Department of Chemistry, University of Delhi, Delhi 110007, India.
Department of Chemistry, University of Delhi, Delhi 110007, India.
J Colloid Interface Sci. 2018 Feb 1;511:174-183. doi: 10.1016/j.jcis.2017.09.095. Epub 2017 Sep 28.
Temperature-responsive polymers (TRPs) with a phase transition temperature close to human physiological body temperature have attracted much attention in biomedical and pharmaceutical fields. Addition of small amount of cosolvent to TRPs is expected to influence the molecular interactions, thereby affecting the phase transition temperature of TRPs. Hence, it is possible to tune the phase behavior of TRPs and also drive transitions in TRPs by variation of chemical structure of cosolvent.
To elucidate the conformational changes of the phase transition of TRP aqueous solution in ionic liquids (ILs), poly(N-vinylcaprolactam) (PVCL), a well known TRP was synthesized by solution polymerization. The lower critical solution temperature (LCST) behavior of polymer aqueous solution, with the addition of imidazolium-based ILs possessing same Cl anion and a set of cations [Cmim] such as 1-ethyl-3-methylimidazolium ([Emim]), 1-butyl-3-methylimidazolium ([Bmim]), 1-hexyl-3-methylimidazolium ([Hmim]), 1-decyl-3-methylimidazolium ([Dmim]), 1-allyl-3-methylimidazolium ([Amim]) and 1-benzyl-3-methylimidazolium ([Bzmim]), was monitored by using various sophisticated experimental techniques.
The modulations on the LCST of PVCL aqueous solutions follow the order of [Emim][Cl]<[Amim][Cl]<[Bmim][Cl]<[Hmim][Cl]<[Bzmim][Cl]<[Dmim][Cl]. This order shows that the LCST value increase with increasing the alkyl chain length of cation from [Emim] to [Dmim] of IL. To the best of our knowledge, this is the first report on comprehensive unequivocal evidence of the phase transition behavior of PVCL in presence of imidazolium-based ILs.
具有接近人体生理体温的相变温度的温度响应聚合物（TRP）在生物医学和制药领域引起了广泛关注。向 TRP 中添加少量助溶剂有望影响分子相互作用，从而影响 TRP 的相变温度。因此，可以通过改变助溶剂的化学结构来调节 TRP 的相行为并驱动 TRP 的转变。
为了阐明 TRP 水溶液在离子液体（ILs）中的相转变构象变化，通过溶液聚合合成了众所周知的温度响应聚合物聚（N-乙烯基己内酰胺）（PVCL）。聚合物水溶液的低临界溶液温度（LCST）行为，随着添加具有相同 Cl 阴离子和一组阳离子[Cmim]的咪唑基 IL，如 1-乙基-3-甲基咪唑鎓([Emim])、1-丁基-3-甲基咪唑鎓([Bmim])、1-己基-3-甲基咪唑鎓([Hmim])、1-癸基-3-甲基咪唑鎓([Dmim])、1-烯丙基-3-甲基咪唑鎓([Amim])和 1-苄基-3-甲基咪唑鎓([Bzmim])，通过使用各种复杂的实验技术进行了监测。
PVCL 水溶液的 LCST 调制顺序为[Emim][Cl]<[Amim][Cl]<[Bmim][Cl]<[Hmim][Cl]<[Bzmim][Cl]<[Dmim][Cl]。该顺序表明，LCST 值随 IL 中阳离子的烷基链长度从[Emim]增加到[Dmim]而增加。据我们所知，这是关于在存在咪唑基 IL 的情况下 PVCL 相转变行为的综合明确证据的首次报道。
