Jan Bartus

Solid-state, optical-rotation measurements on macromolecules using powder-suspensions

SummaryWe report techniques for measuring optical rotation of suspended solids, including dissymmetric molecular crystals (e.g. sodium chlorate and bromate), synthetic polymers, polypeptides and biopolymers. Examples include poly(triphenylmethyl methacrylate), poly-S-lactide, poly-L-hydroxyproline, hemocyanine, cellulose acetate andRNA. The results indicate that optical rotation measurements are sensitive to differences in secondary structure and can serve as a probe for structural differences between solid-state and solution.ZusammenfassungEs wird über eine Methode zur Messung der optischen Rotation von Festkörpern in Suspensionen berichtet, wobei dissymetrische Kristalle (z. B. Natriumchlorat und -bromat), synthetische Polymere, Polypeptide und Biopolymere behandelt werden. Die Beispiele umfassen Poly(triphenylmethylmethacrylat), Poly-S-lactid, Poly-L-hydroxyprolin, Hemocyanin, Celluloseacetat undRNA. Die Ergebnisse zeigen, daß die optischen Rotationen bezüglich Unterschiede in der Sekundärstruktur empfindlich sind und daß diese Messungen als ein Maß für Strukturunterschiede zwischen Festzustand und Lösung herangezogen werden können.

Chiral nucleation@@@Chirale Nukleierung

SummaryThe crystallization of agitated aqueous solutions of sodium chlorate and sodium bromate was nucleated with levo- or dextrorotatory crystal powders of sodium chlorate and sodium bromate to furnish new crystals with a high degree of chiroptical purity.ZusammenfassungDie Kristallisation aus agitierten wässrigen Lösungen von Natriumchlorat und-bromat wurde mittels levo- und dextrorotatorischem pulverförmigem Natriumchlorat und -bromat nukleiert. Es entstanden Kristalle mit einem hohen Grad an optischer Reinheit.

Optical activity measurements on solids. 6. Solid state optical activity and circular dichroism measurements of sodium thioantimonate nonahydrate

SummaryWe have demonstrated that optical circular dichroism (CD) measurements can be carried out on powders suspended in a liquid medium. The refractive indices of the powder and the suspending liquid must be matched, the suspending liquid must not interact significantly with the solid to be measured and must not absorb in the region where the measurements are carried out. Sodium thioantimonate nonahydrate (Na3SbS4·9H2O) powders obtained by grinding oflevo- ordextro-rotatory crystals were found to be excellent examples for the demonstration of this technique. Measurements of the optical rotation forlevo- anddextro-rotatory crystals and powders of Na3SbS4·9H2O were also carried out and provided additional characterization of this salt. In the course of developing the CD measurement technique, CD of NaClO3 and NaBrO3 crystals was also measured.ZusammenfassungWir konnten zeigen, daß Messungen des optischen Circulardichroismus an in flüssigem Medium suspendierten Pulvern durchgeführt werden können. Die Brechungsindizes von Pulver und suspendierender Flüssigkeit müssen aneinander angepaßt werden; das Suspensionsmittel darf nicht wesentlich mit dem zu messenden Feststoff in Wechselwirkung treten und darf im Meßbereich nicht absorbieren. Durch Verreiben von laevo- und dextrorotatorischen Kristallen erhaltene Natriumthioantimonatnonahydratpulver (Na3SbS4·9H2O) erwiesen sich als ausgezeichnete Beispiele zur Demonstration der Methode. Messungen der optischen Drehung von laevo- und dextrorotatorischen Kristallen und Pulvern von Na3Sb4·9H2O wurden ebenfalls durchgeführt und trugen zur Charakterisierung des Salzes bei. Im Verlauf der Entwicklung der Meßtechnik wurden auch CD-Spektren von NaClO3- und NaBrO3-Kristallen aufgenommen.

FUNCTIONAL POLYMERS. 63.* EMULSION COPOLYMERIZATION OF MALEIMIDE TYPE MONOMERS WITH ACRYLONITRILE AND STYRENE IN ABS LATEXES

Copolymerization of maleimide-type monomers: N-phenyl-maleimide, N-(2,6-dimethylphenyl)-maleimide and maleimide-bound 2(2-hydroxyphenyl)2H-benzotriazole with acrylonitrile and styrene was successfully carried out in the presence of acrylonitrile-butadiene or styrene-butadiene latexes. A new type of polymerizable 2(2-hydroxyphenyl)-2H-benzotriazole UV stabilizer with a reactive maleimide group was prepared and gave modi-acrylonitrile-butadience-styrene (ABA) resins with improved thermomechanical properties and increased resistance to ultraviolet radiation. * Functional Polymer 62: J. Bartus, W. J. Simonsick, Jr., and O. Vofl, Polymer J.,25(7), 703 (1995).

