iron complexes embedding influence on pmaa hydrogel
TRANSCRIPT
IOP Conference Series Materials Science and Engineering
OPEN ACCESS
Iron complexes embedding influence on PMAAhydrogelTo cite this article L Khenkin et al 2012 IOP Conf Ser Mater Sci Eng 38 012029
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Iron complexes embedding influence on PMAA hydrogel
L Khenkin1 T Baluyan A Novakova I Rebrin E Makhaeva
MVLomonosov MSU physics department Moscow Russia
E-mail levkhenkingmailcom
Abstract The interaction of weakly cross-linked gel of poly(methacrylic acid) with iron
complexes results in Fe2+
absorption additional cross-links and therefore gel collapses Lattice
dynamics of frozen investigated samples were examined by means of Mossbauer spectroscopy
in order to find out the mechanism of metal-polymer bonding It was established that iron
complexes form strong bonds with polymer functional groups contracting gel network
1 Introduction
Poly(methacrylic acid) (PMAA) groups can show specific interactions such as hydrogen bonding
acidndashbase interactions and ionic interactions of opposite charges which can help to prepare novel self-
organized materials Numerous studies have been also devoted to the interaction of PMAA with metal
ions since knowledge of association phenomena of metal ions with charged macromolecules is of
importance for the understanding of their physicochemical behavior in environmental and biological
systems PMAA could be successfully used as a component of characteristic lsquointelligentrsquo organicndash
inorganic hybrid materials
The interaction of weakly cross-linked PMAA gel with iron complexes results in their absorption
and gel collapse [1 2] This collapse occurs due to iron ionspolymer functional groups bonds that
form additional cross-links contracting gel network The aim of the present work is study of molecular
lattice dynamics and metal-polymer bonds strength in PMAA geliron complexes systems by means of
Mossbauer spectroscopy
2 Experimental section
PMAA gels were prepared through radical polymerization in solution with NN-methyl-bis-
acrylamide as a cross-linker The procedure of PMAA gels treatment was the same as that described
previously [3] The degree of the polymer gel swelling (Φ) in complex solutions is defined by the ratio
of the mass of polymer gel after immersion in iron complex solution to the initial gel mass
In the present study PMAA gel was incubated in two different media aqueous solution of iron(II)
chloride and aqueous solution of ferroin (Fe2+
ndashphenanthroline complex)
Temperature-dependence of their Mossbauer spectra can serve to elucidate the bonding and
dynamical behavior of the iron ions in such systems [4] Mossbauer lattice temperatures θM and
effective vibrating mass Meff were estimated from temperature dependences of recoilless fraction and
second order Doppler shift δSOD Mossbauer spectroscopy data for all incubated PMAA gels and for
1 To whom any correspondence should be addressed
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
Published under licence by IOP Publishing Ltd 1
used frozen solutions were obtained in the temperature interval from 118K up to the Mossbauer effect
disappearance temperature
Mossbauer spectra were obtained in a standard transmission geometry using a 57
Co(Rh) gamma
source The gamma radiation was detected with a NaI(Tl) scintillation detector The spectrometer was
calibrated by a standard α-Fe absorber The spectra were analyzed using the UNIVEM MS program
(2006) which ensures fitting by a combination of Lorentzians with adjustable Mossbauer parameters
isomer shift (δ) quadrupole splitting (Δ) peak width and peak area under the curve (A)
3 Results and discussion
The swelling behavior of PMAA hydrogels was studied in [2] The degree of contraction depends on
the amount of monomers in the parent PMAA gel and the amount of absorbed Fe ions The samples
under investigation after week incubation in iron complex solution were collapsed Degree of their
swelling was Φ=022 for incubation in ferroin aqueous solution and Φ=012 for incubation in iron
chloride aqueous solution
Mossbauer spectra at T=118K and images of investigated samples are shown in figure 1 In iron
salt solution all Fe2+
ions form [Fe(H2O)6]2+
coordination entities of octahedral geometry So the
