Diisocyanate Dimethylformamide

The polyurea is prepd by dissolving equivalent amounts of the monomers (80g total wt) in dime thylformamide. Using separate solns, 125ml of the diisocyanate is slowly added to 120ml of the amine soln while keeping the temp below 20°. After standing 18 days at RT, most of the dimethylformamide is vacuum evapd at 50° and the syrupy residue is kept at 50° for 48 hrs. Acet diln is followed by filtration, then pptn in ice w. The product is vacuum steam distd at 30° then dried over P2Os... 

To obtain the polyurethanes, typically a prepolymer was first prepared by reacting the diisocyanate with various diols in dimethylformamide or dimethylacetamide in a two to one molar ratio at 100-110°C for two hours under nitrogen atmosphere. A solution of chain extenders, such as BEP, was then added to the prepolymer reaction mixture and further reacted another three hours. The polymer was isolated by quenching the reaction mixture in cold water. Fine white powder was obtained with a typical yield of around 90%. 

The catalysts of reactions between 4,4 -diphenylmethane diisocyanate (MDI) and alcohols in N,N-dimethylformamide (DMF) by dibutylin dilaurate has been investigated. The reaction rate of the catalyzed urethane formation in DMF is proportional to the square root of dibutylin dilaurate concentration. This result differs from that of similar studies on apolar solvents. The catalysis in DMF can be explained very well by a mechanism in which a small amount of the dibutylin dilaurate dissociates into a catalytic active species. 

T n continuation of a study of the uncatalyzed reactions between MDI (4,4 -diphenylmethane diisocyanate) and alcohols in DMF (N,N-dimethylformamide) (J), the effect of dibutyltin dilaurate on the same reactions has been studied. The results were compared with those found in studies on the mechanism of catalysis of urethane formation in apolar solvents (2-6). 

Boltom H40 dendritic molecules were covalently linked in this work to make a network with aliphatic 1,6-hexamethylene diisocyanate (HDI). The molar NCO/OH ratio was varied for the reactants from 10 to 50% to prepare networks with different degrees of connectivity of dendritic units. The network samples are designated as H40/Z where Z stands for NCO/OH ratio expressed as a percentage. The network formation reaction of H40 with HDI was carried out in N,N-dimethylformamide (DMF) of 99.8% purity at 90 C. No catalyst was added. Isocyanates react readily with moisture to form urea linkages, therefore special precautionary measures were implemented to prevent moisture uptake either by HDI or DMF. Observation of the reaction vessel was maintained over the course of the reaction to monitor the viscosity of the solution. As viscosity of the solution increased to the desired level, suggesting that the gelation point was near, the solution was cast onto a glass plate which was immediately placed... 

NO2 NO2 0 NO2 -C.N.(CH2)2.N.(CH2)2.N.C.0.CH2.C.CH20-N02 CH2 mw (425.32)n, N 23.06%, OB to CO2 -58.31%, amorph solid, mp 70—80°. Sol m acet. The imtial polymer is prepd by dropwise addition of a sob of the diisocyanate in dimethylforma-mide to a dimethylformamide sob of an equiv wt of diol plus 1x10" mole ferric acetylacetonate catalyst over a period of 15 mbs. Polymerization is completed b 136 hrs at 50°. After dilution with dimethylformamide, the polymer is pptd b w and vacuum dried. Post polymerization nitration is accomphshed by soln of the polymer b 100% nitric acid at 0° b the ratio of 1 g polymer to 15ml acid. Nitration is completed on sob of the polymer. The excess acid is vacuum distd at RT, the polymer is dissolved b acet and pptd in methylene chloride... 

Secondly, the reaction was inhibited by both strong and weak acids. Strong acids, such as HBF4, completely stopped the reaction. Weaker acids, snch as acetic acid, had a much less pronounced and concentration-dependent effect. It has been snggested that the concept of the ionic mechanism mnst be viewed with some degree of caution, since the reaction proceeded faster in non-polar solvents, snch as cyclohexane, compared with a dipolar aprotic solvent, snch as dimethylformamide, whereas one wonld expect that the polarity of the solvent wonld significantly stabilize the ionic catalyst intermediates. However, Urban et al. have demonstrated that an ionic mechanism is likely operative in the reaction of hexamethylene diisocyanate with an acrylic polyol, nsing DBTDL as catalyst. 

