In Situ Nanostructured Polyurethanes with Immobilized Transition Metal Coordination Complexes

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In Situ Nanostructured Polyurethanes withImmobilized Transition Metal CoordinationComplexesYurii Nizelskii a & Nataly Kozak aa Institute of Macromolecular Chemistry, National Academy of Sciences ofUkraine , Kyiv, UkrainePublished online: 24 Apr 2007.

To cite this article: Yurii Nizelskii & Nataly Kozak (2007) In Situ Nanostructured Polyurethanes withImmobilized Transition Metal Coordination Complexes, Journal of Macromolecular Science, Part B: Physics,46:1, 97-110

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In Situ Nanostructured Polyurethaneswith Immobilized Transition Metal

Coordination Complexes

YURII NIZELSKII AND NATALY KOZAK

Institute of Macromolecular Chemistry, National Academy of Sciences

of Ukraine, Kyiv, Ukraine

Mono-, bi- and polyheteronuclear metal complexes were immobilized in situ inhomogeneous polymer based on cross-linked polyurethane (PU). Obtained systemsare described as bottom-up metal-containing nanosystems that include nanoscalestructures both of organic nature (self-similar microheterogeneities typical forsegmented PU) and metal-containing coordination junction points within the micro-phase or at the boundary.

According to x-ray data, the polymer systems obtained possess short-rangeordering in spatial arrangement of both macrochain fragments and inorganicmultiple cluster specimens. They differ in structure depending on metal-containingcomponent symmetry and depend essentially on number of ions in the metal-containingstructuring agent. SEM microphotos of cryogenic cross-fractured surfaces of metal-containing PU films demonstrate the presence of heterogeneities with 10–100 nmlinear dimensions.

EPR analysis shows that the above PU matrices differ essentially in polymer chainmobility depending on symmetry and ionic centers quantity (1–7) in coordinationmetalorganic modifier.

Keywords polyurethane network, metal coordination complex, nanoheterogeneity,EPR, X-ray analysis

Introduction

Formation of nanostructures in multicomponent systems based on an organic polymer

and a coordination metal compound allows to form in situ, structurally unique, high

dispersive nanosystems with polymer immobilized metal complexes. Aggregation of

these metal complexes is hindered as a result of complexation with polar groups of the

polymer matrix.

The above polymer systems are widely used for pyrolytic production of the matrix

isolated metal nanoparticles.[1] In addition these systems can be of independent interest

for polymer science. As a result of the complex formation between the metal compound

and polymer functional groups, the structuring of the forming matrix occurs on a

Received 7 July 2006; Accepted 5 September 2006.In Commemoration of the Contributions of Professor Valery P. Privalko to Polymer Science.Address correspondence to Nataly Kozak, Institute of Macromolecular Chemistry NAS

of Ukraine, Kharkov chaussee, 48, 02160, Kyiv, Ukraine. Fax: þ(38044) 5524064; E-mail:[email protected]

Journal of Macromolecular Sciencew, Part B: Physics, 46:97–110, 2006

Copyright # Taylor & Francis Group, LLC

ISSN 0022-2348 print/1525-609X online

DOI: 10.1080/00222340601044219

97

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nanoscale level.[2,3] Taking into account the processes on a molecular level, it is necessary

to evaluate their influence on macrocharacteristics of the modified polymer system.[4 – 6]

The presence of coordination metal-containing centers in the reaction mixture favors

formation (creation) of a new, hierarchical, structural organization in the polymer as

compared with a metal-free system. The electron configuration of the transition metal

ion determines, also, the specific symmetry and geometry of the complex formation in

the polymer structure formed.[7,8]

Influence of the method of introduction and metal ion nature (metal-contained

monomer polymerization, chemical grafting, filling etc.) on metal-containing polymer

structure and properties was analyzed in.[4 – 9] To our knowledge, the data related to

polymer systems where the metal-containing modifier contains more then one metal ion

in the organic environment are absent in the literature. Structure-properties relationships

of such polymers have not been investigated before.

