Development of Bio-inspired Monomer, Dopamine acrylamide
ムール貝
Masayoshi Matsuno, Masayuki Kabata, and Ryoichi Akaishi*
Advanced Technology Laboratories, Research and Business Development Office,Osaka Organic Chemical Industry Ltd., 18-8 Katayama-cho, kasiwara, Osaka 582-0020, Japan*ryoichi_akaishi@ooc.co.jp
In Quartz crystal microbalance (QCM) analysis, Dopamine acrylamide (DopAm)
accumulated on the surface of SiO2, ITO, and Ag over time. These results suggest that thescaffolds on these surfaces are formed with the catechol groups and DopAm accumulates
by the intermolecular hydrogen bondings. And in the investigation of the surface
adhesion and the tackiness, by adding only 1% of DopAm to UV curing monomers,
DopAm was effective to several materials and several pairs of dissimilar materials.
Considering the behavior of the QCM, these result suggest that DopAm has the effect ofresin reinforcement by intermolecular hydrogen bondings with the functional groups ofother monomers as well as scaffolding by catechol groups. To further applications, a redox
characterization of DopAm was investigated by a cyclic voltammogram (CV).
Keywords: Dopamine acrylamide, QCM, UV curing, Adhesive, Tackiness,
Intermolecular hydrogen bonding, CV

1. Introduction
Bio-inspired chemistry is a fascinating field.
In adhesion and coating, Dopamine structure[1,2] andpolymers containing Dopamine
analogs have been used well [3,4], which weredeveloped as alternatives of L-Dopa [5] (Scheme1). J. H. Waite et al. reported about the adhesivemechanism of marine mussels [6,7] (Scheme 2)
and its applications [8-10]. A. Takahara et al.
investigated adhesive gels of co-polymers withDopamine acrylamide (DopAm) [11] (Scheme 3) .
H. Yabu et al. stadied catechols applied DopAm
in a nanoimprint lithography [12]. Recently, we
synthesized DopAm at large scale as few Kgs sothat we could examine about its characterization
more easily. In QCM analysis, the interactionsof DopAm with inorganic oxides and metals on
those surfaces were confirmed by comparison
with other monomers. And about co-polymers
containning a few amount of DopAm, we also
investigated surface adhesions and tackinesses
between different materials with UV curingsystem. And to further applications, a redox
characterization of DopAm was investigated byCV.

Scheme 1.

Scheme 2.

Scheme 3.

Marine Mussels

2. Experimental
Chemicals
Tetrahydrofrun (THF) (Kishida Chemical Co.
Ltd.), Dimethylsulfoxide (DMSO) (Tokyo
Chemical Industry Co., Ltd.), Dopaminehydrochloride (Tokyo Chemical Industry Co.,Ltd.), tetrabutyl- ammonium perchlorate (TBAP)(TokyoChemicalIndustryCo.,Ltd.),
2,4,6-trimethylbenzoyl- diphenyl phosphineoxide (TPO) (IGM Resins B.V.) as an
UV-initiator,
SilverNitrate(AgNO3)(Sigma-Aldrich Co. LLC.) and other chemicals ofreagent grade were used without furtherpurification. Methacrylic acid and its esters(Mitsubishi Chemical Co. Ltd.),
Dopamine
Acrylamide, i.e., N-[2-(3,4-dihydroxyphenyl)
ethyl]acrylamide (DopAm) and Acrylate esters(Osaka Organic Chemical Industry Ltd.) wereused as recieved.
Materials
In cross-cut peel tests about surface adhesive,
ABS resin plates (Type; N, thickness; 2.0mm)(Taiyukizai Co., Ltd.), glass plates (soda-lime
glass, thickness; 0.7mm) (Foresight), ITO coatedglass plates (thickness; 0.7mm/glass, 0.13μm/ITO) (Electronics Harmonious Chemicals Co.,Ltd.) were used. To the peel tests, an adhesive
tape (CellotapeTM) (Ncthiban Co., Ltd.) was used.
And in 180°peel tests about tackiness, PET films(Lumirror 60, thickness; 75μm) (Toray Industries,Inc.), PP plates (Type; N, thichness; 2.0mm)(Taiyukizai Co., Ltd.), Cu plates (Type; FR-4R
1700, thickness; 1.6mm) (Taiyukizai Co., Ltd.),
Al plates (Type; A1050P, thickness; 0.8mm)(Nippon Testpanel Co., Ltd.) were used. The
surfaces of these materials were cleaned up withacetone or ethanol before use.
Instruments
9MHz Quartz crystal microbalance (QCM)
analysis were carried out on a SEIKO EG&G
QCA922 analyzer. Monomers or mixtures ofthem were coated on sample plates with RDS
Mayer Coating Bar No.10 (coating thickness
22.9μm) and were exposed by a Heraeus LIGHT
HAMMER 10 UV-system. Tension tests werecarried out on an A&D RTG-1310 testingmachine.
Cyclic voltammetry (CV) wasmeasured by an ALS Electrochemical Analyzer,
Model 612D.
UV Curing Polymerization for Cross-cut andPeel Test
On a sample plate (ABS polymer, glass, or ITO
coated glass), a mixture of 4-hydroxybutyl
prop-2-enoate (4-HBA) / [2-(hydroxymethyl)3-prop-2-enoyloxy-2-(prop-2-enoyloxymethyl)
propyl] prop-2-enoate (TMP-3A) / DopAm / TPO(ratio was 94/5/1/10) was coated with the RDS
bar coater. And the coated solution was exposed
by UV curing system.
The procedure without DopAm about a mixtureof 4-HBA / TMP-3A /TPO (ratio was 95/5/10)
was the same as described above.

