水溶性高聚物聚丙烯酰胺的稀溶液性质(Ⅰ)

本工作利用光散射和粘度方法,使用辐射聚合聚丙烯酰胺(PAAM)的级分样品,研究了在较宽分子量范围(10~4-10~7)内PAAM的特性粘数,分子尺寸及第二维利系数对重均分子量的依赖性.从实验上得到了PAAM在0.2mol/lNaCl水溶液中的均方旋转半径与均方末端距之间的关系及高分子-溶剂相互作用参数.     

吲哚方酸菁半导体在场效应晶体管中的应用

研究了2,3,3-三甲基-1-H-吲哚方酸菁的场效应性质, 通过X射线衍射证实了方酸菁分子内电荷分离结构以及分子间面面堆积模式, 并在Si/SiO₂基片上通过真空蒸镀和旋涂的方法制备了p型晶体管器件. 通过对器件性能与沟道形态的研究, 我们发现退火处理能促进方酸菁薄膜由无定形态向多晶态转变, 从而使薄膜晶体管的迁移率从10^-5 cm²?V^-1?s^-1量级提高到10^-3 cm²?V^-1?s^-1量级. 顶接触结构单晶器件获得了7.8×10^-2 cm²?V^-1?s^-1的迁移率. 未封装的方酸菁晶体管在大气中也表现出较好的稳定性.     

辐照三嵌段聚苯乙烯-丁二烯-4-乙烯基吡啶共聚物离子交换膜性能的研究——Ⅱ.共聚物膜的基本性能及分离实验

 本文研究了以辐照聚苯乙烯-丁二烯-4-乙烯基吡啶嵌段共聚物为膜基体所制成的嵌镶离子交换膜的基本性能.研究表明所制备的嵌镶膜在两端浓度分别为0.1及0.001 mol/L KCl 中的水渗析系数及电解质渗析系数分别是2.40×10^-5mol/cm²·min及2.10×10^-8mol/cm²·s.用所制备的嵌镶离子交换膜测试了牛血清白蛋白(M=67,000)与KCl混合溶液,蔗糖(M=343)与KCl混合溶液的膜分离效果.实验表明对上述两种非电解质均不能通过膜、而电解质KCl则可以.上述两种混合溶液中KCl渗透系数分别为J_KCl(牛血清白蛋白)=1.08×10^-8mol/cm²·s及J_(KCl)(蔗糖)=1.10×10^-8mol/cm²·s.     

共聚单体乙烯对结晶性无规共聚聚丙烯平台模量的影响

采用齐格勒－纳塔催化剂制备了具有宽分子量分布和超高分子量的无规共聚聚丙烯(UHPPR)。利用平行板流变仪研究了UHPPR在180, 200 and 220℃的粘弹行为,发现UHPPR 180˚C和200˚C的损耗模量G″(ω)曲线,分别在频率为38.10rad/s 和 84.70rad/s处出现最大值峰。从而可以利用特定温度下的损耗模量曲线G″(ω),计算出具有宽分子量分布的结晶性超高分子量无规共聚聚丙烯(UHPPR)的平台模量(G_N⁰),所得UHPPR的平台模量(G_N⁰)在180 ℃和 200 ℃分别为4.51×10⁵ Pa和3.67×10⁵ Pa。这一结果表明,平台模量随乙烯含量的增加而提高,与分子量无关。     

具有双孔径分布的介孔C-Al2O3-TiO2纳米复合材料的合成及其红外发射率

以嵌段共聚物F127 (PEO₁₀₆PPO₇₀PEO₁₀₆, M_W=12600)为模板剂, 异丙醇铝和钛酸四丁酯为金属源, 低分子量的酚醛树脂为碳源, 通过溶胶-凝胶三元共组装法合成了具有双孔径分布的C-Al₂O₃-TiO₂纳米复合材料.用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)及N₂吸附-脱附对该复合材料进行结构表征. 结果显示, 当铝钛原子的摩尔比为1:10 时, 对应的纳米复合材料具有较好的有序介孔结构, 其双孔径分别为3.9和6.5 nm, 比表面积可达259 m²·g^-1, 孔容0.37 cm³·g^-1. 以三元乙丙橡胶(EPDM)为粘结剂, 与介孔纳米复合材料混合制备涂层. 通过调节复合材料中铝钛摩尔比和涂层厚度, 红外发射率在0.450-0.617之间可调.     

