This work is dedicated to the investigation of protein folding with the emphasis on the aggregation and amyloid fibrils formation. The focus of the research is to elucidate the relationship between polypeptide chain sequence and folding/aggregation properties. For this purpose, (i) libraries of the de novo macromolecular repetitive β-sheet forming polypeptides were designed, and (ii) the strategy for their rapid creation was developed. The strategy enables retention of a basic polypeptide core, yet allowing variations in the repetitive sequence, degree of polymerization and distribution of specific amino acids. The polypeptides were expressed in E. coli, purified, and characterized by various biophysical methods, including circular dichroism (CD), deep UV resonance Raman spectroscopy (DUVRR), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The polypeptides form β-sheet structure along with simultaneous coacervation and self-assembly into amyloid-like fibrils. The repetitive nature eliminates sequence specificity in polypeptide interactions and enables their utilization as macromolecular models of large amyloidogenic proteins. These models were employed for structural characterization of amyloid fibrils and elucidation of the influence of polypeptide chain properties such as charge distribution, number of intramolecular β-strands and hydrophobicity on folding and aggregation.