The objective of this study was to analyze formation of nanostructures in a polymer

matrix modified with mono-, bi- and polyheteronuclear complex metalorganic compounds

of various symmetries as well as to investigate self-organization processes and dynamics

in a polymer matrix. Polyheteronuclear coordination metal complexes can realize unex-

pected coordination states of transition metal ions. That, in turn, can give new properties

to a polymer formed in their presence.

Experimental

Materials

PU based on polypropylene glycol (MM 1000) and toluene diisocyanate forepolymer and

trimethylolpropane as cross-linking agent were synthesized according to a standard

procedure described in detail elsewhere.[4,5]

Transition metal chelates (Aldrich, Germany) of general formulae

were dried under vacuum and dissolved in distilled dimethylformamide before introduc-

tion in the reaction mixture. Hereinafter, we will designate the used metal chelates as

follows: copper ethylacetoacetate, nickel acetylacetonate, chromium acetylacetonate

and cobalt acetylacetonate as Cu(eacac)2, Ni(acac)2, Cr(acac)3, and Co(acac)3,

correspondingly.

Polyheteronuclear metal complexes of Cu2þ, Cd2þ, Zn2þ, Ni2þ, and Co3þ, described

in,[10] were provided by Prof. V. Kokozay (Kiev Shevchenko University). The complexes—

[Cu3Cd2Br6(Me2Ea)4(dmso2)], [Cu2Zn(NH3)Br6(Me2Ea)3], [Cu2Zn2(NH3)2Br2(HDea)4]

Br2, and [Ni(H2Dea)2][CoCu(Dea)(H2Dea)(NCS)]2Br2—where Ea – amino ethanol,

Me2Ea – 2-dimethyl amino ethanol, and Dea – diethanolamine were dried under vacuum

and dissolved in distilled dimethylformamide before introduction in reaction mixture.

The cross-linked metal-containing polyurethanes (PU) were formed in the presence of

1% wt. of coordination active transition metal b-diketonates (metal chelates) and

Yu. Nizelskii and N. Kozak98

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polyheteronuclear coordination complexes of transition metals. In addition two PU

samples were formed in the presence of 5% wt. of b-diketonates of cobalt, and chromium.

Hereinafter, we will designate the PU networks analyzed as follows:

PU-0 – metal-free PU matrix

PU-Cu, PU-Co, PU-Ni, PU-Cr – polyurethane modified with 1% wt. of copper, cobalt,

nickel, and chromium chelate, correspondingly,

PU-Co5%, PU-Cr5% – polyurethane modified with 5% wt. of b- diketonates of cobalt and

chromium, correspondingly

PU-CuCd – polyurethane modified with 1% wt. of [Cu3Cd2Br6(Me2Ea)4(dmso2)],

PU-CuZn – polyurethane modified with 1% wt. of [Cu2Zn(NH3)Br6(Me2Ea)3] or [Cu2Zn2

(NH3)2Br2(HDea)4]Br2

PU-CuCoNi – polyurethane modified with 1% wt. of [Ni(H2Dea)2][CoCu(Dea) (H2Dea)

(NCS)]2Br2

Techniques

Short-range order in spatial arrangement of modified PU macrochains was analyzed using

wide-angle x-ray scattering data (WAXS) from the x-ray diffractometer DPOH-4-07 (Bur-

evestnic, St. Petersburg) in transmission.

Bragg’s period of uniform electronic density scattering elements, heterogeneity range

and interface width of PUs were estimated using small-angle x-ray scattering profiles

(SAXS) from a KPM-1 x-ray camera (NauchPribor, Russia).[11,12]

All the x-ray experiments were carried out using CuKa radiation and Ni-monochro-

matic filter at 22 + 28C with a Schmidt pinhole collimation.[13]

Scanning electron microscopy (SEM) images of cryogenic cross-fractured surfaces of

PU films were obtained using a JSM-5400 (Jeol, Tokyo, Japan) and Digital Image Proces-

sing System 2.3 (Point Electronic GmbH, Germany).

