The classical route for the synthesis of this family of macromolecules is via nucleophilic aromatic substitution using dimethylsulfoxide (DMSO) as a dipolar aprotic solvent and aqueous sodium hydroxide as a base. High molecular weight homopolymers can be synthesized in a short time (1 hour). However, hydrolytic side reactions can limit its scope for the synthesis of block copolymers. An alternate route using potassium carbonate/dimethyl acetamide as base and solvent respectively has been cited in the patent literature. We have used this method for the synthesis of several homopolymers and copolymers derived from various bisphenols. Our investigation into the kinetics and mechanism of this process has demonstrated that this route deviates from simple second order kinetics. This deviation has been rationalized to be due to the heterogeneous nature of the reaction. The utility of these polymers is a direct function of their excellent stability (hydrolytic, thermal and dimensional) wide use range and good mechanical properties. However, their poor solvent resistance can be considered and "Achilles heel". We reasoned that the introduction of a second ordered or crystalline component would vastly improve its solvent resistance. Hydroquinone polysulfone, homopolymer was reported to be semi-crystalline "as made". We thus synthesized and studied "random" copolymers obtained by reacting various mole ratio combinations of bisphenol-A and hydroquinone with dichlorodiphenyl sulfone. The molecular weight (M_n) of these copolymers ranged from 20,000-40,000. Their glass transition temperature (T_g) increased monotonically from 185°C for pure bis-A homopolymer to 210°C for hydroquinone homopolymer. Two different types of mechanical tests together with DSC and SEM measurements showed that improved solvent resistance (especially to liquids of interest to NASA for aerospace functions) could be achieved via a novel liquid induced crystallization process. ¹³C and proton NMR spectral assignments were successfully made using model compounds. The composition of the copolymers by NMR accurage to ±3%. Multiblock (-A-B-) copolymer of bisphenolA polycarbonate and several poly(arylether sulfones) were synthesized from well characterized oligomers. It was possible to prepare one or two phase block copolymers by controlling the molecular weights and/or interaction parameters of the parent oligomers. Surface characterization showed surface segregation even for the single phase material. Triad distribution of monomers in non-equilibrium copolycondensation was investigated by Monte' Carlo simulation. In the one step process, where the intermonomer and/or comonomers had independent functional group reactivities, the resulting copolymer was always random irrespective of the reactivity ratio of the comonomers. A non random distribution was obtained when the reactivity ratio of the funtional groups in the intermonomer and those of the comonomer were much greater than unit. Monomers that resulted in a random copolymer in a one step process could be made with a non random distribution by a multi-step process. / Ph. D.

High resolution liquid chromatographic methods have been developed for the determination of nucleotide pools at the nanogram level in four representative species of ascomycetes (P. citrinum, A. niger, F. moniliforme, and C. herbarum). Nucleotides were extracted from the mycelial mat in high yield with 10% (weight/volume) trichloroacetic acid, and then preseparated from interfering polysaccharides, glycoproteins, etc., on a Biegel P-2 column with double distilled water elution. Resolution of some 18 nucleotides from each fungal species is accomplished on AS-Pellionex-SAX pellicular anion exchanger using a high pressure liquid chromatograph. Identification of nucleotides was by comparing peak retention times; by differential ultra-violet absorption with two detectors in series at selected wavelengths; and by acid or enzymatic hydrolysis with product identification by liquid chromatography. Growth curves of the four fungi in liquid medium were monitored at 1-2 day intervals until growth stopped (~10 days). Pyrimidine bases were present in higher molar concentration than purines by a factor of at least three, with uridine nucleotides often representing 60- 80 mole percent of the total nucleotides. Extractable cytidine nucleotides are in negligible concentration in these species. Uridine diphosphoryl 2-acetamido-2-deoxy-α-D-glucopyranoside dominates all other nucleotides throughout the growth cycles of all four species, representing 30-60% of all nucleotides present. A rapid quantitative procedure using high pressure liquid chromatography is developed for determining the percentage of guanine plus cytosine of DNA preparations after acid hydrolysis in 88% formic acid. As little as 10 μg DNA are amenable to this analysis. Although thymine is sometimes poorly resolved from impurities at the solvent front, percentage of G plus C was found to be accurately determined simply from the ratio of concentrations from C/(A+C) or (G+C)/(2A+G+C). The HPLC method gave values for the percentage G plus C in close agreement with the thermal melting point and buoyant density values determined for the DNA of ten bacterial species and two fungi isolated for this study. / Ph. D.