UV Curing Polymerization for 180° Peel Testin TackinessOn a PET film, a mixture of oxolan-2-ylmethyl
prop-2-enoate (THFA) / DopAm / TPO (ratio was99/1/10) was coated with the RDS bar coater.
And another PET film was lightly placed on thecoated surfaces of the PET film. As the similar
with the PET/PET described above, PP/PET,Cu/PET, and Al/PET were prepared. Thesesamples were exposed from the PET film side by
UV curing system. The procedure without
DopAm about a mixture of THFA / TPO (ratiowas 100/10) was the same as described above.
Cross-cut and Peel Test
Cross-cut and peel test was accordance withJIS K5600-5-6.
180° Peel Test about TackinessThe peel test about tackiness was accordancewith JIS Z 0237.
Cyclic Volammogram (CV) of DopAm
In CV measurement, Ag/10mM AgNO3 asreference electrode, Pt as working electrode, andPt coil as counter electrode were used. In 0.1M
of TBAP/DMSO, 3.3μM of DopAm was used.
Scannig range was -1.5V to 1.5V vs Ag/ AgNO3
at 20℃. Scanning rate was 0.1V/s.
3. Results and discussion
3.1. Strategy
At first, we comfirmed the surface affinities ofDopAm with inorganic oxides and metals on
those surfaces by the QCM. Then, co-polymers
containing DopAm prepared by UV curing wereinvestigated in surface adhesions and tackinesses.
To further applications, an electrochemical
behavior of DopAm was characterized by the CV.
3.2. Confirmation of surface affinities ofDopAm with inorganic oxides and metals on
those surfaces by QCM.
QCM measurement was performed using
quartz oscillators on which an inorganic oxides ormetals were coated.
For comparison withDopAm, the same measurement was performedfor 4-HBA, 2-methlprop-2-enoic acid (MAA),
phenyl 2-methylprop-2-enoate (PHMA), andbutyl 2-methylprop-2-enoate (BMA). Each 1
wt% solutions of monomers in ethanol were
flowed through a cell for 350 seconds. In the cell,silicon dioxide (SiO2) or Ag coated osilator wasset. Resonance frequency change (⊿f); -1 Hz isequivalent to mass change (⊿m);1.071ng. The
data for SiO2 and Ag are shown bellow in Fig. 1.
As a result, it was found that DopAm adheredFig. 1.

Comparision of Surface Adhesions of monomers to SiO2 and Ag by QCM measurement

several times to several tens times comperingwith 4-HBA, MAA, PHMA and BMA, whichhave the hydroxyl group, the carboxyl group, thephenyl group, and the alkyl group.
Inaddition,the frequencies in DopAm weregradually reduced on the surface of the oscillators.
In other words, DopAm was laminated withtime. DopAm also showed specific adhesions
for indium tin oxide (ITO) and gold. Thesephenomenons were not found in other monomers
described above.
3.3. UV Curing Surface Adhesions of aCo-polymer Containing DopAm
In the surface Adhesion tests, a co-polymerof 4-HBA and TMP-3A was used as a
general-purpose hard coat composition. Theco-polymer was coated on each plates of ABS,
Glass and ITO (coated on a glass), and wereexposed by UV light.
After making agrid-shaped cut, to the coating films wereattached commercialable adhesive tapes. After
deattaching the adhesive tapes, in ABS, Glass,and ITO, surface adhesions were improved by theaddition of only 1wt% of DopAm (Fig. 2).
Without DopAm, the co-polymer were almost
peeled off with the adhesive tape after the crosscutting. As a UV-initiator, a typical phospineoxide, TPO was used (Scheme 4).
3.4. UV Curing Tacky Adhesions of aCo-polymer of THFA Containing DopAm
In the 180° peel tests, THFA was used as a
general-purpose tacky adhesive. According tothe experimental section descrived above, thepairs of PET/PET, PET/PP, PET/Cu, and PET/Al

Fig. 2. Cross-cut Adhesion Test
JIS K5600-5-6(ISO2409)
UV Curing Film; Thickness ca.20μm
Evaluation (Unchange;0～Detachment＞65%;5)Scheme 4.

