Polyurethane-semicarbazides

Polyurethane-semicarbazides (in earlier reports, they are also called poly-urethane-acylsemicarbazides) are linear polymers containing urethane and (acyl)semicarbazide groups in their macromolecules. Sulfur or phosphorus can also be included in the macrochains [2]. 

The polyurethane-semicarbazides V are prepared in two steps [2]. As the first step, one obtains the prepolymer 111 through the interaction of an ohgo-ether or oligoester 1 and a diisocyanate 11. In the second step, the prepolymer III is extended by a stoichiometric amount of a dicarboxyhc acid dihydrazide (IV, a difunctional derivative of hydrazine)  

The solution-cast polyurethane-semicarbazide films are elastic and transparent, and are characterized by high mechanical properties. The stability of these polymers at low temperatures grows with the increase of the macrochain flexibility, because of the weakening of the intermolecular interactions at lower concentrations of urethane and semicarbazide groups. 

---

The sulfur-containing polyurethane-semicarbazides are usually called poly-urethane-sulfosemicarbazides. The chemical and thermal properties of these polymers depend on the valent state of the sulfur atom included in the macro-... 

The sulfur-containing polymers are synthesized by a method similar to that described above for the polyurethane-semicarbazides V in donor solvents (DMF, DMSO, HMF, dioxane, etc.). Tertiary amines, organotin compounds, and transition metal /3-diketonates are active catalysts in this synthesis, leading to the obtaining of polymers with a maximal molecular mass of 50 000-60000 [4]. 

The phosphorus-containing polyurethane-semicarbazides VIII are obtained in two steps (i) preparation of the phosphorus-containing prepolymer VII and (ii) chain extension by isophthalic or 0-substituted phenylthiophosphoric acid dihydr azide ... 

The second stage of the obtaining of cation-active polyurethane semicarbazides XVIII can be represented schematically as ... 

The spontaneous dispersion of the cation-active polyurethane-semicarbazide in water takes place at the ionic groups (Table 1) either by precipitation or by phase inversion in polar, water-miscible solvents, such as acetone or dioxane. The salt formation is effected with hydrochloric, acetic, or chloroacetic acid. 

Table 1. Characteristics of the aqueous dispersions of cation-active polyurethane-semicarbazides...

The factors determining the colloid-chemical properties of the cation-active polyurethane-semicarbazides are the nature and concentration of the ionic centers, and their position in the repeat unit of the macromolecule. The aqueous dispersions of the cation-active polyurethane-semicarbazides obtained have long shelf lives and form hydrophilic films. 

Anion-active polyurethane-semicarbazides XIX are obtained using bifunctional anion-containing chain extenders, such as dihydroxy- or diaminocarboxylic acids, dihydroxy- or diaminosulfoacids [9] ... 

Prom the prepolymers based on aromatic diisocyanates containing sulfite groups, aqueous dispersions of anion-active polyurethane-semicarbazides are obtained by phase inversion [10]. The respective repeat units XX can be represented as ... 

Polyurethane-semicarbazides based on crown ether sulfonyl derivatives... 

The incorporation of macroheterocyclic compounds and their derivatives in polymer structures leads to the obtaining of polymers with specific behavor upon complex formation [3,11,12]. Polyurethane-semicarbazides comprising crown ether sulfonyl derivatives in the main chain were obtained by a conventional two-stage method [13-16]. The structure of the repeat unit of the resulting crown ether-containing thermoplastic elastomers XXI can be represented as ... 

Polyurethane-semicarbazides and polyurethane-sulfosemicarbazides were obtained by the conventional two-stage synthesis [2] in the presence of a transition metal acetylacetonate the polymers obtained have the following structure... 

Goncharova L B, Grekov A P, Batjaeva S I and IVoev K D (1986) Phosphorus-containing cation-active polyurethane semicarbazides, UkrKhim Zh 52 1100-1104 (in Russian). 

---