Dip coating of poly(ethyl methacrylate) and composites from solutions in isopropanol-water co-solvent

This paper reports the feasibility of fabrication of poly(ethyl methacrylate) (PEMA) and composite films by a dip coating method. We demonstrate that PEMA can be dissolved in a mixed isopropanol-water co-solvent avoiding the use of traditional toxic solvents. The feasibility of fabricating concentrated solutions of high molecular weight PEMA is a key factor the fabrication of monolayer or multilayer coatings by a dip coating method. The solubilization range is established and 10 g L-1 PEMA solutions are prepared with water/isopropanol volume ratio (RS) of 0.015–0.380. PEMA precipitation is observed at RS> 0.4. It is found that PEMA solutions with concentration as high as 50 g L-1 can be obtained at RS = 0.176. The deposit mass is influenced by RS, PEMA concentration and number of the deposited layers. PEMA coatings provide corrosion protection of stainless steel in 3% NaCl solutions. The dip coating method is used for the fabrication of composite coating, containing layered double hydroxide LiAl2(OH)7 .2H2O (LiAlDH) and PEMA. LiAlDH is prepared by novel solid state synthesis method, which is simple, waste-free and facilitates the control of stoichiometry. The synthesis time decreases with increasing synthesis temperature from 20° to 70 °C. The relatively short synthesis time makes this low-temperature method suitable for the large scale production of LiAlDH. This waste-free method is promising for the fabrication of other advanced DHs. LiAlDH shows advanced properties for its applications as flame retardant additive (FR) for polymer coatings. LiAlDH outperforms traditional inorganic FR materials of hydroxide type. Another finding is that PEMA-LiAlDH interactions facilitated the fabrication of stable suspensions for dip coating of composites. Corrosion protection of PEMA-LiAlDH coatings with different LiAlDH content is investigated. The advantages of bi-layer coatings containing individual layers with different compositions are demonstrated. The proposed method is promising for the fabrication of other composites, containing various functional materials in the PEMA matrix, which can be deposited as monolayers, multilayers or coatings of graded composition.