Narang Payal, Yadav Niketa, Venkatesu Pannuru
Department of Chemistry, University of Delhi, Delhi 110007, India.
Department of Chemistry, University of Delhi, Delhi 110007, India.
J Colloid Interface Sci. 2019 Oct 1;553:655-665. doi: 10.1016/j.jcis.2019.06.074. Epub 2019 Jun 22.
PEG-PPG-PEG contains hydrophobic (PPG) as well as hydrophilic (PEG) blocks have gained popularity due to their different physiochemical properties that make them useful in several scientific areas and industrial applications such as detergency, stabilizers for dispersion, foaming and many more. Scientific communities reported that additives have ability to tune the micellization/demicellization tendency of PEG-PPG-PEG which we further extended by the use of several N-containing additives. Especially, chemists and biochemists are interested to extend the potential role of PEG-PPG-PEG copolymer in biomedical sensing applications, that is why triblock copolymer is chosen with various additives in the present study.
The work reports the results obtained through different kinds of interactions induced among the poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) and additives containing different structural moieties. In order to tune micellization tendency of PEG-PPG-PEG, several additives such as trimethylamine-N-oxide (TMAO), betaine, sarcosine, guanidinium hydrochloride (GdnHCl) and urea are introduced in the current part of work and studied using UV-visible and fluorescence spectroscopy, dynamic light scattering (DLS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy.
The methylamines facilitate the micellization to higher extent in comparison to that in aqueous PEG-PPG-PEG system, thereby decreasing the critical micellization temperature (CMT) values of PEG-PPG-PEG. Among studied methylamines, sarcosine has the highest efficacy in inducing the micellization followed by TMAO and betaine to the least extent. Direct interactions among polymeric segments and sarcosine is thought to be the main driving force for micellization of PEG-PPG-PEG. This is not possible for the case of betaine and TMAO due to the presence of the sterically hindered N atom. In contrast to these methylamines, GdnHCl and urea provided favorable binding sites for bridging interactions among polymer segments and thus lead to higher temperature values for CMT of PEG-PPG-PEG.
聚乙二醇-聚丙二醇-聚乙二醇（PEG-PPG-PEG）含有疏水（PPG）和亲水（PEG）嵌段，由于其不同的物理化学性质，在多个科学领域和工业应用中受到欢迎，如洗涤剂、分散稳定剂、发泡剂等。科学界报道，添加剂有能力调节PEG-PPG-PEG的胶束化/去胶束化趋势，我们通过使用几种含氮添加剂进一步扩展了这一趋势。特别是，化学家和生物化学家有兴趣扩展PEG-PPG-PEG共聚物在生物医学传感应用中的潜在作用，这就是为什么在本研究中选择三嵌段共聚物与各种添加剂。
该工作报告了通过聚（乙二醇）-嵌段-聚（丙二醇）-嵌段-聚（乙二醇）（PEG-PPG-PEG）与含有不同结构部分的添加剂之间诱导的不同相互作用获得的结果。为了调节PEG-PPG-PEG的胶束化趋势，在当前工作部分引入了几种添加剂，如三甲胺-N-氧化物（TMAO）、甜菜碱、肌氨酸、盐酸胍（GdnHCl）和尿素，并使用紫外可见光谱和荧光光谱、动态光散射（DLS）、差示扫描量热法（DSC）和傅里叶变换红外光谱进行研究。
与水性PEG-PPG-PEG体系相比，甲胺更有助于胶束化，从而降低PEG-PPG-PEG的临界胶束化温度（CMT）值。在所研究的甲胺中，肌氨酸诱导胶束化的效果最高，其次是TMAO，甜菜碱的效果最小。聚合物链段与肌氨酸之间的直接相互作用被认为是PEG-PPG-PEG胶束化的主要驱动力。由于存在空间位阻的氮原子，甜菜碱和TMAO的情况并非如此。与这些甲胺相反，GdnHCl和尿素为聚合物链段之间的桥连相互作用提供了有利的结合位点，从而导致PEG-PPG-PEG的CMT温度值更高。
