高聚物玻璃化转变温度和分子参数的关系 Ⅰ.高聚物链柔性与Tg的关系

 本文采用晶格模型,以动力学链段长度作为统计单元大小,推导了高聚物玻璃化温度T_8和链静态刚性因子σ²(T₈),链动态刚性因子β(T₈)以及聚合度DP等分子参数之间的关系。具体讨论了链柔性对T₈的影响。理论预测和几十种聚合物的实验数据能较好吻合,分析结果表明T₈值基本上取决于高聚物链σ(T₈)大小。     

二维层状Ti3C2Tx-MXene@VS2用于高性能锂离子电池负极

为探索一种高性能的锂离子电池负极材料,采用酸刻蚀法制备了高导电性、高稳定性的二维层状Ti₃C₂T_x,通过溶剂热法制备了具有高理论比容量的花瓣状VS₂纳米片,再经过简单的液相混合得到了二维层状Ti₃C₂T_x-MXene@VS₂复合物。通过扫描电子显微镜、透射电子显微镜、X射线光电子能谱、X射线衍射和能谱分析对复合材料的形貌和结构进行了表征,采用循环伏安、恒流充放电、长循环和交流阻抗谱对复合材料的电化学性能进行了研究。结果表明：VS₂纳米片均匀地分布在Ti₃C₂T_x的层间及表面,该复合物具有高的可逆容量(电流密度为0.1A·g^-1时,比容量为610.5mAh·g^-1)、良好的倍率性能(电流密度为2A·g^-1时,比容量为197.1mAh·g^-1)和良好的循环稳定性(电流密度为0.2 A·g^-1时,循环600圈后比容量为874.9 mAh·g^-1;电流密度为2 A·g^-1时,循环1 500圈后比容量为115.9mAh·g^-1)。     

铅离子与镉离子高选择性的大环化合物:对称四甲基六元瓜环与过渡金属及重金属离子的配合作用

利用微分脉冲伏安法研究了对称四甲基六元瓜环(TMeQ[6])与过渡金属的相互作用。结果表明该主体大环化合物对Pb²⁺和Cd²⁺离子具有较好的选择性作用。伏安数据测定表明Pb²⁺及Cd²⁺离子与对称四甲基六元瓜环以n_M²⁺/n_TMeQ[6]=2配位, 其配合平衡常数分别为(K_Pb²⁺=2.12×10⁹ L²·mol^-2, K_Ca²⁺=2.10×10⁹ L²·mol^-2)。Pb²⁺离子与TMeQ[6]的晶体结构进一步证实了上述实验结果。     

新型正极材料三硫代环磷氮烯无机聚合物的合成

采用缩合聚合方法合成了新型三硫代环磷氮烯无机聚合物[(NPS₃)₃]_n，利用红外光谱测试与元素含量分析技术证明了[(NPS₃)₃]_n的分子结构与组成，并对聚合物材料的粒度、比表面积及微观形貌进行了考察。TG/DTA 实验证明材料在200 ℃ 以下具有良好的热稳定性。循环伏安测试表明[(NPS₃)₃]_n正极材料在锂电池体系具有2.15 V的电化学还原电位和2.45 V的电化学氧化电位，经充放电循环实验观察，材料的首次放电容量达到749.0 mAh·g^-1，与理论容量(759.0 mAh·g^-1)十分接近；经过50次充放电循环后，放电容量保持在674.8 mAh·g^-1，具有很高的使用容量和优秀的循环性能。     

Al3+掺杂对Li2FeSiO4结构和电化学性能影响的研究

以CH₃COOLi·2H₂O、C₆H₈O₇·H₂O、FeC₆H₅O₇·5H₂O、Al₂(SO₄)₃·18H₂O和C₈H₂₀O₄Si为起始原料,采用水热辅助溶胶凝胶法及二次煅烧合成了Li₂Fe_1-xAl_xSiO₄/C(x=0.00、0.01、0.03、0.05)正极材料。用IR、XRD、FE-SEM、EDS等方法对材料的晶体结构进行了表征,用ZetaPAL粒度分析仪测量了其粒径分布范围,用SQUID(超导量子干涉仪)测定了样品的磁性,用恒流充/放电对其电化学性能进行了测试。结果表明：n_乙酸锂∶n_柠檬酸=4∶1、掺Al³⁺量为3%,80 ℃回流24 h,350 ℃恒温煅烧5 h,700 ℃恒温13 h,所得试样颗粒集中分布在150 nm左右且未出现团聚。在0.1C(16 mA·g^-1)、0.2C、0.5C下的首次放电比容量为127 mAh·g^-1、103.6 mAh·g^-1和91 mAh·g^-1,15次循环后无明显衰减,具有很好的循环稳定性。     

