-Sub, I-gel strongly bond to the PB-Sub and the number “12” emerges (Movie S2). This demonstration also shows that the I-gel selectively bonds to the PB-Sub through the Suzuki-Miyaura coupling reaction.
We report direct bonding between macroscopic objects through the Suzuki-Miyaura cross-coupling reaction. The adhesion described in this paper is achieved without changing the physical states of the two adherents. Utilizing a certain level of mobility of the functional groups in the gels, covalent bonds are efficiently formed at the surface between gel-gel and gel-glass. PB- and I-gels (or Subs) bond strongly through the Pd-catalyzed reaction, while gels (or Subs) without nucleophilic or electrophilic groups do not. Furthermore, adhesion in this system only occurs between specific surfaces under certain conditions (i.e., in the presence of a Pd catalyst). Another merit is that adhesion is based on covalent bonding, where the bonding strength depends on the number of biphenyl groups formed at the interface by the Suzuki-Miyaura coupling reaction, which can be experimentally controlled by the mol% of the functional groups in the gels, reaction time, etc.
Acrylamide (AAm), dimethyl sulfoxide (DMSO) and D2O were purchased from Wako Pure Chemical Industries, Ltd. Acrylic acid (AA), 2,2′-azobis(isobutyronitrile) (AIBN), triethylamine (Et3N), potassium carbonate and N,N′-methylenebis (acrylamide) (MBAAm) were obtained from Nacalai Tesque Inc. Palladium (II) acetate (Pd(OAc)2), (3-aminopropyl)triethoxysilane, 1H-benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP reagent), 4-iodoaniline, 4-iodobenzoic acid and 4-vinylphenylboronic acid were purchased from Tokyo Chemical Industry Co., Ltd. DMSO-d6 was obtained from Merck & Co., Inc. The glass, No. S1126, which was made from Inorganic Glass (B270) of SCHOTT AG, Plant Grünenplan, was purchased from Matsunami Glass Ind., Ltd. Water, which was purified with a Millipore Elix 5 system, was used to prepare the aqueous solutions. Other reagents were used without further purification.
The 1H NMR spectra were recorded at 500 MHz with a JEOL JNM-ECA 500 NMR spectrometer. The FGMAS NMR spectra were recorded at 400 MHz with a JEOL JNM-ECA 400 NMR spectrometer. The sample spinning rate was 8 kHz. In all NMR measurements, chemical shifts were referenced to the solvent values (δ = 2.49 ppm and 4.79 ppm for DMSO-d6 and D2O, respectively). The contact angles were measured by a Dynamic Contact Angle Analyzer (DCA-700, Kyowa Interface Science Ltd.). The IR spectra of the gels were measured using a JASCO FT/IR-410 spectrometer with a KBr disc, while those of the substrates were measured using a JASCO FT/IR-6000 spectrometer via the attenuated total reflection method (ATR). The mechanical properties of the gels were measured by a mechanical tension testing system (Rheoner, RE-33005, Yamaden Ltd.), while the dynamic viscoelasticity was measured using an Anton Paar MCR301 rheometer. X-ray photoelectron spectroscopy (XPS) data were collected with an AXIS 165 (KRATOS ANALYTICAL) using a monochromatic Al-Kα X-ray source.
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We thank the members of the Comprehensive Analysis Center, ISIR, Osaka University for X-ray photoelectron spectroscopy (XPS)