spectra of all samples comprise one component doublet with big quadrupole splitting for high-spin
Fe(II) ions in chloride salt solution and doublet with small quadrupole splitting for low-spin Fe(II)
ions in ferroin solution (see table 1 for values)
Mossbauer spectral parameters (isomer shift and quadrupole splitting) for both iron complexes
appeared to be the same in investigated aqueous solutions and in gel incubated in these solutions The
invariance of the spectral parameters reflects the iron ions environments uniformity Both ferroin and
aqua-complex remain holistic and stable after embedding to gel matrix
Figure 1 Mossbauer spectra at T=118K and photo of a) FeCl2 aqueous solution b) PMAA gel in
FeCl2 aqueous solution c) ferroin aqueous solution d) PMAA gel in ferroin aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
2
Temperature dependences of all the samples under investigation spectrum intensity (area under
curve) characterizing recoilless fraction are shown in figure 2 All dependence curves have contrary
flexure point at temperatures near 190K This feature is induced by diffusion motion of iron
complexes that will be discussed later
For molecular crystals the normal modes of vibration are usually separated into two groups the
weaker intermolecular modes related to vibrations of the molecular center of mass and the stronger
intramolecular modes of much higher frequencies within the molecule
If the molecule is an ideal rigid body the mass value in the expressions for f and δ SOD would just
be the molecular weight In reality the molecule is not entirely rigid due to some degree of internal
vibration the mass value may be replaced by an effective vibrating mass Meff Its upper limit is the
molecular weight and lower limit is the mass of the Mossbauer iron isotope (57 Da) the latter
corresponds to the situation of Fe atoms as monatomic vibrating entities in a solid
For the lower temperature area theory gives the following equations [4 5]
constTATkcM
Ef
MBeff
)(ln3
ln22
2
(1)
constcM
Tk
eff
BSOD
2
3 (2)
where A is the area under the resonance curve (ln A prop ln f = exp(-k2ltu
2gt) for an optically thin
absorber ltu2gt is the mean square amplitude of the metal atom vibration) kB - Boltzmannrsquos constant
c - velocity of light Eγ - the energy of the emitted γ-ray
Both the δ and ln A temperature dependencies for this compound are well fitted by linear
regressions (ln A for the temperature diapason from 118K to curve contrary flexure point) Curve
slopes values of the fitting lines are given in table 1 After substitution these values to (1) and (2) we
obtained effective vibrating masses and lattice temperatures for all our samples (table 1)
The deviation of the Meff values from 57 Da reflects the covalency of the bonding force between
the Fe atom and its neighbours [6] A comparison of Meff values between complexes in frozen solution
and in the PMAA gel matrix leads to conclusion that strong chemical bonds appear between the iron
complexes and the functional groups of polymer (COO-) Moreover temperature ΘM should consider
as a quantitative measure of such bonds Thus stable metal - polymer complexes formed
Figure 2 Temperature dependence A (area under curve) for a) FeCl2 aqueous solution
PMAA gel in FeCl2 b) ferroin aqueous solution PMAA gel in aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
3
Table 1 Mossbauer parameters and derived quantities of investigated samples
Measurement errors are indicated in brackets
Sample δ mms
at 118K
Δ mms
at 118K
dδ dT
10-4
mmsecK
d lnA dT
10-3
K-1
Meff Da ΘM K
FeCl2 aqueous solution 141(2) 339(3) 75 (5) 101 (5) 111 (7) 83 (7)
PMAA Gel in FeCl2
aqueous solution 138 (2) 333(3) 67 (4) 46 (3) 124 (7) 116 (9)
Feroin aqoueous solution 040 (2) 026(3) 37 (2) 81 (4) 224 (9) 65 (6)
PMAA Gel in ferroin
aqueous solution 040 (2) 027(3) 34 (2) 41 (3) 244 (9) 87 (8)
Temperature dependences of Mossbauer spectra line width (figure 3) give the data about increasing
of diffusion motion with increasing temperature Spectra of samples in the chloride solution had
significantly broader lines than spectra for ferroin solution because of higher molecular mobility of
aqua molecules from nearest iron surrounding On warming towards the melting point the relaxation
time for diffuse jumps of the resonance atoms becomes of the same order of magnitude as excited state
