Polymers exhibit many remarkable features in modern materials science, biotechnologies, and pharmaceutical applications. Achieving better control of polymer structures offers a unique opportunity to understand the structure-activity relationship of materials and enable new applications. In this talk, we will explore how folded single-chain polymer nanoparticles can enhance synthetic chemistry under biological conditions in an enzyme-mimic manner. These polymer nanoparticles have significantly improved catalytic efficiency compared to traditional synthetic catalysts, and they demonstrate unique selectivity when working with proteins. Additionally, I will discuss our strategies to prepare precise macromolecules, including single-molecular-weight polyethylene glycol (PEG) derivatives and a high-throughput method to develop libraries of discrete oligomers and polymers, with applications in self-assembly and antibacterial materials. We will showcase the versatile impact that polymer structures can have on the design and functions of materials, particularly in biological applications.