Synthesis and rheological behavior of cross-linkable poly[N-(methacryl-2-ethyl)-N′-(3-amino(1,2,4-triazole-2-yl))urea-co-methyl methacrylate]

Article abstract of DOI:10.1021/ma010828l

A copolymer poly[N-(methacryl-2-ethyl)-N′-(3-amino(1,2,4-triazole-2-yl) urea)-co-methyl methacrylate] (1) with a low M_n value of about 1300 was prepared via free radical polymerization from the corresponding monomers N-methacrylethyl-N′-triazoyl urea (2) and methyl methacrylate (3). The complex viscosity of a solution of i in N-methyl pyrrolidone decreases with increasing temperature up to 32 °C at the beginning and then passes a minimum at 38 °C. At higher temperatures of about 53 °C, it decreases again. DSC measurements of this solution indicates phase transitions because of two endothermic signals from 32 to 44 °C and from 53 to 74 °C. Furthermore, the copolymer 1 starts to cross-link rapidly above 130 °C. The mechanism of this cross-linking reaction is discussed with respect to a back-formation of isocyanate intermediate that reacts with nucleophiles.

Full text of DOI:10.1021/ma010828l

2050
Macromolecules 2002, 35, 2050-2054
Synthesis and Rheological Behavior of Cross-Linkable
Poly[N-(methacryl-2-ethyl)-N′-(3-amino(1,2,4-triazole-2-yl))urea-co-methyl
methacrylate]
P a tr ick Glo1ck n er ,† Mich a el Oster h old ,‡ a n d Helm u t Ritter *,§
Degussa AG, Paul-Baumann-Strasse 1, 45764 Marl, Germany; DuPont Performance Coatings
GmbH & Co. KG, Christbusch 25, 42285 Wuppertal, Germany; Institute of Organic Chemistry
and Macromolecular Chemistry, University of Duesseldorf, 26.33.00, Universita¨tsstrasse 1,
40225 Duesseldorf, Germany
Received May 29, 2001; Revised Manuscript Received November 23, 2001
ABSTRACT: A copolymer poly[N-(methacryl-2-ethyl)-N′-(3-amino(1,2,4-triazole-2-yl) urea)-co-methyl
methacrylate] (1) with a low Mh n value of about 1300 was prepared via free radical polymerization from
the corresponding monomers N-methacrylethyl-N′-triazoyl urea (2) and methyl methacrylate (3). The
complex viscosity of a solution of 1 in N-methyl pyrrolidone decreases with increasing temperature up to
32 °C at the beginning and then passes a minimum at 38 °C. At higher temperatures of about 53 °C, it
decreases again. DSC measurements of this solution indicates phase transitions because of two
endothermic signals from 32 to 44 °C and from 53 to 74 °C. Furthermore, the copolymer 1 starts to cross-
link rapidly above 130 °C. The mechanism of this cross-linking reaction is discussed with respect to a
back-formation of isocyanate intermediate that reacts with nucleophiles.
In tr od u ction
solvent (Scheme 1). It is interesting to note that the
nitrogen of the triazole-ring preferably reacts with the
isocyanate instead of the primary amino group. The
X-ray structure of 2 clearly shows strong intramolecular
hydrogen bonds between the amidic N-H group of the
urea moiety (N8-H) and the nitrogen (N5) and, in
addition between the CdO of the urea moiety (O7) and
the primary amino group (N17-H). The relative short
bond lengths of these hydrogen bonds of 2.1 and 2.15
Å, respectively, support the postulated high stability of
this interaction and therefore stabilizes a planar struc-
ture of the triazoyl ring in relation to the urea moiety.
There are also two complementary intermolecular hy-
drogen bonds formed between the primary amino group
and a nitrogen of the heterocyclic ring (N17-H‚‚‚N3b)
(2.1 Å) (Figure 1). This structure could be correlated to
the 1H NMR spectra measured in dependence on the
concentration. We found in CDCl3 solution that the
chemical shift of the peak of the NH group involved in
intramolecular hydrogen bonds does not depend on the
concentration (∆δmax ) 0.03 ppm). In contrast, the signal
of the NH group that is responsible for the intermo-
lecular hydrogen bond depends strongly on the concen-
tration of 2. Increasing the concentration of 2 leads to
a significant shift of the chemical shift to lower field.