Cu2+和Cu+对原代培养的小鼠成骨细胞增殖、分化和钙化的影响

利用噻唑蓝(MTT)法、碱性磷酸酶(ALP)比活性测定、油红O染色和矿化结节染色及定量分析,研究了Cu²⁺和Cu⁺对原代培养的成骨细胞增殖、分化及钙化的影响。结果显示：Cu²⁺(1×10^-9~1×10^-6 mol·L^-1)促进成骨细胞增殖,随时间延长,促进作用变弱。Cu⁺(1×10^-7~1×10^-5 mol·L^-1)抑制成骨细胞增殖,随时间延长,浓度为1×10^-6 mol·L^-1的Cu⁺为促进作用,其余浓度则没有影响。对于成骨细胞分化,Cu²⁺和Cu⁺表现出相似的影响,浓度为1×10^-9和1×10^-6 mol·L^-1时均促进成骨细胞分化,而当浓度为1×10^-7和1×10^-5 mol·L^-1时,则抑制成骨细胞分化,随作用时间延长,大多数浓度均表现为促进作用。测试浓度下的Cu²⁺和Cu⁺均对成骨细胞向脂肪细胞的横向分化表现为促进效应。对矿化功能的影响,1×10^-5 mol·L^-1的Cu²⁺和Cu⁺表现出显著的抑制效应,但随浓度降低,抑制效应变弱。1×10^-7 mol·L^-1的Cu²⁺ 促进成骨细胞矿化结节的形成。结果提示：作用浓度、作用时间及铜离子的价态都是影响Cu²⁺和Cu⁺生物效应转变(从毒性到活性,从损伤到保护,从下调到上调)的关键因素。     

健那绿B的荧光猝灭研究及作为核酸测定探针的应用

用紫外可见光谱、稳态荧光发射及荧光寿命测定研究了核酸猝灭十二烷基磺酸钠胶束中的健那绿荧光。水溶液中弱的健那绿荧光在十二烷基磺酸钠胶束中被大大加强，其最大发射从425纳米移至410纳米，核酸的加入将猝灭健那绿的荧光，当健那绿浓度为2.5×10^–5 mol•L^-1时，荧光猝灭(F₀/F)分别与小牛胸腺DNA及鱼精DNA在2.4×10^–8 到 1.08×10^–7及 1.9×10^–8 到 3.8×10^–8 mol•L^-1范围内成正比, 检测限分别为1.3×10^–8 mol•L^-1 (小牛胸腺DNA)及6.3×10^–9 mol•L^-1 (鱼精DNA)。当DNA浓度较高时, 将系统偏离Stern-Volmer方程。这是因为动态猝灭和静态猝灭同时存在。方法已应用于鸡血提取液中DNA的测定, 测定结果与紫外法一致。     

羧化聚苯醚与聚苯乙烯共混体系相分离初期分子量影响的光散射研究

 本文用激光光散射方法研究了具有特殊相行为[(低临界溶解温度(LCST),高临界溶解温度(UCST)共存]共混体系羧化聚苯醚和聚苯乙烯在UCST域内的不稳相分离初期分子量对动力学参数的影响。结果表明:相分离初期动力学过程与Cahn理论吻合;随着分子量增加,表现扩散系数D_app明显减小;该体系的表现扩散系数为10^-14 cm²s^-1数量级。deGennes管子模型可很好地描述不稳相分离初期大分子扩散行为。     