配合物[Mn(bipy)3](ClO4)2的晶体结构和热分析研究

The complex [Mn(bipy)₃]·(ClO₄)₂ was synthesied and characterized by X-ray diffraction. X-ray diffraction result for the single crystal showed that the crystal belongs to triclinic, space group P1, a=0.8123(2),b=1.1024(2), c=1.8646(4)nm,α=102.30(3)°,β=91.00(3)°,γ=99.69(3)°,V=1.6056(6)nm³,Z=2,D_c=1.494g·cm^-3. The thermal decomposition of [Mn(bipy)₃](ClO₄)₂ occurred in a three steps pattern. The reaction mechanism of the first step decomposition was deduced as n(1-α)[-ln(1-α)](n-1)/n with the activation energy of 130kJ·mol^-1.     

二维纳米空洞方格:诺氟沙星锰(Ⅱ)配合物

The reactions of norfloxacin (H-Norf) with Mn(ClO₄)₂·6H₂O and Mn(OH)₂ yield Mn(H-Norf)(ClO₄)₂·2H₂O (1) and [Mn(Norf)₂·4H₂O]_n (2) , respectively. 1 is monomeric while 2 has a novel 2D neutral square grid with an antibacterial drug as building block. Crystal data for 1: triclinic, space group P1 (No.2), a=9.0939(3), b=9.4395(3), c=12.7182(3)?, α=111.447(2), β=90.340(2), γ=112.357(1)°, V=926.34(5)?³, Z=1, ρ_cacl=1.664g·cm^-3. MoKα radiation (λ=0.71073?), T=293(2)K, μ=0.595mm^-1, R₁=0.0692, wR₂=0.1482 for 2320 observed reflections from 4390 independent reflections, GOF=0.940; Crystal data for 2: Monoclinic, P2₁/c, a=5.7530(12), b=21.865(4), c=13.343(3)?, β=98.25(3)°, V=1661.1(6)?³, Z=2, ρ_cacl=1.527g·cm^-3, T=293(2)K, μ=0.477mm^-1, R₁=0.0531, wR₂=0.1552 for 2070 observed reflections from 2870 independent reflections, GOF=1.384. CCDC: 140819; 151063.     

单相多铁性体CaMn7O12的理论研究与固相合成

在理论研究方面,采用基于密度泛函理论(DFT)的第一性原理方法对CaMn₇O₁₂的晶体结构进行了计算和表征,对螺旋桨型磁序的电子结构及相变机制进行了理论分析和研究;在实验方面以TG-DSC为指导,采用固相反应法制备了单相多铁性体CaMn₇O₁₂,并检测表征其磁、电学性能。磁学方面验证了CaMn₇O₁₂的2个磁相转变温度(T_N1=90 K和T_N2=45 K),测得其在10 K温度下存在磁滞回线(M_r=0.02 emu·g^-1,H_c≈1000 Oe);电学方面在室温条件下表征其在10 MHz频率时ε_r=280,tanδ=1.69。     

镍(II)的两种配位聚合物的合成、晶体结构和性质

分别用水热法和溶液法合成了镍的两种配位聚合物[2{Ni(HO-BDC)(bpe)H₂O}]_n·n(py)·nH₂O (1) (HO-H₂BDC=5-羟基-1,3-苯二甲酸，bpe=1,2-二(4-吡啶)乙烷，py=吡啶)和[Ni(HO-BDC)(bipy)]_n·nH₂O (2) (bipy=2,2’-联吡啶)，并对它们进行了元素分析、红外光谱等表征，并用X-射线单晶衍射测定了配合物的单晶结构。配位聚合物1晶体属三斜晶系,P1空间群,晶体学数据为：a= 1.019 2(2) nm, b=1.145 5(3) nm, c=1.246 0(3) nm, α=68.377(5)°, β=67.275(12)°, γ=71.821(7)°,V=1.222 7(5) nm³, Z=1, M_r=979.26, D_c=1.330 g·cm^-3, F(000)=508, μ=0.835, R₁=0.049 4, wR₂=0.112 1；配位聚合物2晶体属单斜晶系, P2/c空间群,晶体学数据为：a= 0.861 1(2) nm, b=1.106 8(3) nm, c=1.839 4(4) nm, β=104.267(9), V=1.699 0(7) nm³, Z=4, M_r=413.00, D_c=1.615 g·cm^-3, F(000)=848, μ=1.182, R₁=0.063 5, wR₂=0.196 9。配合物1中形成了具有纳米孔的2D结构，而配合物2则是一个1D链状结构，它们分别通过氢键和π-π堆积效应形成3D结构。     