The maximal difference of the chemical shift between
the highest and lowest concentration is of about ∆δmax
≈ 0.30 ppm. This result points out that the structure
in solution is similar to the crystal structure.
In general, hydrogen bonds are important in the
formation of highly organized supramolecular structures
in many biopolymers such as proteins or ,e.g., in the
double helix of DNA.1-3 Additionally, many publications
are focused on the synthesis of artificial polymers
bearing functional moieties that are able to build up
several kinds of hydrogen bonds, e.g., amides, carbam-
ates, urea derivates, or simply carboxylic acids.4-7 In
this connection, it has to be pointed out that the typical
mechanical behavior of linear polyamides and polycar-
bamates is a result of the more or less regularly located
hydrogen bonds that strongly improve the intermolecu-
lar interactions.
On the basis of our interest in preparation of various
polymers bearing functionalized side groups, we were
encouraged to synthesize a new type of methacrylate
polymer containing a special kind of a hydrogen bond
forming moiety based on 3-amino-1,2,4-triazole. To
evaluate these intermolecular interactions, we were also
interested in the crystal structure of the monomer and
in the rheological behavior of the corresponding polymer
in solution.
Resu lts a n d Discu ssion
Poly[N-(methacryl-2-ethyl)-N′-(3-amino(1,2,4-triazole-
2-yl)urea)-co-methyl methacrylate] (1) was prepared
from the monomers (methacryl-2-ethyl)-N′-(3-amino-
(1,2,4-triazole-2-yl))urea (2) and methyl methacrylate
(3).
Monomer 2 was obtained simply by reaction of 2-iso-
cyanatoethyl methacrylate (4) with 3-amino-1,2,4-tria-
zole (5) in the presence of catalytic amounts of dibutyl
tindilaurate (DBTL) in dimethylformamide (DMF) as
Monomer 2 and methyl methacrylate (3) (molar ratio
1:5) were copolymerized in DMF as solvent in the
presence of 8 mol % of azoisobutyro nitrile as initiator.
DMF was used due to its very small chain transfer
constant. The molar ratio of incorporated monomers 2
1
and 3 in copolymer was determined by H NMR spec-
troscopy and, according to the integrated signals at 4.13
ppm (OCH2CH2NH) and 4.40-3.10 ppm (OCH3) it was
found to be around 1:5.5. The molecular weight (Mh n) was
about 1300 determined by gel permeation chromatog-
raphy (GPC) with polystyrene as standard. We wanted
† Degussa AG. E-mail: Patrick.gloeckner@degussa.com.
‡ DuPont Performance Coatings GmbH & Co. KG.
§ University
of
Duesseldorf.
E-mail:
H.ritter@
uni-duesseldorf.de.
10.1021/ma010828l CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/02/2002

Macromolecules, Vol. 35, No. 6, 2002
Synthesis and Rheological Behavior 2051
Sch em e 1. Syn th esis of (N-Meth a cr yleth yl-N′-tr ia zoyl)u r ea (2)
to study the viscosity behavior caused by hydrogen-
bonding interactions. In this connection the rather low
Mh n of about 1300 was required to avoid polymer-
polymer interactions such as entanglements.
For characterization of the rheological behavior,
copolymer 1 was dissolved in N-methylpyrollidone (N-
MP) (50 wt %) and the complex viscosity (|η*|) was
investigated in dependence on the temperature, which
is shown in Figure 2.
Between 20 and 32 °C, |η*| decreases significantly.
After a minimum between 32 and 38 °C, there is an
increasing of the complex viscosity, and finally, after a
maximum at about 53 °C, the complex viscosity de-
creases again, but the slope is not as high as in the first
range.
tion between 32 and 44 °C and in addition a further
weaker phase transition between 53 and 74 °C. Obvi-
ously, these phase transitions seems to correlate with
this unusual rheological behavior, as described above.
Furthermore, the complex viscosity of the solution of
1 increases strongly above a temperature of about 130
°C yielding a cross-linked gel (Figure 4). It is well-known
from the literature that the formation of urea deriva-
tives is reversible to build isocyanates. In particular,
triazole- or ꢀ-caprolactam are similar to 3-amino-1,2,4-
triazole. According to model studies, we found a back-
formation of the isocyanate, and therefore, this isocy-
anate moiety reacts at higher temperatures intermole-
cularly with a primary amino group or with one of the
NH groups of urea function (Scheme 2).