Microphoto images in transmission were obtained using an optical microscope MBS-

9 equipped with digital video ocular ICM 532 and AMCAM/VIDCAP (Microsoft) image

processing system.

EPR spectroscopic studies were carried out at 208C using a 3-cm radio spectrometer

PE-1306 (AnalitPribor). The fields calibration was performed using 2,2-diphenyl-1-picryl-

hydrazyl (DPPH) with g ¼ 2.0036 and Mn2þ doped MgO matrix with g ¼ 2.0015.

Nitroxide spin probe 2,2,6,6-tetramethyl-1-piperidinyl-oxy (TEMPO) was introduced

into PU films via diffusion of its saturated vapor at 358C for 2 h with subsequent keeping at

208C for 24 h.

Results and Discussion

The PU networks modified with transition metal complexes contain both chemical and

coordination junctions. Scheme 1 shows the structure of chemical cross-linkage in a PU

network. Scheme 2 illustrates the possible structure of additional physical junction

points of a PU matrix in the presence of metal-containing modifiers. According to other

studies,[4 – 6,14,15] they can act as coordination cross-linking agent.

It is known that organic polymer systems are nanostructured systems themselves.

Introduction in a reaction mixture of additional coordination sites of structuring leads

to formation of in situ, polymer-immobilized metal compounds. Such polymer matrix

can contain simultaneously organic and metal-containing nanoscale structural

fragments.

In Situ Nanostructured Polyurethanes 99

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Short-range Ordering and Microheterogeneity of PUs

Wide-angle x-ray difractograms and small-angle x-ray scattering profiles are presented in

Figures 1 and 2. Values of Bragg’s period D, heterogeneity range lp[16 – 18] and interface

width E[19] obtained from SAXS profiles are listed in Table 1.

According to the WAXS data, all of the samples analyzed are amorphous with a

short-range ordering. Obtained using Bragg’s equation d ¼ 2p/qm the small-scale

order parameter d is equal to 0.44 nm (where qm ¼ (4p/l)sinum and 2um is the

position of the asymmetric diffusive maxima I(um) on the WAXS difractograms). We

found different ordering in PUs containing metal complexes of different symmetry.

WAXS diagrams of PU-Co and PU-Cr demonstrate two diffuse maxima at

2u � 19.78 (primary) (Fig. 1b and c) and 2u � 11.98 or 2u � 12.78 (secondary)

(marked with arrows in Fig. 1b). The secondary diffraction maximum is absent on

WAXS diagrams of PU modified with bivalent metal chelate or polynuclear metal

complex (Fig. 1a).

Increasing of trivalent metal complex content in the reaction mixture (5% wt. in PU-

Co5% and PU-Cr5% instead of 1% wt. in PU-Co and PU Cr) reveals the phenomenon of

saturation of the coordination-able sites in the PU matrix. The saturation results in

formation of Co(acac)3 and Cr(acac)3 enriched microregions in the amorphous PU

matrix and even segregation of the crystalline phase. We can arrive at a conclusion

Scheme 2. Possible coordination bonds and structure of physical junction point of PU.

Scheme 1. The PU networks chemical cross-point.


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based on the number and half-width of the discrete diffraction maxima that appear on

WAXS diagram of PU-Co5% and PU-Cr5% (Fig. 1c). In addition, the crystalline

regions in the PU matrix can be seen on SEM and optical micrographs described in the

next section. It should be noted that the angular positions of the discrete diffraction

maxima of PU-Co5% and PU-Cr5% WAXS diagrams coincide with the angular

positions of the secondary diffuse maxima on the PU-Co and PU-Cr diagrams,

respectively.

