I. Kinetic evaluation of copolymerization of lactide with substituted lactides. II. Synthesis and characterization of polyacenes .

摘要

Because of its environmental and biodegradability, polylactide has important applications as materials in medicine and as an environmentally friendly commodity plastic. One major deficiency of polylactide is its limited range of physical properties. Copolymerization of lactide with substituted lactides is a strategy that can provide polylactides with new properties. Evaluation of the kinetics of these copolymerizations is necessary since the kinetics define the structure of polylactide copolymers, which in turn defines the physical properties of the copolymers. A protocol was developed to analyze the compositions of LA/substituted LA copolymers, which allowed us to evaluate the kinetic parameters of the copolymerization of lactide with ethylglycolide, isopropyl glycolide, and D-ethylglycolide. The data show that these copolymerizations can be described as ideal polymerizations, but due to the monomer reactivity differences, poly(lactide- co-isopropylglycolide) and poly(lactide-co-D-ethylglycolide) tend to be blocky. These polymers show single glass transitions. A study of the degradation of poly(lactide-co-isopropylglycolide) showed that the degradation process can be described by a random chain scission mechanism.; Polyacene is expected to have the lowest band gap among conjugated polymers. Despite its promise as an electrical conductor, and as a material for optics and battery electrodes, it has yet to be synthesized. We developed the synthesis of polyacene materials through the acid-catalyzed condensation of bis(methoxymethyl)benzenes. TGA, IR and Raman characterization support the formation of an extended π-conjugated system. To improve solubility, we developed a scheme to prepare n -octylated bis(methoxymethyl)benzene. Polymerization of this monomer yielded materials with molecular weights as high as 7000. However, fluorescence data show that the acene segments have a maximum length of only ∼5 units. We also designed a synthesis of two-dimensional graphite by applying similar chemistry to poly(p-phenylene). TGA, IR and Raman data support formation of a graphitic structure after the material is heated to >500°C.