丙烯酰胺-丙烯酸交联共聚凝胶结构与分子运动的~1H NMR自旋晶格弛豫研究

用1HNMR方法测定了交联度分别为10％,7.5％，5％，25％，1％，0．5％及0．25％的丙烯酰胺-丙烯酸与N，N’－亚甲基双丙烯酰胺交联共聚水凝胶中水及主链质子的化学位移谱及自旋晶格弛豫时间T1，并用BBP模型进行了讨论。结果表明，水和凝胶主链的质子线宽随交联度加大而明显增宽，只有在低交联度下，由空间立规度造成的精细分裂才能呈现出来；水凝胶体系中水自旋晶格弛豫时间T1随交联度加大而非单调地减小，寓示凝胶内部有较强的键合束缚水存在，并满足双相快交换模型。聚合物主链质子T1与水质子的T1弛豫行为相反，随交联度加大主链运动受限加强而使其运动减慢，反映了聚合物主链的大分子运动特征，发现主链（-CH-）与（－CH2－）质子T1之比可表征凝胶内部分子链运动的强弱；讨论了NMR弛豫与凝胶孔径结构的关联。     

交联共聚丙烯酰胺—丙烯酸水凝胶溶胀态分子动力学的NMR驰豫研究

用反相悬浮聚合法制备了交联度分别为１０％、７．５％、５％、１％、０．５％及０．２５％的丙烯酰胺－丙烯酸交联共聚水凝胶，用＾１ＨＮＭＲ驰豫方法测定了水及聚合物主链上基团中质子的自旋－自旋驰豫时间并结合质子线型分析，     

丙烯酰胺—丙烯酸交联共聚凝胶结构与分子运动的^1HNMR自旋…

用＾Ｈ ＮＭＲ方法测定了交联度分别为１０％，７．％，５％，２．５％，１％，０．５％及０．２５％４ 丙烯酰胺－丙烯酸与Ｎ，Ｎ‘－亚甲基双丙烯酰胺交联共聚水凝胶中水及主链质子的化学位移谱及自旋晶格驰豫时间Ｔ１，并用ＢＢＰ模型进行了讨论。     

交联网络和浓溶液中高分子链运动的NMR研究 Ⅱ质子自旋-自旋弛豫与凝胶和浓溶液体系中高分子链段运动

用自旋－自旋弛豫时间考察了线型聚苯乙烯溶液与溶胀交联聚丙烯酰胺－丙烯酸凝胶的质子弛豫行为。发现在溶胀交联体系中，不论交联度高低，聚丙烯酰胺－丙烯酸质子的弛豫时间弛豫都呈现出双指数衰减特征；而在线型溶液体系中，聚苯乙烯质子的弛豫时间弛豫符合单指数衰减特征。说明在线性聚苯乙烯溶液中，高分子的链段运动是一种均匀行为，而在溶胀交联聚丙烯酰胺－丙烯酸体系中，不论交联度高低，高分子链段运动始终存在快慢不同的两部分。     

交联网络和浓溶液中高分子链运动的NMR研究Ⅲ.质子自旋-晶格弛豫时间与凝胶和浓溶液体系中高分子链段的运动

用自旋－晶格弛豫时间（Ｔ１）研究了溶胀的交联聚丙烯酰胺－丙烯酸网络和线型聚苯乙烯溶液中质子的弛豫行为。交联网络中，随着交联度增大，Ｔ１ＣＨ／Ｔ１ＣＨ２的值由１．１７逐渐趋近于１；而线型聚苯乙烯溶液中，Ｔ１ＣＨ／Ｔ１ＣＨ２的值由最稀浓度下的１．７过渡到１。说明在交联网络中，交联度很低时，链段的运动已经相当受约束；但交联度很大时，充分溶胀的交联网络中链段运动仍有一定自由度。而在线型高分子浓溶液中，链段的运动严重受阻，导致自旋扩散效应非常完全，彻底平均掉了各质子间Ｔ１时间的差异。     

交联网络和浓溶液中高分子链运动的NMR研究：Ⅱ质子自旋—自旋？…

用自旋－自旋弛豫时间考察了线型聚苯乙烯溶液与溶胀交联聚丙烯酰胺－丙烯酸凝胶的质子弛豫行为。发现在溶胀交联体系中，不论交联度高低，聚丙烯酰胺－丙烯酸质子的弛豫时间弛豫都呈现出双指数衰减特征；而在线型溶液体系中，聚苯乙烯质子的弛豫时间弛豫符合单指数衰减特征。     