Terpolymers of Maleic Anhydride, 2-Ethylhexyl Acrylate, and Styrene

Abstract Terpolymerization of maleic anhydride, 2-ethylhexyl acrylate, and styrene in homogeneous and heterogeneous conditions was studied. The apparent monomer reactivity ratios were calculated by using the optimization method.

Electrically Conducting Thiophene Polymers

Abstract Electrically conducting 3-alkylthiophene polymers with pentyl, octyl, dodecyl, and hexadecyl alkyl groups were prepared. Iodine, trifluoroacetic acid, and dodecylbenzenesulfonic acid were used as dopants of the polymer backbone. The conductivities of the doped films were in the range 10−6 to 10−1S/cm. Applications of the prepared materials in electronics and optoelectronics were examined.

The influence of initiator type on emulsion copolymerization of styrene with butyl acrylate

Abstract The emulsion copolymerization of styrene (St) and butyl acrylate (BA) was studied in two polymerization systems with different initiators. In System I a water-soluble initiator (K2S2O8/Na2S2O4 · 2H2O) was used. System II contained hydroperoxidic groups bound to water-insoluble oxidized polypropylene (OPP) powder in combination with the Fe2+/ethylenediaminetetraacetic acid activator. The influence of the initiator type on the overall rate of copolymerization, reactivity ratios, and on the molecular-weight characteristics of St/BA copolymers was studied. The reactivity ratios were r st = 0.72, r BA = 0.27 for System I; and r st = 0.79, r BA = 0.12 for System II. It was found that the presence of initiation centers on the surface of OPP in System II was responsible for the lower values of the overall rates of polymerization. However, the molecular weights of St/BA copolymers were much higher in System II than in System I with the water-soluble initiator.

Measurement of optical activity of isotropic compounds in suspension

SummaryA reliable method for the measurement of the optical activity of optically active isotropic solid substances in suspension was developed using two miscible liquids as media for suspending the fine solid powders. The optical rotation was measured after precise matching of the refractive index of the suspending media with that of the solid particles. Sodium chlorate and sodium bromate were used as optically active solids for the development of this method. The measurements were in complete agreement with the measurements of the optical rotation of the corresponding large crystals.ZusammenfassungEs wurde eine verläßliche Methode zur Messung der optischen Aktivität isotroper Verbindungen in Suspensionen unter Verwendung zweier mischbarer Flüssigkeiten als Medium zur Suspension feiner Pulver entwickelt. Die optische Rotation wurde nach einer präzisen Anpassung des Brechungsindex des Suspensionsmediums an den der Festpartikel gemessen. Zur Entwicklung der Methode wurden Natriumchlorat und Natriumbromat als Festkörper eingesetzt. Die Messungen waren in perfekter Übereinstimmung mit Rotationswerten aus entsprechenden großen Kristallen.

Stereospecific Polymerization and Chiral Crystallization

Configurationally and conformationally specific polymerization processes which lead to helical macromolecules can be successfully carried out when monomer structure, polymerization mechanism, and spatial restrictions for monomer addition are all carefully considered. Under certain conditions, optically active polymers having a single helical screw sense can be prepared. Surprisingly, the chiral crystallization of certain inorganic salts has much in common with stereospecific polymerization mentioned above. Achiral sodium chlorate and sodium bromate can crystallize spontaneously from aqueous solutions to give a mixture of pure levorotatory and pure dextrorotatory isotropic crystals. The crystallization of these salts can also be nucleated with traces of levo- or dextro- rotatory crystals to furnish new crystals with a high degree of chiroptical purity. Our varied efforts within the confines of these two related fields are summarized.

HALOALDEHYDE POLYMERS. 63. DIACYL-TERMINATED TRIHALOACETALDEHYDE OLIGOMERS

Mixtures of diacyl-terminated trichloroacetaldehyde (chloral) oligomers were synthesized using tertiary amines as initiators followed by end-capping with diacyl anhydrides. Not only were the oligomeric alkoxide molecules acyl end-capped when the reaction mixture was treated with the acid anhydride, but the initiator fragment that was attached to the initiated end was also replaced by an acylate group. Eight different anhydrides were used for end-capping reactions allowing us to synthesize a number of symmetric chloral oligomers diacylates. A mechanism for the oligomerization of the chloral monomer was proposed on the basis of the results obtained from these investigations. Similar oligomerizations of bromal initiated with tertiary amines, and end-capped with acetic anhydride, gave the corresponding oligomeric bromal diacetates. All the trihaloacetaldehyde oligomer mixtures were analyzed by gas chromatography and the individual components were identified by K+IDS mass spectrometry.