The amine-based Henry reaction catalyst was encapsulated via the interfacial polymerization of oil-in-oil emulsions. PEI was encapsulated by dispersing a methanolic PEI solution into a continuous cyclohexane phase. Upon emulsification, 2,4-tolylene diisocyanate (TDI) was added to initiate crosslinking at the emulsion interface, forming polyurea shells that contain free chains of PEI. The microcapsules crenate when dry and swell when placed in solvents such as methanol and dimethylformamide, suggesting a hollow capsule rather than a solid sphere formation. The catalyst loading was determined to be 1.6 mmol g . ... 

All chemicals used in this study were reagent grade. Butyl isocyanate (BuNCO, 99% from the Upjohn Chemical Co.), hexamethy-lene diisocyanate (HDI, 99% from the Mobay Chemical Co.), phenyl isocyanate (PhNCO, 99%, from the Upjohn Chemical Co.), p-tolyl isocyanate (MePhNCO, 99% from the Aldrich Chmical Co.), p-chloro-phenyl isocyanate (CIPhNCO, 99%, from the Aldrich Chemical Co.) and cyclohexyl isocyanate (CHI, 98%, from the Aldrich Chemical Co.) were purified by vacuum distillation. Methylene diphenyl diisocyanate (MDI, 99%+, from the Mobay Chemical Co.) was used without further purification. N,N-Dimethylformamide (DMF, reagent grade, from the Mallinckrodt) was dried by molecular sieves 4a. The NCO-terminated prepolymers were prepared from poly(oxy-tetramethylenediol) (POTMD, mol. wt. 650, 1000, 2000, Quaker Oats Chem. Co.) and MDI. 

The reaction of cotton cellulose with phenyl isocyanate, to give a cellulose phenylurethan, has been investigated further. The extent of the reaction depends on the ability of the solvent to swell the cellulose, methyl sulfoxide being the best medium, followed by i r,f T-dimethylformamide and P3Tidine. The reaction is catalyzed by the addition of di-w-butyltin diacetate, but toluene 2,4-diisocyanate and 1,2,4,5-tetramethylbenzene diisocyanate do not show high reactivity. A survey of the relative behavior of chitin and cellulose toward esterification under comparable conditions, mainly to give arylsulfonate esters, concluded that, of the two, chitin is the less reactive. 

Nuclear Magnetic Resonance Spectroscopy. Like IR spectroscopy, NMR spectroscopy requires little sample preparation, and provides extremely detailed information on the composition of many resins. The only limitation is that the sample must be soluble in a deuterated solvent (e.g., deuterated chloroform, tetrahydro-furan, dimethylformamide). Commercial pulse Fourier transform NMR spectrometers with superconducting magnets (field strength 4-14 Tesla) allow routine measurement of high-resolution H- and C-NMR spectra. Two-dimensional NMR techniques and other multipulse techniques (e.g., distortionless enhancement of polarization transfer, DEPT) can also be used [10.16]. These methods are employed to analyze complicated structures. C-NMR spectroscopy is particularly suitable for the qualitative analysis of individual resins in binders, quantiative evaluations are more readily obtained by H-NMR spectroscopy. Comprehensive information on NMR measurements and the assignment of the resonance lines are given in the literature, e.g., for branched polyesters [10.17], alkyd resins [10.18], polyacrylates [10.19], polyurethane elastomers [10.20], fatty acids [10.21], cycloaliphatic diisocyanates [10.22], and epoxy resins [10.23]. 

Diisocyanate and acid dianhydride are mixed in equimolar amounts, often previously dissolved in a suitable solvent. 3,3, 4,4 -Benzophenone dianhydride (4,4 -BTDA) is mixed at room temperature with in diphenyl-methanediisocyanate using AW-dimethylformamide (DMF) as a solvent and subsequently heated in vacuum up to 210°C. A PI with a molecular... 