According to turbidity measurements in dependence
on temperature dissolving or precipitation effects are
not visible. The DSC measurement of the solution of 1
indicates the existence of an endothermal phase transi-
For a better understanding of this cross-linking
reaction, a low molecular model substance (7) was
synthesized from aminotriazole (5) and ethyl isocyanate
(6) (Scheme 3).
The (aminotriazolyl)ethyl))urea (7) was heated to 130
°C in the presence of benzylamine (12). According to
mass spectrometry we found aminotriazole, (benzyl-
ethyl)urea (10), and, in addition, dibenzylurea (11). The
absorption of the free isocyanate was found at 2250 cm-1
in the FT-IR spectrum.
F igu r e 1. X-ray structure of (N-methacrylethyl-N′-triazoyl)-
urea (2)
F igu r e 3. DSC diagram [°C] of 1 (50 wt % in N-methyl
pyrrolidone; heating rate, 30K‚min-1).
F igu r e 2. Complex viscosity |η*| [Pa‚s] vs temperature [°C]
(20-70 °C) of 1 (50 wt % in N-methyl pyrrolidone; oscillating
F igu r e 4. Complex viscosity |η*| [Pa‚s] vs temperature [°C]
(70-140 °C) of 1 (50 wt % in N-methyl pyrrolidone; oscillating
measurement, 10 K‚min-1, frequency, 1 s-1).
measurement, 5 K‚min-1, frequency, 1 s-1
)

2052 Glo¨ckner et al.
Macromolecules, Vol. 35, No. 6, 2002
Sch em e 2. P ostu la ted Mech a n ism of Cr oss-Lin k in g of Cop olym er 1
Sch em e 3. Syn th esis a n d Su bsequ en t Rea ction s of (N-Meth a cr yleth yl-N′-tr ia zoyl)u r ea (7) (Bz: Ben zyl)
Due to the fact that the copolymer 1 contains poorly
reactive primary amino groups and methyl ester groups
from methyl methacrylate units there is a certain
probability for cross-linking reaction yielding amides.
In fact, the model molecule 7 and caproic acid methyl
ester (8) leads to N-(3-amidohexyl-(1,2,4-triazol-2-yl)-

Macromolecules, Vol. 35, No. 6, 2002
Synthesis and Rheological Behavior 2053
atmosphere at 40 °C, 1.55 g (10 mmol) of 2-isocyanatoethyl
methacrylate (4) was added dropwise. After 16 h at 50-55 °C,
DMF was evaporated partially and the mixture was precipi-
tated in water. The crude product was washed three times with
30 mL of water and dried in a vacuum (1.64 g (69%) of a
colorless product; mp 129 °C). 1H NMR (200 MHz), DMSO-d6,
N′-ethyl)urea (9) but only at very high temperatures
above 135 °C and only in very low yields. This indicates
that this amide formation may not be the preferred
reaction leading to cross-linked structures.
From the results described above, it can be concluded
that the new monomer (N-methacrylethyl-N′-triazoyl)-
urea (2) can be polymerized to obtain cross-linkable
copolymers showing certain unusual rheological behav-
ior in N-MP solution. This monomer may be practically
used as a comonomer for development of special coatings
or adhesives. In addition, we have found a new protec-
tive group for isocyanates that starts the back-formation
at relative low temperature in the region of about 130
°C.