were prepared using THFA for tests of tackiness(Fig. 3). In comparison with the tests withoutDopAm, the adhesions of PET/PET, PET/Cu, andPET/Al were improved by adding only 1wt% ofDopAm. In using 5wt% of DopAm, the effects
weren’t so different from those at 1wt%. In thetest of PET/PP, DopAm was slightly effective.
These result shows that DopAm is effective on
the polar surfaces. Considering QCM results,
these result suggest that DopAm has the effect ofresin reinforcement by intermolecular hydrogenbondings with the functional groups of othermonomers as well as scaffolding by catechol

groups.
The effects of DopAm and its
analogues were known about adhesive lap shear
strength tests of some pairs of single material[13,14].
3.5. Redox Characterization of Dopam by
Cyclic Volanmetry..
To further applications, a redox characterization of DopAm was investigated by CV. The
oxidation potential of DopAm (0.37V vsAg/AgNO3) is relatively lower than that of
Dopamine (0.42V vs Ag/AgNO3) [15-18].
Dopamine is famous about nano-coating [19] andreduction of metal ions [1,20] used the low
oxidation potential. There are potentials inDopAm and its polymers for these applications.
4. Conclusion
In QCM analysis, DopAm accumulated on thesurface of SiO2, ITO, and Ag over time. Theseresults suggest that the scaffold on these surface
is formed with the catechol groups and DopAm
accumulates by the intermolecular hydrogenbondings. In the tests of cross cut and peel for
ABS, Glass and ITO coated glass, the surface
adhesion with UV curing were improvement byadding 1wt% of DopAm to the acrylates. In
180 ℃ peel tests, the tackinesses were also
improved by adding 1wt% of DopAm to THFA.
DopAm was effective to several pairs ofdissimilar materials (Cu/PET, Al/PET, PP/PET).
These result suggest that DopAm has the effect ofresin reinforcement by intermolecular hydrogenbondings with the functional groups of othermonomers as well as scaffolding by catecholgroups. In the redox characterization of DopAm,
the oxidation potential of the CV was relatively
lower than that of Dopamine.
References
1. H. Lee, S. M. Dellatore, W. M. Miller, P. B.
Messersmith, Science, 318 (2007) 426.
2. A. Postma, Y. Yan, Y. Wang, A. N. Zelikin, E.
Tjipto, F. Caruso, Chem. Mater. 21 (2009)3042.
3. H. Kakeshima, K. Satoh, M. Kamigaito,ACS Sustainable Chem. Eng., 6 (2018) 13681.
4. C. Zhang, Y. Bai, W. Liu, B. Cheng, Int. J.
Adhes. Adhes., 90 (2019) 126.
5. H.G. Silverman, F.F. Roberto, Mar.
Biotechnol., 9 (2007) 661.
6. J. H. Waite, M. L. Tanzer, Biochem.
Biophys. Res. Commun., 96 (1980) 1554.

.

Fig. 3. 180° Peeling Test Using PET Film
JIS Z 0237
UV Curing Adhesion; Thickness ca.20μm

7. J. H.Waite, J. Biol. Chem., 258 (1983) 2911.
8. J. Heo, T. Kang, S. G. Jang, D. S. Hwang, J.
M.Spruell, K. L. Killops, J. H. Waite, C. J.
Hawker, J. Am. Chem. Soc., 134 (2012) 20139.
9. B. K. Ahn, D. W. Lee, J. N. Israelachvili, J. H.
Waite, Nature Materials, 13 (2014) 867.
10. S. Seo, D. W. Lee, J. S. Ahn, K. Cunha, E.
Filippidi, S. W. Ju, E. Shin, B.-S. Kim, Z. A.
Levine, R. D. Lins, J. N. Israelachvili, J. H.
Waite, M. T. Valentine, J. E. Shea, B. K. Ahn,Adv. Mater, 29 (2017) 1703026.
11. J. Nishida, M. Kobayashi, A. Takahara, J.
Polym. Sci.: Part A: Polym. Chem., 52 (2013)1058.
12. H. Yabu, Y. Saito, M. Shimomura, Y. Matsuo,
J. Mater. Chem. C, 1(2013) 1558.
13. C. R. M.-Péres, J. D. White, J. J. Wilker, J.
Am.Chem. Soc., 134 (2012) 9498.
14. K. Zhan, C. Kim, K. Sung, H. Ejima, N.
Yoshie, Biomacromoplecules, 18 (2017)2959.
15. J. E. Baur., E. W. Kristensen, L. J. May, D. J.
Wiedemann, R. M. Wightman, Anal. Chem.,
60 (1988) 1268.
16. Y. Li, M. Liu, C. Xiang, Q. Xie, S. Yao, Thin
Solid Films, 497 (2006) 270.
17. Y. Liu, B. Yu, J. Hao, F. Zhou, J. Colloid
Interf. Sci., 362 (2011) 127.
18. S. Seo, S. Das, P. J. Zalicki, R. Mirshafian, C.
D. Eisenbach, J. N. Israelachvili, J. H. Waite,
B. K. Ahn, J. Am. Chem. Soc., 137 (2015)9214.
19. M. Kohri, Y. Nannichi, J. Jpn. Soc. ColourMater, 87 (2014) 279 (in Japanese).
20. Y. Saito, T. Higuchi, H. Jinnai, M. Hara, S.
Nagano, Y. Matsuo, H. Yabu, Macromol.
Chem. Phys., 217 ( 2016), 726.