Exploratory polymer synthesis Quarterly status report, 1 Aug. - 31 Oct. 1969
Heterocyclic Schiff base type monomer prepared by reaction carbon compounds with amino compounds
Dalelio, G. F.↗
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Exploratory polymer synthesis Quarterly report, 1 Feb. - 30 Apr. 1970
Polymerization of prototype monomer xylylidene-2- aminopyridine
Dalelio, G. F.↗
Scalar spectral characteristics of one- dimensional solids
Polymer optical properties in terms of interaction matrix coupling monomers, applying to polypeptide alpha helix, beta sheets and polyproline helices
Pysh, E. S.↗
Thermally stable polyimides from solutions of monomeric reactants
A method for preparing thermally stable resin-fiber-reinforced composites by using solutions of appropriate monomers is described. Solutions containing a dimethyl ester of an aryl tetracarboxylic acid, the monomethyl ester of nadic acid, and an aryl diamine were used to impregnate graphite fibers. Composites fabricated from these prepregs exhibited excellent thermo-oxidative stability and retention of mechanical properties at 315 C (600 F). These results compare favorably to those obtained from composites made from amide-acid prepolymers capped with reactive alicyclic rings. Monomeric solutions provide excellent shelf life and improved solubility compared to amide-acid prepolymer solutions.
Serafini, T. T.↗
Thermally stable laminating resins
Improved thermally stable laminating resins were developed based on the addition-type pyrolytic polymerization. Detailed monomer and polymer synthesis and characterization studies identified formulations which facilitate press molding processing and autoclave fabrication of glass and graphite fiber reinforced composites. A specific resin formulation, termed P10P was utilized to prepare a Courtaulds HMS reinforced simulated airfoil demonstration part by an autoclave molding process.
Jones, R. J.↗
Hydrocarbon polymeric binder for advanced solid propellant
Various experimental factors were examined to determine the source of difficulty in an isoprene polymerization in the 5-gallon reactor which gave a non-uniform product of low functionality. It was concluded that process improvements relating to initiator and monomer purity were desirable, but that the main difficulty was in the initiator feed system. A new pumping system was installed and an analog simulation of the reactor, feed system and initiator decomposition kinetics was devised which permits the selection of initial initiator concentrations and feed rates to use to give a nearly uniform initiator concentration throughout a polymerization run. An isoprene polymerization was run in which the process improvements were implemented.
Potts, J. E.↗
Preferential polymerization and adsorption of L-optical isomers of amino acids relative to D-optical isomers on kaolinite templates.
Experiments on the polymerization of the L- and D-optical isomers of aspartic acid and serine using kaolinite as a catalyst showed that the L-optical isomers were polymerized at a much higher rate than the D-optical isomers; racemic (DL-) mixtures were polymerized at an intermediate rate. The peptides formed from the L-monomers were preferentially adsorbed by the clay. In the absence of kaolinite, no significant or consistent difference in the behavior of the L- and D-optical isomers was observed. In experiments on the adsorption of L- and D-phenylalanine by kaolinite, the L-optical isomer was preferentially adsorbed.
Jackson, T. A.↗
Origins of life; Proceedings of the First Conference, Princeton, N.J., May 21-24, 1967.
The dialogs on the origin of life commence with the fossil record. They deal with the age of the earth; the primitive atmosphere; precambrian microfossils; the Fig Tree series of rocks, which is part of the Swaziland system; the Bitter Springs Formation in Australia; and simulated Precambrian microfossils. The syntheses of biologically important monomers, amino acids, and nucleic acid derivatives are discussed. Polymerization mechanisms; the thermal origin of amino acid polymers; nonnucleic acid information carriers; the relationship between amino acid and nucleic acid polymers; the origin of the triple code; early reciprocating systems; and the evolution of the ribosomal system receive attention. Some brief comments on extraterrestrial life are presented. An appendix deals with the geological evidence for the thermal origin of living systems.
Margulis, L.↗
Preparing thermoplastic aromatic polyimides
Method prepares aromatic polyimides with significantly reduced glass-transition temperatures and without accompanying loss of high-level thermo-oxidative stability which has been typical. This has been made possible by use of diamine monomers with specific stereoisomeric features.
Bell, V. L.↗
Development of thermally stable phosphonitrile elastomers for advanced aerospace structures
Attempts to prepare low molecular weight, curable poly-(fluoroalkoxyphosphazenes) have been successful. Derivatization of /Cl2PN/n polymer with alkoxides gave functionally reactive terpolymers. These terpolymers could be crosslinked with polyisocyanates at room temperature. Attempts to control molecular weight have not been as successful. The effects of (Cl2PN)3 monomer purity, use of (Cl2PN)3,4 mixture, and early termination of the bulk polymerization of (Cl2PN)3 were studied briefly. Both low and high molecular weight polymers were obtained. Reaction of NH4Cl with PCl5 with subsequent heating to give chain extension gave either gels of oils with molecular weights of several thousand. The stabilization of poly-(fluoroalkoxyphosphazene) was investigated. The results generally were inconclusive, but acids were found to be deleterious while bases had little discernible effect. Improvements in stability by modification of end groups was inconclusive.