自聚集在纳米金粒上的烷基硫醇单分子层的NMR驰豫时间研究

通过质子的自旋-晶格驰豫时间（T_1）、自旋-自旋驰豫时间（T_2）研究烷基 巯基[X(CH_2)_nS-]单分子层保护的纳米金粒中配体分子的运动。本研究涉及两种 典型配体：CH_3(CH_2)_7SH和Py(CH_2)_(12)SH及该两配体的不同配比的测合配体 。实验监测了配体中不同位置的质子的NMR驰豫时间随空间距离及配体比例改变的 变化情况。不同位置的质子，因主要影响因素的不同，表现出各自特殊的运动特征 。配体与金粒配位后，2，3位T_1，T_2值减少，1，4位T_1，T_2值增加。混合配体 中Py(CH_2)_(12)SH含量增加，1，2，3位T_1，T_2值都会减小；而4位T_1值减小， T_2值却增加；不同位置T_1，T_2值变化快慢有别。2位因其特殊位置，在配体配比 PY:C_8 = 1:1[PY代表Py(CH_2)_(12)SH，C_8代表CH_3(CH_2)_7SH]时，分子运动最 自由。实验结果显示T_1总是大于T_2，这说明配体处于低频运动区。     

辐射交联顺1,4-聚丁二烯的NMR研究

用１３Ｃ ＮＭＲ方法,测定了辐射交联顺１,４ 聚丁二烯在室温下的自旋 晶格弛豫时间（Ｔ１）,核Ｏｖｅｒｈａｕｓｅｒ因子（ＮＯＥ）,和１３Ｃ ＮＭＲ线宽．以及凝胶本体１Ｈ ＮＭＲ的Ｔ１和Ｔ２弛豫时间,结果表明,辐射交联顺１,４ 聚丁二烯体系中,随着凝胶含量的增加各碳核质子的Ｔ１值变化很小,而—ＣＨ２—核的ＮＯＥ因子明显降低和１３Ｃ ＮＭＲ线宽增宽．以及１Ｈ ＮＭＲ的Ｔ１和Ｔ２表现的双指数弛豫特性反映了交联体系中大分子链段长程运动受阻以及饱和交联叔碳核—ＣＨ对链段运动的影响．     

应用HNMR谱直接检测生物样品中的微量药物毒物和代谢产物

本文报告了一种新的、有效的用于生物体液的＾１Ｈ ＮＭＲ方法－选择自旋旋翻转回波法，在驰豫剂氨基磺西安铵的存在下，通过去偶道对水质子施加１８０°－△选择性脉冲序列，得到自旋回波图谱。在ｐＨ４．６～７．８的范围内，应用该法可有效地抑制水峰，并可准确地测得药物和毒物的信号。在此方法的基础上，测定了水性生物样品中的某些药物和毒物，例如二氢埃托啡、梭曼等。这－方法也已用来研究催醒安和甲胺磷在灌流大鼠肝脏中的     

辐射交联顺1,4-聚丁二烯的NMR研究

用１３ＣＮＭＲ方法,测定了辐射交联顺１,４聚丁二烯在室温下的自旋晶格弛豫时间（Ｔ１）,核Ｏｖｅｒｈａｕｓｅｒ因子（ＮＯＥ）,和１３ＣＮＭＲ线宽．以及凝胶本体１ＨＮＭＲ的Ｔ１和Ｔ２弛豫时间,结果表明,辐射交联顺１,４聚丁二烯体系中,随着凝胶含量的增加各碳核质子的Ｔ１值变化很小,而—ＣＨ２—核的ＮＯＥ因子明显降低和１３ＣＮＭＲ线宽增宽．以及１ＨＮＭＲ的Ｔ１和Ｔ２表现的双指数弛豫特性反映了交联体系中大分子链段长程运动受阻以及饱和交联叔碳核—ＣＨ对链段运动的影响．     

