Fundamental studies on the synthesis of heat-resistant polymers Summary report no. 12, 31 Jan. - 15 Sep. 1966

Synthesis and thermogravimetric analysis of heat resistant polymer

Novel polymer coupling chemistry based upon latent cysteine-like residues and thiazolidine chemistry

Chain end functional polymers were prepared via reversible addition–fragmentation transfer (RAFT) polymerization techniques that were further chain extended with acrylonitrile. Under reducing conditions, latent cysteine-like residues were exposed at the chain ends. A variety of reduction conditions were explored and base polymers were then tethered together via thiazolidine chemistry

Linear versus cyclic inorganic/organic hybrid oligomeric molecules

The synthesis of the new aryl bis(β-diketone) ligand m-phenylenebis(acetylacetone) (m-pbaH2) allowed for complexation with copper(II) to form a 4-membered ring Cu4(m-pba)4. An alternate route, via a phospholene adduct, was implemented after difficulties in preparing the ligand via an azo sulfide conversion from m-phenylenediamine. The connection of two m-pba ligands coordinated to a Cu(II) metal ion causes a distortion along the axial position of the metal center. The pore has a diameter of (Cu-----Cu = 14.317 Å) when viewing opposite metal centers. An open coordination site along Cu(II) axial position may facilitate host-guest binding interactions. The concave shape of the host may allow for molecules with a spherical shape such as C60 to favorably interact. UV-Vis spectroscopy monitored the host-guest binding interaction of Cu4(m-pba)4 & C60

Hydroxy Polybenzimidazoles for High Temperature Fuel Cells and the Solution Polymerization of Polybenzimidazole

In this dissertation, two different hompolymers of polybenzimidazole (PBI) containing hydroxyl functional units were synthesized via the PPA Process to produce gel membranes. These polymers and their phosphoric acid doped membranes were characterized to further explore structure-property relationships in functionalized PBI\u27s. Fuel cell performance of the doped membranes was evaluated and compared to previously reported PBI membrane chemistries. Copolymers of p-OH PBI and para-PBI were prepared at five different copolymer compositions to examine the effects of hydroxy content on membrane properties and compared to the respective homopolymers. The reactivity of the hydroxy groups and the formation of phosphate bridges were important in the final properties of the doped membranes. A new method for producing high inherent viscosity (IV) PBI directly in organic solution was studied. Initially, small molecule studies were performed in order to find appropriate chemical functionalities that allow for the formation of benzimidazole in dimethyl acetamide (DMAc). Once appropriate chemical functionalities were identified, polymerization studies were conducted to determine the critical variables for the synthesis of high molecular weight polymers. Insights on the mechanism of polymerization and complete benzimidazole ring closure were important for developing a method to produce PBI at high molecular weight and at high polymer concentrations that are relevant for the processing of films, coatings and fibers. Finally the synthesis of PBI analogs containing an ether linkage was explored. These polymers were synthesized via the new solution polymerization method to demonstrate the utility of the method for different monomer and polymer structures. Thermal studies were performed on the ether-PBI analogs to understand the effect of the ether linkage on the potential processability of polymers

Benzo‐extended cyclohepta[def]fluorene derivatives with very low‐lying triplet states

Open-shell non-alternant polycyclic hydrocarbons (PHs) are attracting increasing attention due to their promising applications in organic spintronics and quantum computing. Herein we report the synthesis of three cyclohepta[def]fluorene-based diradicaloids (1–3), by fusion of benzo rings on its periphery for the thermodynamic stabilization, as evidenced by multiple characterization techniques. Remarkably, all of them display a very narrow optical energy gap (Egopt=0.52–0.69 eV) and persistent stability under ambient conditions (t1/2=11.7–33.3 h). More importantly, this new type of diradicaloids possess a low-lying triplet state with an extremely small singlet–triplet energy gap, as low as 0.002 kcal mol−1, with a clear dependence on the molecular size. This family of compounds thus offers a new route to create non-alternant open-shell PHs with high-spin ground states, and opens up novel possibilities and insights into understanding the structure–property relationships

Transitional metallacycles with nitrogen and phosphorous ligands

The metalcycles are compounds that are contained within organometallic chemistry and that can have a very different nature depending on the metal as well as on the ligands attached to it; Due to this, their properties and reactivity cover a large field of research. In this work, the study of this type of compounds using nitrogen and phosphorus ligands, which may have very different characteristics, will be addressed. This allows the design of the synthesis of families of compounds that have the usual properties and applications of the metalcycles, such as their use as catalysts in industrial processes, the evaluation of their potential cytotoxicity or luminescent properties related mainly to metal

Doctor of Philosophy

dissertationPactamycin was isolated in 1961 by the former UpJohn Company and to date is the most complex aminocyclopentinol known. This natural metabolite is decorated by six contiguous stereocenters, three of which are quaternary, with each position of the cyclopen

A New bis(rhodamine)-Based Fluorescent Chemosensor for Fe3+

A new bis(rhodamine)-based fluorescent probe 4 was synthesized, and it exhibited high selectivity for Fe3+ over other commonly coexistent metal ions in both 50% ethanol and Tris–HCl buffer. Upon the addition of Fe3+, the spirocyclic ring of 4 was opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm was observed

Polyenamines from aromatic diacetylenic diketones and diamines

The synthesis and characterization of several polyenamine ketones are discussed wherein conjugated diacetylenic diketones and aromatic diamines are used as a route to the formation of high molecular weight polyenamine ketones which exhibit good mechanical properties and can be cast into creasible films. Typical polymerization conditions involved the reaction of stoichiometric amounts of 1,4- or 1,3-PPPO and a diamine at 60 to 130 C in m-cresol at (w/w) solids content of 8 to 26% for a specified period of time under a nitrogen atmosphere. Novel polyenamine ketones were prepared with inherent viscosities as high as 1.99 dl/g and tough, clear amber films with tensile strengths of 12,400 psi and tensile moduli of 397,000 psi were cast from solutions of the polymers in chloroform. In most cases, the elemental analyses for the polyenamine ketones agree within + or - 0.3% of the theoretical values