Synthesis And Properties Of Cellulose-based Polymeric Surfactant

Cellulose is one of the most abundant, naturally occurring polymers usedcommercially. In this paper, a new kind of cellulose-based polymeric surfactant wasdeveloped and synthesized. The potential of this project seems to be great in the viewof either the efficient use of energy and raw material, or the environmental protect.A kind of cellulose with DP=280 was employed as raw materials. After solventexchanged, cellulose was dissolved in LiCl/DMAc, then reacted with octanoylchloride to produce cellulose octanoate in homogeneous solution. The celluloseoctanoate obtained was sulfated with HClSO₃/DMF, after neutralizing with NaOH,the cellulose polymeric surfactant was obtained. And the surface tension, micellesconformation and size of polymeric surfactants were also investigated. This projectchanged the conventional synthesis pathway of cellulose-based polymeric surfactants,and the LiCl/DMAc solvent system was employed in the process of polymericsurfactant synthesis.The overall results as following:Three types of cellulose with different DPs (280, 643, 850) were used as raw material,after solvent-exchanged, dissolved in LiCl/DMAc. Rheological measurements wereused to characterize the behavior of cellulose solution. Results showed that in therange of experimental frequency, three cellulose solutions all showed viscoelasticbehavior. An important characteristic of cellulose solutions is the crossover point forG′ and G″ . At strain rates lower than the crossover strain rate, the G′ values are lessthan G″ , indicating the viscous response dominates. Above the crossover strain rate,the G′ values are greater than G″ . And with the increase of ω , tan δ decreased.From the G_c at the crossover point, the order of polydispersity of three cellulose canbe concluded as following: 2#>3#>4#. The temperature of cellulose solutionincreased from 50℃ to 80℃, the G_c values of decreased, but tan δincreased.Cellulose octanoate with DS=0.43 was synthesized in homogeneous solution usingLiCl/DMAc as solvent and TEA as acid-scavenger. The concentration of cellulosesolution was 2.5wt% with DP of 280. By the CP/MAS ¹³C-NMR,FT-IR,X-ray,SEM,elemental analysis measurements,the cellulose octanoate was characterized. And thecellulose octanoate (DS=0.43) obtained was employed as raw material for furtherhydrophilization. By sulfating with HClSO₃/DMF, then neutralized, a new type ofcellulose polymeric surfactant-cellulose octanoate sulfate was developed andsynthesized. By the FT-IR,13C-NMR measurements and ICP, the cellulose octanoatesulfate obtained was characterized with degree of sulfation as 0.543.By the measuring the surface tension of ESC,the critical congregate concentrationwas obtained as 0.04-0.2wt% and the corresponding surface tension was about 55mN/m. But critical congregate concentration of cellulose sulfate cannot be found in theplot of relationship between the concentration and surface tension. Results showed thatthe surface activity of ESC was superior to cellulose sulfate. In this paper, micellesconformation of polymeric surfactants ESC in aqueous solution was systemicallyinvestigated by dynamic scattering and environmental scanning electron microscopymeasurements. Results showed that polymeric surfactant could also form micellessimilar to conventional ones. When the concentration of ESC was low,the micelleswere spheroidal or ellipsoidal mono-molecule micelles. And at the low concentration,the normalized first-order autocorrelation function ( )g(t )1 of ESC can not berepresented by single-exponential decays. At the higher concentration the micelles inaqueous solution would aggregate and form network structure further, but thenormalized first-order autocorrelation function ( )g(t )1 of ESC represented bysingle-exponential decays. With the increasing of ESC concentration, the lower sizeregion remained from 50nm to 170nm. The results of rheology test of ESC in aqueoussolution showed that the surfactant had polymeric rheology.