Reynard, K. A.↗
Processable high temperature resistant addition type polyimide laminating resins
Basic studies that were performed using model compounds to elucidate the polymerization mechanism of the so-called addition-type (A-type) polyimides are reviewed. The fabrication and properties of polyimide/graphite fiber composites using A-type polyimide prepolymers as the matrix are also reviewed. An alternate method for preparing processable A-type polyimides by means of in situ polymerization of monomer reactants (PMR) on the fiber reinforcement is described. The elevated temperature properties of A-type PMR/graphite fiber composites are also presented.
Serafini, T. T.↗
Chemical evolution - Recent syntheses of bioorganic molecules.
Review of the important developments that have occurred in abiological biomonomer and biopolymer synthesis since about 1967, and discussion of their significance for the field of chemical evolution and the origin of life. The major portion of the review is devoted to important developments in the abiotic formation of bioorganic monomers and their condensation to biopolymers under conditions presumed to have prevailed on the primeval earth. Special attention is given to contributions shedding light on the mechanism of synthesis and selection of amino acids and on interactions of amino acids and polypeptides with nucleotides and oligonucleotides.
Stephen-Sherwood, E.↗
Condensation in CO2 free jet expansions. II - Growth of small clusters.
An investigation into the kinetics of molecular clustering processes which occur in the highly supersaturated vapor of a CO2 free jet is described. Terminal cluster concentrations in expansions from room temperature and reservoir pressures in the range from 400 to 900 torr were determined for trimeric CO2 for nozzle diameters of .0076 cm, .015 cm, and .023 cm and in the case of CO2 tetramer and pentamer for .015 cm nozzle diameter. The measurements were made mass spectrometrically in a supersonic molecular beam apparatus. A kinetic analysis was developed from an extension of the critical nucleus concept of nucleation theory and rate equations based on intermolecular collisions. The observed cluster populations could be accounted for by the theory by adopting sticking probabilities of approximately .03 for monomer impinging on dimer, trimer, and tetramer.
Dorfeld, W. G.↗
Tailor making high performance graphite fiber reinforced PMR polyimides
Studies performed to demonstrate the feasibility of using the polymerization of monomer reactants (PMR) approach to tailor make processable polyimide matrix resins are described. Monomeric reactant solutions containing the dimethyl ester of 3,3',4,4' -benzophenonetetracarboxylic acid, 4, 4' -methylenedianiline and the monomethyl ester of 5-norbornene-2, 3-dicarboxylic acid were used to impregnate Hercules HTS graphite fiber. Six different monomeric reactant stoichiometries were studied. The processing characteristics and elevated temperature mechanical properties of the PMR polyimide/HTS graphite fiber composites are described.
Serafini, T. T.↗
Polybenzimidazoles, status report
Particular attention is given to polybenzimidazoles derived from the condensation of tetraaminobiphenyl and diphenylisophthalate. The polybenzimidazoles can be prepared by the condensation of equimolar amounts of the monomers in the absence of solvent. However, the polymerization has also been carried out in a variety of solvents. The polybenzimidazoles have excellent technical possibilities. These possibilities have currently not yet been commercially realized.
Leal, J. R.↗
Tailor making high performance graphite fiber reinforced PMR polyimides
Studies have demonstrated versatility of PMR approach for tailor making polyimide matrix resins with side range of flow characteristics. By simply adjusting molar ratio of reactants in monomer mixture, resins having flow values of as much as 20% can be achieved.
Serafini, T. T.↗
Method of preparing water purification membranes
Allyl amine and chemically related compounds are polymerized as thin films in the presence of a plasma discharge. The monomer compound can be polymerized by itself or in the presence of an additive gas to promote polymerization and act as a carrier. The polymerized films thus produced show outstanding advantages when used as reverse osmosis membranes.
Hollahan, J. R.↗
Resin/graphite fiber composites
Processing techniques were developed for the fabrication of both polyphenylquinoxaline and polyimide composites by the in situ polymerization of monomeric reactants directly on the graphite reinforcing fibers, rather than using previously prepared prepolymer varnishes. Void-free polyphenylquinoxaline composites were fabricated and evaluated for room and elevated flexure and shear properties. The technology of the polyimide system was advanced to the point where the material is ready for commercial exploitation. A reproducible processing cycle free of operator judgment factors was developed for fabrication of void-free composites exhibiting excellent mechanical properties and a long time isothermal life in the range of 288 C to 316 C. The effects of monomer reactant stoichiometry and process modification on resin flow were investigated. Demonstration of the utility and quality of this polyimide system was provided through the successful fabrication and evaluation of four complex high tip speed fan blades.
Cavano, P. J.↗