The PUs SAXS profiles (Fig. 2a) are characterized by the presence of one amorphous

maxima with the Bragg’s period D of about 3.0–9.0 nm (Table 1) (D ¼ 2p/qm, where

qm ¼ (4p/l)sinum). The position of the scattering intensity maxima as well as the

Figure 1. WAXS difractograms of: (a) PU-0 (1), PU-Cu (2), PU-CuCd (3), PU-CuZn (4) PU-

CuNiCo (5). (b) PU-Co (1), PU-Cr (2), the arrows indicate the secondary maxima. (c) PU-Co5%

(1), PU-Co (2), PU-Cr5% (3), PU-Cr (4).

Figure 2. SAXS profiles of: (a) PU-0 (1), PU -Cu (2), PU -Ni (3), PU -Cr(4) and PU-Co(5). (a) PU-0

(1), PU-Co5% (2), PU-Co (3), PU-Cr5% (4) and PU-Cr(5). (b) PU-0 (1), PU-CuNiCo(2), PU-

CuCd(3) and PU-CuZn (4), the arrows indicate the maxima positions.


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obtained D values of PUs are inverse for tri and bivalent chelate modifiers and can be

arranged as follows:

DPU�Cu � DPU�Ni . DPU�0 . DPU�Co � DPU�Cr

Increasing trivalent metal complex content in modified PUs (5% wt. in PU-Co5% and

PU Cr5% instead of 1% wt. in PU-Co and PU Cr) results in decreasing scattering intensity

I(qm) and shift of qm to smaller values (Fig. 2b) as compared with PU-Co and PU Cr.

The changes in SAXS profiles of the PUs modified by polyheteronuclear complexes

are more significant. We can see both increasing of the scattering intensity I(q) at q values

of 0.1–0.6 nm21, as compared with metal chelate modifiers, and existence of the

shoulders at qm ¼ 1.04 nm21 and at qm ¼ 0.68 nm21 (marked with arrows in Fig. 2c).

This indicates significant increase in the dimensions of the microregions of heterogeneity

as well as existence of a much greater value of the Bragg’s period D as compared with PU-

0, PU-Cu, PU-Cr etc (Table 1).

The lp parameter (lp ¼ w2,l1. ¼ w1,l2. where w1, w2 and l1, l2 – volume content

and diameter of microheterogeneities of type 1 and 2) has been used to differentiate micro-

heterogeneous entities of different nature (organic and metal-containing) in a pseudo two-

phase system.[17,18] This structural heterogeneity parameter changes from 3.1 to 4.2 for

metal chelates and from 5.3 to 12.0 for polyheteronuclear complexes.

For PU-Cr and PU-Co as well as for PU-CuZn and PU-Co 5% lp . D. The

situation is characteristic for pseudo two-phase systems. The results obtained we can

explain if we assume the existence in the PUs of heterogeneities of several types.

One of the microheterogeneities with dimensions that exceed D is formed by coordi-

nation sites with participation of metal complexes. Other heterogeneities with dimen-

sions smaller than D are the result of segregation processes of rigid and soft

segments of organic polymer.

According to the data presented in the Table 1, period D and heterogeneity range lp

are sensitive to the structure of coordination centers whereas value of E remains practi-

cally unchanged (E ¼ 0,9–1,1 nm).

Table 1Structural characteristics of the polyurethanes

Polyurethane

Intensity maxima

position qm

(nm)21

Bragg’s

period D

(nm)

Heterogeneity

range lp (nm)

Interface

width E

(nm)

PU-0 1,65 3,8 4,5 0,87

PU-Cu 1,48 4,2 3,7 1,03 (1,47)

PU-Ni 1,54 4,1 3,7 1,10 (1,39)

