Thermo-responsive triblock copolymer phase transition behaviour in imidazolium-based ionic liquids: Role of the effect of alkyl chain length of cations

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• 作者：Reddicherla Umapathi ; Pannuru Venkatesu ; ^{venkatesup@hotmail.com" class="auth_mail" title="E-mail the corresponding author} ; ^{pvenkatesu@chemistry.du.ac.in" class="auth_mail" title="E-mail the corresponding author}
• 关键词：ILs ; ionic liquids ; CMT ; critical micellization temperature ; LCST ; lower critical solution temperature ; PEG-PPG-PEG ; poly(ethylene glycol)-block-poly(propylene glycol)-block-poly-(ethylene glycol)
• 刊名：Journal of Colloid and Interface Science
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：485
• 期：Complete
• 页码：183-191
• 全文大小：2237 K

文摘

Different biophysical techniques such as fluorescence spectroscopy, dynamic light scattering (DLS), viscosity (η) and Fourier transform infrared (FTIR) spectroscopy have been carried out to characterize the effect of imidazolium-based ionic liquids (ILs) on the thermo-responsive triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly-(ethylene glycol) (PEG-PPG-PEG). In addition, to demonstrate the distinct morphological changes of various self-assembled morphologies, we further employed field emission scanning electron microscope (FESEM). To investigate the effect of alkyl chain length of the cation, concentration of the ILs and the related Hofmeister series on the phase behaviour of PEG-PPG-PEG, we used a series of ILs possessing same Cl⁻ anion and a set of cation [C_nmim]⁺ with increasing alkyl chain length of cation such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]) and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]). The critical micellization temperature (CMT) of the copolymer in the presence of well hydrated cations is directly correlated to their hydration. The overall specific ranking of ILs in decreasing the CMT of PEG-PPG-PEG in aqueous solution was [Emim][Cl] > [Bmim][Cl] > [Hmim][Cl] > [Dmim][Cl]. The trend of these ILs followed the well-known Hofmeister series of cations of ILs. The present study provides important information about the solution properties that can be helpful to tune the IL or temperature-sensitive copolymer CMT and micelle shapes which are crucial for understanding the drug delivery mechanisms.