Study On The Preparation And Performance Of Biomass Starch Polyelectrolyte Complex Materials

Starch was a kind of natural polymer materials with wide source and low price and can be biodegraded, which was used in industrial and agricultural production or various fields for a long time. Due to its character of higher viscosity, poor mechanical performance, weak seepage force and poor dispersion property at low temperature, native starch can only find limited applications.The graft copolymerization of vinyl monomers onto starch was an important way for the chemical modification of starch. As grafted starch had double characteristics of native starch and synthetic polymer, having both advantages, its use value was improved. Starch graft copolymers had extensive application. It could be used in super-absorbent, biodegradable plastics, environment effluent disposal, petroleum industry and medical pesticide industry.In this paper, a sort of ploycationic starch and polyanionic starch were synthesized by grafting polymerization modification of starch, respectively. Polyelectrolyte complex (PEC) membranes were obtained from polycationic starch self-assembling with polyanionic starch, and then the structures and properties of synthesized starch-polyion (St-PI) and starch-polyelectrolyte (St-PEC) materials were characterized. St-PEC membranes were applied in purification of organic solvent and urea released materials.The synthesis and characterization of St-PI: Two polyionic starch materials including starch-grafting-polyacrylate sodium (St-g-PAS) and starch-grafting-polyvinyl ammonium (St-g-PVAM) were synthesized from starch with acrylamide and acrylate sodium using K2S2O8-NaHSO3 as initators, respectively. The influence of gelatinization temperature, gelatinization time, reaction temperature, reaction time, monomer dosage and initiator dosage on grafting parameters of the graft copolymer was investigated. All the structures were characterized by infrared (IR) spectroscopy and scanning electron microscope (SEM). The characterized peaks showed the existence of carboxylate at 1556 cm-1and 1411 cm-1 in the IR spectrum of St-g-PAS.The asymmetric and symmetric bending vibrations of NH3+ were observed at 1667 cm- 1and 1569 cm-1 from IR spectrum of St-g-PVAM. It can be recognized from photos of SEM that the morphology of modified starch membranes was markedly changed compared with starch. Also conductivity and thermal stability of both St-PI materials were investigated. The results of DSC indicated that thermal stability of St-PI was improved compared with starch. The experiment results indicated that the conductivity of St-PI was relatively strong.The preparation and characterization of St-PEC: St-PEC membranes were synthesized by St-g-PAS self-assembling with St-g-PVAM. The characterized peaks of St-PI groups were identified at 1660 cm-1, 1560 cm-1and 1410 cm-1 from IR spectrum of St-PEC. The results showed that St-PEC had been synthesized by self-assembling of St-PI. The random crosslinking morphology appeared in the SEM photos of St-PEC membrane, which was beneficial to water absorption.The water-resistance property of St-PEC membranes, was best when the pH of St-PEC solution was 5, namely, counterion mixed equimolar close to the isoelectric point, which also improved with the increase of annealing temperature. The weaker organic solvents polarity was, the better St-PEC membranes separation selectivity in organic aqueous solution was. The water-absorption rate of St-PEC membranes was enhanced.The IR characterization of St-PEC membranes pervaporation performance: The water pervaporation behaviors of St-PEC membrane were analyzed with 1D-IR and 2D-IR correlation spectroscopy in ethanol aqueous solution. The results indicated that two states of water, free water and associating water existed during pervaporation. The free water was firstly absorbed into membrane and associated with St-PI groups through electrostatic interaction to form associating water with the increasing of water in ethanol. The free water was first desorbed, and then associating water with the increase of temperature, which were separated from ethanol aqueous solution.The property of starch grafted copolymers as controlled release film was researched, and this conclusion was achieved: when urea was packed with starch, St-g-PVAM, St-g-PAS and St-PEC membranes, the release effect was better. In special, the release rate was slower with the higher of grafting degree, the better controlled release effect. Among the comparison of four samples, we could see that: the controlled release effect of starch graft copolymers was better than starch. The St-PEC was firstly used to urea released and the results were satisfying.In this paper, St-PEC membranes are prepared once through simple techonology, and no precipitation exists. The 1D-IR and 2D-IR are used to research dehydration of organics which provides a fast simple method of choosing membranes and new theoretical basis for explaining pervaporation process.St-PEC membranes synthesized by St-g-PAS self-assembling with St-g-PVAM which can be applied in pervaporation membranes and urea complex membranes, not only fine performance but also biodegradable, are a kind of materials having the prospect, benefit to environment. 2D-IR analytical techonology used in membrane structure and performance is promoted to choice of pervaporation membrane materials and study of membrane separation process.