PU-Cr 1,90 3,3 4,1 1,05

PU-Co 2,01 3,1 6,7 1.05

PU-Cr5% — — 14,0 —

PU-Co5% 1,65 3,8 5,4 —

PU-CuCd — — 4,9 —

PU-CuZn 1,04 6,0 12,0 —

PU-CuNiCo 0,68 9,2 5,3 —


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Heterogeneity Scale According to Microscopic Data

The electron configuration of transition metal ion in coordination junctions of a polymer

determines the ability of metal compound to form complexes of a particular geometry and

symmetry as well as the ability of the metal compound to additional complexation with

polymer groups. In that way the electron configuration of a metal in small additives can

influence both the local structure and macrocharacteristics of a polymer (e.g., specific

density or mechanical characteristics).[7,8]

Formation of nanoscale and microscale heterogeneities in modified PUs is also illus-

trated by SEM and optical microscopy data. The representative SEM images of cryogenic

cross-fractured surfaces of PU films and optical light transmission microimages are shown

in Figures 3 and 4, respectively.

The SEM images of metal-containing PU films demonstrate the presence in the films

of various heterogeneities with 10–100 nm as well as heterogeneities with 10–100 mm

linear dimensions. The images reveal spherical species homogeneously dispersed

in amorphous phase (Fig. 3b) and segregation of the aggregated crystals (Fig. 3b and c)

in PU-Cr5%. As it can be seen from Figure 3 such crystals are built of small spherical

and ellipsoidal species. According to SEM, the polyheteronuclear coordination

complexes form in the PU matrix inhomogeneities of complex structure and of the micro-

scale dimensions. The shape of detected species makes their formation unlikely because of

the fracture process.

Figure 3. Representative SEM images of cryogenic cross-fractured surface of PU films: (a) PU-0

magnification of 5000, (b) PU-Cr5% magnification of 5000, (c) PU-Cr5% magnification of

15000, (d) PU-CuCoNi magnification of 10000.


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Optical microscopy images with relatively small magnification as compared with any

type of electron microscopy have important advantage of the direct character of measure-

ment. The light transmission microscopy gives images of thin films “as it is” without

additional procedure capable interfere in the results and/or destroy the sample.

The optical microimages also detect the crystals in the PU-Cr5% and PU-Co5% films

(Fig. 4) that correlate with WAXS and SEM data. These needle-like crystals in PU-Cr5%

are relatively short and tend to branching films (Fig. 4c)whereas in PU-Co5% the crystals

are linear and much longer films (Fig. 4d). Detected crystals are colored like relative

trivalent metal chelates—Cr(acac)3 (red) and Co(acac)3 (green). It should be noted that

the modified PUs are transparent and homogeneously colored in accordance with color

of modifier used. Contrary to visual observation, optical microimages reveal inhomogen-

eity of the films coloration that can be caused both by heterogeneity of the PUs density and

by microscale dispersion of colored centers in the PU matrix.

Both SEM and optical microscopy images of PUs with 5% of Co3þ and Cr3þ chelates

indicate formation of crystalline microregions in the polymer matrix. Such microregions

are absent in micrographs of all other PUs. Taking into account the ability of transition

metal chelates to crystallize and the amorphous structure of the polyether and isocyanate

components used, we can conclude that the crystalline regions are enriched with metal

complexes. At the moment we can’t determine the nature of the crystals segregated in

PUs modified with 5% of Co(3þ) and Cr(3þ) chelates. The crystalline regions can be

formed by the modifier itself and/or by complexes of modifier with PU chains as

macroligands.

Figure 4. Optical microimages of PU films: (a) U-CuZn, (b) PU-Co (c) PU-Cr5% (d) PU-Co5%.


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The last conclusion agrees with the x-ray data that register several discrete peaks in

PU-Cr5% and PU-Co5% WAXS diagrams (Fig. 1c).

