Optimizing the boron-loaded pH/temperature dual responsive polymer for controlled release of boron from wood

Disodium octoborate tetrahydrate (DOT) is a well-received and eco-friendly preservative. However, it is prone to leaching from wood in humid conditions or rainy seasons, causing problems such as decreased efficiency in resisting fungi and poor surface performance in surface finishing. To obtain enhanced leaching resistance and simultaneously achieve controlled release of DOT, a pH and temperature dual responsive poly (2-hydroxyethyl methacrylate/2-(Dimethylamino) ethyl methacrylate) (PDH) was prepared and optimized for in situ construction of DOT-loaded PDH (PDHD) in wood. Results showed that PDH displayed obvious pH and temperature-responsive swelling, and when loaded with DOT, the PDHD consequently released DOT in a pH and temperature-responsive way. Fourier transform infrared spectroscopy, Solid-13C NMR analysis and Dynamic mechanical analysis confirmed the copolymerization of 2-Hydroxyethyl methacrylate (HEMA) and 2-(Dimethylamino) ethyl methacrylate (DMAEMA), as well as the presence of crosslinked structure formed from hydrogen bond between the hydroxyl group of HEMA and the N,N-dimethylamino groups of DMAEMA. After that, the PDHD was in situ constructed in wood for controlled release of boron. During the water leaching test, the modified wood exhibited a boron fixation rate of 49.05% compared with 0.72% of the neat DOT-treated wood. Besides, it presented controlled release activity in response to pH and temperature. This work provides new approaches to the fixation of boron preservatives and notably realizes responsive releasing of boron compounds for long-term wood preservation.