3
δ/ppm: 8.37 (t, 1H, J NHCH ) 5.9 Hz, CH2NH); 7.54 (s, 1H,
2
NdCH-triazolyl); 7.20 (s, 2H, NH2); 6.02 (s, 1H, CHcisHtransd
3
CC(O)); 5.65 (s, 1H, CHcisHtransdCC(O)); 4.20 (t, 2H, J CH
CH
1
2
2
) 5.4 Hz, OCH2); 3.46 (m, 2H, CH2NH); 1.84 (s, 3H, CH3). H
NMR (400 MHz), CDCl3, δ/ppm: 7.43 (s, 1H, NdCH-triazolyl);
7.11 (t (br), 1H, CH2NH); 6.28 (s (br), 2H, NH2); 6.12 (s, 1H,
CHcisHtransdCC(O)); 5.60 (s, 1H, CHcisHtransdCC(O)); 4.31 (t,
2H, 3J CH
) 5.3 Hz, OCH2); 3.67 (dd, 2H, 3J CH 2 ) 5.3 Hz,
CH
CH
2
2
2
3J NHCH 2 ) 5.9 Hz CH2NH); 1.93 (s, 3H, CH3). 13C NMR (50.3
CH
MHz), 2DMSO-d6, δ/ppm: 166.42 (CH2dC(CH3)C(O)); 156.51
(NHC(O)); 151.16 (CH-triazolyl); 149.74 (H2N-C); 135.70
(CH2dCC(O)); 125.79 (CH2dCC(O)); 62.75 (OCH2); 38.44 (CH2-
NH); 17.84 (CH3). FT-IR (KBr), ν˜/ cm-1: 3430, 3380, 3290, 3230
(ν, NH, br); 2960, 2930 (ν, CH3, CH2, CH, m); 1720 (ν, CdO
ester (R,â-unsatuared), vs); 1630 (ν, CdO, amide I (urea), s);
1540 (δ, NH, amide II (urea), s); further signals at 1405, 1320,
1300, 1170, 1040, 955. MS (FD): m/z ) 239.4 [M+]. Anal. Calcd
for C9H13N5O3: C, 45.18; H, 5.48; N, 29.27. Found: C, 45.22;
H, 5.45; N 29.26.
Exp er im en ta l P a r t
Ma ter ia ls a n d Meth od s. Ethyl isocyanate (Sigma-Aldrich
Chemie GmbH, Taufkirchen, Germany, purity > 97.0%),
2-isocyanatoethyl methacrylate (Sigma-Aldrich Chemie GmbH,
purity g 95.0%) and methyl methacrylate (Fluka Chemie AG,
Buchs, Switzerland, purity g 99.0%) were obtained and were
distilled under reduced pressure. Azoisobutyronitrile (purity
g 98.0%), 3-amino-1,2,4-triazole (purity g 97.0%), benzylamine
(purity g 99.5%), and caproic acid methyl ester (purity g
99.5%) were also obtained from Fluka. Chloroform-d1 (99.8 at.
% deuterium) and dimethyl-d6 sulfoxide (99.8 at. % deuterium)
were purchased from Deutero GmbH, Kastellaun, FRG. If not
mentioned otherwise, all materials were used as received. The
1H NMR spectra (200 MHz) and 13C NMR spectra (50.29 MHz)
were recorded on a Bruker AC 200 (room-temperature) in
Cop olym er iza tion of (Meth a cr yl-2-eth yl)-N′-(3-a m in o-
(1,2,4-tr ia zole-2-yl))u r ea (2) a n d Meth yl Meth a cr yla te (3).
A monomer mixture of 1.0 g (4.18 mmol) of 2 and 2.09 g (20.91
mmol) of 3 were dissolved in 30 mL of DMF, and 0.33 g (2.01
mmol) of AIBN (8 mol %) was added. The solution was heated
to 80 °C while stirring under nitrogen atmosphere. After 12
h, the polymerization reaction was stopped by cooling and the
solution was poured into 250 mL of water yielding colorless
polymeric products. The resulting crude polymer was dissolved
in 10 mL of THF, poured into 100 mL of water yielding
colorless, solid polymeric product after drying (86% of a
colorless polymer). 1H NMR (CDCl3), δ/ppm: 7.10-6.90 (m (br),
(H-triazolyl); 4.13 (s (br), OCH2CH2NHC(O)); 4.40-3.10 (s,
OCH3); 2.30-1.25 (m, CH2); 1.20 (s, CH3-it); 1.00 (s, CH3-at);
0.80 (s, CH3-st). FT-IR (KBr), ν˜/ cm-1: 3430 (ν, NH, vbr); 2995,
2950 (ν, CH3, CH2, CH, m); 1730 (ν, CdO-ester, vs); 1670 (ν,
CdO, amide I (urea), s); 1555 (δ, NH, amide II (urea), m);
further signals, 1440, 1270, 1240, 1195, 1155, 990. DSC
(heating rate: 10 °C‚min-1): onset ) 117 °C; end ) 138 °C;
Cp1/2 ) 126 °C. GPC: Mh n ) 1300, Mh w) 3.780, D ) 2.9.
