (MT), i.e., (PCL-b-MT)(x) (x = 3, 4, and 6, respectively), with comparable arm lengths and MT volume fractions were synthesized in three steps involving the ring-opening polymerization of epsilon-caprolactone, chain end modification, and click reaction. Small angle X-ray scattering experiments revealed that the (PCL-b-MT)(x) microphase separated into hexagonally close-packed cylindrical structures with a d of 6-8 nm. The d value and morphology of (PCL-b-MT) x are essentially the same as those of the corresponding arm unit, i.e., linear diblock copolymers (PCL-b-MTs). In other words, the d value can be fixed at less than 10 nm even though the total molecular weight of the BCP is increased by increasing the arm number. In addition, (PCL-b-MT)(x) had the advantages of an increased order-disorder transition temperature as well as better quality of the nanostructure formed in the thin film state compared to PCL-b-MT. Overall, well-ordered microphase-separated structures with a d value less than 10 nm were obtained, while the total molecular weight of the BCPs is higher than 10 000 g mol(-1).