Storage-stable and self-crosslinkable combinations of boronic acid containing polymers and diol containing polymers enabled by the latex system

Abstract

Boronic ester is a kind of well-known and active dynamic covalent bond. Yet preparing an even boronic ester crosslinked network from boronic acid containing polymers and diol containing polymers remains challenging because the reaction between boronic acid and diol is so fast that by now blocking boronic acid/diol (in the form of boronic ester) or special mixing procedures are required. In this work, a series of storage-stable and self-crosslinkable combinations of boronic acid (2%, 4% and 8%, in mol%) containing polymer latices and diol (2%, 4% and 8%, in mol%) containing polymer latices were achieved by simply mixing the two types of latex dispersions, without using any blocking agents or special mixing procedure. In the combined dispersions, water as the dispersion medium isolates boronic acids and diol groups, while the combined latices can undergo self-crosslinking via the encounters of boronic acid and diols during the latex film formation. Target synthetic products were confirmed by NMR, UV–vis absorption, FT-IR and Raman spectra. The combined latices have simultaneously ensured the even mixing, storage stability (60 °C for 1 month or room temperature for 6 months) and self-crosslinking (examined by DMA, Soxhlet extractions, up to 97% gel content). The method of respectively preparing and then combining the two types of latices is better in polymerization stability, toughness, and wettability, compared to the method of preparing crosslinked polymer with the comparable divinyl boronic ester crosslinker (1%, 2% and 4%, in mol%). With these advantages, the method of combining such highly reactive polymers by utilizing the features of latex systems is inspirational in the fields of colloid science and reactive polymers.