Defesa de Tese de Doutorado #402 – Bruno Barbosa Rodrigues – 12/08/2022

In this work, we propose a model to study the thermal and elastic properties of diluted polymers with randomly placed charges. This work is motivated by re- cent discoveries of bond-bond correlations in polymers incompatible with Flory’s hypothesis. According to this hypothesis, there exists a condition under which at- tractive and repulsive interactions cancel out in polymers immersed in a solvent, thus resulting in an exponential decay of the correlations. We first reviewed the analytical and computational minimalistic models available in the Literature. In a second step, we constructed a coarse-grained polymer model with excluded volume and repulsive monomers randomly distributed along the chain interacting via a screened repulsive Coulomb potential. We implemented the Monte Carlo (MC) method with the algorithms of Metropolis Simulated Annealing and Replica Exchange Wang Landau (REWL) for sampling the monomer-monomer correlations and the density of states, respectively. We reported the results of thermodynamic, elastic, and conformational properties for N = 20,50 and 70 monomers, showing the hyperphase diagram in the T,η (temperature and charged monomers concentration) plane. We classified the phase transitions liquid-globular (LG) and globular-solid (GS) as second and first-order, respectively, using microcanonical analysis. Then, we simulated longer chains of N = 70, 200 e 1200 monomers, and calculated the bond-bond orientations near the LG transition. The correlations follow a power-law decay with exponents consistent with the de Self-Avoiding Walk (SAW) universality class. We finish this work by discussing the implications of our findings for the diluted polymers theory and future lines of investigation.

Tópico: Defesa de Tese – Bruno Barbosa Rodrigues
Hora: 12 ago. 2022 03:00 da tarde São Paulo

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