Water properties in the super-salt-resistive gel probed by NMR and DSC

The so-called "super-salt-resistive gel", or poly(4-vinylphenol) (P4VPh) hydrogel, of different water contents ( H = 97-51%) was prepared by cross-linking with different amounts of ethylene glycol diglycidyl ether. 1H NMR spectroscopy was used to investigate the dynamic properties of water in the gel samples in terms of the spin-spin relaxation. The T2 values in those hydrogels were analyzed by assuming a two-component system, namely, T 2(long) and T2(short), and their fractions were obtained. In the higher water content region (75% < or = H < or = 97%), T2(long) for P4VPh gel was almost constant or even slightly increased with decreasing temperature. On the other hand, T2(long) for poly(vinyl alcohol) (PVA) gel (80% < or = H < or = 96%) significantly decreased with decreasing temperature, showing a natural behavior for water mobility in common hydrogels. Water in P4VPh gels of lower water contents ( H = 70% and 51%) also showed intriguing behaviors: the T2 values are much larger than those of gels with higher water contents and decreased with decreasing temperature only in the lower temperature range (<10 degrees C). The fraction of T2(long) values of P4VPh gel showed another contrast to those of PVA gel; the latter decreased with decreasing water content (normal behavior), while in the former gel the highest fraction (ca. 60% at 20 degrees C) was observed for a sample with the lowest water content ( H = 51%). On the other hand, the results of DSC measurements for P4VPh gel were less specific than those of T2 and comparable to those of common hydrogels such as PVA; with decreasing water content, the total amounts of free water and freezable bound water per polymer mass (g/g) decreased, while the amount of nonfreezing water per polymer also decreased.     

Characterization of free,restricted, and entrapped water environments in poly(N‐isopropyl acrylamide) hydrogels via 1H HRMAS PFG NMR spectroscopy

Different water environments in poly(N‐isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using ¹H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro‐gels. For photo‐initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spin R₂ relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. By combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self‐diffusion rate for these different water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1521–1527     

H NMR studies of poly(N-isopropylacrylamide) gels near the phase transition

The phase transition and critical phenomenon of equilibrium swollen poly(N-isopropylacrylamide) (NIPA) hydrogels were studied by ¹H NMR spectroscopy in liquid solution mode. The quantitative NMR observation shows that the peak height and line width of polymer proton and of the HOD proton, and relaxation times of HOD proton all transitionally change as the temperature approaches the transition temperature. The relaxation times of water protons are also measured quantitatively, which shows that the temperature dependence of relaxation times of HOD on temperature before the transition is not consistent with relaxation theory based on the assumption of dominated dipolar interaction between like-spin nuclei and isotropic rotational motion. To explain the surprising relaxation behavior of HOD, we suggest that the amount of bound water in gels increases gradually with temperature at the approach of the phase transition. The pulsed-gradient spin-echo NMR experiments of NIPA gel confirm this suggestion. We believe that these results have important implications concerning the mechanism of the phase transition of NIPA hydrogels.     

基于光聚合星型PEG-b-PCL大分子单体可生物降解水凝胶的合成及表征

以辛酸亚锡为催化剂 ,通过星型聚乙二醇 (PEG)引发ε 己内酯 (CL)开环聚合 ,制备了PEG b PCL嵌段共聚物 ,进一步以丙烯酸酯封端 ,合成了 3种水溶性大分子单体 .以 2 ,2 二甲氧基 2 苯基苯乙酮为引发剂 ,在紫外光作用下 ,大分子单体在水中由于胶束的形成能够迅速聚合形成水凝胶 .利用1 H NMR、FTIR、DSC、TGA、ESEM、凝胶含量、溶胀比等分析测试手段对大分子单体及其形成的水凝胶进行了表征 .结果表明 ,干胶迅速吸水而达到溶胀平衡 ,水凝胶具有较大的溶胀比和高的水含量 ;随着PEG臂数的增加 ,干胶的熔融峰顶温度下降 ,凝胶的溶胀比减小 ;ESEM图片上清晰地表明水凝胶的网络结构     

Physicochemical characterization of chemical hydrogels based on PVA

In this paper, we report on the physicochemical characterization of hydrogels recently obtained by crosslinking poly (vinylalcohol), PVA, with telechelic PVA (telPVA, bearing terminal aldehydic groups) via acetalization in aqueous solution. These gels were studied by equilibrium swelling, compression modulus measurements, and proton relaxometry experiments. Swelling and compression modulus data allow to estimate the average molecular weight of PVA chain between crosslinks, the average mesh size of the networks, and the polymer–solvent interaction parameter χ₁. The average mesh size of PVA‐telPVA compares well with domain dimensions of diffusionally confined water as detected by NMR relaxometry. Proton relaxometry also showed different network domains in which water is compartmentalized, indicating a complex heterogeneity. The study of the temperature behavior of the nuclear spin–spin relaxation times of the confined water was also considered. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1225–1233, 1999     

Instrumental analyses of nanostructures and interactions with water molecules of biomass constituents of Japanese cypress

