Synthesis And Properties Of Thermosensitive 3-Alkoxy-2-Hydroxypropyl Starch Derivatives

A series of etherifying starches containing different hydrophilic ethoxyl chain lengths and hydrophobic groups were prepared by the reaction of starch with 2-[(2-butoxyethoxy) methyl]oxirane,2-[(2-(2-butoxyethoxy)ethoxy)methyl]oxirane,2-[(2-(hexyloxy)ethoxy)meth yl]oxirane in aqueous solution using sodium hydroxide as catalyst and were conformed by 'H-NMR spectroscopy. The DS of etherifying starches were determined using 1H-NMR. The structures of three etherifying agents were analyzed by means of MS spectroscopy. The degree of substitution can be monitored by altering the molar ratio of etherifying agents to anhydroglucose unit (AGU) in starches. The solubility of etherifying starches with different DS values in different solvents was investigated.The tensioactive properties depended on the DS values were investigated. Samples with the higher DS values have lower Surface tensions.It was also found that the amphiphilic starch derivatives prepared by using 2-[(2-butoxyethoxy)methyl]oxirane,2-[(2-(2-butoxy ethoxy)ethoxy)methyl]oxirane as hydrophobic agents were sensitive to temperature,while those that prepared by using 2-[(2-(hexyloxy)ethoxy)methyl]oxirane as the hydrophobic agent didn't show the thermosensitivity. The influences of the ethoxyl group on the thermosensitive properities of starch derivates were studied.The paper is aimed at the properity research of thermosensitive etherifying starches.Cmc values were determined using different methods and the amphiphilic starch derivatives have much lower cmc values. Samples with the higher DS values have lower cmc values. Critical micelle concentration (cmc) of these assemblies was investigated using fluorescence excitation spectra of pyrene. The changing of micellar sizes receiving the signal of temperature was measured using dynamic light scattering. In addition, the LCSTs of thermosentive etherifying starch were measured by UV-VIS Spectroscopy and the influences of aqueous concentration and salt on LCST were investigated and the influence of ethoxyl group on LCST was also studied. The LCST of thermosentive etherifying starch was easily controlled by changing the degree of substitution.