lifetime [7] So at elevated temperatures diffusive motion increases rapidly Line broadening in frozen
PMAA gel incubated in ferroin solution started at the temperature on 20K higher
4 Conclusion
All obtained data allow us to conclude that investigated iron complexes (ferroin and aquacomplex)
embed in PMAA gel network without destruction and form strong bonds with polymer functional
groups These bonds are stronger than iron complexes bonds in frozen aqueous solutions crystal And
these bonds have higher degree of covalence Such stability of iron complexes inside the polymer gel
matrix could be widely used in practical applications
References
[1] Grigorrsquoev T E Nguen K H Skryabina I V Makhaeva E E and Khokhlov A R 2008
Polym Sci A 50 68
[2] Starodoubtsev S G Khokhlov A R Sokolov E L and Chu B 1996 Macromolecules 28 3930
Figure 3 Line width temperature dependence for all investigated samples
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
4
[3] Khenkin L V Shishakov A I Novakova A A Kozhunova E Yu and Makhaeva E E 2011
Inorganic Materials 47 1271
[4] Chen Y L and Yang D P 2007 Mossbauer Effect in Lattice Dynamics (Weinheim Wiley-VCH)
[5] Herber R H and Nowik I 2008 J Nucl Radiochem Sci 9 33
[6] Long G J Hautot D Grandjean F Morelli D T and Meisner G P 2000 Phys Rev B 62 6829
[7] Singwi K S and Sjolander A1960 Phys Rev 120 1092
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
5
Iron complexes embedding influence on PMAA hydrogel
L Khenkin1 T Baluyan A Novakova I Rebrin E Makhaeva
MVLomonosov MSU physics department Moscow Russia
E-mail levkhenkingmailcom
Abstract The interaction of weakly cross-linked gel of poly(methacrylic acid) with iron
complexes results in Fe2+
absorption additional cross-links and therefore gel collapses Lattice
dynamics of frozen investigated samples were examined by means of Mossbauer spectroscopy
in order to find out the mechanism of metal-polymer bonding It was established that iron
complexes form strong bonds with polymer functional groups contracting gel network
1 Introduction
Poly(methacrylic acid) (PMAA) groups can show specific interactions such as hydrogen bonding
acidndashbase interactions and ionic interactions of opposite charges which can help to prepare novel self-
organized materials Numerous studies have been also devoted to the interaction of PMAA with metal
ions since knowledge of association phenomena of metal ions with charged macromolecules is of
importance for the understanding of their physicochemical behavior in environmental and biological
systems PMAA could be successfully used as a component of characteristic lsquointelligentrsquo organicndash
inorganic hybrid materials
The interaction of weakly cross-linked PMAA gel with iron complexes results in their absorption
and gel collapse [1 2] This collapse occurs due to iron ionspolymer functional groups bonds that
form additional cross-links contracting gel network The aim of the present work is study of molecular
lattice dynamics and metal-polymer bonds strength in PMAA geliron complexes systems by means of
Mossbauer spectroscopy
2 Experimental section
PMAA gels were prepared through radical polymerization in solution with NN-methyl-bis-
acrylamide as a cross-linker The procedure of PMAA gels treatment was the same as that described
previously [3] The degree of the polymer gel swelling (Φ) in complex solutions is defined by the ratio
of the mass of polymer gel after immersion in iron complex solution to the initial gel mass
In the present study PMAA gel was incubated in two different media aqueous solution of iron(II)
chloride and aqueous solution of ferroin (Fe2+
ndashphenanthroline complex)
Temperature-dependence of their Mossbauer spectra can serve to elucidate the bonding and
dynamical behavior of the iron ions in such systems [4] Mossbauer lattice temperatures θM and
effective vibrating mass Meff were estimated from temperature dependences of recoilless fraction and
second order Doppler shift δSOD Mossbauer spectroscopy data for all incubated PMAA gels and for
1 To whom any correspondence should be addressed
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
Published under licence by IOP Publishing Ltd 1
used frozen solutions were obtained in the temperature interval from 118K up to the Mossbauer effect
disappearance temperature
Mossbauer spectra were obtained in a standard transmission geometry using a 57
