Takehide Tanaka

Nucleophilic attack on halogeno(phenyl)acetylenes by halide ions

Nucleophilic reactions between halogeno(phenyl)acetylenes and halide ions, ArCCX + Y–, where Ar = C6H5 or p-ClC6H4, X = Cl or Br, and Y = Cl or Br, have been examined. Halogen exchange of the Finkelstein type was observed for the first time in acetylene halides in anhydrous dimethyl sulphoxide when X = Br and Y = Cl. This exchange did not occur with other X–Y combinations. In the presence of up to 20% water in dimethyl sulphoxide, or under aqueous–organic phase-transfer catalytic conditions, nucleophilic addition (formally of HY) took place for all the X–Y combinations studied. In the additions, the nucleophile Y– invariably attacked the carbon to which the phenyl group was bound. The mode of HY addition was stereospecifically trans; accordingly, the resulting dihalogenostyrenes always had the (Z)-1,2-dihalogeno-configuration.

Heterogeneous network polymers: 7. Cholesteric liquid crystal structure of poly(glutamic acid) fixed by crosslinking

Abstract The phase structure of the heterogeneous network polymers prepared from poly(glutamic acid) (PGA) and poly(oxyethylene glycol) ( PEG , M n = 302 ) was investigated by polarizing microscopy. The solid films had a layered structure comprising cholesteric liquid crystal domains. In each domain α-helices of PGA are aligned nearly parallel to the film surfaces. The cholesteric liquid crystal structure was not destroyed even when the films were heated in dimethylformamide (DMF) at 100°C for a week in spite of the fact that DMF can easily dissolve PGA and PEG at 50°C. This suggests that the cholesteric liquid crystal structure formed in the concentrated solutions of PGA, PEG and DMF is perpetuated by crosslinking.

Poly(L-glutamic acid)-poly(oxyethylene glycol) systems: Perpetuated cholesteric liquid crystal structures in noncrosslinked and crosslinked solid films

Abstract The origin of the peculiar microphase structures of so-called PGA/PEG polyblends and PGA-PEG heterogeneous network polymers cast from dimethylformamide or dioxane-water was studied by means of phase diagrams, infrared spectra, x-ray diffractions, polarizing optical microscopy, and small-angle light scattering. It was demonstrated that in such solvents, poly(ethylene oxide) (PEO) or poly(oxyethylene glycol) (PEG) can fill the interstitial space between the parallel arrays of the α-helices of poly(L-glutamic acid) (PGA) and become an integral constituent of the lyotropic cholesteric liquid crystals. Such structures were found to be perpetuated in the solid films of both the noncrosslinked PGA/PEO and the crosslinked PGA-PEG after the solvent was evaporated. The dynamic mechanical behavior of the solid films was consistently interpreted on the basis of such phase structures.

The Relation between Structure and Physical Properties in Polyurethans

Abstract The field of polyurethans is rapidly growing in commercial importance, especially in form and elastomer applications. This group of polymers includes a very broad region of chemical structures and chain length. In many cases polyurethans are synthesized from polyester glycols or polyether glycols and diisocyanates so that the urethan groups are even fewer in number than other functional groups. This process of synthesis enables us to deal with a very wide range of polymer properties, adding interest to the studies of relation between structure and properties. Though a considerable number of publications dealing primarily with the properties of urethan polymers have been published, few of them contribute to better understanding of the relation between these properties and the corresponding polymer structure. Within the last few years information of value has become available, and Saunders has established some semi-quantitative relations by the use of such data. He also discusses in his reports gen...

Methods for the Determination of Internal Energy Contribution to Rubber Elasticity

Abstract In order to determine exactly the contribution of internal energy component to retractive force (fe/f), two methods (one is Single Specimen Method [Successive Contraction Method] and the other Multi Specimen Method), two different reference lengths (one is the initial length of undeformed specimen and the other the final length including permanent set), and two instruments of different type (one is automatic balance type relax-o-meter [ROM] and the other tensile tester) were examined by using natural rubber, cis-1,4-polyisoprene, and polyurethane rubber. The apparent mechanical and thermo-dynamic properties were significantly dependent upon these methods and reference lengths. In spite of the variation of C1 and C2 in Mooney-Rivlin plot, fe/f was almost unaffected and the sign of this value coincided with that expected from the chain conformation as far as ROM-Single or Multi Specimen Method and the final length were adopted. The influences of permanent set, the time used to attain equilibrium, e...

