Isocyanate groups, pendant

The principal members of the Uvimer series are uniquely designed unsaturated urethanated oligomers. One method of Incorporating unsaturated functionality Is by reaction of pendant Isocyanate groups with unsaturated compounds containing active hydrogen (See, e.g.. Ref. 1). 

Urethane-Based Hybrid Foams. Hydroxyl-terminated ester oligomers or vinyl esters which have terminal vinyl groups and pendant hydroxyl groups can react simultaneously with isocyanate groups and vinyl monomers in the presence of catalysts to obtain crosslinked hybrid polymers. 

An exploratory study was also conducted to evaluate urethane-methacrylates containing pendant isocyanate groups as bone adhesives. The following adducts were studied ... 

The prepolymers can be different types of materials. They must, however, contain residual unsaturation in order to react and crosslink with the monomers. Examples of such materials may be polyurethane acrylates that are prepared from urethane prepolymers. The excess isocyanate groups are treated with hydroxyethyl or hydroxypropyl acrylates. Other prepolymers with terminal and/or pendant hydroxy groups are also often esterified with acrylic acid. The oligomers might also be bisphenol A diglycidyl ethers prereacted with acrylic acid to form terminal acrylate groups. An example of these would be ... 

G.M. Brauer, C.H. Lee, Oligomers with pendant isocyanate groups as tissue adhesives. 2. Adhesion to bone and other tissues, J. Biomed. Mater. Res. 23 (July 1989) 753-763. 

Nishizawa, N. Nishimura, J. Saitoh, H. Fujiki, K Tsubokawa, N. (2005) Graftig of branched polymers onto nano-sized silica surface Postgrafting of polymers with pendant isocyanate groups of polymer chain grafted onto nano-sized silica surface. Progress in Organic Coatings., 53. 306-311. 

Fig. 14 Decrease in characteristic absorption peaks as the reaction proceeds of PU/VERA (the resin with pendant hydroxyl group capped with acetyl groups) (50/50) SIN at 100 °C a isocyanate group at 2274 cm" b styrene at 910 cm c vinyl ester at 812 cm h Reprinted from (1996) J Appl Polym Sci 59 1417 [141] with permission...

The term silylated or endcapped is applied to the resulting polymer which comes from the termination of pendant isocyanate groups with the amino group of the amino alkylalkoxysilane, and the molecule used to terminate the isocyanate groups is referred as to endcap . 

A cross linked film suitable for use as a surface coating may be obtained by reacting the pendant OH groups of a copolymer with isocyanate groups. The reaction between the OH group and the NCO group results in the formation of a urethane group. 

Lastly, mention will be made of two further amide block copolymer syntheses not mentioned above. The first employs living polymer anions from styrene, isoprene or methyl methacrylate to initiate the polymerization of isocyanates to diblock polymers containing nylon 1 sequences. In this approach, selective polymerization can be achieved at the unhindered isocyanate group of diisocyanates such as tolylene 2,4-diisocyanate to give products with pendant NCO groups (32) which are crosslinkable with diols to give tough resins. 

Their main point of difference is that the phenoxies are of much higher molecular weight ( 25 000). The phenoxies are also said to be slightly branched. Like the epoxide resins they are capable of cross-linking via the pendant hydroxyl groups, in this instance by di-isocyanates and other agents. 

A tertiary amine such as triethylamine is then added to the isocyanate-terminated prepolymer (containing carboxylic acid groups). The tertiary amine reacts with the pendant carboxylic acid groups, forming a carboxylic acid salt. The presence of this salt, together with adequate stirring, allows the dispersion of the prepolymer in water by the so-called melt dispersion process [57]. 

Polyurethanes are thermoset polymers formed from di-isocyanates and poly functional compounds containing numerous hydroxy-groups. Typically the starting materials are themselves polymeric, but comprise relatively few monomer units in the molecule. Low relative molar mass species of this kind are known generally as oligomers. Typical oligomers for the preparation of polyurethanes are polyesters and poly ethers. These are usually prepared to include a small proportion of monomeric trifunctional hydroxy compounds, such as trimethylolpropane, in the backbone, so that they contain pendant hydroxyls which act as the sites of crosslinking. A number of different diisocyanates are used commercially typical examples are shown in Table 1.2. 

Polymers containing pendant carbamate functional groups can be prepared by the reaction of phenyl isocyanate with poly(vinyl alcohol) in homogeneous dimethylsulfoxide solutions using a tri-ethylamine catalyst. These modified polymers are soluble in dimethyl sulfoxide, dimethylacetamide, dimethylformamide and formic acid but are insoluble in water, methanol and xylene. Above about 50% degree of substitution, the polymers are also soluble in acetic acid and butyrolactone. The modified polymers contain aromatic, C = 0, NH and CN bands in the infrared and show a diminished OH absorption. Similar results were noted in the NMR spectroscopy. These modified polymers show a lower specific and intrinsic viscosity in DMSO solutions than does the unmodified poly(vinyl alcohol) and this viscosity decreases as the degree of substitution increases. 

Polymers with pendant carbodiimide groups 27 are also synthesized from crossUnked polystyrene. In this synthetic route crossUnked polystyrene beads are chloromethylated and converted to the amines. Reaction with isopropyl isocyanate gives the corresponding ureas, which are treated with tosyl chloride and triethylamine to produce the crossUnked polycarbodiimides. This polymer is used in the polymer supported Moffatt oxidation of alcohols into aldehydes or ketones using benzene/DMSO. ... 

Coreactive and prereacted. All polyurethanes can be subdivided into two broad categories, using the reactive isocyanate functional group to distinguish them. Those that have available NCO (for further reaction) can be called coreactive and those that have essentially no pendant NCO are prereacted. Table I contains an outline and description of some of the available materials that fit each type. It should be noted that some of the prereacted urethanes do contain other chemical functional groups that may be available for non-urethane forming reactions. 

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... 

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