Polysiloxane/poly(fluorinated acrylate) core-shell latexes and surface wettability of films

The core-shell polysiloxane/fluoroacrylate copolymer latexes p(D ₄/D₄^V)/p(BA/MMA/FA) are prepared for coating materials. P(D₄/D₄^V) core is synthesized by ring-opening polymerization of octamethylcyclotetrasiloxane (Si ₄O₄(CH₃)₈, D₄) and tetravinyltetramethylcyclotetrasiloxane (Si₄O₄(CH ₃)₄(C₂H₃)₄, D ₄^V). P(BA/MMA/FA) shell is obtained by semi-continuous seed emulsion copolymerization of methyl methylacrylate (MMA), butyl acrylate (BA) and fluorinated acrylate (FA) via. Four different FA are used in this paper: hexafluorobutyl acrylate (6FA), trifluoroethyl methacrylate (3FMA), hexafluorobutyl methacrylate (6FMA) and dodecafluoroheptyl methacrylate (12FMA). The as-prepared latexes are characterized by Fourier transforms infrared (FT-IR) spectroscopy and ¹H NMR measurement. The typical core-shell structure is proved by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The effect of different shells on the core-shell particles and the surface properties of films are characterized by TEM, dynamic light scattering (DLS), scanning electron microscope coupled with the energy dispersive spectrometry (SEM-EDX), static contact angles (SCA) for surface free energy, and quartz crystal microbalance with dissipation (QCM-D) monitoring for surface water absorption. With the increase of fluoridated side chain in the shell, the individual core-shell particles as 70-90 nm are obtained. The surface free energy for p(D₄/D₄^V)/p(BA/MMA/12FMA) film (19 mN/m) is much lower than other three films (28-29 mN/m). During the film formation, the self-aggregation of CF₃ groups onto the film surface for lower surface free energy and the polysiloxane groups onto the substrate for better adhesion. Therefore, p(D₄/D₄^V)/p(BA/ MMA/12FMA) film is much more homogeneous, less wettability and less water absorption.