用NMR弛豫研究溶液中聚苯乙烯的缠结特性

详细研究了在θ溶剂环已烷和二氧六环中聚苯乙烯(PS)链的弛豫特性随分子量、浓度和温度的变化规律,发现在PS的溶液中同时存在拓扑缠结和凝聚缠结.前者的形成强烈的依赖于分子量、浓度和温度,而后者主要同浓度和温度有关.侧基苯环的层叠作用(即凝聚缠结)对PS的溶解过程及主链的运动有很大影响,从而对PS的溶液性质乃至固体性质起着决定性作用.另外还发现在不同分子量范围内,分子量对PS的弛豫特性的影响明显不同.这被解释为同溶液中PS链的缠结的形成,单位体积内缠结点数的增加等因素有关.     

甲基丙烯酸甲酯—萘乙烯共聚物的NMR研究Ⅱ.甲基丙烯酸甲酯—萘乙烯共聚物的核弛豫研究

用核弛豫研究了溶液中甲基丙烯酸甲酯-萘乙烯共聚物体系中高分子链间的凝聚态结构．通过对溶液中甲基丙烯酸甲酯-萘乙烯共聚物的变温13CNMR自旋-晶格弛豫的研究，发现此体系具有类似小分子在溶液中的弛豫特性．变温1HNMR自旋-自旅弛豫呈现出双指数特性，弛豫快的部分随温度升高而减少对应于聚合物链间凝聚缠结的解缠，当温度继续升高时，主链的这种组分又开始增加，说明主链中形成新的缠结．研究结果还表明，在这种共聚物中，例基萘环的叠加较少．     

甲基丙烯酸甲酯-萘乙烯共聚物的NMR研究Ⅱ.甲基丙烯酸甲酯-萘乙烯共聚物的核弛豫研究

用核弛豫研究了溶液中甲基丙烯酸甲酯-萘乙烯共聚物体系中高分子链间的凝聚态结构.通过对溶液中甲基丙烯酸甲酯-萘乙烯共聚物的变温¹³C NMR自旋-晶格弛豫的研究,发现此体系具有类似小分子在溶液中的弛豫特性.变温¹H NMR自旋-自旅弛豫呈现出双指数特性,弛豫快的部分随温度升高而减少对应于聚合物链间凝聚缠结的解缠,当温度继续升高时,主链的这种组分又开始增加,说明主链中形成新的缠结.研究结果还表明,在这种共聚物中,例基萘环的叠加较少.     

激光散射研究聚甲基丙烯酸烷基磺酸钠／氯化钠水溶液的性质

本文用激光散射技术研究了具有不同长度烷基侧链的聚甲基丙烯酸烷基磺酸钠（ＰＳＳＲＭＡ）在０．１ＭＮａＣｌ水溶液中的性质。用静态光散射测定了这一系列聚合物的重均分子量Ｍ＿ｗ，均方半径Ｒ＿ｇ以及第二维利系数Ａ＿２．用动态光散射测定了光强的时间相关函数，运用Ｌａｐｌａｃｅ反演得到线宽分布Ｇ（Г）。当高聚物溶液的浓度大于１０￣（－３）ｇ／ｍＬ时，特性平均线宽〈Г〉迅速增加、表面张力降低；在２５℃－４７℃的范围内，〈Г〉随温度增加；烷基侧链越长，在０．１ＭＮａＣｌ水溶液中ＰＳＳＲＭＡ的分子排列更紧密。静态与动态光散射的结果建立以下方程：Ｄ＝ｋ＿ＤＭ￣ａ＿Ｄ，当α＿Ｄ～０．５６，对应于不同侧链，Ｋ＿Ｄ在１．５４×～１０￣（－４）－２．０７×１０￣（－４）（ｍＬ／ｇ）时，从线宽分布Ｇ（Г）得到ＰＳＳＲＭＡ的分子量分布。     

