Design,Synthesis And Properties Of Thermoresponsive Hydroxyethyl Cellulose Derivatives

Thermoresponsive polymers can make stimulus response to changes in temperature.Thermoresponsive polymers obtained extensive attention in various application fields,such as separation engineering,biological medicine and catalysis field.However,most of the thermoresponsive polymers currently prepared are synthetic polymers,which have many problems,for examples,low biodegradability and biocompatibility,and high toxicity of some monomers.In order to solve these problems,hydroxyethyl cellulose which has many benefits,such as non-toxic,low price,and good biocompatibility and biodegradability,has been used as raw material to synthesize alkyl hydroxyethyl celluloses derivatives.Influences of polymer structures and small molecule additives on phase separation temperature were investigated systematically.The alkyl hydroxyethyl celluloses have also been used in the applications of hydrophobic pollutant separation and temperature-controlled release.2-Hydroxy-3-alkyloxypropyl hydroxyethyl celluloses(HAPEC)were prepared by etherification reaction,which grafted alkyl glycidyl ether onto hydroxyethyl cellulose(HEC).Reaction conditions were discussed in details,such as solvent quantity,amount of NaOH,reaction temperature and time.The criterion is the degree of molar substitution(MS)of the product and the reaction efficiency.The optimal condition and satisfactory results are given.Under the optimal condition,MS of 2-hydroxy-3-butoxypropyl hydroxyethyl celluloses(HBPEC)and 2-hydroxy-3-isopropoxypropyl hydroxyethyl cellulose(HIPEC)can be tune from 0.98 to 2.32 and 1.21 to 2.32,respectively.The HBPEC and HIPEC were characterized by 1H NMR,13C NMR,and 2D HSQC NMR.The themioresponsive of HBPEC and HIPEC were researched in details.The research results indicated that HBPEC and HIPEC had good thermoresponsive ability in a specific MS range.The lower critical solution temperature(LCST)of HBPEC and HIPEC can be tuned from 43.1 to 15.1 ? and 56.1 ? to 21.1 ? by changing MS of hydrophobic groups from 0.98 to 2.23 and 1.21 to 2.88,respectively.The LCST of HAPEC also can be tuned by add additives into sample solution,such as inorganic salts and organic solvent.The research results indicated that the LCSTs of HBPEC and HIPEC were largely influenced by the variation of anionic and cationic species and concentration,and obeyed the rules of the classical Hofmeister series.Additionally,the alcoholic solvents with longer carbon chain have more large influences on phase seperation behaviors of samples.Fluorescence spectroscopy,dynamic light scattering(DLS)and transmission electron microscopy(TEM)were used to research the self-assembly behaviors of HAPEC in aqueous solution,and measured critical micelle concentrations(CMC).The research results showed that HAPEC assembled into micelles,and micelles aggregated as temperature increasing.Using Nile Red as a model of hydrophobic pollutants,the performance of HBPEC-2 for the removing hydrophobic pollutants from aqueous solutions was investigated in detail.When the temperature up to critical flocculation temperature(CFT),the Nile Red which had been encapsulated in HBPEC-2 micelles was flocculated.The flocs seperated from the aqueous solution by filtration,and 99.4%of Nile Red was removed.HBPEC was recycled and reused by method of solvent extraction.Furthermore,the recycle efficiency and maximum loading capacity remained little loss with the number of cycles.Fluorescence spectroscopy and confocal laser scan microscope(CLSM)were applied to the HIPEC aqueous solution to examine the encapsulation of Nile Red aqueous solutions of the HIPEC.The results indicated that Nile Red was not released apparently at 25 ? in 120 h.When the temperature up to 38 ?,the Nile Red which was capsulated in HIPEC micelles can be released from HIPEC micelles over a much longer period of time,and the release process can be controlled by changing temperature.