Ultrathin, Biomimetic, Superhydrophilic Layers of
Cross-Linked Poly(phosphobetaine) on Polyethylene by Photografting
- Publication date
- Publisher
Abstract
Ultrathin, biomimetic, superhydrophilic
hydrogel layers, composed
of cross-linked poly(2-methacryloyloxyethyl phosphorylcholine), are
formed on low-density polyethylene films via ultraviolet-initiated
surface graft polymerization. The layers are 19–58 nm thick
as revealed by electron microscopy and have three-dimensional networks;
the unique network structure, along with its zwitterionic nature,
rather than surface roughness results in superhydrophilicity, that
is, the water contact angle around 5°. This superhydrophilicity
depends on a variety of factors, including the concentration of the
monomer and cross-linker, the type of reaction solvents, the reaction
and drying time, the intensity of UV light, and the way of measurement
of water contact angles. Superhydrophilicity is obtained under a fixed
ratio (e.g., 1/1) of the monomer to cross-linker, a reaction time
over 120 s, a short drying time, (75%) ethanol as the reaction solvent,
and low-intensity UV light, largely because these factors together
generate optimal three-dimensional networks of cross-links