Activities of Anionic Catalysts in Network Formation of Diisocyanate through lsocyanurate Formationt

The catalytic activities of the sodium salts of Br6nsted acids sodium cyanide, sodium benzoate, sodium phenoxide, etc in the network formation of 4, 4 -diphenylmethane diisocyanate (MDI)by the formation Of isocyanurate were studied in DMF at 30 C determining the gelation time of the reaction mixture. The activities of the sodium salts some increased with mcreasmg pKa of the conjgate acids. However, the activity of salts, such as sodium thiosulfate and sodium trichloroacetate was found tobe greater than that predicted from their pKa values. In cases of alkoxides, mercaptides and carboxylate salts, the catalysts with aromatic substituents showed higher activity in spite of their lower Z Ka values than those with aliphatic ones. The activities of substituted benzoate salts were found to decrease with increasing electrondonating character of ther substituents. From these results, it was concluded that the catalytic activities of the sodium salts depend not only on the basities of the nucleophiles, but also on the polarizabilities of the nucleophiles as well as on the degrees of dissociation of the salts. In the series of lithium, sodium, and potassium benzoates, the activity increased with decreasing electronegativities of alkali metals. The gelation of MDI was accelerated in aprotic solvents in the order of hexamethylphosphoramidedimethylacetamide dimethylformamide but the acceleration was not observed in dimethylsulfoxide.

Network Formation of Polyether-diisocyanate with Anionic Catalystt

It was found that urethane prepolymers, that is, diisocyanate adducts of polyether glycol, in DMF solution were rapidly crosslinked by the catalytic action of sodium cyanide. By evapolating to dryness, three-dimensional polymers were obtained. Anionic catalysts such as nbutyl lithium, sodium benzophenone ketyl and sodium benzoate were also found to be effective for the crosslinking of prepolymers. The crosslinking reactions of prepolymers with sodium cyanide in DMA solution were studid by determining the gel point. Gelation time decreased with increasing catalyst concentration and prepolymer concentration. The apparent activation energy of gelation was ca.18 kcal for polypropylene glycol-tolylene diisocyanate at 0∼25°C and ca.35 kcal for polypropylene glycol-hexametylene diisocyanate at 55∼80°C. The crosslinking reaction of prepolymers, prepared from polypropylene glycol and tolylene diisocyanate, in DMA solution with sodium cyanide catalyst was followed at 25°C by the titration of unreacted isocyanate groups, and was found to obey apparent third-order. The infrared spectrum of the resulting polymer shows an absorption at 1410 cm-1 corresponding to isocyanurate ring. From these results, it was considered that the crosslinking is effected by trimerization of isocyanate groups. The resulting network polymers were rubbery at room temperature and gel fractions of these polymers were mostly near 1. Densities, swelling properties, glass transition temperature, Youngs modulus, tensile strengths and elongations were also measured. Polyurethanes prepared from hexametylene diiscyanate have good mechanical properties (tensile strength 130∼320 kg/cm2 and elongation 450∼1000%). DTA and TGA measurement showed these polymers were stable up to 280∼320°C.

Polymerization of Styrene byn-Amyllithium orn-Amylsodium

アミルナトリウム, アミルリチウムの重合触媒を用いてスチンンの重合を行ない, 重合溶媒によってポリマーの重合度,X 線結晶図等に多くの相違をもたらすこと, 均一重合では温度の効果が比較的少ないこと, 触媒に対して不均一, ポリマーに対して均一重合の場合にも低分子量ポリマーが得られて温度による変化はみられないこと,アミルナトリウム単独でも-40℃,不均一重合したものに非常に明瞭なX 線結晶図を示したこと, ジエチルエーテル( 以下エーテルと略す) , アミルリチウムの組和わせではエーテラート形成によって重合速度に影響し,少量の場合は比例すること,完全なエーテル溶媒中での重合速度はアミルリチウムの濃度には無関係でモノマー濃度の二乗に比例すること等がみとめられた。