Nanostructures consisting of the biomass constituents of the denatured Japanese cypress (Chamaecyparis obtusa) were examined by instrumental analyses at multiple hierarchical levels. Delignification with NaClO₂ solution smoothly proceeded to reveal a distorted cell by scanning electron microscopy; however, a trace amount of lignin still remained in the delignified sample according to attenuated total reflection infrared spectra (ATR-IR). Although hemicellulose could be removed by a treatment with NaOH solution, thermogravimetric analysis and ¹³C cross-polarization/magic angle spinning (CP-MAS) NMR showed a certain amount of hemicellulose remaining. Reaction of the delignified sample with NaOH solution produced a shrunken cell wall that consisted of cellulose with small amounts of lignin and hemicellulose, which were detected by ATR-IR and ¹³C CP-MAS NMR, respectively. These samples from which lignin and/or hemicellulose had been removed easily released water molecules, producing a decrease in the ¹H signal intensity and longer ¹H spin–lattice relaxation time (T₁H) values in variable temperature ¹H MAS NMR. The T₁H values provided information about nano-scale molecular interaction difficult to obtain by other instrumental analyses and they greatly changed depending on the water content and ratio of the biomass constituents. The spin–lattice relaxation of all samples occurred via water molecules under humid conditions that provided sufficient water. Under heat-dried conditions, the spin–lattice relaxation mainly occurred via lignin for the samples with lignin remaining while it occurred via cellulose/hemicellulose for the samples without lignin. The variable temperature T₁H analysis indicated that predominant spin–lattice relaxation route via lignin was caused by higher molecular mobility of lignin-containing samples compared with lignin-free samples.     

Internal water molecules and magnetic relaxation in agarose gels

Agarose gels have long been known to produce exceptionally large enhancements of the water 1H and 2H magnetic relaxation rates. The molecular basis for this effect has not been clearly established, despite its potential importance for a wide range of applications of agarose gels, including their use as biological tissue models in magnetic resonance imaging. To resolve this issue, we have measured the 2H magnetic relaxation dispersion profile from agarose gels over more than 4 frequency decades. We find a very large dispersion, which, at neutral pH, is produced entirely by internal water molecules, exchanging with bulk water on the time scale 10(-8)-10(-6) s. The most long-lived of these dominate the dispersion and give rise to a temperature maximum in the low-frequency relaxation rate. At acidic pH, there is also a low-frequency contribution from hydroxyl deuterons exchanging on a time scale of 10(-4) s. Our analysis of the dispersion profiles is based on a nonperturbative relaxation theory that remains valid outside the conventional motional-narrowing regime. The results of this analysis suggest that the internal water molecules responsible for the dispersion are located in the central cavity of the agarose double helix, as previously proposed on the basis of fiber diffraction data. The magnetic relaxation mechanism invoked here, where spin relaxation is induced directly by molecular exchange, also provides a molecular basis for understanding the water 1H relaxation behavior that governs the intrinsic magnetic resonance image contrast in biological tissue.     

States of water in poly(vinyl alcohol) derivative hydrogels

We studied the behavior of absorbed water in equilibrium‐swollen poly(vinyl alcohol) derivative hydrogels by differential scanning calorimetry (DSC), ¹H nuclear magnetic resonance, and wide‐angle X‐ray diffraction. By DSC, three types of water were detected, and their relative fractions were estimated. With this technique we also calculated the pore size for every sample. From the nonexponential decay of the spin–spin relaxation data, we distinguished two environmental states of the absorbed water in the samples. The relaxation times were determined. From these data, we calculated the fractions of each type of water for every hydrogel and related them to the degree of crosslinking. The X‐ray study indicated that the water absorbed in these hydrogels forms a single crystalline phase on cooling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1462–1467, 2003     

Hydrogels prepared from unsubstituted cellulose in NaOH/urea aqueous solution

Novel cellulose hydrogels were synthesized through a "one-step" method from cellulose, which was dissolved directly in NaOH/urea aqueous solution, by using epichlorohydrin as crosslinker. Structure and properties of the hydrogels were characterized by using SEM, NMR, and water absorption testing. The hydrogels are fully transparent and display macroporous inner structure. The equilibrium swelling ratios of the hydrogels in distilled water at 25 degrees C are in the range from 30 to 60 g H(2)O/g dry hydrogel. Moreover, the reswelling water uptake of the hydrogels could be achieved to more than 70% compared with their initial swelling states. This work provided a simple and fast method for preparing eco-friendly hydrogels from unsubstituted cellulose.