Syn th esis of N-(3-Am in o(1,2,4-tr ia zol-2-yl)-N′-eth yl)-
u r ea (7). First, 3.2 g (38.1 mmol) of 3-amino-1,2,4-triazole (5)
and 0.1 g of DBTL were suspended in 100 mL of acetone. With
stirring under nitrogen atmosphere, 2.84 g (40.0 mmol) ethyl
isocyanate (6) dissolved in 50 mL of acetone was added slowly,
and the turbidic mixture changed into a clear solution. After
this mixture was stirred for 6 h at 50 °C, the solvent was
removed and the crude product was washed three times with
25 mL of hexane (5.4 g (91%) of a colorless product; mp 91
1
dimethyl-d6 sulfoxide. For H NMR titration a Bruker AM 400
spectrometer and CDCl3 were used. The δ scale relative to
TMS was calibrated by the deuterium signal of the solvent as
internal standard. The FT-IR spectra were recorded on a
Nicolet FT-IR-5 SXB.
GPC measurements were performed with an setup of the
company PSS with DMF (0.5 wt % LiBr) as eluent at 75 °C.
Calibration was done with polystyrene-standards (PSS) with
a range of molecular weight between 374 and 106. Applying a
flow rate of 1 mL/min, 150 µL of a 0.125 wt % polymer solution
in DMF (0.5 wt % LiBr) was put onto a column combination
consisting of an HEMA, 10 µm with porosity of 40 Å, as
precolumn and 40, 100, and 3000 Å as analytical columns.
Detection of the signals was performed with a TSP UV2000
UV-vis detector (254 nm) and a modified Knauer RI detector
with toluene as internal standard. The evaluation was per-
formed using PSS-WinGPC 6.1 software.
Melting points (mp) were recorded with a Mettler Toledo
FP62 of Mettler Toledo GmbH and are not corrected. The DSC
measurements were performed with a DSC-7 of Perkin-Elmer.
The heating rate was at 10 and 30 °C‚min-1, respectively. The
calibration was done with lead and indium as standards. The
elemental analyses were performed with a Foss Heraeus vario
EL and the mass spectra (FD) with a Finnigan MAT 95
(emitter heating rate: 10 mA/min).
The X-ray structure analysis was prepared on a Diffracto-
meter CAD4 (Enraf-Nonius): radiation, Cu KR. Tables of
crystal data, structure refinement data, atomic coordinates,
bond lengths and angles, and anisotropic displacement pa-
rameters for (methacryl-2-ethyl)-N′-(3-amino(1,2,4-triazole-2-
yl))urea (2) may be ordered from the Cambridge Crystallo-
graphic Data Centre (CCDC) (www.ccdc.cam.ac.uk) referring
to the deposit number CCDC 153136.
Rheological oscillating measurements were performed in the
Central Physical Lab of DuPont Performance Coatings, Wup-
pertal, Germany, with a Bohlin Rheometer VOR system (cone/
plate; oscillating frequency, 1 s-1; strain, 0.1-0.2; heating rate,
5 or 10 K‚min-1).
3
°C). 1H NMR (DMSO-d6), δ/ppm: 8.23 (t, 1H, J NHCH ) 5.9
Hz, NHCH2); 7.52 (s, 1H, CH); 7.20 (s (br), 2H, NH2); 32.21 (m,
3
2H, CH2); 1.04 (t, 3H, J CH
) 7.3 Hz, CH3). 13C NMR
CH
(DMSO-d6), δ/ppm: 156.46 (C(O2)); 150.76 (CNH2); 149.53 (Cd
N-triazolyl); 34.26 (CH2); 14.67 (CH3). MS (FD): m/z ) 155,6
[M+]. Anal. Calcd for C5H9N5O: C, 38.70; H, 5.85; N, 45.14.
Found: C, 39.17; H, 5.81; N, 44.26.