三嵌段共聚物PAN-b-PEG-b-PAN的合成及其自组装行为的研究

利用原子转移自由基聚合(ATRP)制得了分子量可控、分子量分布窄的聚丙烯腈-b-聚乙二醇-b-聚丙烯腈P(AN-b-PEG-b-PAN)嵌段共聚物. 通过¹H NMR, FTIR, 凝胶渗透色谱(GPC)对所得产物的结构和分子量进行了表征并通过TG和DTA考察了该嵌段共聚物的热稳定性; 运用透射电子显微镜(TEM)、荧光探针技术和动态光散射(DLS)研究了P(AN)₂₇-b-P(EG)₄₅-b-P(AN)₂₇在溶剂水中胶束的形成、结构、形貌和胶束粒径. 结果表明, 三嵌段共聚物P(AN)₂₇-b-P(EG)₄₅-b-P(AN)₂₇的热稳定性较纯聚乙二醇P(EG)好, 且柔性链PEG的引入对嵌段共聚物的放热峰位置没有显著的影响. 当改变此嵌段共聚物溶液浓度时, 该嵌段共聚物会自组装成不同形状的胶束, DLS测量的胶束粒径大于TEM观察的结果, 其临界胶束浓度(cmc)约为4.46×10^－4 g•L^－1.     

C9pPHCNa与C10TABr混合水溶液的表面吸附和胶团形成

羧酸盐Gemini表面活性剂C9pPHCNa与季铵盐表面活性剂十烷基三甲基溴化铵(C10TABr)混合水溶液的胶团生成能力、降低水表面张力的能力和效率均出现明显的增效. 当C9pPHCNa在溶液中的摩尔分数(α1)为0.33时，cmcT(临界胶团总浓度)、γcmc(临界胶团总浓度对应的表面张力)、c20,T(降低20 mN•m^-1水表面张力所需的表面活性剂总浓度)这3个指标均达到最低值，分别为0.60 mmol•L^-1、23.5 mN•m^-1和1.58×10^-5 mol•L^-1. 在所有考察的溶液比例范围内，二组分在混合胶团和表面吸附层中的组成均接近等摩尔比，表现出强烈的分子间相互作用.     

pH-effects in the complex formation of polymers I. Interaction of poly(acrylic acid) with poly(acrylamide)

The effects of polymer concentration, molecular weight of poly(acrylic acid) (PAA), addition of sodium, potassium, ammonium and copper (II) chlorides on the complex formation ability of the system PAA-poly(acrylamide) (PAAM) have been studied in aqueous solutions. The critical pH values of the complexation were determined in different conditions. The complex formation ability of PAAM is compared with other non-ionic polymers. It was shown that an increase in polymers concentration, molecular weight of PAA and ionic strength favours the complexation and shifts the critical pH values to the higher pH region. An addition of CuCl₂ to the mixture of two polymers enhances the complexation drastically due to the formation of triple complexes.     

Studies of micro-brownian motion of a polymer chain by the fluorescence polarization method. I. Fluorescent conjugates of polyacrylamide

Polyacrylamide having a fluorescent residue at the chain end was prepared by polymerization of acrylamide in the presence of a fluorescent dye. The segmental motion of the chain end in dilute solution was studied by the fluorescence polarization method on the fluorescent polyacrylamide conjugates thus obtained. The linear relation between 1/p and T/η₀ held for every sample studied in aqueous media, where p is the degree of polarization of the fluorescence, T is the absolute temperature, and η₀ is the viscosity of the medium. The mean relaxation time 〈ρ〉 of the conjugate was evaluated from these data as a function of the molecular weight of the conjugate. The value of 〈ρ〉 increased slightly with molecular weight, varying from 3.3 × 10^?9 to 7 × 10^?9 sec. The absolute values of 〈ρ〉 and its molecular weight dependence suggest that 〈ρ〉 represents the mean rotational relaxation time for the cooperative motion of about ten monomeric units at the chain end. The effect of the mean extension of polymer chain on the segmental motion was found to be negligible.     

