Polyolefins have dominated global polymer production for the past 60 years, revolutionizing fields of medicine, construction, travel, packaging, and many more. However, with steadily increasing polyolefin production each year and traditionally long polyethylene (PE) and polypropylene degradation times, estimated on the order of 500 years or more, a massive challenge arises with accumulating plastic waste. While the end-of-life of polyolefins previously manufactured must be addressed, incorporation of sustainability and circularity into future commodity plastic design at the molecular level offers an opportunity to decrease their negative effects on the environment going forward. Herein, several approaches are described which aim to address the need for polymeric materials while introducing a sustainable approach to their design, either through incorporation of biosynthesized polymers or degradable units. In the first project, polymer blends of two biodegradable polymers were studied, and compared to the same blends containing a graft copolymer compatibilizer comprised of the two homopolymer counterparts. The compatibilized blends were expected to have superior mechanical performance to the uncompatibilized blend and potentially offer industrially relevant benefits. While this was not achieved, valuable insight into the polymer blend interactions were gained. The idea of compatibilizing polymer blends was further explored with blends of PE and a cellulose derivative with the aid of a custom ABA triblock compatibilizing agent. It was discovered that the compatibilizer reinforced the polymer blend by providing mechanical strength at the cost of flexibility. To approach sustainability from a different perspective, several segmented copolymer series based on telechelic PE oligomers were then synthesized and analyzed. The segmented systems exhibited similar structure to high density PE (HDPE), retained similar mechanical and thermal properties to commercial HDPE, but contained degradable units throughout the polymer backbone. Several fundamental principles were explored through the segmented and chain-extended polyolefin architecture, including the influence of reactive linkage (amide vs. ester), random vs. alternating segment structure, and PE segment molecular weight. The effects of tailoring polymer structure on thermal, mechanical, and morphological properties are described herein. The relationships established from these experiments may further guide future polymer design and contribute toward more sustainable polyolefin manufacturing.