Co(Rh) gamma
source The gamma radiation was detected with a NaI(Tl) scintillation detector The spectrometer was
calibrated by a standard α-Fe absorber The spectra were analyzed using the UNIVEM MS program
(2006) which ensures fitting by a combination of Lorentzians with adjustable Mossbauer parameters
isomer shift (δ) quadrupole splitting (Δ) peak width and peak area under the curve (A)
3 Results and discussion
The swelling behavior of PMAA hydrogels was studied in [2] The degree of contraction depends on
the amount of monomers in the parent PMAA gel and the amount of absorbed Fe ions The samples
under investigation after week incubation in iron complex solution were collapsed Degree of their
swelling was Φ=022 for incubation in ferroin aqueous solution and Φ=012 for incubation in iron
chloride aqueous solution
Mossbauer spectra at T=118K and images of investigated samples are shown in figure 1 In iron
salt solution all Fe2+
ions form [Fe(H2O)6]2+
coordination entities of octahedral geometry So the
spectra of all samples comprise one component doublet with big quadrupole splitting for high-spin
Fe(II) ions in chloride salt solution and doublet with small quadrupole splitting for low-spin Fe(II)
ions in ferroin solution (see table 1 for values)
Mossbauer spectral parameters (isomer shift and quadrupole splitting) for both iron complexes
appeared to be the same in investigated aqueous solutions and in gel incubated in these solutions The
invariance of the spectral parameters reflects the iron ions environments uniformity Both ferroin and
aqua-complex remain holistic and stable after embedding to gel matrix
Figure 1 Mossbauer spectra at T=118K and photo of a) FeCl2 aqueous solution b) PMAA gel in
FeCl2 aqueous solution c) ferroin aqueous solution d) PMAA gel in ferroin aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
2
Temperature dependences of all the samples under investigation spectrum intensity (area under
curve) characterizing recoilless fraction are shown in figure 2 All dependence curves have contrary
flexure point at temperatures near 190K This feature is induced by diffusion motion of iron
complexes that will be discussed later
For molecular crystals the normal modes of vibration are usually separated into two groups the
weaker intermolecular modes related to vibrations of the molecular center of mass and the stronger
intramolecular modes of much higher frequencies within the molecule
If the molecule is an ideal rigid body the mass value in the expressions for f and δ SOD would just
be the molecular weight In reality the molecule is not entirely rigid due to some degree of internal
vibration the mass value may be replaced by an effective vibrating mass Meff Its upper limit is the
molecular weight and lower limit is the mass of the Mossbauer iron isotope (57 Da) the latter
corresponds to the situation of Fe atoms as monatomic vibrating entities in a solid
For the lower temperature area theory gives the following equations [4 5]
constTATkcM
Ef
MBeff
)(ln3
ln22
2
(1)
constcM
Tk
eff
BSOD
2
3 (2)
where A is the area under the resonance curve (ln A prop ln f = exp(-k2ltu
2gt) for an optically thin
absorber ltu2gt is the mean square amplitude of the metal atom vibration) kB - Boltzmannrsquos constant
c - velocity of light Eγ - the energy of the emitted γ-ray
Both the δ and ln A temperature dependencies for this compound are well fitted by linear
regressions (ln A for the temperature diapason from 118K to curve contrary flexure point) Curve
slopes values of the fitting lines are given in table 1 After substitution these values to (1) and (2) we
obtained effective vibrating masses and lattice temperatures for all our samples (table 1)
The deviation of the Meff values from 57 Da reflects the covalency of the bonding force between
the Fe atom and its neighbours [6] A comparison of Meff values between complexes in frozen solution
and in the PMAA gel matrix leads to conclusion that strong chemical bonds appear between the iron
complexes and the functional groups of polymer (COO-) Moreover temperature ΘM should consider
as a quantitative measure of such bonds Thus stable metal - polymer complexes formed
Figure 2 Temperature dependence A (area under curve) for a) FeCl2 aqueous solution
