Molecular Interactions between Amino Silane Adhesion Promoter and Acrylic Polymer Adhesive at Buried Silica Interfaces

Abstract

In this study, the influence of an amino silane (3-(2aminoethylamino)-propyldimethoxymethylsilane, AEAPS) on the interfacial structure and adhesion of butyl acrylate/methyl methacrylate copolymers (BAMMAs) to silica was investigated by sum frequency generation vibrational spectroscopy (SFG). Small amounts of methacrylic acid, MAA, were included in the BAMMA polymerizations to assess the impact of carboxylic acid functionality on the glass interface. SFG was used to probe the O− H and CO groups of incorporated MAA, ester CO groups of BAMMA, and CH groups from all species at the silica interfaces. The addition of AEAPS resulted in a significant change in the molecular structure of the polymer at the buried interface with silica due to specific interactions between the BAMMA polymers and silane. SFG results were consistent with the formation of ionic bonds between the primary and secondary amines of the AEAPS tail group and the MAA component of the polymer, as evidenced by the loss of the MAA O−H and CO signals at the interface. It is extensively reported in the literature that methoxy head groups of an amino silane chemically bind to the silanols of glass, leaving the amine groups available to react with various chemical functionalities. Our results are consistent with this scenario and support an adhesion promotion mechanism of amino silane with various aspects: (1) the ionic bond formation between the tail amine group and acid functionality on BAMMA, (2) the chemical coupling between the silane head group and glass, (3) migration of more ester CO groups to the interface with order, and (4) disordering or reduced levels of CH groups at the interface. These results are important for better understanding of the mechanisms and effect of amino silanes on the adhesion between acrylate polymers and glass substrates in a variety of applications.

Elucidating the Molecular Structure of Hydrophobically Modified Polyethylenimine Nanoparticles and Its Potential Implications for DNA Binding

“…Figure C showcases the Lorentzian-fitted SFG plots of pristine dsDNA, NPEI-ONPs, and NPEI-ONPs with dsDNA addition in the bending region (fitting values are provided in Table S4). The spectral signature shows two strong peak features at 1596 cm –1 (assigned as the N–H bending mode) and 1704 cm –1 (attributed to the CO stretch), which are characteristic of PEI and naphthalimide moieties of pristine NPEI-ONPs. − The changes in the characteristic peak intensity profile of the N–H bend and the CO stretch with consecutive dsDNA addition suggest that the interaction of dsDNA with NPEI-ONPs indeed perturbs the interfacial signature of NPEI-ONPs. We also noticed a clear shift in position and a decrement in intensity of amide I (∼1662 cm –1 ) on introducing dsDNA, which is a characteristic feature of naphthalimide moieties of NPEI-ONPs. − The above observations, demonstrated in Figure , reveal that the dsDNA addition causes structural changes in the NPEI-ONPs at the air–aqueous interface.…”

Molecular Behavior of 1K Polyurethane Adhesive at Buried Interfaces: Plasma Treatment, Annealing, and Adhesion

“…SFG is a unique and powerful technique for in situ studying surfaces and interfaces, including buried interfaces. Detailed SFG experiment procedures and SFG theory have been reported in the literature ,− and will not be repeated. SFG has been extensively applied to investigate polymer surfaces and interfaces. ,− Previously, we studied surfaces and interfaces of PU adhesives, focusing on the behavior of isocyanate groups. , In a typical SFG experiment, two input beams, a frequency fixed visible beam and a frequency-tunable IR beam, were spatially and temporally overlapped at the sample surface/interface.…”

“…Sum frequency generation (SFG) vibrational spectroscopy is a unique and powerful technique to study surfaces and buried interfaces. ,− SFG can probe buried interfaces in situ nondestructively, without the need to break the interface apart for study. Extensive research has been reported to use SFG to study molecular behavior at buried interfaces, including the studies of real-time chemical reactions happening at the interface. − SFG is second-order non-linear optical spectroscopy.…”

“…Extensive research has been reported to use SFG to study molecular behavior at buried interfaces, including the studies of real-time chemical reactions happening at the interface. − SFG is second-order non-linear optical spectroscopy. Its excellent surface/interface selectivity was determined by its selection rule. ,− According to the selection rule, only the media with broken inversion symmetry could contribute an SFG signal, which means that only surfaces/interfaces can produce SFG signals because most bulk materials have inversion symmetry and thus are not SFG-active.…”

Enhanced Sum Frequency Generation for Monolayers on Au Relative to Silica: Local Field Factors and SPR Effect

“…The SFG spectra were collected using ppp (p-polarized sum frequency beam, p-polarized visible beam, and p-polarized infrared beam) polarization combination. The basic theory of the SFG has been extensively described in a lot of studies, − and a brief introduction of the SFG and relative equations (eqs S1–S9) used for the calculation can be found in the Supporting Information.…”