Ureas Urethanes

Type I Urea-Urethane Oligomers. To 30g (0.5 mole) ethylene diamine and lOg dimethoxy ethane in a three-neck flask equipped with an overhead stirrer was added over a one-hour period, 185g (0.5 mole) of butanol half-blocked dllsocyanate. After the addition, the reaction was stirred overnight at room temperature. 

Type II Urea-Urethane Oligomers. To 11.6g (0.1 mole) of melted 1,6-hexanediamine was added 76.9g of t-butanol half-blocked isophorone diisocyanate. During about a 30-minute addition, the temperature rose to 50-60°C. After an additional one hour of heating at 50-60°C, the oligomer solution was thinned with 40g of 2-hexoxy-ethanol. 

Table II. Infrared Absorption Data on the Cure of (t-Butyl Carbamate) Terminated Urea-Urethane Coating3...

Figure 2. Infrared spectra of baked and unbaked Type I urea-urethane/epoxy formulations respectively.

Figure 3. Infrared spectra for Type II urea-urethane/epoxy formulations, respectively, showing decreases in the intensity of the urethane absorption as the1 temperature of the cure reaction is increased from 50-180°C.

Acid-like includes carboxylic acid, tetrazole, sulphonamide (ionizable NH) etc. Amide like includes (substituted) amide. Tetrazole, sulfonamide, etc. Ester-like includes tertiary amide (substituted, no NH) ureas, urethane, sulfonamide, etc. 

Wagner et al. (3) prepared elastomeric materials consisting of biodegradable poly(urea-urethanes), (II), containing microintegrated cells that were useful as pulmonary valves, vocal chords, and blood vessels. 

Crosslinked poly(urea-urethane)s consisting of tris(4-isocyanatophenyl)-methane, trimethylolethane, and 4,4 -methylenebis(3-chloro-2,6-diethyl-aniline) were prepared by Rukavina et al. (2) and used in optical lenses. Polycaprolactone diol derivatives were also prepared by Rukavina et aL (3) and used in optical lenses. 

A wide variety of alkenes have been shown to undergo aminomercuration-demercuration, including alkenes bearing alcohol, ester, acid, amide, imide, urea, urethane, ether, sulfide and aryl groups.194... 

Careful XPS analysis of a series of poly(dimethylsiloxane-urea-urethane) multiblock copolymers demonstrated that, as well as a surface layer of siloxane, there was a layer enriched in the hard block immediately beneath this. The thickness of both these layers depended on the molecular weights of the soft and hard block segments, respectively112. Annealing of these copolymers increased the thickness of both layers. The same authors have also shown that the thickness of these layers of hard and soft blocks could be modified by use of solvent mixtures which selectively precipitate the polar hard block during film formation by solvent casting113. 

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. 

One of the most important uses of end-functionalized polymers is the preparation of block copolymers.73,74 The reactions are identical to the chain extensions already mentioned, except that the sequences being joined are chemically different. In the case of the -OSilCR Y chain ends mentioned above, R is typically (CH2)3 5 and Y can be NH2, OH, COOH, CH=CH2, and so on The siloxane sequences containing these ends have been joined to other polymeric sequences such as carbonates, ureas, urethanes, amides, and imides. 

A broad spectrum of hydrogen-containing nucleophiles react with both aromatic and aliphatic isocyanates compounds containing OH groups (H20, alcohols, phenols, oximes, acids), SH groups (H2S, mercaptans), NH groups (NH3, amines, hydrazines, amides, ureas, urethanes), enolizable compounds such as malonic and aceto acetic esters, etc. Some reactions are given in Table 2.5. 

F. Bachmann, M. Ruppenstein, and J. Thiem, Synthesis of aminosaccharide-derived polymers with urea, urethane, and amide linkages, J. Polym. Sci. Part A Polym. Chem., 39 (2001) 2332-2341. 

Diols are predominantly used for chain extensions to give a product with only urea bonds. The progress is similar to the formation of the poly(urea-urethane), but with only urethane bonds. See Figure 2.32. 

Infra-red analysis unreacted NCO plus high concentration of urea unreacted NCO plus urethane and urea urethane... 

Block copolymers were developed rapidly in the 1960s when living anionic polymerization was first utilized to synthesize triblock thermoplastic elastomers or elastoplastics. At the same time, step or condensation polymerization to produce thermoplastic polyurethanes, urea-urethane spandex fibers, and later more specialized materials, such as the semicrystalline polyester-polyether copolymers were developed [10]. Imide block or segmented copolymers utilizing... 

Figure 12. Plots of log Abcrb (upper panel) and ( b — 1) (lower panel) against temperature. Data were evaluated at an extension rate of 1 min 1 and are for poly(urea-urethane) and polyurethane elastomers (87).

High purity and high molecular weight siloxane-urea/urethane copolymers, (1), were prepared by Kuepfer [ 1] at ambient temperature using dibutyl tin diacetate as catalyst under anhydrous conditions. Additional siloxane-urea/urethane copolymer derivatives were prepared by Schafer [2]. 

Random Urea-Urethane Copolymer of Polyether Glycol,... 

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