PMAA gel in FeCl2 b) ferroin aqueous solution PMAA gel in aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
3
Table 1 Mossbauer parameters and derived quantities of investigated samples
Measurement errors are indicated in brackets
Sample δ mms
at 118K
Δ mms
at 118K
dδ dT
10-4
mmsecK
d lnA dT
10-3
K-1
Meff Da ΘM K
FeCl2 aqueous solution 141(2) 339(3) 75 (5) 101 (5) 111 (7) 83 (7)
PMAA Gel in FeCl2
aqueous solution 138 (2) 333(3) 67 (4) 46 (3) 124 (7) 116 (9)
Feroin aqoueous solution 040 (2) 026(3) 37 (2) 81 (4) 224 (9) 65 (6)
PMAA Gel in ferroin
aqueous solution 040 (2) 027(3) 34 (2) 41 (3) 244 (9) 87 (8)
Temperature dependences of Mossbauer spectra line width (figure 3) give the data about increasing
of diffusion motion with increasing temperature Spectra of samples in the chloride solution had
significantly broader lines than spectra for ferroin solution because of higher molecular mobility of
aqua molecules from nearest iron surrounding On warming towards the melting point the relaxation
time for diffuse jumps of the resonance atoms becomes of the same order of magnitude as excited state
lifetime [7] So at elevated temperatures diffusive motion increases rapidly Line broadening in frozen
PMAA gel incubated in ferroin solution started at the temperature on 20K higher
4 Conclusion
All obtained data allow us to conclude that investigated iron complexes (ferroin and aquacomplex)
embed in PMAA gel network without destruction and form strong bonds with polymer functional
groups These bonds are stronger than iron complexes bonds in frozen aqueous solutions crystal And
these bonds have higher degree of covalence Such stability of iron complexes inside the polymer gel
matrix could be widely used in practical applications
References
[1] Grigorrsquoev T E Nguen K H Skryabina I V Makhaeva E E and Khokhlov A R 2008
Polym Sci A 50 68
[2] Starodoubtsev S G Khokhlov A R Sokolov E L and Chu B 1996 Macromolecules 28 3930
Figure 3 Line width temperature dependence for all investigated samples
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
4
[3] Khenkin L V Shishakov A I Novakova A A Kozhunova E Yu and Makhaeva E E 2011
Inorganic Materials 47 1271
[4] Chen Y L and Yang D P 2007 Mossbauer Effect in Lattice Dynamics (Weinheim Wiley-VCH)
[5] Herber R H and Nowik I 2008 J Nucl Radiochem Sci 9 33
[6] Long G J Hautot D Grandjean F Morelli D T and Meisner G P 2000 Phys Rev B 62 6829
[7] Singwi K S and Sjolander A1960 Phys Rev 120 1092
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
5
used frozen solutions were obtained in the temperature interval from 118K up to the Mossbauer effect
disappearance temperature
Mossbauer spectra were obtained in a standard transmission geometry using a 57
Co(Rh) gamma
source The gamma radiation was detected with a NaI(Tl) scintillation detector The spectrometer was
calibrated by a standard α-Fe absorber The spectra were analyzed using the UNIVEM MS program
(2006) which ensures fitting by a combination of Lorentzians with adjustable Mossbauer parameters
isomer shift (δ) quadrupole splitting (Δ) peak width and peak area under the curve (A)
3 Results and discussion
The swelling behavior of PMAA hydrogels was studied in [2] The degree of contraction depends on
the amount of monomers in the parent PMAA gel and the amount of absorbed Fe ions The samples
under investigation after week incubation in iron complex solution were collapsed Degree of their
swelling was Φ=022 for incubation in ferroin aqueous solution and Φ=012 for incubation in iron
chloride aqueous solution
Mossbauer spectra at T=118K and images of investigated samples are shown in figure 1 In iron
salt solution all Fe2+
ions form [Fe(H2O)6]2+
coordination entities of octahedral geometry So the
spectra of all samples comprise one component doublet with big quadrupole splitting for high-spin
Fe(II) ions in chloride salt solution and doublet with small quadrupole splitting for low-spin Fe(II)
ions in ferroin solution (see table 1 for values)
Mossbauer spectral parameters (isomer shift and quadrupole splitting) for both iron complexes
appeared to be the same in investigated aqueous solutions and in gel incubated in these solutions The
invariance of the spectral parameters reflects the iron ions environments uniformity Both ferroin and
aqua-complex remain holistic and stable after embedding to gel matrix
Figure 1 Mossbauer spectra at T=118K and photo of a) FeCl2 aqueous solution b) PMAA gel in
