A study was made of the polymerization of siloxances with transient basic catalysts. These catalysts are active as polymerization catalysts for siloxanes and will decompose rapidly to inactive products at elevated temperatures with the formation of stable polymers. Several quaternary ammonium bases were studied as polymerization catalysts. It was found that bases such as tetramethylammonium hydroxide and benzyltrimethylammonium hydroxide were efficient catalysts. Similar bases having β‐hydrogen atoms decomposed too rapidly via an elimination reaction and were not good catalysts. The polymerizations of organosiloxanes with quanternary phosphonium hydroxides were also studied. The phosphonium bases decomposed thermally in a different manner than the ammonium bases to give phosphine oxides and hydrocarbones. The most efficient transient catalysts were found to be phosphonium silanolates. Tetrabutylphosphonium silanolate was conveniently prepared in an anhydrous form and it proved to be extremely efficient for the preparation of homopolymers and copolymers of organosiloxanes.
REARRANGEMENT OF BENZYL ETHERS TO CARBINOLS 1437TABLE I1 ANALYSIS OF SAPONIFIED POLYMERS FOR CARBOXYL -COOH Softening Max. in Ester:styr. Sol. of point of M. e. of m. e. sapon. ratio in polymer original -COOH/g. of polypolymer, in CaHs, poljmer, of sapon. -COOH mer, moles NEWARK, DELAWARE (14) J. E. Waltz and G.The objective of this investigation was to establish the mechanism of intramolecular isomerizations of carbanions involving 1,a-shifts of alkyl groups without their bonding pair of electrons. These isomerizations, which include the Stevens rearrangement of quaternary ammonium and sulfonium ions by bases and the Wittig rearrangement of benzyl ethers by lithium phenyl, are to be distinguished from the common rearrangements of carbonium ions in which alkyl groups shift with their bonding pair of electrons. The work of Wittig was extended using lithium butyl and particularly potassium amide with which there can be no doubt that carbanions are actually the intermediates. The relative ease of isomerization of the carbanions of several ethers was established. The carbanion of dibenzyl ether not only isomerized to form the anion of benzylphenylcarbinol but also underwent partly @-elimination to form benzaldehyde and benzyl ion-a type of reaction that predominated with the carbanion of dibenzohydryl ether. These isomerizations as well as those reported previously are in agreement with an internal displacement mechanism.
A novel liquid-crystalline polyurethane (LCPU) was synthesized by the condensation of 2,4-toluenediisocyanate and 4,4'-bis(6-hydroxyhexoxy)biphenyl. Solution polymerization in dimethylformamide produced intrinsic viscosities in the range 0.30457 dL/g. Differential scanning calorimetry shows a crystalline melting transition that is highly dependent on molecular weight and thermal history and a clearing transition that is virtually independent of both. Parallel-plate rheometry results are consistent with the presence of a liquid-crystalline phase, coexisting with a small amount of three-dimensional crystallinity, between 152 and 166 "C. Dynamic mechanical measurements reveal an unusually high elastic modulus of 180 MPa in the plateau region above Tg, compared with 6 MPa for an amorphous polyurethane with a chemical structure based on 1,4-butanediol.
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