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論文

In situ neutron reflectometry analysis of interfacial structure formation between phenolic resin and silica during curing

和泉 篤士*; 首藤 靖幸*; 柴山 充弘*; 宮田 登*; 宮崎 司*; 青木 裕之

Langmuir, 37(47), p.13867 - 13872, 2021/11

 被引用回数:2 パーセンタイル:24.57(Chemistry, Multidisciplinary)

The structural formation mechanism of phenolic resin-silica interfaces was investigated in situ by neutron reflectometry during curing. There was a 4 nm thick novolac resin adsorption layer on the silica surface before curing. The curing reaction of the novolac resin with hexamethylenetetramine (HMTA) increased the coherent neutron scattering length density of the resin due to the cure shrinkage accompanied by the volatilization of ammonia, which is a byproduct of HMTA decomposition. As curing proceeded at 180$$^{circ}$$C, the thickness of the bulk layer increased despite the cure shrinkage, and the thickness of the interfacial layer decreased from 4 to 1 nm. This is attributed to the diffusion of decomposed HMTA fragments generated in the bulk layer into the interfacial novolac adsorption layer during diffusion throughout the bulk layer, incorporating the upper part of the interfacial layer reacting with the fragment into the bulk layer. On the other hand, the fragments could not diffuse into the tightly bound immobile segments of novolac resin in direct contact with the silica surface, retaining the 1-2 nm thick interfacial layer in the cured resin. This structural formation mechanism caused interfacial cross-link inhomogeneity in the cured resin on the silica surface.

論文

Interfacial cross-link inhomogeneity of a phenolic resin on a silica surface as revealed by X-ray and neutron reflection measurements

和泉 篤士*; 首藤 靖幸*; 柴山 充弘*; 吉田 鉄生*; 宮田 登*; 宮崎 司*; 青木 裕之

Macromolecules, 53(10), p.4082 - 4089, 2020/05

 被引用回数:6 パーセンタイル:36.95(Polymer Science)

The interfacial structure of a hexamethylenetetramine-cured phenolic resin on a silica surface was investigated by the complementary use of X-ray and neutron reflectivity (XRR and NR, respectively). The contrast-variation technique was applied using D$$_{2}$$O for the NR analysis in which the coherent neutron scattering length density (SLD) largely changed owing to the D$$_{2}$$O absorption of the dry phenolic resin and the hydrogen-to-deuterium exchange of phenolic hydroxyl groups. The XRR profile indicated no clear interfacial structure in terms of the mass density, whereas the NR profile indicated the presence of an interfacial nanolayer on the native silica surface according to the SLD. The thickness of the interfacial layer was 1-2 nm, which was independent of the thickness of the bulk resin layer. The formation of the interfacial layer on the silica surface could be caused by preferential adsorption of the novolac resin on the silica surface via strong hydrogen bonding between phenolic units in the novolac resin and silica surface comprising silanol and silyl ether groups resulting in interfacial cross-link inhomogeneity of the phenolic resin on the silica surface in the thickness direction. To the best of our knowledge, this is the first report of an experimental elucidation of the buried interfacial structure between the phenolic resins on the silica surface at a nanometer level.

論文

Diffusion behavior of methanol molecules confined in cross-linked phenolic resins studied using neutron scattering and molecular dynamics simulations

首藤 靖幸*; 和泉 篤士*; 萩田 克美*; 山田 武*; 柴田 薫; 柴山 充弘*

Macromolecules, 51(16), p.6334 - 6343, 2018/08

 被引用回数:10 パーセンタイル:42.35(Polymer Science)

The dynamics of methanol confined in highly cross-linked phenolic resins was investigated using incoherent quasielastic neutron scattering (QENS) and atomistic molecular dynamics (MD) simulations. The QENS analysis for adeuterated phenolic resin and both deuterated and nondeuterated methanol indicated the presence of resin dynamics induced by methanol invasion and confined diffusion of the methanol molecules. QENS results suggested that methanol had a diffusion coefficient of 1.6 $$times$$ 10$$^{-6}$$ cm$$^{2}$$/s, which is 1 order of magnitude smaller than the bulk value (2.3 $$times$$ 10$$^{-5}$$ cm$$^{2}$$/s. The MD trajectories also showed that the methanol diffusion was limited by the resin network, consistent with QENS results in terms of the diffusion coefficient and diffusion-like behavior.

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