Synthesis and characterization of random semi-flexible thermotropic liquid crystalline poly(ester-imide)s

A series of novel poly(ester-imide)s were prepared by the reaction of meta- and para-substituted trimellitimide dicarboxylic diacid chlorides with various diols containing four, five, six, seven, eight, nine, 10, and 12 methylene groups by a solution polymerization technique utilizing refluxing 1,2,4-trichlorobenzene as a solvent. The poly(ester-imide)s were characterized by dilute solution viscosity, infrared spectroscopy, differential scanning calorimetry, and polarized light microscopy. The inherent viscosities of the meta-substituted poly(ester-imide)s ranged from 0.06 to 0.25 dL/g while those of the para-substituted poly(ester-imide)s ranged from 0.10 to 0.65 dL/g and were obviously of higher molecular weight. The meta series were amorphous and showed no mesophase formation. All para-substituted poly(ester-imide)s exhibited monotropic mesophase identified as smectic A order. © 1994 John Wiley & Sons, Inc.     

Der Satz von Beckmann-Quarles im rationalen Raum

Ohne ZusammenfassungHerrn Günter Pickert zum 70. Geburtstag gewidmet.     

Mass spectrometric characterization of poly(ethylene terephthalate-co-p-oxybenzoate)

Copolyesters containing ethylene terephthalate and p-oxybenzoate units in mole ratios of ca. 80:20, 70:30, 40:60, and 20:80, respectively, were examined by direct pyrolysis–mass spectrometry to obtain information about the thermal stabilities and the sequences distributions of the two types of units as a function of composition. Thermal stability as measured by rate of volatilization increased with increasing oxybenzoate content, as did the amount of char residue formed. The electron impact mass spectrum of the volatile fragments showed the formation of predominantly linear fragments with carboxyl and vinyl end groups. Dimer, trimer, and tetramer fragments containing either or both types of units could be identified and their relative amounts could be estimated from peak intensities. The results were consistent with those expected for random distributions of the two units, i.e., for statistical copolymers.     

Preparation of esters of styrene sulfonic acid and their emulsion copolymerization with isoprene

Sulfonate-containing rubbers were prepared by emulsion copolymerization of isoprene and the secondary butyl ester of styrene sulfonic acid. Substantially gel-free copolymers of relatively high sulfonate content were prepared. It was shown that hydrolysis of the ester copolymers with a suitable base can lead to the formation of ionically crosslinked elastomers.     

Thermometrische F?llungstitrationen

Zusammenfassung Es werden die theoretischen Grundlagen der thermometrischen Fällungstitration behandelt und bereits bekannte Einzelergebnisse durch eine Reihe von Beispielen für die möglichen Typen von Fällungsreaktionen erweitert, um die Anwendbarkeit der Methode aufzuzeigen.

---

Summary The fundamental theoretical aspects of the thermometric precipitation titration are discussed, and a number of examples for different types of precipitation reactions are given, in order to point out fields of application for this method.

     

Synthesis and characterization of poly[2,5-bis(triethoxy)-1,4-phenylene vinylene]

The synthesis of a highly soluble, 2,5-disubstituted poly(p-phenylene vinylene) with pendant side chains containing ether groups was accomplished by a dehydrochlorination route. Specific interactions of the oxygen-containing side chains with the solvent are presumably responsible for the high solubility of the polymer, especially in protogenic solvents. The polymer microstructure was characterized by ¹H- and ¹³C-NMR. The polymer showed solvatochromic properties when dissolved in a variety of solvents. The relatively high molecular weight (M_n = 17,000) permitted the fabrication of free-standing films. The electrical conductivity of iodine-doped films was approximately 2 × 10^–2 S cm^–1. © 1995 John Wiley & Sons, Inc.     

