Innovative polymer materials play an important role in achieving a sustainable future. I will present two types of polymers we have developed toward this goal. The first type is microporous ladder-shaped polymers that function as size sieving membranes for energy efficient gas separations. We discovered an interesting structure-dependent aging behaviour for the membranes – selectivity is significantly increased over time. By tuning the polymer chain configurations, we have obtained mechanically robust membranes with an unprecedented combination of ultrahigh selectivity and permeability, setting the record performance for many gas separations. The other type is degradable/recyclable thermosets based on dicyclopentadiene (DCPD) and cyclic enol ether. An overlooked reactivity of Grubbs catalysts allowed us to synthesize polyDCPD thermosets and composites with a wide range of remarkable mechanical properties and on-demand degradability. I will present the enabling chemistry for these developments, optimization of material properties and performance, and paths toward real-world applications.