Super-hydrophilic polymer brushes were prepared by surface-initiated atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) on initiator-immobilized silicon wafers. The graft density was estimated to be ca. 0.22 chains nm 22 based on the linear relationship between M n and the layer thickness. The contact angle against water was very low, and air bubbles in water hardly attached onto the brush surface, indicating a super-hydrophilic surface. Neutron reflectivity measurements of the poly(MPC) brush showed that the grafting polymer chains extended a fair amount in the vertical direction from the substrate in a good solvent such as water, while they shrunk in a poor solvent. Frictional properties of the poly(MPC) brushes were characterized by sliding a glass ball probe in air and various solvents under a load of 0.49 N at a sliding velocity of 90 mm min 21 . An extremely low friction coefficient of the poly(MPC) brush was observed in humid atmosphere because water molecules adsorbed into the brush layer acted as a lubricant.

Effect of alkyl chain spacer length between the charged groups (CSL) in zwitterionic poly(sulfobetaine) (PSB) brushes on the hydration state was investigated. PSB brushes with ethyl (PMAES), propyl (PMAPS), or butyl (PMABS) CSL were prepared by surface-initiated atom transfer radical polymerization on silicon wafers. Hydration states of the PSB brushes in aqueous solutions and/or humid vapor were investigated by contact angle measurement, infrared spectroscopy, AFM observation, and neutron reflectivity. The PSB brushes are swollen in humid air and deionized water due to the hydration of the charged groups leading to the reduction of hydrated PSB brushes/water interfacial free energy. The hydrated PSB brushes exhibit clear interface with low interfacial roughness due to networking of the PSB brush chains through association of the SBs. The hydrated PSB brushes produce diffusive swollen layer in the presence of NaCl because of the charge screening followed by SB dissociation by the bound ions. The ionic strength sensitivity in the hydration got more significant with increasing the CSL in SBs because of the augmentation in partial charge by charged group separation.

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We report the first operando measurement of solid electrolyte interphase (SEI) formation at an electrode using in situ neutron reflectometry. The results revealed the growth of the SEI and intercalation of ions during the charge reaction. Furthermore, we propose a way of evaluating the charge used for the SEI formation.

A self-repairable high density polymer brush of poly(ethylene glycol) (PEG) is formed at the interface between cross-linked poly(dimethyl siloxane) (PDMS) and water by spontaneous surface segregation of an amphiphilic diblock copolymer consisting of PEG and PDMS. The surface reconstruction by the formation of the brush was observed as the large hysteresis of the contact angle of the water droplet. Neutron reflectivity measurement revealed that the grafting density of the polymer brush is 2.8 chain/ nm 2 , which is comparable to those of polymer brushes by the surfaceinitiated polymerization method. The formation of such a remarkably dense polymer brush by segregation can be well supported by the balance between the mixing enthalpy of PEG and water and the stretching energy of PEG.