碳氢碳氟表面活性剂混合胶束的NMR和ESR研究

用ＮＭＲ，ＥＳＲ和表面张力测量研究了３－十二烷氧基－２－羟丙基磺酸钠（ＳＤＥＨＳ）与全氟辛酸钠（ＳＰＦＯ）混合溶液微环境性质，表面张力测定表明长链烷基磺酸盐中嵌入羟丙基后，其表面活性提高，而与ＳＰＦＯ混合溶液的表面活性高于单一的ＳＤＥＨＳ和ＳＰＦＯ，ＮＭＲ和ＥＳＲ研究表明，ＳＤＥＨＳ的碳氢链与ＳＰＦＯ的碳氟链之间有强烈的相互作用，ＳＤＥＨＳ与ＳＰＦＯ形成混合胶束，混合胶束“界面”的微观粘度较ＳＤＥ     

高分子熔体和浓溶液的流变性能研究：一种能预测线性粘弹性同…

本文得到了一组线性粘弹性函数同高分子熔体的起始分子量和其分布间的新定量关系式。基于多重缠结模型和两类松驰机理，我们首次创立了两类缠结链组在高分子链近程缠结空间的平均限制维数ｖ的新概念，推导出了它同起始分子量（单分散）、数均分子量（多分散）Ｍｂ和缠结点间平均分子量Ｍｅ等间的定量关系式，并提出了它的相应测定新方法。进而又从高分子熔体粘弹性分子理论和缠结链组的平均限制维数定量表征出发，用统计方法计算出了     

聚丙烯酸水溶液及α-A12O3悬浮液的流变性研究

研究了pH、聚丙烯酸（PAA）浓度和分子量对PAA水溶液的粘度的影响,发现溶液的流变行为与溶液中PAA高分子链的离子化程度和构型密切相关,高分子链刚性程度的增加和链的伸展使溶液在pH为7－9时的粘度最大;研究了在PAA溶液中引入陶瓷粉体后悬浮液的粘度变化,发现当陶瓷粉体和PAA的量达到一定比值时悬浮液体系的粘度达到最小值,同时发现陶瓷粉体的粒径大小与这一粘度最小值和悬浮液流变特性也有关。     

聚丙烯腈热裂解产物的ESR和固体￣（13）CNMR研究

用电子自旋共振（ＥＳＲ）和固体￣（１３）ＣＮＭＲ研究了聚丙烯腈（ＰＡＮ）在不同裂解温度（Ｔ＿Ｐ）下的结构变化，当Ｔ＿Ｐ从２５０℃增加到６００℃，ＥＳＲ信号线形没有变化，ｇ值与Ｔ＿Ｐ无关，ΔＨ＿（ＰＰ）减小，自旋浓度（Ｎ＿Ｓ）开始增加，Ｔ＿Ｐ进一步升高，Ｎ＿Ｓ又减少．￣（１３）ＣＮＭＲ谱指出在不同Ｔ＿Ｐ下谱峰发生很大变化，与另文报道的红外及Ｘ－射经衍射结果一致，随Ｔ＿Ｐ升高，ＰＡＮ逐渐脱去小分子形成具有环化共轭结构的产物．     

Pr￣（3＋）在SBN晶体中的发光特性

通过测量Ｐｒ：ＳＢＮ晶体的吸收光谱和荧光光谱来确定Ｐｒ￣（３＋）在ＳＢＮ晶体中的能级位置。由于Ｐｒ￣（３＋）离子占据晶体中的不同格位而引起荧光带呈现双峰结构。测量荧光寿命随温度的变化关系，表明Ｐｒ￣（３＋）在ＳＢＮ晶体中￣３Ｐ＿０态的无辐射弛豫主要是￣３Ｐ＿０→￣１Ｄ＿２多声子弛豫过程。     

