Molecular simulation techniques played a significant role in understanding the molecular-level characteristics of solvents, polyelectrolytes, polymer-surfactant complexes and polymer-polymer complexes in solutions. The present research intends to investigate the effect of polyelectrolyte hydrophobicity and charge density, surfactant aggregation number, and organic solvent compositions on specific problems in given systems in a systematic manner. Solvation shells of different moieties of polymer chains significantly influence bound water molecules' rotational dynamics and residence time. Regarding charge density, dicarboxylic acid polyelectrolytes' conformational, hydration and thermodynamic behavior differed from reported monocarboxylic polyelectrolytes. The complexation of polyelectrolytes with surfactants is purely driven by electrostatic interactions for ionized chains and dispersion interactions for unionized chains. The anionic chains show distinct shrinkage into their conformation upon adsorption onto the oppositely charged micelle. Depending on the charge density of the chain, the adsorbed location of the polyelectrolyte chain on the micelle surface varies. The anionic chain in oppositely charged surfactant solution efficiently acts as a polymeric counter-ion via displacing the monovalent counter–ions into the bulk solution. The interpolymer complexation becomes difficult at higher organic solvent compositions. The swelling behavior of the interpolymer complex was observed when cosolvent volume fractions increased by measuring the SASA of the entire complex.