高聚物玻璃化转变温度和分子参数的关系 Ⅱ.分子量对玻璃化转变温度的影响

根据前文提出的理论模型,本文推导出下述表征高聚物数均分子量(M_n)与玻璃化转变温度T_8关系的理论公式: T_g=T_g~∞-K_g/M_n K_g=T_g~∞·σ~2(T_g)·M_u十几种高聚物的K_g理论计算位能较好地和实验值吻合。应用理论关系式具体计算了聚苯乙烯、聚氯乙烯、聚二甲基硅氧烷和聚α-甲基苯乙烯的T_g随分子量的变化,其结果是令人满意的。     

Glass transition study of blends of poly(N-methyldodecano-12-lactam) with poly(styrene-co-acrylic acid)

The blends of poly(N-methyldodecano-12-lactam) (MPA) with poly(styrene-co-acrylic acid) (PSAA) prepared from dioxane solutions were studied by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The experimental DSC data of glass transition temperature T_g as a function of composition of amorphous phase were fitted for the as-prepared and re-scanned samples using theoretical approaches. The as-prepared blends show monotonic single-T_g dependence. The values of the Gordon-Taylor coefficient not far from unity suggest miscibility of the blend system in amorphous phase in the whole concentration range. As documented by FTIR, this miscibility is associated with hydrogen bonds between COOH groups of the acrylic acid units in PSAA molecules acting as the H-bond donor and CO groups of MPA acting as the H-bond acceptor. The T_g-dependencies obtained form the second runs have a profound sigmoid character. The Schneider treatment induced an idea of partial limited miscibility in the MPA/PSAA blends caused by prevalence of homogeneous contacts. The difference in T_g between the first and second run can partly be attributed to higher crystallinities in the former.     

Glass transitions in hydrogen-bonded polymer complexes

Mutual precipitates of poly (N, N-dimethyl acrylamide) and poly (4-hydroxystyrene) were collected from dioxane, methanol, or acetone. The glass transition (T_g) temperatures of the precipitates are higher than the weight-average values. Clear films cast from dimethylformamide solutions have lower T_g values. Complexation also occurred between poly (ethyl oxazoline) and poly (4-hydroxystyrene) in dioxane and between poly (vinyl pyrrolidone) and poly (4-hydroxystyrene) in methanol. Again, the glass transition temperatures of the precipitates are higher than the values for the blend films. The ΔC_p values associated with the glass transitions of the complexes are smaller than those of the blends having the same compositions. Negative excess heat capacities of mixing have been observed for several precipitates.     

Molecular simulation of the glass transition of polyphosphazenes

Molecular dynamics simulation (NPT ensemble) has been used to obtain specific volume as a function of temperature for four polyphosphazenes. From these results, the volumetric glass transition temperature has been determined as the temperature marking the discontinuity in slope of the V–T simulation data. The molecular mechanics force field used in this study was COMPASS (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) which has been extensively parameterized and validated for phosphazenes in a previous communication. The polyphosphazenes include poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PTFEP) and three isomers of poly(dibutoxyphosphazene)—poly[bis(n-butoxy)phosphazene] (PnBuP), poly[bis(iso-butoxy)phosphazene)] (PiBuP), and poly[bis(sec-butoxy)phosphazene] (PsBuP). In all cases, there was reasonable agreement between experimental results and values of density and T_g obtained from the simulations. In the case of PnBuP, two different methods for amorphous cell building are compared to explore the relationship between the state of equilibration and the T_g obtained from simulation.     

Prediction of Physical Properties of Dimethacrylate Polymer Networks by a Group Contribution Approach

In this work, the correlation between experimental and theoretical values of density (ρ) and glass transition temperature (T _g ) of dimethacrylate polymer networks is elaborated. The developed methodologies are based on the additive principle of the known monomer chemical structures. The predicted values of ρ differed by a maximum of 1% from the experimental values. The methodology developed for T _g prediction is based on the assumption that dimethacrylate structural units are treated as main chains between ?CH₂C(CH₃)? tri-functional volumeless cross-links. Three-quarters of the calculated T _g values differed less than 20 K from the experimental ones.     

