**6. Catalytic properties of coordination compounds of copper in the reaction with isocyanate and urethane groups**

The next step was to change the ligand composition of metal complex modifying system based on CuCl2 and DEHA. The aminopropyltriethoxysilane (AGM) was used as a part of modifying system. The use of the AGM as an additional component to the DEHA was caused by some reasons. The first reason is that the AGM is able to take part in the reactions of sol-gel synthesis, resulting in the hydrolysis of ethoxy-component and subsequent polycondensation of the forming silanol groups. The second reason is the presence of electron-donor amine groups in the AGM which are able to form complexes. Besides, amines can lead to reduction of copper (II) to copper (I). Thereby this substance is interesting in terms of the influence on the reactivity of isocyanate groups and the supramolecular structure of polyurethane, which has domain nature.

The Modification of Polyurethanes by Highly Ordered Coordination Compounds of Transition Metals 43

The titration data confirm the results of IR-spectroscopic studies. It is established that the absorption band at 1731 sm-1 due to the stretching vibrations of carbonyl component of urethane group decreases at low concentrations of metal complex in the first ten minutes from the start of the reaction process. At the same time the intensity of the absorption band at 2273 sm-1 due to the stretching vibrations of isocyanate group grows. Later the growth of the intensity of the absorption band at 1731 sm-1 and the decrease at 2273 sm-1 are observed. Besides in the first ten minutes from the start of the reaction the IR-spectroscopy shows the reduction of the intensity of the absorption band at 3293 sm-1 due to the stretching vibrations of N-H-bond that is a part of urethane group. At relatively high concentrations of metal complex (≥0.25%) the interaction is accompanied by the growth of the intensity of the

The research suggested that at relatively low concentration of metal complex the urethane group dissociates to isocyanate and hydroxyl groups, while at high concentrations of metal complex the isocyanate groups consume to the formation of carbodiimide groups. The part of isocyanate groups is hypothetically consumed on the formation of the azoaromatic groups. It is known that it is impossible to analyze azoaromatic groups using infrared

Electronic spectrum (Fig. 10) showed absorption at 350 nm, typical for trans-azoaromatic compounds. The absorption in the area 480 nm characterizes the coordination compounds

**Figure 10.** Electron spectrum of urethane prepolymer (1) and prepolymer (2) modified by 0.5% (wt.)

metal complex system based on CuCl2 - DEHA – AGM.

absorption band at 2120 sm-1 due to the formation of carbodiimide group.

spectroscopy. In this regard, studies were carried out using electron spectroscopy.

of copper (II).

Titrimetric determination of concentration of isocyanate groups in UPTI during its interaction with metal complex system based on CuCl2, DEHA and AGM at 100ºC, was carried out. UPTI is industrial prepolymer synthesized on the base of 1 mol polyoxitetramethyleneglicol and 2 mols 2,4-toluene diisocyanate.

It was found that at relatively low concentrations of metal complex (0.01 and 0.05% in terms of CuCl2) in the first ten minutes from the start of the reaction process, the concentration of isocyanate groups started to rise, and only after that it fell. When the content of metal complex was 0.1, 0.5 and 0.75% in terms of CuCl2 the concentration of isocyanate groups began to fall significantly (see fig. 9).

**Figure 9.** Isocyanate groups consumption curves in system UPTI – CuCl2-DEHA-AGM, Т=100°С, at a content of CuCl2: 1 - 0,05%; 2 - 0,1%; 3 - 0,25%; 4 - 0,5%; 5 - 0,75% (wt.).

The titration data confirm the results of IR-spectroscopic studies. It is established that the absorption band at 1731 sm-1 due to the stretching vibrations of carbonyl component of urethane group decreases at low concentrations of metal complex in the first ten minutes from the start of the reaction process. At the same time the intensity of the absorption band at 2273 sm-1 due to the stretching vibrations of isocyanate group grows. Later the growth of the intensity of the absorption band at 1731 sm-1 and the decrease at 2273 sm-1 are observed. Besides in the first ten minutes from the start of the reaction the IR-spectroscopy shows the reduction of the intensity of the absorption band at 3293 sm-1 due to the stretching vibrations of N-H-bond that is a part of urethane group. At relatively high concentrations of metal complex (≥0.25%) the interaction is accompanied by the growth of the intensity of the absorption band at 2120 sm-1 due to the formation of carbodiimide group.

