固体NMR研究PAA/PEO共混物中氢键相互作用与结构演化  

Solid-State NMR Studies on Hydrogen Bonding Interactions and Structural Evolution in PAA/PEO Blends

作　　者：王粉粉[1] 王芃[1] 牛洪瑶 余莹凤 孙平川[1] Fenfen Wang;Peng Wang;Hongyao Niu;Yingfeng Yu;Pingchuan Sun(Key Laboratory of Functional Polymer Materials of Ministry of Education and College of Chemistry,Nankai University,Tianjin 300071,P.R.China;School of Physics,Nankai University,Tianjin 300071,P.R.China)

机构地区：[1]南开大学化学学院,功能高分子材料教育部重点实验室,天津300071 [2]南开大学物理学院,天津300071

出　　处：《物理化学学报》2020年第4期115-124,共10页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(21534005,21374051)资助项目。

摘　　要：分子间相互作用是决定材料结构和性能的关键因素之一,而如何在分子水上实现对复杂相互作用分子的检测仍然是一个挑战性课题。本工作首先在不同pH值条下以聚丙烯酸/聚环氧乙烷(PAA/PEO)的混合水溶液制备了系列的固体薄膜,然后采用多种基于连续相调制多脉冲技术的一维和二维1H多脉冲去耦(CRAMPS)固体NMR新技术,并结合高分辨13C交叉极化魔角旋转(CPMAS)、23Na多量子(MQ)等多核固体NMR实验,对PAA/PEO聚合物共混物的微观结构和动力学进行了原位和系统的研究。通过不同类型的1H高分辨CRAMPS实验检测到共混物中包含多种不同类型质子:通过氢键相互作用形成二聚体的COOH基团、自由COOH基团、与水结合的COOH基团和主链基团。随着pH值的升高,除主链质子外,大部分其它区域的信号都明显降低,这是由于PAA与PEO以及水的氢键作用减弱所致。这些CRAMPS NMR技术也被用来阐明不同pH值制备的样品中不同基团的分子运动性。此外,二维1H-1H自旋交换NMR实验提供了关于聚合物PAA与PEO大分子链间、以及水与聚合物的相互作用。1H自旋扩散实验表明,在这些共混物中明显存在相微观相分离的结构,并且测定的分散相区尺寸约为17 nm。23Na MQMAS实验揭示了在共混物中存在两种类型23Na位,一种是自由的钠离子,另一种是与大分子相互作用的Na离子。特别是通过1H-检测的23Na-1H CPMAS实验揭示了Na^+离子的位置远离PEO而与PAA临近。上述这些SSNMR实验结果在分子水平上提供了氢键相互作用对PAA/PEO共混物微观结构和动力学影响的详细信息,可以获得不同pH值对PAA与PEO的氢键作用、相容性、微观结构、水-聚合物相互作用和不同组分分子运动性的影响。在上述核磁共振研究的基础上,我们提出了一种新的PAA/PEO共混物的结构模型,该模型首次成功地揭示了不同的pH值对PAA/PEO共混物中微观结构和动力学Intermolecular interactions are the key to control the final structure and properties of polymers;however,molecularlevel detection of complex interactions remains a challenge.In this study,a series of poly(acrylic acid)/poly(ethylene oxide)(PAA/PEO)solid films were prepared from aqueous solutions at different pHs.Multinuclear solid-state NMR(SSNMR)experiments,including one-and two-dimensional(1D and 2D)1H CRAMPS(Combined Rotation and Multiple Pulse NMR Spectroscopy)based on the continuous phase modulation technique,high-resolution 13C CPMAS(Cross-Polarization and Magic-Angle Spining),and 23Na MQMAS(Multiple-Quantum MAS)experiments,were used to this in situ investigation of the structure and dynamics of these polymer blends.The 1H CRAMPS experiments revealed different types of protons in the blends from the mutually hydrogen-bonded COOH groups,from the free COOH groups,the COOH groups bounded with water that undergo fast chemical exchange mutually,and the COOH groups interacting with PEO and from main chain groups.With increasing pH,most of these peaks decreased except for the main chain protons owing to the decrease in the hydrogen bonding interaction among PAA and PEO as well as water.These CRAMPS NMR techniques were also used to elucidate the molecular mobility of the different groups.Furthermore,2D 1H-1H spin-exchange NMR experiments provided more detailed information about the interpolymer and water-polymer interactions.1H spin-diffusion experiments indicated the presence of phase separation in these blends,and the determined domain size of the mobile phase was approximately 17 nm.Two types of 23Na sites were revealed by MQMAS experiment;in particular,the Na+ionic location and interaction between individual polymers was revealed by 1H detected 23Na-1H CP experiments,which showed that 23Na is in the proximity of PAA instead of PEO.These SSNMR experimental results provide detailed information about the influence of hydrogen bonding interactions on the microcosmic structure and dynamics of PAA/PEO blends at the

关 键 词：聚丙烯酸 聚环氧乙烷 高分子共混物 氢键相互作用 分子运动 固体NMR 

分 类 号：O641[理学—物理化学]