PEO/PVAc共混体系辐射交联反应中溶胶分数与辐照剂量间的关系

In this paper, the relationship between T_m and composition of PEO/PVAc blend were studied and the Flory-Huggins parameter of the blend system were calculated. The experimental results show that this blend system is compatible and have only one glass transition temperature (T_g), so we can extend the relationship between sol fraction (S) and radiation dose (R) of linear polymer to the PEO/PVAc system. The Bb value of PEO/PVAc system were calculated, which is in good agreement with the experimental value.     

Poly(N-phenyl-2-hydroxytrimethylene amine): Its blends with poly(ϵ-caprolactone) and water-soluble polyethers

A new polymer with pendant hydroxyl groups, namely, poly(N-phenyl-2-hydroxytrime-thylene amine) (PHA), was synthesized by a direct condensation polymerization of aniline and epichlorohydrin in an alkaline medium. The new polymer is amorphous with a glass transition temperature (T_g) of 70°C. Blends of PHA with poly(ϵ-caprolactone) (PCL), as well as with two water-soluble polyethers, poly(ethylene oxide) (PEO) and poly(vinyl methyl ether) (PVME), were prepared by casting from a common solvent. It was found that all the three blends were miscible and showed a single, composition dependent glass transition temperature (T_g). FTIR studies revealed that PHA can form hydrogen bonds with PCL, PEO, and PVME, which are driving forces for the miscibility of the blends. © 1997 John Wiley & Sons, Inc.     

Viscoelasticity of nanobubble‐inflated ultrathin polymer films: Justification by the coupling model

The nanobubble inflation method is the only experimental technique that can measure the viscoelastic creep compliance of unsupported ultrathin films of polymers over the glass–rubber transition zone as well as the dependence of the glass transition temperature (T_g) on film thickness. Sizeable reduction of T_g was observed in polystyrene (PS) and bisphenol A polycarbonate by the shift of the creep compliance to shorter times. The dependence of T_g on film thickness is consistent with the published data of free‐standing PS ultrathin films. However, accompanying the shift of the compliance to shorter times, a decrease in the rubbery plateau compliance is observed. The decrease becomes more dramatic in thinner films and at lower temperatures. This anomalous viscoelastic behavior was also observed in poly(vinyl acetate) and poly (n‐butyl methacrylate), but with large variation in the change of either the T_g or the plateau compliance. By now, well established in bulk polymers is the presence of three different viscoelastic mechanisms in the glass–rubber transition zone, namely, the Rouse modes, the sub‐Rouse modes, and the segmental α‐relaxation. Based on the thermorheological complexity of the three mechanisms, the viscoelastic anomaly observed in ultrathin polymer films and its dependence on chemical structure are explained in the framework of the Coupling Model. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Studies of polylactone/poly(vinyl chloride), polylactone/poly(vinyl fluoride), and polylactone/poly(vinylidene fluoride) blends

It is shown that polyvalerolactone/poly(vinyl chloride) (PVL/PVC) blends are miscible over all compositions since a single glass transition temperature T_g is observed, intermediate between those of pure PVL and pure PVC. Melting points, enthalpies of fusion and morphologies of PVL/PVC blends are also reported. It is also shown that polyvalerolactone, poly(α-methyl-α-n-propyl-β-propiolactone), poly(α-methyl-α-ethyl-β-propiolactone), and poly(caprolactone) are immiscible with poly(vinyl fluoride) and poly(vinylidene fluoride), despite the fact that all these polylactones are miscible with PVC. Differences in electronegativity, in atomic radius, and in molar attraction between the fluoride and the chlorine atoms are probably responsible for this difference in behavior.     

Interpolymer complexation in hydrolysed poly(styrene-co-maleic anhydride)/poly(styrene-co-4-vinylpyridine)

Complexation between hydrolysed poly(styrene-co-maleic anhydride) (HSMA) copolymers containing 28% and 50% maleic anhydride and a poly(styrene-co-4-vinylpyridine), St4VP32 copolymer with 32% of 4-vinylpyridine content has been investigated. Formation of interpolymer complexes from 1,4-dioxane solutions is observed, over the entire composition range and the stoichiometry of these complexes has been determined from elemental analysis.Quantitative FTIR study of the system HSMA50/StV4Py32 shows that the ideal complex composition leads to 2:1 unit mole ratio of interacting component. FTIR results are in good agreement with DSC and TGA ones, since this complex composition gives the maximum value of the glass transition temperature and the best thermic stability.For the systems investigated, the T_g versus composition curve do not follow any of the commonly accepted models proposed for polymer blends. A new model proposed by Cowie [Cowie JMG, Garay MT, Lath D, McEwen IJ. Br Poly J 1989;21:81] is used to fit the T_g data and found to reproduce the experimental results more closely.