Crystalline polymeric materials play an increasingly important role in daily life.Understanding and controlling the development of crystallinity is integral to improving the performance of crystalline polymers in packaging, drug delivery, water treatment, gas separations, and many other industries. Herein, fluorescence and Raman spectroscopy have been applied for the first time to study the crystallinity of polymers, including traditional semicrystalline thermoplastics and covalent organic frameworks (COFs; an emerging class of crystalline polymers with highly ordered pore structures). On one hand, by incorporating a fluorescent dye segment into a semicrystalline polymer matrix, it is feasible to accurately monitor its crystallization and melting. The flexibility of dye incorporation allows for new fundamental insights into polymer crystallization in the bulk and at/near interfaces that may otherwise be out of reach for established techniques like differential scanning calorimetry (DSC). On the other hand, Raman spectroscopy has been identified as a technique sensitive to the crystallinity of COFs and applied alongside well-established characterization techniques (X-ray diffraction and N2 adsorption) to monitor the crystallization of COFs during synthesis. This has enabled careful control of COF crystallinity during solvothermal synthesis for improved application in the field of drug delivery. The monitoring of COF crystallinity has been extended to more complex film geometries produced by interfacial polymerization. The high molecular sieving potential of COFs remains out of reach in part due to a lack of understanding of the interplay between crystallinity, crystallite orientation, and filtration performance. A careful study of these relationships is suggested for future work to provide key insight toward applying COFs as molecular sieving materials in water treatment and other separation applications.

The combustion of fossil fuels accounts for over a third of total CO2 emissions in the United States. Carbon capture and storage technology is gaining influence as a method of reducing the release of greenhouse gas into the atmosphere. Mixed ionic-electronic conducting (MIEC) dual-phase membranes are in development for selective CO2 separation at high temperatures. The application of these membranes is limited by chemical instability in a CO2-rich atmosphere. Pr0.6Sr0.4Co0.2Fe0.8O3-δ (PSCF) was selected as a potential material for development into a dual-phase CO2 selective disk membrane because of its high oxygen permeation properties and preliminary CO2 stability measurements. Porous supports demonstrated highly repeatable synthesis with an average porosity of 36.9%, He permeance on the order of 10-6 mol·s-1·m-2·Pa-1, and pore diameter of 330 nm. Infiltration with a eutectic mixture of Li2CO3/Na2CO3/K2CO3 resulted in a 16.1% weight gain and reduction in He permeance to 10-9 mol·s-1·m-2·Pa-1. CO2 permeance measurements of the dual-phase membrane were inconclusive due to mechanical failure during heating. XRD, SEM imaging, and EDXS compositional analysis revealed significant strontium carbonate formation on the membranes surface after testing. More thorough CO2 permeance testing of dual-phase PSCF is recommended as the focus of future study.