3
Syn th esis of N-(3-Am id oh exyl-(1,2,4-tr ia zol-2-yl)-N′-
eth yl)u r ea (9). First, 1.0 g (6.44 mmol) of 7, 0.2 g of
ammonium chloride and 5 mL of methyl caproate (8) were
stirred under nitrogen atmosphere for 10 h at 135 °C. The
residual methyl caproate was removed, and the crude product
was dissolved in methanol. After filtration the solvent was
removed and the product was dried in a vacuum (0.8 g (49%)
1
of a slightly yellow powder (mp 64 °C). H NMR (DMSO-d6),
3
δ/ppm: 13.33 (s, 1H, NHC(O)CH2CH2); 8.24 (t, 1H, J NHCH
)
2
Syn t h esis of (Met h a cr yl-2-et h yl)-N′-(3-a m in o(1,2,4-
tr ia zole-2-yl))u r ea (2). First, 0.84 g (10 mmol) of 3-amino-
1,2,4-triazole (5) and 0.05 g of DBTL were dissolved in 40 mL
of DMF, and then 0.1 g of 4-methoxyphenol was added to
inhibit radical polymerization. Under stirring in nitrogen
5.9 Hz, NHCH2); 7.67 (s, 1H, CH); 2.97 (m, 2H, NHCH2); 2.36
(t, 2H, 3J CH2CH ) 7.3 Hz, NHC(O)CH2CH2); 1.57 (m, 2H, NHC-
2
(O)CH2CH2); 1.28-1.00 (m, 7H, CH2CH2CH3, NHCH2CH3);
3
0.86 (t, 3H, J CH
) 6.4 Hz, CH2CH2CH3). MS (FD) (253.3):
CH
3
2
m/z ) 253.5 [M+].

2054 Glo¨ckner et al.
Macromolecules, Vol. 35, No. 6, 2002
Syn th esis of (N-Ben zyl-N′-eth yl)u r ea (10) a n d d iben -
zylu r ea (11). First, 0.4 g (2.58 mmol) of 7 was dissolved in
3.0 g (28 mmol) of benzylamine (12). The suspension was
stirred under nitrogen atmosphere for 10 min at 120 °C. The
residual benzylamine was removed and the product was dried
in a vacuum. MS (FD): m/z ) 84.5 (4) [aminotriazole], 178.7
(11) [10], 240.8 (100) [11].
Ba ck -F or m a tion of Eth yl Isocya n a te (6) fr om N-(3-
Am in o(1,2,4-tr ia zol-2-yl)-N′-eth yl)u r ea (7). First, 0.5 g (3.2
mmol) of N-(3-amino(1,2,4-triazol-2-yl)-N′-ethyl)urea (7) was
heated under nitrogen atmosphere for 15 min at 140 °C. The
resulting fluid was collected on a KBr pellet. FT-IR (KBr), ν˜/
cm-1: 2990, 2940 (ν, CH, m); 2280 (ν, NCO, vs); further signals
at 3435, 3100, 1690, 1360, 1350.
Dr. Bernhardt Anton Wolf (University of Mainz) for
turbidity measurements. For X-ray structure analysis
we wish to thank Dr. Dieter Schollmeyer.
Refer en ces a n d Notes
(1) Lehn, J . M. Angew. Chem. 1988, 100, 91.
(2) Falbe, J .; Regitz, M. Ro¨mpp Chemielexikon, 9th ed., G.
Thieme Verlag: Stuttgart, Germany, 1995.
(3) Braun, D.; Cherdron, H.; Ritter, H. Polymer Synthesis:
Theory and Practice, 3rd ed., Springer: Heidelberg, Germany
2001.
(4) Sijbesma, R. P.; Beijer, F. H.; Brunsveld, L.; Folmer, B. J .;
Hirschberg, J . H.; Lange, R. F.; Lowe, J . K.; Meijer, E. W.
Science 1997, 278, 1601.
(5) Folmer, B. J . B.; Sijbesma, R. P.; Versteegen, R. M.; van der
Rijt, J . A. J .; Meijer, E. W. Adv. Mater. 2000, 12, 874.
(6) Beijer, F. H.; Sijbesma, R. P.; Kooijman, H.; Spek, A. L.;
Meijer, E. W. J . Am. Chem. Soc. 1998, 120, 6761.
(7) de Lucca Freitas, L.; Stadler, R. Macromolecules 1987, 20,
2478.
Ack n ow led gm en t. Financial support of this study
by DuPont Performance Coatings is gratefully acknowl-
edged. In particular, we thank David Deters, Dr. Peter
Klostermann and Dr. Dietrich Saatweber. In addition
we thank Yvonne Voskuhl (DuPont) for rheological
measurements and Andreas Eich in the group of Prof.
MA010828L