Segmented Poly(urethane-urea)s Synthesized Directly from Isocyanate-Terminated Prepolymers and Masked Diamines II. Kinetic and Mechanistic Study on Masking and Demasking Reaction

Abstract

ABSTRACT:An attempt was made to clarify the mechanism of the reactions of acetone with propylenediamine (PDA) or ethylenediamine (EDA) for direct synthesis of poly(urethane-urea) (DSPUU reaction) by using the reaction products (masked diamines) and an isocyanate-terminated prepolymer. In the masking reaction of acetone with PDA at 40°C, 1-(N-isopropylidene )propanediamine (1), 2-(N-isopropylidene )propanediamine (l '), 2,2-dimethyl-4-methylimidazolidine (3) as main product, N,N' -diisopropylidenepropylenediamine (2) were formed in this order due to the dominant rate (k 30 = 3.0kgmol-1 min -1 ) of the water-catalyzed reaction to form (3) in addition to the slow rate (k20 = 3.2 x 10-3 kgmol-1 min-1 ) of (2). The concentration of (l ') remained lower than (1) because of the steric hindrance of the methyl group of the former. The formation reactions of (1) and (2) were more acid-catalyzed than the reverse reactions, leading to shorter equilibrated time and larger molar fractions of these compounds. The reaction profiles for acetone-EDA were analogous except for lower molar fraction of 2,2-dimethylimidazolidine (6) and larger N,N'-diisopropylideneethylenediamine. The rates of demasking reactions which are of importance in DSPUU reactions using masked ED As were as follows; (i) the water-and acid-catalyzed ring opening reaction rate of (6), k _ 30 and k_ 3 = 1.43 and 0.26 kg mo!-1 min -, and (ii) the acid-catalyzed hydrolysis reaction rates of the ketimine groups, k_ 1 = 5.09 and k_ 2 =3.13kg 2 mo1-2 min-1 , respectively.

Viscometric Study of Poly(ester Urethane) Solutions: 2. Influence of Hard-Segment Composition on the Unperturbed Dimensions

“…The samples containing segmented block copolyurethanes were prepared by the reaction of aromatic diisocyanates such as MDI or TDI, both from Merck, distilled under reduced pressure, with PEGA, from Fibrex Savinesti (P O = 2000 g mol 4 ) and DEDS [17] as chain extender by using a two-step polyaddition process in dimethyl formamide (DMF) [18]. In the first stage of reaction, the NCO-terminated prepolymer was formed; PEGA was dehydrated for 3 h at 120 C followed by the addition of MDI or TDI.…”

Viscometric Study of Segmented Poly(ester-urethane) Solutions in Dilute and Extremely Dilute Concentration Domains

“…The samples containing segmented block copolyurethanes were prepared by the reaction of aromatic diisocyanates such as MDI or TDI, both from Merck and distilled under reduced pressure, with PEGA from Fibrex Savinesti (M n ¼ 2000 g/mol) and 4,4 0 -dihidroxydiethoxydiphenyl sulphone as chain extender (DEDS) [18][19] using a two steps polyaddition process in DMF [20]. The 4,4 0 -dihidroxydiethoxydiphenyl sulphone chain extender utilized in this work introduces high performance having excellent chemical and thermal stability, because of the strong resonant aryl-sulphone groups, and because of the hexavalent sulfur [19].…”

Influence of Ester and Ether Groups on Solution Properties of Polyurethanes

“…The samples containing segmented block copolyurethanes were prepared by the reaction of aromatic diisocyanates such as 4,4 1 -methylene diphenylene diisocyanate (MDI), or 2,4tolylene diisocyanate (TDI) with poly(ethylene glycol)adipate (PEGA), poly(propylene glycol) (PPG) or polytetrahydrofurane (PTHF) and 4,4 1 -dihydroxydiethoxydiphenyl sulfone (DEDS), thiodiglycol (TDG) or diethylene glycol (DEG) as chain extender by using a two-step polyaddition process in dimethyl formamide (DMF) [7][8][9][10].…”