乙烯基吡咯烷酮－醋酸乙烯酯共聚物对1－苯胺基萘－8－磺酸盐水溶液的荧光特性的影响

将荧光探针１－苯胺基萘－８－磺酸盐（ＡＮＳ）加入到乙烯基吡咯烷酮（ＶＰ）－醋酸乙烯酯（ＶＡＣ）共聚物溶液中，共聚物组成分别为ＦＶＰ＝０．８４；０．７４；０．７０；０．５５（以乙烯基吡咯烷酮结构单元的分子数表示）。实验结果表明：ＶＰ－ＶＡＣ共聚物对ＡＮＳ水溶液的荧光强度增强效应与共聚物中乙烯基毗咯烷酮在链节中的比例有关，其组成为ＦＶＰ＝０．５５的共聚物对ＡＮＳ水溶液有显著的荧光增强效应，相对荧光强度比ＰＶＰ均聚物大一倍，而其他组成的共聚物／ＡＮＳ溶液的相对荧光强度只与溶液中ＶＰ结构单元的含量有关。这种现象说明接近等分子比的乙烯基吡咯烷酮－醋酸乙烯酯共聚物与ＡＮＳ分子间形成的过渡态结构有利于能量转移，能产生较高的量子收率，可作为电子转移反应能量转移介质。在生化反应中，可模拟酶反应机理，因而有一定的理论意义和实际意义。     

Study on O-Terphenyl/Polystyrene Blends: How Plasticizer Affects the Glass Transition of Polystyrene?

The effect of plasticizer o-terphenyl on the glass transition of polystyrene was investigated by Fourier transform infrared spectroscopy from a new aspect. The peak areas of four conformation insensitive bands as a function of temperature were studied, these being assigned to the vibrational modes of main chain groups and side groups of polystyrene. It was shown that the reorientation relaxation temperature of the main chain around glass transition was lower than that of the side groups when polystyrene was plasticized by o-terphenyl. It was explained on the basis of cohesional entanglements of polystyrene chains. The reorientation relaxation region of the side groups was nearly the same as the macroscopically observable glass transition region of polystyrene, implying that the glass transition process of polystyrene was dominated by the reorientation of side groups.     

凝聚态下聚苯乙烯的构象

由NMR弛豫测量提供了在环已烷溶剂中聚苯乙烯侧基苯环凝聚缠结的证据.文中用HyperChem程序中的分子力学和分子动态学的分子模型计算对真空状态中凝聚态下聚苯乙烯([CH₂CH]_n,n=6,18,21和60)的构象进行了计算.结果如下:1)聚苯乙烯(头-尾相接,当n=6在240℃(熔点)下进行不同时间的分子动态学拟合后,冷却到室温(25℃).随着拟合时间的增长,体系的平衡能量逐渐降低,结构中苯环的重叠更加明显.在拟合时间不太长(小于20ps)的情况下,体系即达一稳定构象状态.此时,聚苯乙烯中部份相邻的苯环以一对一对的形式基本上重叠,两苯环间相距~0.3nm;但各对苯环的方向各异.延长拟合时间(60-100ps)体系能量更低,出现相邻三个和四个苯环相互重叠的现象;升高拟合起始温度到1727℃,可以缩短拟合时间得到同样结果.2)为使计算结果更能符合真实高聚物,必须增大n值.由于计算速度所限,只能进行不太长时间的计算,取n=18,21和60的结果与n=6时完全一致.3)头-头或尾-尾相接的聚苯乙烯(n=6)在相同的条件下不能得到类似结果,相互平行的苯环均相距在0.6nm以上.计算结果充分说明凝聚态聚苯乙烯的构象存在有相邻侧基苯环(2,3,4个)呈相距~0.3nm的重叠状态,但重叠在一起的聚集体取向不尽相同.它为聚苯乙烯中存在有短程有序的凝聚缠结提供了理论依据.     