A spectrophotometric method was used to determine the rate law in buffered aqueous iodine-iodide solutions. Three iodinating agents other than iodine were considered: direct attack by hypoiodous acid, acid catalyzed attack by hypoiodous acid, and the iodinium ion. The first two were discarded because of the observed dependence of the rate on the buffer concentration and the observed independence of the rate on the hydrogen ion concentration. The postulated mechanism is in agreement with the mechanisms for aniline and pyrazole. The rate determining step is the removal of the proton from the intermediate by the buffer. However, it was found that iodine was the major iodinating species and that the iodinium ion had a much smaller effect. A qualitative discussion of the reactivities of pyrazole, J-methylpyrazole., and l-methylpyrazole was made. An attempt was made to show possible reasons for the observed results. / M.S.

For the past several years an investigation has been carried out,under the supervision of Dr. P. C. Scherer, of the physical, or chemical reactions which occur in the xanthation of soda-cellulose. A study has been made of the rate of xanthation of the soda-cellulose under various conditions. Following up the previous work, the present investigation was to determine the rate of xanthation of the soluble cellulose xanthate, using a sodium hydroxide solution as a solvent. By this study it was hoped that further information could be obtained concerning the reaction which occurs when soda-cellulose is treated with carbon disulfide. It is concluded from the results of this investigation that a definite carbon disulfide-cellulose ratio is reached before cellulose xanthate will assume properties which will render it soluble in a solvent such as a sodium hydroxide solution. Also, that this carbon disulfide-cellulose ratio will remain constant throughout further xanthation. / M.S.

M.S.

M.S.

M.S.

A kinetic study of the oxidation of arsenic(III) by chromium(VI) was made in acetic acid-acetate buffers at ionic strengths 1.5M and 3.0M. The reaction rate showed a first order dependence on the arsenic(III), total chromium(VI), and acetic acid concentrations. Two possible mechanisms for the reaction have been suggested. One possibility is the formation of an arsenic-chromium adduct in which either the acid chromate or dichromate ion is involved. A second possible mechanism postulates adduct formation involving only the acid chromate ion, followed by a CrO₄= catalyzed decomposition of the adduct. In either suggested mechanism, the acetate and hydroxide ion catalyzes the decomposition of the adduct. The rate dependence on total chromium(VI) concentration is contrary to previous reports which postulate an adduct or ester mechanism. Induced reaction studies show the initial step involves the oxidation of one arsenic(III) species by chromium(VI) with the formation of tetravalent chromium as-a reactive intermediate. The stoichiometry or the overall reaction was found to be 3 As(III) + 2 Cr(VI) = 3 Aa(V) + 2 Cr(III). / M.S.

The effects of solvent, base strength, nature of halide, number of equivalents of base, and number of equivalents of halide on the course of C-alkylation of 2,4-oxazolidinedione and 5-phenyl-2,4-oxazolidinedione were investigated. The highest isolated yield (49%) of 5-benzyl-5-phenyl-2,4-oxazolidinedione was obtained using 2.1 equivalents of lithium amide in liquid ammonia followed by alkylation with 1.1 equivalents of benzyl chloride. Although the yield of 5-benzyl-5-phenyl-2,4-oxazolidinedione using lithium diisopropylamide in THF-hexane-HMPA was only 39% (determined by pmr analysis), the addition of HMPA as a co-solvent had a beneficial effect on the ratio of 5-phenyl-2,4-oxazolidinedione to the benzyl derivative. The addition of HMPA as a co-solvent in the ethylation of 5-phenyl-2,4- oxazolidinedione using lithium diisopropylamide in THF-hexane increased the yield of the ethyl derivative by 60% over that obtained in the absence of HMPA. Using potassium amide in liquid ammonia, lithium amide in liquid ammonia, lithium diisopropylamide in THF-hexane, or lithium diisopropylamide in THF-hexane-HMPA failed to produce 5-benzyl-2,4-oxazolidinedione in a significant yield. Several attempts were made to form the dianion of oxindole and selectively alkylate it at the 3-position without the interference of dialkylation at that position. No evidence was obtained which indicated that the dianion had been successfully formed, and the major products afforded from these attempts were the 3,3-dialkyl derivatives of oxindole. / M.S.

M.S.