EPR Measurements

Analysis of a polymer system using a nitroxyl spin probe (TEMPO in our case) is

grounded on dependence of the EPR spectrum of the probe on its rotational and transla-

tional mobility in the polymer. The last characteristics, in turn, are determined by the

structure and mobility of the polymer matrix surrounding the probe. To evaluate the

probe rotational mobility in modified polymers in the range of fast probe motion (10211

,t , 1029 s) the correlation time t of nitroxyl radical rotation was calculated,

according to,[20] using formulae

t ¼ 6; 65DHðþ1ÞðffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiðIþ1=I�1

pÞ � 1Þ � 10�10c

where DH(þ1) – is width of the EPR spectrum low field component and Iþ1, I21 – are

intensities of the EPR spectrum components in low and high field, respectively.

The calculated t values are listed in Table 2.

The EPR spectra of TEMPO in PU matrices that contain Cu2þ, Ni2þ, Zn2þ, Cr3þ,

Co3þ, Cd2þ ions are of complex structure and have asymmetric shape (Fig. 5c) instead

of isotropic three-component spectra typical for TEMPO in the range of fast rotational

motion. In some EPR spectra of the spin probe, recorded at room temperature, the low

field component split. In all of the spectra the central component increases and visible

splitting of high field component occurs.

The complex structure and broadened components of EPR spectra of the probe in the

PU matrix at room temperature are most likely the result of signal superposition of “fast”

and “slow” probes located in polymer regions with different mobility (examples of the

signal are given in Fig. 5b). This supposition is confirmed by narrowing of the EPR

spectrum components under heating as well as by more isotropic shape of the spectrum

at 1208C (see Fig. 5c-d) because of the increasing of mobility of earlier “freezed” PU

Table 2

Nitroxyl probe correlation times

in PU matrices

System t 1010, (sec)

PU-0 48

PU-Ni 42

PU-Cr 50

PU-Co 49

PU-Cu 43

PU-Cr5% 50

PU-Co5% 49

PU-CuCd 45

PU-CuZn 32

PU-CuNiCo 51


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blocks (e.g., PU’s rigid component under Tg). This implies that in such polymer there

exists a so-called spectrum of correlation times caused by the matrix heterogeneity.

All the correlation times calculated are of the same order as compared with metal-free

PU-0. Most noticeable t changes were observed for polyheteronuclear complexes.

As can be seen from the Table 2 the valency of the metal ion in chelate modifier influ-

ences the rotational mobility of spin probe as follows:

tPU�Cr � tPU�Co . tPU�0 . tPU�Cu . tPU�Ni

These results correlate with x-ray data where a similar arrangement was constructed

for mono ionic chelate modifiers.

The state of paramagnetic metal ion in copper containing modifiers influences

the anisotropy effects in the electron spin parameters (A- and g-tensors) of their

EPR spectra. Analyzing the shape and calculated parameters of the EPR spectra of

isolated Cu(eacac)2, [Cu2Zn(NH3)Br6(Me2Ea)3], [Cd2Cu3Br6(Me2Ea)4(dmso2)], and

Figure 5. EPR spectra of nitroxyl probe (a) Components assignment for calculation of the corre-

lation time t, (b) TEMPO in liquid and glassy polypropylene glycol (MM 1000), (c) PU-CuZn at

208C, (d) PU-CuZn at 1208C.


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[Ni(H2Dea)2][CoCu(Dea)(H2Dea)(NCS)]2Br2 as well as characteristics of EPR spectra of

corresponding PU-Cu, PU-CuZn, PU-CuCd, and PU-CuCoNi (see Materials section), we

used the dependence of the principal values of g-and A- tensors on the symmetry of metal

neighborhood, covalent character of metal–ligand bond and nature of polymer functional

groups involved in complexation with modifier.

Figure 6 illustrates the EPR spectra of some copper containing modifiers both isolated

and immobilized in PU. The EPR spectra parameters calculated from parallel spectral

components according to[21] are given in Table 3.

