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The Effect of Tacticity and Side Chain Structure on the Coil Dimensions of Polyolefins
preprintsubmitted on 04.06.2018, 19:16 and posted on 05.06.2018, 20:57 by Mohammad Atif Faiz Afzal, Jarod M. Younker, George Rodriguez
The key to the discovery of materials with targeted properties lies in the understanding of structure-property relationships. In this work, we evaluate the relationship between the polymer structure and their coil dimensions, and explore new polymers based on these relations. Coil dimensions are important features of polymers which affect their performance in various applications, including drug delivery, waste-water treatment, and engine oils. Coil dimensions of the polyolefins are dependent on the number, size, and stereo orientation of side chains along the backbone. Thus, controlling these attributes allows us to tailor the coil dimensions of polyolefins. In the proposed scheme, we calculate the radius of gyration (Rg) of polyolefin chains using molecular dynamics simulations and validate against experimental results. Simulated annealing is implemented to ensure the capture of different configurations. This model affords the ability to quantify the effect tacticity has on the coil dimensions of polyolefins. The results show the suppression of tacticity effects when the polymer chains transition to bottlebrush structures, demonstrating that the side chain steric hindrance plays an important role in the rigidity of the chain backbone. Further, the model is used to evaluate the compositional effects by determining the rigidity of propylene and 1-hexene copolymers. Combining our model with virtual high-throughput screening techniques, we evaluated the coiling behavior of hundreds of new polymers. Using the screening results, we established correlations between the structure of the side chain and the coil dimensions of polymers.
The supplementary material accompanying this paper includes the library of 275 polymers and their corresponding Ks values.