Substituted, thermal characterization

The thermal characterization of 3,4 - and 4.4 -dicarboxy diphenyl ether containing polyesters has shown better thermal-stability than the corresponding 3,4 - and 4,4 -dicarboxy diphenyl ketone polyesters. Furthermore, higher degrees of substitution with the kinked monomer is necessary in case of the ketone containing polyesters to achieve the same depression of the melt transitions, compared to the ether polyesters. Crystalline-nematic transitions may be as low as approx. 200°C. 

Lage, L. G., Delgado, P. G., and Kawano, Y. 2004b. Vibrational and thermal characterization of Nafion membranes substituted by alkaline earth cations. European Polymer Journal 40 1309-1316. 

R. Antony, Synthesis, Characterization and Thermal Behaviour of Chemically Modified Phenolic and Substituted Phenolic Polymers, Ph.D thesis. Regional Research Laboratory, Trivandrum and Kerala University, Trivandrum, India (1993). 

This method is attractive, since polymers with good thermal stability are obtained, especially with aryl or halogeno substituents.165 174 Moreover, a number of substituted polyester LCPs exhibit solubility in common organic solvents, thus facilitating their structural characterization. However, the cost of starting monomers has hampered the commercial development of thermotropic polyesters based on substituted monomers. 

The aryl-substituted derivatives of [Bi(SeC6H2R3-2,4,6)3] (R = Me, Pr, Bu) are the only isolated examples of selenolate complexes. They have been characterized by mp, elemental analysis, NMR spectroscopy, and thermal gravimetric analysis, and the solid-state structure of the isopropyl-substituted derivative reveals a tricoordinate environment for bismuth [Bi-Se 2.630(8)-2.711(8) A Se-Bi-Se 92.3(2)-103.3(2)°], imposed by the steric bulk of the ligands (38). 

The present study reports the synthesis, characterization and thermal reactions of phenyl and carbomethoxy substituted norbornenyl imides. These substrates were designed to model the reactive end-caps of the PMR-15 resin and allow an assessment of the effect that conjugating substituents would have on the high temperature cure of such systems. The effect of these substituents on both monomer isomerization and polymerization is reported and a possible use of the phenyl substituent as a probe of polymer structure is suggested. 

The first phase of our efforts was the unambiguous synthesis of each model substrate. PN and PX were already well characterized materials (1) While direct synthesis of the phenyl and carbomethoxy compounds from PN and/or PX was attempted, this approach was unsuccessful due to the sluggish reactivity of the norbornenyl double bonds in these molecules (2). A successful approach to CBN and (fiBN based on N-phenyl maleimide (NPMI) trapping of the respective thermodynamically favored 1-substituted cyclopentadienes is shown in Equation 1. Similarly, kinetic trapping of 2-phenyl cyclopentadiene, from the in situ dehydration of 3-hydroxy, 3-phenyl cyclopentene, gives a clean yield of (f)VN (Equation 2). The remaining phenyl isomer (VX) and the three other carbomethoxy isomers (CBX, CVN, CVX) were all obtained by the thermal isomerization chemistry described in the next section of this paper. They were each isolated in pure form by liquid chromatography We were unable to obtain any (f)BX or any of the 7-substituted isomers by any means. 

Relatively few additions of the lower molecular weight alkyl azides have been performed, mainly because of their volatility and thermal sensitivity simple alkyltriazoles are normally obtained by alkylation of the w-triazoles. On the other hand, a very wide range of less volatile substituted alkyl azides has been added to acetylenes Their addition to acetylenic esters usually proceeds readily and provides a useful method of characterizing the azides. Benzyl azide has often been used because it is relatively stable (up to 150°), it is readily prepared, and the benzyl group can be removed from the resulting triazoles (Section IV, E). 

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