Hydroxyalkyl urethane

A novel concept for generating new multifunctional modifiers was developed [26], Hydroxyurethane modifiers (HUMs), which possess a wide range of hydrogen bonds, are embedded in an epoxy polymer network without a direct chemical interaction. Some new hybrid materials obtained by introducing hydroxyalkyl urethane into the polymer network structure, without any additional chemical reactions, are described in the following sections. 

The chemical reaction of obtaining hydroxyalkyl urethane modifier by reaction of monocyclic carbonate with polyamine is shown in Scheme 4.5 where R1 is a residue... 

It is possible to synthesize various hydroxyalkyl urethanes by changing the nature of the radicals R1, R2, and R3. 

By glycolysis of urea groups a hydroxyalkyl carbamate (or hydroxyalkyl urethane) and an amine are formed (reaction 20.6). 

The scission of urethane groups is explained by the following two consecutive reactions (20.13 and 20.14). The first reaction is the addition of alkylene oxide to the active hydrogen of urethane groups (20.13). The resulting hydroxyalkyl urethane, by an intramolecular transesterification, leads to the splitting of the urethane bonds of PU, the PU network is destroyed with the formation of an oxazolidone and a polyether polyol. 

Therefore, we developed a carbamate group, which is cleavable under mild, alkaline conditions. The N-[2-(ferf-butyldiphenylsilyloxy)-ethyl)]-N-isopropyl-carbamoyl group (Cbse) [135,137] in tertiary esters 232 can be removed by de-silylation and subsequent neighboring group participation in the hydroxyalkyl-urethane 233 to give the alcohols 234. Some examples of compounds synthesized by this method are collected [Eq. (63)] [137]. 

Synthesis of siloxane-urethane copolymers from various hydroxyalkyl-terminated PDMS oligomers and aliphatic diisocyanates, such as tetramethylene- and hexame-thylene diisocyanate and HMDI was reported 333,334). Reactions were conducted either in chloroform or 1,4-dioxane and usually low molecular weight, oily products were obtained. No data were available on the molecular weights or the thermal and mechanical properties of the copolymers obtained. These products were later cross-linked by a peroxide. Resulting materials were characterized by IR spectroscopy and water contact angle measurements for possible use as contact lenses. 

Synthesis of a Urethane Vinyl Ether Oligomer. A urethane vinyl ether oligomer was prepared by the procedure discussed by Lapin.15 Reacting a hydroxyalkyl vinyl ether, an oligomeric diol and a diisocyanate gave and oligomer that had a Brookfield viscosity of 3.7 million mPa-s and a theoretical equivalent weight of 1000 g per vinyl ether double bond. 

Several poly(urea urethane) oligomers 28 (Figure 12) were prepared by one-component polycondensation of iV-(hydroxyalkyl)-2 -oxo-1,3-diazepane-l-carboxamides, which act as intramolecular blocked isocyanates <2005PLM 1459>. These oligomers are semicrystalline materials and their melting points show the odd/even effect observed earlier for [ ]-polyamides, [ ]-polyurethanes, poly(ester amide)s, and poly (amide urethane)s. Further analysis showed that the polymers are stable up to ca. 205-230 °C, the polymers with the lower number of methylene groups in the amino alcohol decomposing at the lowest temperature. 

Urethane - polyisocyanuric foams (PU/PIR) foams) contain isocyanuric rings. Isocyanuric rings are glycolysed at lower reaction rates than the urea or urethane groups, with the formation of hydroxyalkyl carbamates and an amine (reaction 20.7) [11] ... 

The disadvantage of hydroxyalkyl urea formation is an intramolecular reaction which leads to an oxazolidone, a cyclic urethane (reaction 20.10) [33]. 

Urethane acrylates may be obtained by reacting hydroxyalkyl acrylates, diisocyanates and diols. A typical example of the overall reaction is ... 

The best-known vinyl ester is made by reacting the diglycidyl ether of bisphenol-A (DGEBA see Section 16.4.2) with a monocarboxylic unsaturated acid such as methacrylic or acrylic acid see Scheme 16.24. This addition reaction occurs at a temperature of 120-140°C. The vinyl ester urethanes, on the other hand, are synthesized from a low molecular weight (unsaturated) polyester diol, mostly based on bisphenol-A, a diisocyanate, and a hydroxyalkyl (meth)acrylate (see also Schemes 16.30 and 16.31, Section 16.8.3.3). As for standard UP resins, the most commonly used reactive solvent is styrene. Both types of products have only a few ester linkages (which are the points of greatest vulnerability to chemical attack) in the mole-... 

Addition of bromine to allylsuccinic anhydride 1 gives rise to the dibromo derivative 75. Inclusion of such material in polyesters has been claimed to improve fire retardancy of the product. The resin made with 75 was described as having self-extinguishing properties. " " Bis-(2-hydroxyalkyl)-esters of 75 has been converted to flame-retardant urethanes. ... 

There is another type of dimethacrylate that is finding significant use in dental monomers. These are the urethane dimethacrylates, which are synthesized from hydroxyalkyl methacrylates and aliphatic diisocyanates (7,8). The synthesis of this non-aromatic type of monomer is shown in Fig. 2A. The molecular bulk of these monomers is similar to that of BIS-GMA. 

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