**3. Influence of metal chelate modifiers on surface properties of polyurethanes**

62 Polyurethane

containing PUs (Figure 6).

formed on the air).

with the X-ray data that register several discrete peaks in Cu(2+), Cr(3+) and Co(3+)

**Figure 7.** The optical microscopy (a, b) and SEM microscopy micro images of the LPU-0,5%Cu(acac)2

(a) (b) (c)

**Figure 8.** Micro images of LPU-1%Eu(fod)3 (a,b) and CPU-1%Cr(acac)3 (c, d) surfaces formed at the

(c) (d)

(a) (b)

"polymer-air" boundary (а, c) and the "polymer- support" boundary (b, d).

Optical microscopy allows obtain information concerning two surfaces of one PU film. One of them formed on the boundary "polymer-support" (the PU's surface formed on the Teflon support) and another formed on the boundary "polymer-air" (the PU's surface

(in polarized light) (a), LPU-5%Cu(acac)2 (b) and CPU-5%Cr(acac)3.

The presence of metal chelate compounds in reaction mixture can influence the surface tension of the formed polyurethane. In (Lipatov, 1997) the surface properties were studied of PU with metal ions introduced through in four different ways. There are filling, metal ion cross-linking, metal ion chain-extending and diffusion of metal chelate compound from its solution to polymer being formed earlier. It has been shown that the surface properties of metal containing PU depend on metal quantity much less than on the way of metal chelate compound introduction in polymer. For example, the γsg of PU filled with Cr(acac)3 (0.18% wt.) changes up to 8 mN/m. On the contrary the γsg of Pb (15% wt) cross-linked PU changes up to 0.3 mN/m as compared with metal free PU.

Obviously, the PU's surface structure depends on the boundary "polymer-support" or "polymer-air". Data of ESCA and IR-spectroscopy by (Lipatova et al., 1987; Lipatova & Alexeeva, 1988) point on possibility of the chemical unequivalenсe of the polymer surfaces formed at the different boundaries. In addition in (Kozak et al., 2010) it was observed substantial difference in luminescence intensity at different surfaces of the PU films modified with europium (3+) chelate compounds. Therefore, the surface properties of europium containing LPU and CPU were compared for surfaces formed at the "polymerair" and "polymer-support" boundary using measurement of contact wetting angle. The data obtained are listed in the table 4.

The values of surface tension of metal containing PU obtained using Wilgelmy method(with water as wetting liquid) (Lipatov et al., 1997) are consistent with values of the surface tension calculated using measurement of contact wetting angle (Table 5) of standard liquid.

The wetting angles at the "polymer-air" boundary for all of CPU and LPU are from 5.5 to 15.5 degrees less than the wetting angles at the "polymer-support" boundary (table 4). The difference between relative values of surface tension (1-2) takes values from 2.18 to 5.59 mN/m. As it is known, the higher compound polarity is the greater surface energy and surface tension it possesses. Obtained results allow conclude that PU surface formed at the "polymer-air" boundary is enriched with more polar groups (e.g. urethane ) and PU surface formed at the "polymer-support" boundary is enriched with less polar groups (e.g. glycol segments).

Concentration of PU less polar groups that form the weak complexes with metal chelate compound at the "polymer-support" boundary can facilitate the partial segregation of metal containing centres at this boundary. That conclusion is consistent with microscopic data and photoluminescence measurements.

Bottom-Up Nanostructured Segmented Polyurethanes with Immobilized in situ Transition and Rare-Earth Metal Chelate Compounds – Polymer Topology – Structure and Properties Relationship 65

LPUs and CPUs modified with Eu(3+) chelates when exposed in 365 nm UV-light demonstrate the intensive photoluminescence in red region. Figure 9 represents

The luminescent spectra of europium containing PU are diffuse, while luminescence spectrum of Eu(fod)3 is enough well-resolved. According to (Poluectov et al., 1989) the luminescence spectra of europium *β*-diketonate solutions contain bands corresponding to the 5D0-7F*<sup>і</sup> -*transitions (where *і* = 0,1,2,3,4). The spectra of Eu *β*-diketonate in PU matrices demonstrate the intensive wide band of photoluminescence in the region of λ=610-635 nm (5D0-7F2-transition), narrow band λ=660 nm (5D0-7F3 –transition) and bands of 5D0-7F0, 1, 4 transitions (580, 600,700 nm, accordingly) of low-intensity. It is possible to explain the diffuse spectrum of luminescence of europium containing PU in the region of λ =610-635 nm by distortion of the Eu (3+) chelate geometry in PU due to complex "polymer-metal

**Figure 9.** The spectra of luminescence of LPU *(a)* and CPU *(b)*, modified with europium chelate (λUV =

The intensity of PU-Eu luminescence depends both on the europium chelate content and polymer topology. The luminescence intensity increases with increasing of europium chelate compound content. The luminescence intensities of 5D0 → 7F2 transition (λ=612nm) for LPU with 05%, 1% and 5%wt. of Eu(fod)3, correspond as 1:1,8:2,4. The relationship of luminescence intensity *vs.* modifier percentage in CPUs is linear (1:3,3:9,2). The CPU-Eu with low modifier content has the lower luminescent intensity as compared with LPU-Eu. Where as CPU-5%Eu luminescence intensity is 1,5 higher, than LPU-5% Eu luminescence intensity. Taking into account data of Sections 2, 3, 6 we can suppose that due to difference in PU topology this effect is associated with higher concentration of polymer photo

The tetra coordinated Eu (3+) chelate compounds with different additional ligands in an external coordination sphere were used to analyse the influence of additional coordination

transmitting sites near the modifier in CPU as compared with LPU.

the luminescent spectra of LPU and CPU, modified with various amount of Eu(fod)3.

chelate compound" formation and due macroligand steric hindrances.

365 nm): (1) 0.5%; (2) 1%; (3) 5%.


θ1, θ2 – the wetting angles at the "polymer‐air" and the "polymer-support" boundaries, respectively, degree; γ1, γ2 – the surface at the "polymer‐air" and the "polymer-support" boundaries, respectively, mN/m; \* the unbalanced wetting angles

**Table 5.** The contact wetting angle (θ) and surface tension () of PU films. The standard liquid is ethylene glycol (EG) γЕG-air = 48,36 mN/m.

Varying of the metal containing modifier amount (from 0,5 to 5% wt.) in CPU practically does not affect surface tension. In the contrary, change of metal chelate compound content in LPU from 0,5 to 3%wt. lead to decreasing of both 1 and 2.

The difference of the tendency in changing of surface tension in LPU and CPU clearly depend on polymer topology. Different PU topology results in different segmental mobility of the polymer, that agrees with DRS data. This effect described detailed in Section 5 and Section 2.4. At that time we can't formulate the certain reason for non monotonous influence of the modifier's amount on the surface tension.
