Isocyanates bifunctional

The weak nucleophilic nature of polynitroaliphatic alcohols is also reflected in their slow reactions with isocyanates to yield carbamates. These reactions often need the presence of Lewis acids like ferric acetylacetonate or boron trifluoride etherate. The reaction of bifunctional isocyanates with polynitroaliphatic diols has been used to synthesize energetic polymers.33°... 

Another example of the step-growth polymerization is the synthesis of polyurethanes. Here, linear polyurethanes are produced by the reaction of bifunctional alcohols, HO — R — OH, with bifunctional isocyanates, OCN — R — NCO, to produce a polyurethane (see Figure 3.21). 

Fiaire 4. Hypothetic mechanism for bonding of preoxidized wood with ethylenediamine (left), and bonding of wood with a bifunctional isocyanate... 

This is achieved by the reaction of the pendant hydroxyl groups with an excess of a bifunctional isocyanate, such as toluene diisocyanate. In the second step, an acid group or hydroxyl group containing an azo initiator is fixed on the modified surface. Two azo initiators, 4,4 -azobis-(4-cyano-pentanoic acid) and 2,2 -azobis-(2-cyanopropanol) are bearing the desired... 

The reaction of the isocyanate and the epoxide group, to produce an oxazolidone ring, was studied through the model reaction between the monofunctional epoxide, PGE and the bifunctional isocyanate MDI. Their reaction was followed by DSC. Two catalysts for the reaction were evaluated tetraethyl ammonium bromide (R NBr) and ethylmethylimidazole (EMI). 

Model networks were prepared using hydroxyl terminated polymer and isocyanates, (a) Bifunctional hydroxyl terminated polybutadiene (Butarez, from Phillips Petroleum) was crosslinkined with tris (p-isocyanatophenyl)-thiophosphate (Desmodur RF, from Mobay Chemical Co.). This crosslinked... 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

Diazoazoles, because of charge polarization and potential bifunctional reactivity of the derived betaine, react with dipolarophiles to give cycloaddition products. Generally all the diazoazoles react with electron-rich, unsaturated derivatives. The cycloaddition reaction with isocyanates is readily observed in the case of the reactive 3-diazopyrazoles, but it is much slower with other diazoazoles. By contrast, reaction with ylides and diazoalkanes is only observed for 3-diazopyrazoles and 3-diazoindazoles. 

The kinetics and mechanism of the phosphorus-catalysed dimerization of acrylonitrile to give 1,4-dicyanobut-l-ene and 2,4-dicyanobut-l-ene have been studied.114 The reactions of aryhminodimagnesium (138) with //-substituted p-cyanobenzophenones, l-cyano-9-fluorenenone, o-, m-, and p-dicyanobcnzcnes, and o-, m-, and p-nitrobenzonitriles have been examined.115 The effect of pressure on the reaction of 3 -methyl- l-(4-tolyl)triazene (139) and benzoic acid in chloroform and acetonitrile has been studied.116 The effect of acids on the rate of urethane formation from alcohols and isocyanates in the presence of alkyltin carboxylates has been examined.117 A Hammett a value has been reported for the amidine group N=CHNMe2 and used for the prediction of the basicity of sites in bifunctional amidines.118... 

Functionalized polymers of the type B and C (Scheme 1) can be formed via polyaddition processes of bifunctional reactants, without splitting off of low molecular weight compounds. Most syntheses of stabilizers have been based on reactions of bis-isocyanates with H-acid nucleophiles. Some reactions of oxiranes may be listed here too (syntheses involving oxiranes are listed in Sect. 3.1.1.2 if polymerization aspects are more evident syntheses of stabilizers formed via reactivity of oxirane moieties attached to an oligomeric or polymeric chain are classified as reactions on polymers. Sect. 3.2.2.1... 

A bifunctional material, such as an isocyanate, may be combined with a polyester or other liquid polymer. 

The modification of a filler surface with isocyanates is a simple process which involves the reaction of hydroxyl groups on the filler surface with monomeric isocyanate. 2,4-toluene diisocyanate or hexamethylene diisocyanate are commonly used. Since isocyanates are bifunctional they can be further reacted with polyols to form a coating on the surface or they can be used for the reinforcement of polyurethane. A strong covalent bonding can be verified by controlled extraction with the solvent. Bound material will not be removed from the fillefs surface. 

The preparation of polyamides having metallocenes incorporated into the backbone can be achieved by the use of bifunctional ferrocene derivatives, such as diacid chlorides or diamines. In the following, a few examples of such reactions are presented. In the early 1960s Knobloch and Rauscher reported the preparation of polyamides and polyesters by the reaction of 1,1 ferrocenyldicarbonyl chloride 14 with several diamines and diols by interfacial polycondensation.80 The synthesis of elastomeric polyamides 54a, Mn = 10,000-18,000) in high yields was reported by Rausch and co-workers from 1,1 -bis((3-aminoethyl)ferrocene 53 and diacid chlorides (Scheme 12.11). The reaction with bis-isocyanates allows the formation of ferrocene-containing polyureas 54b. 

Duong, H.T.T. Huynh, V.T. de Souza, R Stenzel, M.H. Core-cross-linked micelles synthesized by clicking bifunctional Pt(IV) anticancer drugs to isocyanates. Biomacromolecules 2010, 11 (9), 2290-2299. 

Unbranched chains are formed when the functionality of the molecule is equal to 2. The bifunctionality of the molecule can result from a single bifunctional group, as occurs with the base-initiated polymerization of isocyanate groups ... 

Using this technique, a large variety of polyurethanes have been prepared from different vegetable oils. Natural polyols like castor oil (generally trifunctional) are directly reacted with diisocyanates to obtain branched polyurethanes, although it is difficult to control the reactivity. However, bifunctional castor oil can be polymerised with diisocyanates in the presence of suitable chain extenders and catalysts to produce polyurethanes in a more controlled manner (Fig. 6.4). A castor oil polyol-based polyurethane network can also be prepared from epoxy terminated polyurethane pre-polymer with 1,6-hexamethylene diamine. Epoxy terminated pre-polymer is obtained by the reaction of glycidol and isocyanate terminated polyurethane pre-polymer of castor oil polyol, poly(ethylene glycol) (PEG) and 1,6-hexamethylene diisocyanate. ... 

Thus, since two isocyanate groups react with one hydroxyl group to form allophanates, the isocyanate group is semifunctional. With polymerization initiators, however, the isocyanate group is always bifunctional ... 

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