FeCl2 aqueous solution c) ferroin aqueous solution d) PMAA gel in ferroin aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
2
Temperature dependences of all the samples under investigation spectrum intensity (area under
curve) characterizing recoilless fraction are shown in figure 2 All dependence curves have contrary
flexure point at temperatures near 190K This feature is induced by diffusion motion of iron
complexes that will be discussed later
For molecular crystals the normal modes of vibration are usually separated into two groups the
weaker intermolecular modes related to vibrations of the molecular center of mass and the stronger
intramolecular modes of much higher frequencies within the molecule
If the molecule is an ideal rigid body the mass value in the expressions for f and δ SOD would just
be the molecular weight In reality the molecule is not entirely rigid due to some degree of internal
vibration the mass value may be replaced by an effective vibrating mass Meff Its upper limit is the
molecular weight and lower limit is the mass of the Mossbauer iron isotope (57 Da) the latter
corresponds to the situation of Fe atoms as monatomic vibrating entities in a solid
For the lower temperature area theory gives the following equations [4 5]
constTATkcM
Ef
MBeff
)(ln3
ln22
2
(1)
constcM
Tk
eff
BSOD
2
3 (2)
where A is the area under the resonance curve (ln A prop ln f = exp(-k2ltu
2gt) for an optically thin
absorber ltu2gt is the mean square amplitude of the metal atom vibration) kB - Boltzmannrsquos constant
c - velocity of light Eγ - the energy of the emitted γ-ray
Both the δ and ln A temperature dependencies for this compound are well fitted by linear
regressions (ln A for the temperature diapason from 118K to curve contrary flexure point) Curve
slopes values of the fitting lines are given in table 1 After substitution these values to (1) and (2) we
obtained effective vibrating masses and lattice temperatures for all our samples (table 1)
The deviation of the Meff values from 57 Da reflects the covalency of the bonding force between
the Fe atom and its neighbours [6] A comparison of Meff values between complexes in frozen solution
and in the PMAA gel matrix leads to conclusion that strong chemical bonds appear between the iron
complexes and the functional groups of polymer (COO-) Moreover temperature ΘM should consider
as a quantitative measure of such bonds Thus stable metal - polymer complexes formed
Figure 2 Temperature dependence A (area under curve) for a) FeCl2 aqueous solution
PMAA gel in FeCl2 b) ferroin aqueous solution PMAA gel in aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
3
Table 1 Mossbauer parameters and derived quantities of investigated samples
Measurement errors are indicated in brackets
Sample δ mms
at 118K
Δ mms
at 118K
dδ dT
10-4
mmsecK
d lnA dT
10-3
K-1
Meff Da ΘM K
FeCl2 aqueous solution 141(2) 339(3) 75 (5) 101 (5) 111 (7) 83 (7)
PMAA Gel in FeCl2
aqueous solution 138 (2) 333(3) 67 (4) 46 (3) 124 (7) 116 (9)
Feroin aqoueous solution 040 (2) 026(3) 37 (2) 81 (4) 224 (9) 65 (6)
PMAA Gel in ferroin
aqueous solution 040 (2) 027(3) 34 (2) 41 (3) 244 (9) 87 (8)
Temperature dependences of Mossbauer spectra line width (figure 3) give the data about increasing
of diffusion motion with increasing temperature Spectra of samples in the chloride solution had
significantly broader lines than spectra for ferroin solution because of higher molecular mobility of
aqua molecules from nearest iron surrounding On warming towards the melting point the relaxation
time for diffuse jumps of the resonance atoms becomes of the same order of magnitude as excited state
lifetime [7] So at elevated temperatures diffusive motion increases rapidly Line broadening in frozen
PMAA gel incubated in ferroin solution started at the temperature on 20K higher
4 Conclusion
All obtained data allow us to conclude that investigated iron complexes (ferroin and aquacomplex)
embed in PMAA gel network without destruction and form strong bonds with polymer functional
groups These bonds are stronger than iron complexes bonds in frozen aqueous solutions crystal And
these bonds have higher degree of covalence Such stability of iron complexes inside the polymer gel
matrix could be widely used in practical applications
References