The spectrum of chelate copper modifier (copper ethylacetoacetate) in frozen glassy

solution exhibits narrow components, hyper fine splitting (HFS) and anisotropy of g-factor

(Fig. 6a) that indicate the D2 h or D4 h symmetry of the chelate node. The peculiarity of the

PU-Cu EPR spectrum is the appearance of HFS at room temperature (Fig. 6b) although

with broadened components of the SHF. This spectrum also is characteristics for tetra-

gonal copper complexes.

It can be seen from Table 3 that the calculated parameters of Copper ion in PU-Cu

differ from the parameters of the unperturbed complex. The changes found we can

consider as significant taking into account the accuracy of gII calculation (+0.002) and

Figure 6. EPR spectra of isolated copper containing complexes and of complex modifiers intro-

duced in PU matrix: (a) Diamagnetically isolated Cu(eacac)2 in glassy chloroform-toluene at

21968C, (b) PU-Cu at 208C, (c) polycrystalline [Cu2Zn2(NH3)2Br2(HDea)4]Br2. at 208C, (d) PU-

CuZn at 208C.


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the narrow area of gII changes when complexing (2.29–2.40[22]). This confirms the partici-

pation of the modifier in complex formation with the PU network. According to Kivelson

and Neiman,[22] that process is accompanied with monotonous increasing of gII and

reducing of the HFS constant. Comparison of AII and gII values in analyzed PU systems

with model systems[21,22] allows supposing preferred interaction of the copper chelate with

ether oxygen of PU.

The EPR spectra of polyheteronulcear polycrystalline samples have anisotropic shape

with weakly marked HFS in the gII region because of the broadening of the component

(representative spectrum is given in Fig. 6c) and possible tetragonal symmetry distortion

of the copper ion surrounding in the polynuclear complex. The resonance EPR signal

shape in PU network modified with [Cu2Zn2(NH3)2Br2(HDe)4]Br2 indicates formation

of complexes of modifier-polymer of various content and structure.

Introduction of such complexes in a PU network results in decreasing of Cu2þ EPR

signal intensity (Fig. 5 spectrum 4) and in some cases the signal decreases essentially.

The most reasonable explanation for this effect is distortion of the modifier’s symmetry

or geometry in PU-CuCd, PU-CuNiCo, and PU-CuZn.

Conclusions

It was shown that metal-containing modifiers favor formation in PU of nanoscale coordi-

nation structuring sites. The later contains one or several metal ions in the organic

environment.

The relationship was found between modified the PU structure and the spatial

symmetry of the coordination sites, formed by metal cations of various valences. The

effect of metal ion content in metal-containing compounds on the PU networks microhe-

terogeneity was described. Increasing of metal chelate concentration in the PU matrix or

introduction of poly heteronuclear complexes is accompanied both by increasing of the

period D and changes of heterogeneity range lp of PUs.

It was found that there is a limit for saturation of PU with trivalent metal b-diketonate

coordination centers. According to x-ray data and SEM as well as optical transmission

microscopy, the presence of 5% metal chelate complex in PU leads to the polymer

matrix saturation and partial separation of metal-containing sites as crystalline

microregions.

Table 3Electron-spin parameters of copper complexes

System g k

A k . 104

(cm21)

Cu(eacac)2 2,243 192

PU-Cu 2,249 150

[Cu2Zn2(NH3)2Br2(HDea)4]Br2 2,370 122

PU-CuZna 2,370; 2.300 132; 142

aEvaluated parameters of two complexes that can be approximately resolvedin the EPR spectrum of PU-CuZN.


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EPR data confirm the participation of metal-containing modifiers in complex

formation with the PU matrix. These PU matrices can be arranged according to rotational

diffusion of spin probe TEMPO as

tPU�Cr � tPU�Co . tPU�0 . tPU�Cu . tPU�Ni

These EPR results correlate with x-ray data where the similar arrangement was con-

structed for monoionic modifiers.

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Documents

In Situ Nanostructured Polyurethanes with Immobilized Transition Metal Coordination Complexes