Failure and Mechanical Properties of Glassy Diblock Copolymer Thin Films
Failure and Mechanical Properties of Glassy Diblock Copolymer Thin Films
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DOI：
10.1021/acs.macromol.2c01031
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发表时间：
2022-12
期刊：
影响因子：
5.5
通讯作者：
Tianren Zhang;Ningkang Wang;Robert A. Riggleman
中科院分区：
文献类型：
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作者：
Tianren Zhang;Ningkang Wang;Robert A. Riggleman
嵌段共聚物的自组装受到纳米尺度限制的影响，纳米尺度限制长期以来一直被认为会影响聚合物的链间缠结和动力学。虽然大多数以前关于受限聚合物玻璃的工作都集中在均聚物的性能上，但玻璃态嵌段共聚物薄膜的机械响应仍然相对未被探索。通过单轴变形的玻璃状层状二嵌段共聚物膜具有不同的形态，通过分子动力学模拟，我们证明了指纹形态的膜的韧性是较高的均聚物和取向层状膜相比，由于增加的随机性域取向和缠结。我们发现，厚度对嵌段共聚物的力学性能的影响并不像均聚物系统那么大。在嵌段共聚物薄膜的应变局部化分析中，存在塑性重排，该塑性重排最初聚集在层片的两相之间的边界处，直到接近失效时，塑性过渡到域的中心。在嵌段共聚物体系中，与较厚的膜相比，最薄的膜中的银纹表现出不同的行为。我们对薄膜力学的研究提供了分子的见解，了解链段的流动性和缠结如何与位置和形态相互作用，以控制薄聚合物薄膜的力学。
Block copolymer self-assembly is affected by nanoscale confinement, which has long been known to affect interchain entanglements and dynamics of polymers. While most previous work on confined polymer glasses has focused on the properties of homopolymers, the mechanical response of glassy block copolymer thin films is still relatively unexplored. By uniaxially deforming glassy lamellar diblock copolymer films with different morphologies via molecular dynamic simulations, we demonstrate that the toughness of the films with fingerprint morphologies is higher compared to homopolymers and oriented lamellar films due to the increase in the randomness of domain orientations and entanglements. We show that the thickness impact on the mechanical properties of the block copolymers is not as big as that of the homopolymer systems. In the strain localization analysis of the block copolymer films, there are the plastic rearrangements initially clustered at the boundary between the two phases of the lamellae until close to failure when the plasticity transitions to the center of a domain. In the block copolymer systems, crazes in the thinnest films exhibit distinct behaviors compared to thicker films. Our studies of the film mechanics provide molecular insights into how segmental mobility and entanglements interplay with position and morphology to control the mechanics of thin polymer films.