Iso Cyanates

The composition of starting materials for the PU s studied in the present investigation are listed in Table I. Five series of PU films were synthesized in which PEG of different molecular weights were applied. The iso-cyanate/hydroxyl group (NCO/OH) ratio was kept constant (1.2) in all samples since variations in the NCO/OH ratio may also lead to variations in crosslink density (8). 

C. Allyl Alcohol (15) is not compatible with Group 12, Iso-cyanates. 

The potential for novel phase behaviour in rod-coil block copolymers is illustrated by the recent work of Thomas and co-workers on poly(hexyl iso-cyanate)(PHIC)-PS rod-coil diblock copolymers (Chen etal. 1996). PHIC, which adopts a helical conformation in the solid state, has a long persistence length (50-60 A) (Bur and Fetters 1976) and can form lyotropic liquid crystal phases in solution (Aharoni 1980). The polymer studied by Thomas and co-workers has a short PS block attached to a long PHIC block. A number of morphologies were reported—wavy lamellar, zigzag and arrowhead structures—where the rod block is tilted with respect to the layers, and there are different alternations of tilt between domains (Chen et al. 1996) (Fig. 2.37). These structures are analogous to tilted smectic thermotropic liquid crystalline phases (Chen et al. 1996). 

If one of these structural conditions is not fulfilled, the molecule loses its unique properties. This is exemplified byTV-methyl substituted poly(p-phenylene terephthalamide) Its equilibrium rigidity (Table 10) is 20 times lower than that of the unsubstituted analog (Table 9) and approaches that of poly(m-phenylene isophthalamide). Probably, in this ase, the coplanar rrans-structure of the amide group is distorted by steric interactions of the pendant methyl group as in poly(alkyl iso-cyanate)s. 

Two reactions of the iso-cyanides have been used as supporting either of the last two formulas. Methyl isocyanide forms a compound, CHa—N=C=Cl2, which in turn by means of silver oxide yields methyl iso-cyanate the constitution of which is CHa—N = C = O as we shall presently show. These reactions are analogous to similar ones which occur with carbon monoxide, CO, a compound in which carbon considered as bivalent. 

The isomerism existing in the case of cyanides or nitriles and isocyanides or iso-nitriles, which we have just discussed, is found also, in part, in their oxidation products the iso-cyanates and in analogous sulphur compounds the thio-cyanates and iso-thio-cyanates. We have referred to the fact that hydrocyanic acid like hydrochloric acid yields an oxygen acid which though unknown itself is represented by well known salts. 

The alkyl derivatives of this cyanic acid, viz., alkyl cyanates, are not known for reactions which should yield them do not do so though there are obtained derivatives of the polymeric compound cyanuric acid (p. 418). The isomeric alkyl compounds or alkyl iso-cyanates are, however, known. These compounds may be made by the oxidation of the corresponding alkyl iso-cyanides. 

The constitution of the alkyl iso-cyanates has been established as above by the following facts. 

Alkyl Thio-cyanates Alkyl Iso-thio-cyanates.—In the alkyl derivatives of thio-cyanic acid we again have isomerism exactly analogous to that in the unknown cyanates and the known iso-cyanates. 

Oil of Mustard.—Only the last compound named is important, viz., allyl iso-thio-cyanate, CH2 = CH—CH2NCS. Strange as it may seem, from statements made in connection with the cyanates and iso-cyanates of the saturated series, this compound is made by treating allyl-iodide, not with silver thio-cyanate, but with potassium thio-cyanate. As, however, the tautomeric iso-compounds are made from the cyanates and thio-cyanates by heat, the conversion of the first formed thio-cyanate into the iso-thio-cyanate can readily be understood. 

These iso compounds are obtained from the thio-cyanates by heat and their constitution is analogous to that of the alkyl iso-cyanates. They are not true sulphur esters but the alkyl radical is linked to nitrogen as is proven by their hydrolysis to primary amines. 

Iso-cyanate, -thiocyanate, Carbodiimide, Ketene, Diketene, Ketenimine... 

Few studies have been made of ionic (iso)cyanates. The fact that the sodium salt is isostructural with the azide confirms the linear structure of the ion, but the bond lengths N—C, 1 21 A, and C—0, M3 A, were not claimed to be highly accurate. 

The IJ,2-diphenylhydrazinecarboxamides were readily syn= theslzed In moderate to excellent yields. Briefly, the method Involved addition of a substituted phenyl iso cyanate to a solution or slurry containing the appropriately substituted phenylhydrazine. When reaction was complete, the product was Isolated by filtration (if precipitated) or by evaporation of the solvent and re-crystallization of the residue. 

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