磺酸基丙烯酸酯三元无规共聚物胶束的聚集行为

Aggregation Behaviors of Sulfonic Acrylate Ternary Random Copolymer Micelles

采用自由基溶液共聚合法,合成了系列磺酸基丙烯酸酯三元无规共聚物表面活性剂(APSA).利用FTIR、1H-NMR、13C-NMR、GPC及元素分析证实了APSA的结构及组成.APSA胶束为核壳结构,随磺酸基含量增加,亲水层增厚.低剪切速率下,APSA溶液的黏度随磺酸基含量的增加而增加,胶束间的相互作用增强,假塑行为增强;高剪切速率下,黏度基本保持一致.DLS和表面张力表明,APSA1可将水溶液的表面张力降至43.26 m N/m.随亲水基团增加,表面张力增加,临界胶束浓度(cmc)增加.溶液浓度在cmc以下时,光散射强度较低且变化缓慢,高于cmc后,光散射强度呈现急剧的线性增长趋势,胶束聚集数急剧增加.随溶液浓度和亲水基团增加,胶束尺寸和分布系数增加.荧光光谱表明,随APSA浓度增加,I1/I3值从1.8降低到约1.2,芘的(0,0)吸收峰从334 nm迁移到338 nm,I338/I334值从0.7增大到1.45,表明疏水基团聚集形成疏水微区,芘分子从水相极性环境转移到胶束疏水内核.随亲水基团含量增加,分子聚集形成胶束的难度增加,速率降低.

A series of sulfonic acrylate ternary random copolymer surfactants（APSA） were synthesized through radical solution copolymerization,using styrene（St）,butyl acrylate（BA） and 2-acrylamide-2-methylpropanesulfonic acid（AMPS） as raw materials.The structure of APSA copolymers was demonstrated by Fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance spectroscopy（1H-NMR,13CNMR）,gel permeation chromatography（GPC） and elemental analysis.In addition,the micromorphology,size and aggregation behaviors of APSA micelles were investigated by dynamic light scattering（DLS）,transmission electron microscopy（TEM）,surface tension analysis,steady state rheological analysis and steady-state fluorescence.TEM results showed that APSA micelles displayed as core-shell spheres,and the thickness of hydrophilic layer on the surface of APSA micelles increased with increasing the content of anionic hydrophilic sulfonic groups.Steady rheology analysis indicated that the viscosity of APSA solutions increased with increasing the content of sulfonic groups at lower shear rates,the interactions among micelles increased,and the pseudoplastic behavior was also improved.However,the viscosity of APSA solutions was almost invariable at higher shear rates.DLS and surface tension results suggested that the surface tension of APSA1 solution decreased to 43.26 m N / m.The surface tension and critical micelle concentration（cmc） increased with increasing the content of hydrophilic groups.When the APSA concentration was lower than cmc,the light scattering intensity was very low and increased very slowly,but the light scattering intensity displayed abrupt linear increasing trend when the APSA concentration was greater than cmc.At the same time,the aggregation number of APSA micelles increased greatly.DLS analysis also showed that aggregation behavior among micelles was enhanced with increasing APSA concentration,as well as the number of molecules inside the micelles,resulting in the increase of micelle size and dispersion index.Furthermore,the micelle size and dispersion index also increased with increasing the content of hydrophilic groups.It was also found from the fluorescence spectra that I1/ I3 values decreased from 1.8 to 1.2 and then leveled off with increasing APSA concentration,the absorption peak of pyrene（0,0） shifted from 334 nm to 334 nm,I338/ I334 increased from 0.7 to 1.45.The above-mentioned results certified that the hydrophobic groups tended to aggregate and form hydrophobic microdomains,and pyrene molecules transferred from the aqueous polar phase to micellar interphase.It became more difficult for molecules to aggregate to form micelles with increasing the content of hydrophilic groups,and the formation velocity of micelles was also decreased.