Isocyanate functionality

Carboxylic acids or hydroxy groups with multi-functional isocyanates. 

Brzezinska KR, Curtin SA, Deming TJ (2002) Polypeptide end-capping using functionalized isocyanates preparation of pentablock copolymers. Macromolecules 35 2970-2976... 

All polyurethanes have been obtained by reacting 1 1 molar ratios of isosorbide and diisocyanate. A slight excess of about 5-10% of the diisocyanate or of the diol resulted in the generation of soluble polyurethanes with lower molecular weight and possessing either functional isocyanate or hydroxyl groups, respectively. 

Isocyanates. The most common isocyanates encountered in polyurethane propellants are 2,4-tolylene diisocyanate, TDI, and hexamethyl-ene diisocyanate, HDI. 3-Nitrazapentane diisocyanate has also been used in high density propellants. In some polyurethane liners Adiprene L (duPont), a NCO-terminated condensation product of poly (1,4-oxybutyl-ene)diol and TDI is used, as well as some of the more highly functional isocyanates, such as polymethylenepolyphenyl isocyanate (Papi, Carwin Chemical Co.). 

The -functionalized isocyanate (504 X = O) reacts with methylhydrazine to give (505) (77S756), and (504 X = S) reacts with both alkylhydrazines and hydrazine itself to give the (506) ring system. 

The structures of five protected functionalized isocyanate building blocks AP3-EP3 (94,95) are reported in Fig. 11.18, top. The protected side chains for each building block allowed further increase of ramification and loading (n —> 3n sites after an isocyanate coupling), but above all allowed a combinatorial deprotection/decoration strategy reported for a specific example in Fig. 11.18, bottom. The starting polyamine dendrimer 11.14 (32-PPl, schematically represented as in Fig. 11.18) (96) was treated with a stoichiometeric mixture of isocyanates DP3 and EP3 (0.5 eqs. each, step a. Fig. 

The crosslink density can be varied by the polycocyclotrimer-ization of difunctional isocyanates of variable chain length or by polycocyclotrimerization of difunctional isocyanate with mono-functional Isocyanate ... 

Polyols used for this purpose include trimethylol propane and propylene glycol. Systems containing urethane-acrylate oligomers bearing doubly-functionalized isocyanate groups are commercially available [24]. The chemical structure... 

Meta-Unked oUgoureas n = 4) were prepared in a step-wise/convergentester-functionalized isocyanate molecules (9 Figure 9.3) [15]. 

The reaction between these three components leads to the formation of segmented copolymers characterised by the alternation of hard and soft segments. Hard segments are based on blocks formed by reaction of the di- or multi-functional isocyanate with the chain extender, while the polyol-based units form the soft segments. As a result of the thermodynamic incompatibility between hard and soft segments, PURs are characterised by a biphasic morphology (GunatiUake et al., 2011) (Fig. 6.2). 

The hard segments are formed from diisocyanates and low molecular weight diols or diamine chain extenders. Higher functional isocyanates and/or chain extenders may be used to provide chemical crosslinking. The hard segment domains are mainly responsible for reinforcing the soft polymer matrix and for the ultimate high-temperature performance of the urethane polymer. 

Monomer(s) structure - diols, triol, tetrafunctional polyols 1-3 functional isocyanates ... 

The major fatty acid component of lesquerella oil (LO) is lesquerolic acid (55%), a C20 hydroxy fatty acid with an isolated double bond. Other than castor oil lesquerella is the only commercially available oil with a hydroxyl functional fatty acid. Two types of LO methacrylates, methacrylated lesquerella oil (MALO) and hydroxyethyl methacrylate modified lesquerella oil (HEMALO), were synthesized by reacting the oil with methacryloyl chloride and an methacrylic functional isocyanate, respectively (Scheme 2). 

The basic reactions are similar to the Inside-out methodology. However, the reaction sequence starts with reaction of HEA (the outside of the polymer) with the diisocyanate instead of the polyol (the inside). The reaction vessel is charged with diisocyanate, catalyst, and stabilizer to which the HEA is added, resulting in an acrylate-functional isocyanate. Next the polyol is added, and a urethane acrylate can be obtained. 

The traditional synthesis of PUs involves a step polymerization between a di- or poly-isocyanate with a diols/polyols. A Hnear polymer is obtained if di-functional isocyanates and polyols are used (see Figure 12.11). Both the isocyanates and polyols used to make polyurethanes contain on average two or more functional groups per molecule. 

A different type of reinforcement is achieved by the use of poly functional isocyanates. As... 

Isocyanates react with materials having active hydrogen atoms and in the production of a polyurethane foam a whole series of reactions of this type takes place. For simplicity, only one functional isocyanate group, and the functional parts of the reaction products are illustrated. 

The second component in the two pack is a polymeric multi functional isocyanate. The isocyanate group is extremely hydrogen acquisitive and will therefore abstract hydrogen from the hydroxy functional acrylic resin, forming a urethane link in the process. The multi functionality of the isocyanate ensures the formation of a network structure. Reactions take place at ambient temperatures or can be forced along at slightly above ambient temperatures, e.g. 60°C for 20 minutes as a typical cure cycle. 

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