Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 1. Microscopic Structure, Water Absorbency, and Degradation Performance

Few studies have been conducted on the use of general nanotechnology-based principles for providing nutrients to crops. Water and fertilizer are the most important inputs in determining crop yield and profit. In this paper, super-absorbent polymers SAP WS (grafting wheat straw (WS) to poly(acrylic- co -acrylamide), which is WS- g -P(AA- co -AM)) and SAP HEC (HEC (hydroxyethyl cellulose)- g -P(AA- co -AM)) and their semi-interpenetrating polymer network (semi-IPN) nanocomposites SI-PSRF/SAP WS and SI-PSRF/SAP HEC (formed by chemical bonding of SAP WS or SAP HEC with PSRF (NPK-containing polymeric slow-release fertilizer)) were prepared. Due to the differences between activity and number of functional groups in WS and HEC, the water absorption properties and degradation performances of SAP WS and SAP HEC and their chemically bonded function nanocomposites SI-PSRF/SAP WS and SI-PSRF/SAP HEC are different. The maximum water absorption ratios of SAP WS, SAP HEC, SI-PSRF/SAP WS, and SI-PSRF/SAP HEC can reach 200.00 g/g, 240.00 g/g, 119.91g/g, and 127.43 g/g, respectively. Effects of the structures of these four materials on their degradation performances were studied via a tomato pot experiment. The changes in microstructures of these materials during the degradation processes were characterized by TEM, SEM, FTIR, XRD, XPS, and other techniques. Results show that the degradation rate of the chemically bonded functional nanocomposites with a semi-IPN structure SI-PSRF/SAP system is higher than that of SAP+PSRF (the simple physically mixed system of PSRF and SAP). Due to the differences among the activities and quantities of functional groups in WS and HEC, the water absorption properties of SI-PSRF/SAP WS and SI-PSRF/SAP HEC are different, and there are different degradation rates for these two functional nanocomposites.