RESEARCH Polymers at Prague N e w i n o r g a n i c polymers claim metals as well as c a r b o n a n d silicon as their important elements
tL, AJUBON
AND SILICON are
no
longer
the only important elements forming polymer chains, according to K. A. Adrianov of the institute for Organic Chemistry, Academy of Sciences of the U.S.S.R. at Moscow. Aluminum, titanium, phosphorus, and many other elements falling in the second, third, fourth, and fifth groups of the periodic table can be used to make polymers. At the International Symposium on Macromoleculaj· Chemistry sponsored by IUPAC and the Czechoslovak Chemical Society at Prague, Adrianov told of new polymers he and A. A. Zhdanov have made. While the synthesis of polyorganosiloxanes is based on attaching organic groups to inorganic siliconoxygen chains, the skeletons of Adria-
nov's new polymers correspond to metallic silicates. Enveloping the skeleton with organic groups makes it possible to vary properties within wide limits. Attaching R 3 SiO- groups to the chain gives even more possibilities. • New Organic Polymers. No matter what the future for inorganic polymers is, organic ones are still most important today. A. Conix of Gevaert Photo Products in Belgium has made some new polyanhydrides. Polymerized aliphatic anhydrides were first prepared many years ago. But they do not make good materials for fibers because the anhydride link doesn't resist moisture and melting points are low. Now Conix has succeeded in making
No matter w h a t the future holds for inorganic polymers, the organics are still the most important ones today. Karl Ziegler (right) of Germany's Max Planck Institute for Coal Research discusses polymer research with J. Pelnar, one of the Czechoslovakian organizers of t h e symposium 58
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polyanhydrides from dibasic aromatic acids. These acids have the general formula of a carboxyphenyl group attached to each end of an aliphatic grouping. The - C O O H groups aie in either para or meta positions. Some of the polyanhydrides have excellent fiber-forming qualities. The dibasic acid is first converted into mixed anhydrides with acetic acid. These polymerize by polycondensation on heating, with acetic anhydride splitting off. This can b e done at atmospheric pressure, although under vacuum acetic anhydride is removed and higher molecular weights are reached. The reaction is much easier than those for polyesters. No catalyst is needed, and polymerization can be completed in about an hour. Fiber-forming properties depend strongly upon the aliphatic group. One of the better fiber materials is the polyanhydride made from di-(p-carboxyphenoxy) 1,3-propane, annealed at 110° C. under constant load. Tensile strength is 40 kg. per square mm., with elongation of 17.2%. Young's modulus is 505 kg. mm-. These figures compare favorably with polyesters, polyamides, and polyacryionitrile. Polyviny lamine is a poly electrolyte with simple structure and also with reactive groups, but it has always been difficult to prepare. The monomer, for all practical purposes, does not exist. So polyviny lamine has to be prepared from some other polymer. Previous syntheses have involved expensive starting materials. Nc ' R. Hart of Gevaert Photo Product? s developed a new synthesis fro. ;ly-2V-vinylcarbamic acid. This can be made by starting with acrylic acid, which is readily available. T h e steps: acrylic acid, acrylic chloride, acrylic azide (which does not have to be isolated), vinyl isocyanate, and then an ester of iV-vinylcarbamic acid. Yields for these steps are excellent. N-vinylcarbamic acid can be converted into polyvinylamine by solvolysis in acid or alkaline solution or by glacial acetic acid. The N-vinylcarbamates can also b e copolymerized with other vinyl or acrylic compounds and be used to make corresponding vinylamine copolymers. • Cellulose Fibers. T h e first successful man-made fibers—cellulosics— are again getting their share of research effort. A new method of synthesizing new cellulose esters a n d ether- has been developed in t h e
New Polymers Have Skeletons Matching
R I — Si — I R
Ο
— AI 1 Ο
Metal Silicates
0
--
(S) R I Si I R
U.S.S.R. at the Moscow Textile Insti tute b y Z. A. Rogovin and his co workers. "Cellulose-ONa" reacts with methyl chlorocarbonate to give a triester of cellulose and carbonic acid. An analo gous reaction using methyl monothiocarbonic acid gives a sulfur-containing ester. Since fiber and film properties of cellulose derivatives of this type vary considerably with the acid residue part of the molecule, synthesis of a whole series of compounds of this type is be ing pushed in the U.S.S.R. Rogovin's group has also prepared phenyl esters of cellulose by an inter change reaction: Here, sodium phenoxide reaets with cellulose tosylate to give as products the phenyl ester of cellulose and the sodium salt of toluene sulfonic acid. Benzylation of cellulose is also of in terest in the U.S.S.R. S. V. Goncharov of the Botanical Institute, Ukrainian Academy of Sciences at Kiev, says that the most important factor in develop ing a large-scale process is the alkali concentration in the cellulose-sodium hydroxide-benzyl chloride reaction mix ture. Benzyl chloride prepared on a large scale is not a uniform product. It can be fractionated into a number of frac tions which appear uniform from batch to batch.
--
R I Si I R
0
OR I — Ti I Ο I
Hydronium Ion Found Long-standing doubts erased b y infrared detection o f h b O * in solutions o f strong acids YDRONiujvi ION ( H 3 0 + ), a familiar chemical concept for more than 50 years, has been detected conclusively in solutions of strong acids by Michael Falk a n d Paul A. Giguère, Laval University, Quebec. They did it with infrared spectroscopy. Their data support the idea that a true chemical bond forms between the proton (H + ion) and an adjacent water molecule, and that it lasts long enough for the resulting hydronium ion to undergo normal vibrations (source of distinct infrared absorption b a n d s ) . Besides its theoretical value, this success should lead to a new way to measure directly the concentration of hydronium ion and degree of ionization of strong acids in concentrated solutions. Evidence collected through the years for existence of hydronium ion in acid solutions has been mostly indirect. In 1951 it was detected by nuclear magnetic resonance in crystalline hydrates of H N 0 3 and HC10 4 . By 1956 the ion's infrared and Raman spectra had been identified but only in the solid state. NMR could not be used on
R I
Si I R
0
liqui«d solutions, w h i c h hold the most interest for chemists. And a long series of Raman a n d infrared studies on liquids produced only negative or inconclusive results. Fatlk a n d Ciguère used very thin layer-s of sample (roughly 5 to 10 microns) held between plates of optical silveir chloride. Mew infrared absorption l>ands appeared a t 1205, 1750, and 290O cm. -1 i n concentra:3d solutions of mCl H&r, H I , HNO3, HCIO4, H 2 S 0 4 , N a H S 0 4 ) a n d H 3 P 0 4 . These bands are Ixroad a n d diffuse, says Gigmère. but n o more so than those of wate^zr. Earlier workers' failure to detect hydrondum ion in solution, G i g u è r e believers, was dixe most likely t o the great brea-dth of its bands plus t h e fact that they lie quite close t o those of water. Also^ the ion's low polarizability suggests that t h e Raman effect, used by most earlier workers, must be quite wealk. In* its present f o r m the method is only roughly quantitative, Giguère says- Making it accurate enough to measure ionization in strong acids \vou3d require; knowing the exact thickness of the sample, a n d ways to correct for irnutual interference of water and acid bands. Canada's National Research Council supported the work; Falkz is on a Consolidated Mining and Smelting Fellowship. Ο CT_
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