Recovery of wastewater is a global and environmental matter on the sustainability of water sources. Pressure-driven membrane technology is one of the most commonly used methods for wastewater treatment because of energy efficiency and less chemical need. Poly(arylene ether sulfone)s (PAES) are widely used in the membrane technology due to their chemical and thermal resistance. The linear structure of PAESs limits their functionality, besides, hyperbranched polymers contain a multitude of terminal groups which impart functionality to the polymer backbone. Hyper-branched polymer chains naturally show no entanglement, consequently, their solubility in organic solvents is higher than linear analogous, however, they usually have lower mechanical properties. Yet, the terminal groups of branched polymers can be easily turned to cross-linkable end groups which can enhance their thermal and mechanical properties. In this study, highly branched poly(arylene ether sulfone)s (HBPAES) were synthesized using the A₂+B₃ copolymerization approach in order to investigate the effect of the degree of branching and the type of functional end-groups systematically. Additionally, various strategies were developed to introduce functional terminal groups such as silane units in comparison with phenol end-groups final branched PAES products, which were characterized by FT-IR and NMR spectroscopies, Size Exclusion Chromatography (SEC), Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC) and stress-strain tests. Silane functionalities of the terminal groups enabled the crosslinking in the presence of moisture or heat. Also, films formed from HBPAESs with silane terminal groups possessed inorganic domains which can have higher thermal and chemicals properties. To enhance the thermal and mechanical properties of PAES-based UF membranes, the designed HBPAESs were proportionately blended with the commercial linear PAES prior to the UF membrane fabrication. Moreover, sulfonated, water-soluble HBPAES (S-HBPAES) were synthesized in a similar manner, which was utilized for the preparation of novel thin film composite (TFC) membranes.