[1] Grigorrsquoev T E Nguen K H Skryabina I V Makhaeva E E and Khokhlov A R 2008
Polym Sci A 50 68
[2] Starodoubtsev S G Khokhlov A R Sokolov E L and Chu B 1996 Macromolecules 28 3930
Figure 3 Line width temperature dependence for all investigated samples
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
4
[3] Khenkin L V Shishakov A I Novakova A A Kozhunova E Yu and Makhaeva E E 2011
Inorganic Materials 47 1271
[4] Chen Y L and Yang D P 2007 Mossbauer Effect in Lattice Dynamics (Weinheim Wiley-VCH)
[5] Herber R H and Nowik I 2008 J Nucl Radiochem Sci 9 33
[6] Long G J Hautot D Grandjean F Morelli D T and Meisner G P 2000 Phys Rev B 62 6829
[7] Singwi K S and Sjolander A1960 Phys Rev 120 1092
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
5
Temperature dependences of all the samples under investigation spectrum intensity (area under
curve) characterizing recoilless fraction are shown in figure 2 All dependence curves have contrary
flexure point at temperatures near 190K This feature is induced by diffusion motion of iron
complexes that will be discussed later
For molecular crystals the normal modes of vibration are usually separated into two groups the
weaker intermolecular modes related to vibrations of the molecular center of mass and the stronger
intramolecular modes of much higher frequencies within the molecule
If the molecule is an ideal rigid body the mass value in the expressions for f and δ SOD would just
be the molecular weight In reality the molecule is not entirely rigid due to some degree of internal
vibration the mass value may be replaced by an effective vibrating mass Meff Its upper limit is the
molecular weight and lower limit is the mass of the Mossbauer iron isotope (57 Da) the latter
corresponds to the situation of Fe atoms as monatomic vibrating entities in a solid
For the lower temperature area theory gives the following equations [4 5]
constTATkcM
Ef
MBeff
)(ln3
ln22
2
(1)
constcM
Tk
eff
BSOD
2
3 (2)
where A is the area under the resonance curve (ln A prop ln f = exp(-k2ltu
2gt) for an optically thin
absorber ltu2gt is the mean square amplitude of the metal atom vibration) kB - Boltzmannrsquos constant
c - velocity of light Eγ - the energy of the emitted γ-ray
Both the δ and ln A temperature dependencies for this compound are well fitted by linear
regressions (ln A for the temperature diapason from 118K to curve contrary flexure point) Curve
slopes values of the fitting lines are given in table 1 After substitution these values to (1) and (2) we
obtained effective vibrating masses and lattice temperatures for all our samples (table 1)
The deviation of the Meff values from 57 Da reflects the covalency of the bonding force between
the Fe atom and its neighbours [6] A comparison of Meff values between complexes in frozen solution
and in the PMAA gel matrix leads to conclusion that strong chemical bonds appear between the iron
complexes and the functional groups of polymer (COO-) Moreover temperature ΘM should consider
as a quantitative measure of such bonds Thus stable metal - polymer complexes formed
Figure 2 Temperature dependence A (area under curve) for a) FeCl2 aqueous solution
PMAA gel in FeCl2 b) ferroin aqueous solution PMAA gel in aqueous solution
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
3
Table 1 Mossbauer parameters and derived quantities of investigated samples
Measurement errors are indicated in brackets
Sample δ mms
at 118K
Δ mms
at 118K
dδ dT
10-4
mmsecK
d lnA dT
10-3
K-1
Meff Da ΘM K
FeCl2 aqueous solution 141(2) 339(3) 75 (5) 101 (5) 111 (7) 83 (7)
PMAA Gel in FeCl2
aqueous solution 138 (2) 333(3) 67 (4) 46 (3) 124 (7) 116 (9)
Feroin aqoueous solution 040 (2) 026(3) 37 (2) 81 (4) 224 (9) 65 (6)
PMAA Gel in ferroin
aqueous solution 040 (2) 027(3) 34 (2) 41 (3) 244 (9) 87 (8)
Temperature dependences of Mossbauer spectra line width (figure 3) give the data about increasing
of diffusion motion with increasing temperature Spectra of samples in the chloride solution had
significantly broader lines than spectra for ferroin solution because of higher molecular mobility of
aqua molecules from nearest iron surrounding On warming towards the melting point the relaxation
time for diffuse jumps of the resonance atoms becomes of the same order of magnitude as excited state
lifetime [7] So at elevated temperatures diffusive motion increases rapidly Line broadening in frozen
