Effect of cyclic tensile deformations on tensile behaviours of polymer-fullerene composite materials: insights from molecular dynamics simulation

• Main Author: Zhang, Jingqi
• Other Authors: Li Shuzhou
• Format: Thesis-Master by Research
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Materials science; Molecular dynamics; Polymer materials
• Online Access: https://hdl.handle.net/10356/181665
• Institution: Nanyang Technological University

Poly(3-hexylthiophene) (P3HT)-fullerene blends are promising candidates for stretchable photovoltaics, which require materials that can endure repeated mechanical deformations. Understanding the cyclic tensile behaviour of these materials is essential for their application. Recent research has highlighted the relationship between these materials’ molecular morphology and tensile properties as well as electronic performance. This thesis aims to investigate the relationship between molecular morphology and mechanical properties during cyclic tensile processes, in order to provide deeper understanding on the performance of the polymer-fullerene blend under application scenarios. Coarse-grained molecular dynamics (CGMD) simulation is used to study the cyclic tensile properties of the polymer-fullerene blend P3HT:C60 and pure P3HT. Through analyses of polymer chain configurations and comparative study of the blend material and pure polymer, this research reveals the potential grounds for cyclic tensile behaviour, the effects of different strain amplitudes, and the role of C60 particles within polymer system. Observations of the trends of polymers spatial span, alignment and entanglement with tensile cycles showed consistent connections between each other, offering molecular level details of polymer configurational changes. It is found that P3HT:C60 is more susceptible to cyclic softening, especially at higher strain amplitudes, which is associated with the less alignment and entanglement of polymer chains in the blend system compared to pure P3HT. Although P3HT:C60 showed higher tensile modulus, similar to other particle-reinforced polymer materials, this finding of cyclic softening highlights the necessity of understanding cyclic tensile behaviours for similar materials to ensure stability of performance in application.