具有Dzyaloshinskii-Moriya相互作用的三量子比特海森伯模型中的对纠缠

研究了一维三量子比特海森伯模型中的对纠缠的提高和控制问题,在该系统中引入了Dzyaloshinskii-Moriya（DM)相互作用,通过求解共生来计算两量子比特之间的热纠缠,结果表明：对于XXX模型,引入DM相互作用D,可以诱导铁磁和反铁磁自旋链产生热纠缠,尽管它们产生热纠缠所需的D值大小不同.对于XXZ模型,引入DM相互作用后,可以使原本不存在热纠缠的反铁磁自旋链产生纠缠,而且对于铁磁和反铁磁这两种XXZ自旋链,DM相互作用和各向异 关键词： 纠缠 XXX模型')" href="#">XXX模型 XXZ模型')" href="#">XXZ模型 Dzyaloshinskii-Moriya相互作用     

A comprehensive molecular dynamics study of a single polystyrene chain in a good solvent

In this study, molecular characteristics of polystyrene (PS) was calculated measuring its dilute-solution properties in toluene at 288.15 K via molecular dynamics (MD) simulations. The solution models consisted of PS chains with different number of repeating units all of which were in a dilute regime. In order to investigate the compatibility between the polymer and the solvent molecules, interaction energy and Flory-Huggins (FH) interaction parameter were estimated. The simulation results indicate that increasing the chain repeating units enhanced the interaction between the solute and the solvent. Additionally, the chain dimensions were evaluated calculating the radius of gyration (R_g) and end-to-end distance, r0. To determine the dynamic behavior of the chains in the solutions, mean square displacement (MSD) and diffusivity coefficient were calculated. The simulation results indicated that the chain rigidity at low molecular weight and chain flexibility with increasing the molecular weight influenced chains dynamic behavior and diffusivity. Moreover, radial distribution function (RDF) illustrated the effect of steric hindrance of the chains in dilute solution on capturing the solvent molecules. In addition, solution viscosity was calculated by performing non-equilibrium molecular dynamics simulation (NEMD). The obtained results of chain characteristics and viscosity showed a good agreement with experimental results published previously. This agreement confirms the accuracy of the applied simulation method to characterize the dilute solutions and the chains characteristics.     

Structural Relaxation of Polystyrene Glasses with Dis‐interpenetrated Chains Studied by Differential Scanning Calorimetry

The polystyrene (PS) samples were prepared by freeze‐drying solutions with different concentrations. The structural relaxation behaviors and the chain conformation were studied by differential scanning calorimetry and nonradiative energy transfer, respectively. The results showed that PS prepared by freeze‐drying from very dilute solution was in a disinterpenetrated state, and the structural relaxation was faster than that for interpenetrated coils and the cross‐linked samples.     

几个酰胺/水(重水)二元体系中N-14弛豫的溶剂同位素效应

本文测定了己内酰胺7水(重水).二甲基乙酰胺/水(重水)和丙烯酰胺7/水(重水)体系中N-14在低浓度区域的弛豫时间,考察了四极弛豫的溶剂同位素效应,虽然所研究的酰胺分子大小不一,但在无限稀释的溶液中,仍然可以表明这些酰胺分子的运动完全受溶剂分子的控制。     

Quantum entanglement in a molecular magnet with itinerant electrons

We study the behaviors of pairwise and multipartite entanglement in a molecular magnet with itinerant electrons. In different ground states, the ratio of pairwise to multipartite entanglement is different. The monogamy of quantum entanglement is shown. Both charge correlation and spin correlation play important roles in the entanglement. The entanglements are generally suppressed by the on-site repulsion U and are mainly determined by spin correlation for large U and by charge correlation for small U. At finite temperature, in general, the thermal fluctuation suppresses the entanglements. However, in some cases, the multipartite entanglement can be enhanced by increasing temperature. Comparing the Heisenberg model with the Hubbard model, it is found that thermal entanglement in the itinerant electron system is more robust because charge correlation can survive at much higher temperature than spin correlation.