PMAA gel incubated in ferroin solution started at the temperature on 20K higher
4 Conclusion
All obtained data allow us to conclude that investigated iron complexes (ferroin and aquacomplex)
embed in PMAA gel network without destruction and form strong bonds with polymer functional
groups These bonds are stronger than iron complexes bonds in frozen aqueous solutions crystal And
these bonds have higher degree of covalence Such stability of iron complexes inside the polymer gel
matrix could be widely used in practical applications
References
[1] Grigorrsquoev T E Nguen K H Skryabina I V Makhaeva E E and Khokhlov A R 2008
Polym Sci A 50 68
[2] Starodoubtsev S G Khokhlov A R Sokolov E L and Chu B 1996 Macromolecules 28 3930
Figure 3 Line width temperature dependence for all investigated samples
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
4
[3] Khenkin L V Shishakov A I Novakova A A Kozhunova E Yu and Makhaeva E E 2011
Inorganic Materials 47 1271
[4] Chen Y L and Yang D P 2007 Mossbauer Effect in Lattice Dynamics (Weinheim Wiley-VCH)
[5] Herber R H and Nowik I 2008 J Nucl Radiochem Sci 9 33
[6] Long G J Hautot D Grandjean F Morelli D T and Meisner G P 2000 Phys Rev B 62 6829
[7] Singwi K S and Sjolander A1960 Phys Rev 120 1092
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
5
Table 1 Mossbauer parameters and derived quantities of investigated samples
Measurement errors are indicated in brackets
Sample δ mms
at 118K
Δ mms
at 118K
dδ dT
10-4
mmsecK
d lnA dT
10-3
K-1
Meff Da ΘM K
FeCl2 aqueous solution 141(2) 339(3) 75 (5) 101 (5) 111 (7) 83 (7)
PMAA Gel in FeCl2
aqueous solution 138 (2) 333(3) 67 (4) 46 (3) 124 (7) 116 (9)
Feroin aqoueous solution 040 (2) 026(3) 37 (2) 81 (4) 224 (9) 65 (6)
PMAA Gel in ferroin
aqueous solution 040 (2) 027(3) 34 (2) 41 (3) 244 (9) 87 (8)
Temperature dependences of Mossbauer spectra line width (figure 3) give the data about increasing
of diffusion motion with increasing temperature Spectra of samples in the chloride solution had
significantly broader lines than spectra for ferroin solution because of higher molecular mobility of
aqua molecules from nearest iron surrounding On warming towards the melting point the relaxation
time for diffuse jumps of the resonance atoms becomes of the same order of magnitude as excited state
lifetime [7] So at elevated temperatures diffusive motion increases rapidly Line broadening in frozen
PMAA gel incubated in ferroin solution started at the temperature on 20K higher
4 Conclusion
All obtained data allow us to conclude that investigated iron complexes (ferroin and aquacomplex)
embed in PMAA gel network without destruction and form strong bonds with polymer functional
groups These bonds are stronger than iron complexes bonds in frozen aqueous solutions crystal And
these bonds have higher degree of covalence Such stability of iron complexes inside the polymer gel
matrix could be widely used in practical applications
References
[1] Grigorrsquoev T E Nguen K H Skryabina I V Makhaeva E E and Khokhlov A R 2008
Polym Sci A 50 68
[2] Starodoubtsev S G Khokhlov A R Sokolov E L and Chu B 1996 Macromolecules 28 3930
Figure 3 Line width temperature dependence for all investigated samples
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
4
[3] Khenkin L V Shishakov A I Novakova A A Kozhunova E Yu and Makhaeva E E 2011
Inorganic Materials 47 1271
[4] Chen Y L and Yang D P 2007 Mossbauer Effect in Lattice Dynamics (Weinheim Wiley-VCH)
[5] Herber R H and Nowik I 2008 J Nucl Radiochem Sci 9 33
[6] Long G J Hautot D Grandjean F Morelli D T and Meisner G P 2000 Phys Rev B 62 6829
[7] Singwi K S and Sjolander A1960 Phys Rev 120 1092
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
5
[3] Khenkin L V Shishakov A I Novakova A A Kozhunova E Yu and Makhaeva E E 2011
Inorganic Materials 47 1271
[4] Chen Y L and Yang D P 2007 Mossbauer Effect in Lattice Dynamics (Weinheim Wiley-VCH)
[5] Herber R H and Nowik I 2008 J Nucl Radiochem Sci 9 33
[6] Long G J Hautot D Grandjean F Morelli D T and Meisner G P 2000 Phys Rev B 62 6829
[7] Singwi K S and Sjolander A1960 Phys Rev 120 1092
International Conference on Functional Materials and Nanotechnologies (FMampNT2012) IOP PublishingIOP Conf Series Materials Science and Engineering 38 (2012) 012029 doi1010881757-899X381012029
5