Abstract

Polymer properties including molecular weight and radius of gyration influence thermal and mechanical properties. Fundamental characterization was performed to analyze approximately 80 novel polycarbonates by gel permeation chromatography/size exclusion chromatography (GPC/SEC) coupled with multi-angle light scattering (MALS), a differential refractive index (DRI) detector and viscometer to determine specific refractive index increment (dn/dc), molecular weight and radii of gyration. Preliminary dn/dc measurements were painstaking and time-consuming, requiring approximately 4-5 hours for each polymer investigated. Mw measurements, on the other hand, required approximately 30 minutes. Characterization results and the comparison of those results gave insight into the new materials and their properties.

Polycarbonate blends investigated were miscible in the bulk on all proportions as previously demonstrated. The rule of mixtures was investigated to study solution property including specific refractive index increment (dn/dc) using offline differential refractometry to overcome several challenging research problems including long times required for dn/dcdetermination. Investigations were conducted to check whether the (dn/dc) values for a copolymer or mixture of two homopolymers would lie on a straight line between two homopolymers values as expected. Copolymers and mixtures showed a positive deviation from the ideal behavior with regard to dn/dc. It was observed that the dn/dc values of both systems did not lie on a line between the dn/dc values of the homopolymers likely because the Mw of the polymers were not identical.

A fundamental fluorescence baseline of information was sought for novel fluorescent copolycarbonates containing blue-light-emitting fluorophores and the corresponding monomers that would provide a suitable and unique system in order to study the molecular motion of polymer chain by tracking directly the motion of fluorophores. Structural characterization, thermal, light scattering and optical investigations were conducted using different techniques. Two novel blue-light-emitting copolycarbonates containing anthracene moieties, DPA:BPA-PC and BFPA:BPA-PC, were synthesized successfully by interfacial polymerization in specific ratios to enable solubility. The DPA and BFPA content was determined by integration of the downfield anthracene ring signals at 7.74 and 7.73 ppm and were found to be 18.85 and 14.02 mol percent, respectively. Both copolycarbonates were found to have enhanced thermal properties compared with BPA-PC and strongly emissive in their solution and film states having high quantum yields. The quantum yield values ranged from 91% to 98% for the two polymers and 62% to 90% for monomers. The incorporation of an electron withdrawing group had an influence on their respective fluorescence parameters and properties. The quantum yields of the fluorescent polymers were solvent-dependent. Quantum yields were higher within the copolymers and monomers when a low-polarity solvent was used.