May be harmful if swallowed 5 Warning >2000 to <5000 Acetic acid, carbon disulfide, carbon tetrachloride, dimethylformamide, methyl ethyl ketone, sulfuric acid, tetrahydrofuran, toluene diisocyanate... 

Polyethylene glycol (PEG) is another well-known molecule used to reduce protein adsorption and/or platelet adhesion. Surface enrichment of a triblock oligomeric PEG containing additive from a polyurethane matrix was reported [54,55]. The authors used PEG as the active groups to suppress protein and platelet adhesion. The authors first synthesized a methylene diphenyl diisocyanate (MDI)-poly (tetramethylene oxide) (PTMO) 1000 prepolymer with a MW of approximately 4750 (PU4750), and then this prepolymer was terminally functionalized with mono amino-polyethylene oxide (PEG) with different MW (PEO550, 2000, or 5000, Table 2.3). This triblock copolymer was mixed with a polyurethane (MDI/ PTMO 1000/ethylene diamine (ED)) at different ratios in dimethylformamide (DMF) and cast into polymer films. The surface compositions of these films were evaluated by XPS. 

All ligands were synthesized fi-om the appropriate hydrazide and either the appropriate diacid chloride, dihydrazide or diisocyanate. Reagents include phthalo i dichloride, hydrazine hydrate, adipic dihydrazide, adipoyl chloride, 1,6-diisocyanohexane, A/-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF) and all were obtained from Sigma-Aldrich Co. 

Polyurethane fibres of a kind different to those described above have become important within the last decade these are elastomeric fibres, which are commonly called spandex fibres. These products are made either by solution spinning or by reaction spinning. In the first process, a hydroxy-terminated polyester (e.g., an adipate) or polyether (e.g., poly(oxytetramethylene) glycol) is treated with an excess of diisocyanate (e.g., tolylene diisocyanate) to give an isocyanate-terminated pre-polymer similar to those used for cast elastomers (Section 14.6.1). The pre-polymer is dissolved in a strongly polar solvent (e.g., dimethylformamide) and treated with an aliphatic diamine or hydrazine to effect chain extension with hydrazine the following reaction occurs ... 

Polymer Synthesis. Polyethylene glycol (PEG) 600,1000, and 1500 were obtained from Aldrich Chemical Company and dried by azeotroping with toluene. Molecular weights for the polyethylene glycols were determined from hydroxyl numbers. DieSiylene glycol (DEG) from Fisher Scientific was purified by vacuum distillation over metallic sodium. Hexamethylene diisocyanate (HMDI) from Aldrich Chemical Company was vacuum distilled. Dicyclohexylmethane-4,4 -diisocyanate (DCDI) (Desmodur W) from Mobay Chemical Company was used as received. Dibutyltin bis-(2-ethylhexanoate) from Kodak was stored over phosphorus pentoxide. N,N-dimethylformamide (DMF) from EM Science and 4-methyl-2-pentanone from Aldrich Chemical Company were dried over 3A molecular sieves. 

The pyridine unit, which is responsive to moisture, can be used to improve the moisture absorption in polyurethane. Chen et al. (2009) introdueed a pyridine unit into SMPU by N-bis(2-hydroxyletliyl) isonieotinamine (BINA) and prepared a moisture-responsive SMPU with high strain reeoveiy. The synthesis route of the SMPU with the pyridine unit is presented in Fig. 9.9. First, 1,6-hexamethylene diisocyanate (HDl) reacts with BINA to form a prepolymer, before the prepolymer is extended with 1,4-butanediol (BDO). It ean be dedueed that SMPs that are sensitive to their suitable solvents, and similarly hydrophilic SMPs that are sensitive to water/moisture, can be obtained in this way. Lv et al. (2008b) observed the DMF (N,N -dimethylformamide) (a good solvent of SMPU) responsive SME of SMPU. 

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