Das Fibrillierungsverhalten von monoaxial verstreckten und unter Spannung getemperten Folien aus isotaktischem Polypropylen

Zusammenfassung Monoaxial gereckte Folienbändchen aus Polypropylen wurden 20 Sekunden unter Streckspannung bei Temperaturen bis maximal 210 °C getempert. Es wurde die Abhängigkeit der Spleißfähigkeit und der Auffaserbarkeit von der Folientemperatur während des Temperns untersucht. Die Spleißfähigkeit, gemessen als Weiterreißkraft quer zur Streckrichtung, ändert sich bis 196 °C nicht und nimmt dann infolge einer Umwandlung der Fibrillentextur in eine bimodale Lamellentextur schlagartig ab. Bei dieser Temperatur durchlaufen die kristalline Orientierungsfunktion, die Kristallinität und die Langperiode ein ausgeprägtes Maximum. Die Auffaserbarkeit, gemessen als Anzahl der Faserrißenden, nimmt dagegen schon ab 165 °C stetig ab und verschwindet letztlich vollständig. Dieser Vorgang wird auf eine Diffusion der vorher in den Mikrofibrillen regellos verteilten Störstellen zu den Grenzflächen der kristallinen Bereiche zurückgeführt. Bei einer schockartigen Zugbelastung der Folie reißen die einzelnen Mikrofibrillen daher nicht mehr an Stellen hoher Fehlstellenkonzentration, wodurch Faserenden differierender Länge entstehen, sondern auf Bahnen quer zur Streckrichtung, welche durch die regelmäßige Anordnung der nichtkristallisierten Bereiche vorgezeichnet sind. Die Abnahme der Auffaserbarkeit korreliert mit einem Abfall der Reißfestigkeit als Ergebnis der schwächeren Koppelung der Kristallite in Streckrichtung.

---

Uniaxial stretched polypropylene filmtapes were annealed under stretching tension during 20 seconds up to an annealing temperature of 210 °C. The splittability and the fibrillability were investigated as function of the annealing temperature. The splittability, measured as tearing force in transverse direction, remains constant up to 196 °C and there upon drops abruptly as a result of a transformation of the fibrillar texture into a bimodal lamellatexture, which was visualised by TEM. At this annealing temperature the crystalline orientationfunction, the crystallinity, and the long identity period pass through a distinct maximum. Compared with this the fibrillability, measured as the number of fibrilruptureends, decreases constantly away from an annealing temperature of 165 °C down to a complete disappearance. This phenomenon is explained by the diffusion of the originally irregularly in the microfibrils distributed defects to the crystallite boundaries, where they accumulate in lateral direction. For this reason the single microfibrils do not rupture anymore under tensile tension at the points of defect concentration but along the regular pattern of the uncrystallized regions. The decrease of the fibrillability correlates well with the drop of the tenacity as result of the weaker linkage of the crystallites in the longitudinal axis.

     

Preparation of triblock styrene–tert-butylstyrene–styrene copolymers by living radical polymerization with a heterogeneous polymeric initiator

Triblock copolymers containing the sequence styrene, p-tert-butylstyrene, styrene were prepared in an emulsion system by using isotactic polypropylene hydroperoxide as the initiator together with triethylenetetramine as an activator, according to the method of Mikulasova and co-workers. Polymerization of styrene continued after removal of the initiator from the emulsion by filtration and eventually reached 100% conversion after 4 hr at 35°C. tert-Butylstyrene at 80°C and styrene at 35°C were added successively to the system, with each polymerization reaction carried to 100% conversion before the next monomer was added. Thin-layer chromatography was used to separate the homopolymers and block copolymers in order to determine the purity of the product. Monomer compositions of the block copolymers was verified by infrared analysis. The existence of two separate phases in the extracted block copolymer was indicated by the observation of two distinct glass transition temperatures.     

Linear polybenzyls. III. Sterically assisted linear polymerization of 2,5-dimethylbenzyl chloride and α-methylbenzyl chloride

The low-temperature Friedel-Crafts step-growth polymerization reactions of 2,5-dimethylbenzyl chloride with TiCl₄—(C₂H₅)₂AlCl catalyst, and of α-methylbenzyl chloride with AlCl₃ catalyst were investigated for the effect of reaction conditions on polymer molecular weight, linearity, glass transition temperature, and crystalline properties. Premature precipitation of highly crystalline poly(2,5-dimethylbenzyl) prevented the preparation of high molecular weight products from this monomer, while most likely an indanyl-type termination reaction limited the molecular weight of poly(α-methylbenzyl). Model reactions indicated that, under proper conditions, the latter could be prepared with 99% para substitution, and these polymers were crystalline.