42 Polyurethane

**6. Catalytic properties of coordination compounds of copper in the** 

The next step was to change the ligand composition of metal complex modifying system based on CuCl2 and DEHA. The aminopropyltriethoxysilane (AGM) was used as a part of modifying system. The use of the AGM as an additional component to the DEHA was caused by some reasons. The first reason is that the AGM is able to take part in the reactions of sol-gel synthesis, resulting in the hydrolysis of ethoxy-component and subsequent polycondensation of the forming silanol groups. The second reason is the presence of electron-donor amine groups in the AGM which are able to form complexes. Besides, amines can lead to reduction of copper (II) to copper (I). Thereby this substance is interesting in terms of the influence on the reactivity of isocyanate groups and the

Titrimetric determination of concentration of isocyanate groups in UPTI during its interaction with metal complex system based on CuCl2, DEHA and AGM at 100ºC, was carried out. UPTI is industrial prepolymer synthesized on the base of 1 mol

It was found that at relatively low concentrations of metal complex (0.01 and 0.05% in terms of CuCl2) in the first ten minutes from the start of the reaction process, the concentration of isocyanate groups started to rise, and only after that it fell. When the content of metal complex was 0.1, 0.5 and 0.75% in terms of CuCl2 the concentration of isocyanate groups

**Figure 9.** Isocyanate groups consumption curves in system UPTI – CuCl2-DEHA-AGM, Т=100°С, at a

content of CuCl2: 1 - 0,05%; 2 - 0,1%; 3 - 0,25%; 4 - 0,5%; 5 - 0,75% (wt.).

**reaction with isocyanate and urethane groups** 

supramolecular structure of polyurethane, which has domain nature.

polyoxitetramethyleneglicol and 2 mols 2,4-toluene diisocyanate.

began to fall significantly (see fig. 9).

The research suggested that at relatively low concentration of metal complex the urethane group dissociates to isocyanate and hydroxyl groups, while at high concentrations of metal complex the isocyanate groups consume to the formation of carbodiimide groups. The part of isocyanate groups is hypothetically consumed on the formation of the azoaromatic groups. It is known that it is impossible to analyze azoaromatic groups using infrared spectroscopy. In this regard, studies were carried out using electron spectroscopy.

Electronic spectrum (Fig. 10) showed absorption at 350 nm, typical for trans-azoaromatic compounds. The absorption in the area 480 nm characterizes the coordination compounds of copper (II).

**Figure 10.** Electron spectrum of urethane prepolymer (1) and prepolymer (2) modified by 0.5% (wt.) metal complex system based on CuCl2 - DEHA – AGM.

Metal complex system, derived on the basis of CuCl2, DEHA and AGM was further used to modify polyurethanes. We measured the dependence of the volume resistivity (*ρv*) of polyurethanes on the concentration of metal complex modifier (Fig. 11).

The Modification of Polyurethanes by Highly Ordered Coordination Compounds of Transition Metals 45

**7. The use of highly ordered coordination compounds of copper for** 

Metal complexes derived from CuCl2, DEHA and AGM were also tested as modifiers of the polyol component used in the manufacturing of rigid polyurethane foam. It was found that metal complex system based on CuCl2, DEHA and AGM had a significant impact on the rise

**Figure 12.** Rise (1) and curing (2) time of foam as a function of metal complex concentration based on

It was also established that the increasing of the molar ratio of the AGM in metal complex

In order to establish the role of the AGM in the foaming process it was loaded alone in polyol component (Figure 14). It was found that the AGM also reduces the rise and curing time of the foam. However, these parameters were more than two times higher than the

We also used metal complex system based on CuCl2 and DEHA as the control modifying system. In this case, in the wide range of concentrations of modifier the foam "collapsed". That is, the foam rose and the subsequently settled out. It should be also mentioned that the density of foam produced using metal complex system CuCl2 - DEHA - AGM did not change in comparison with polyurethane foam obtained by the unmodified polyol

Thus, these studies show a significant catalytic effect of the metal complex modifier on foaming. In this connection it should be noted that the polyol component is a complicated balanced system that contains catalysts of amine nature and organotin compounds already.

system led to even greater decrease in rise and curing time of foam (Fig. 13).

parameters that caused the addition of metal complex system.

Our results suggest that the metal complex systems act as a cocatalyst.

**receiving the rigid polyurethane foam** 

and curing time of foam, reducing it (Fig. 12).

[CuCl2]:[DEHA]:[АGМ]=1:1,48:0,25 in terms of CuCl2 (%)

component.

It turned out that the use of the worked out metal complex system caused the leap of *ρv* by 4 orders (10 000 times) observed at low concentrations of metal complex 0.01%. Here we should note that while using metal complex system based on CuCl2 and DEHA (no AGM) a stepwise drop of *ρv* was observed at much higher concentration of the complex - 0.1%.

**Figure 11.** Volume resistivity-concentration diagram of modified polyurethanes under molar ratio of [UPTI]: [Diamed-X] = 1:Y:


It was found that the use of metal complex systems based on CuCl2, DEHA and AGM could significantly reduce the dosage of curing agent 4,4-methylene-bis-o-chloroaniline (Diamed-X) for urethane forming system based on UPTI.