Dilute solution properties of cellulose in LiOH/urea aqueous system

Cellulose was dissolved rapidly in 4.6 wt % LiOH/15 wt % urea aqueous solution and precooled to –10 °C to create a colorless transparent solution. ¹³C‐NMR spectrum proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The result from transmission electron microscope showed a good dispersion of the cellulose molecules in the dilute solution at molecular level. Weight‐average molecular weight (M_w), root mean square radius of gyration (〈s²〉_z^1/2), and intrinsic viscosity ([η]) of cellulose in LiOH/urea aqueous solution were examined with laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 4.6 wt % LiOH/15 wt % urea aqueous solution was established to be [η] = 3.72 × 10^?2 M in the M_w region from 2.7 × 10⁴ to 4.12 × 10⁵. The persistence length (q), molar mass per unit contour length (M_L), and characteristic ratio (C_∞) of cellulose in the dilute solution were given as 6.1 nm, 358 nm^?1, and 20.8, respectively. The experimental data of the molecular parameters of cellulose agreed with the Yamakawa–Fujii theory of the worm‐like chain, indicating that the LiOH/urea aqueous solution was a desirable solvent system of cellulose. The results revealed that the cellulose exists as semistiff‐chains in the LiOH/urea aqueous solution. The cellulose solution was stable during measurement and storage stage. This work provided a new colorless, easy‐to‐prepare, and nontoxic solvent system that can be used with facilities to investigate the chain conformation and molecular weight of cellulose. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3093–3101, 2006     

Dissolution and regeneration of cellulose in NaOH/thiourea aqueous solution

A novel cellulose solvent, 1.5 M NaOH/0.65 M thiourea aqueous solution, was used to dissolve cotton linters having a molecular weight of 10.1 × 10⁴ to prepare cellulose solution. Regenerated cellulose (RC) films were obtained from the cellulose solution by coagulating with sulfuric acid (H₂SO₄) aqueous solution with a concentration from 2 to 30 wt %. Solubility of cellulose, structure, and mechanical properties of the RC films were examined by infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, ¹³C NMR, and tensile tests. ¹³C NMR analysis indicated that the novel solvent of cellulose is a nonderivative aqueous solution system. The presence of thiourea enhanced significantly the solubility of cellulose in NaOH aqueous solution and reduced the formation of cellulose gel; as a result, thiourea prevented the association between cellulose molecules, leading to the solvation of cellulose. The RC film obtained by coagulating with 5 wt % H₂SO₄ aqueous solution for 5 min exhibited higher mechanical properties than that with other H₂SO₄ concentrations and a homogenous porous structure with a mean pore size of 186 nm for free surface in the wet state. The RC film plasticized with 10% glycerin for 5 min had a tensile strength of 107 MPa and breaking elongation of 10%, and about 1% glycerin in the RC film plays an important role in the enhancement of the mechanical properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1521–1529, 2002     

Behavior of cellulose in NaOH/Urea aqueous solution characterized by light scattering and viscometry

Cellulose was dissolved in 6 wt % NaOH/4 wt % urea aqueous solution, which was proven by a ¹³C NMR spectrum to be a direct solvent of cellulose rather than a derivative aqueous solution system. Dilute solution behavior of cellulose in a NaOH/urea aqueous solution system was examined by laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 6 wt % NaOH/4 wt % urea aqueous solution at 25 °C was [η] = 2.45 × 10^?2 weight‐average molecular weight (M_w)^0.815 (mL g^?1) in the M_w region from 3.2 × 10⁴ to 12.9 × 10⁴. The persistence length (q), molar mass per unit contour length (M_L), and characteristic ratio (C_∞) of cellulose in the dilute solution were 6.0 nm, 350 nm^?1, and 20.9, respectively, which agreed with the Yamakawa–Fujii theory of the wormlike chain. The results indicated that the cellulose molecules exist as semiflexible chains in the aqueous solution and were more extended than in cadoxen. This work provided a novel, simple, and nonpollution solvent system that can be used to investigate the dilute solution properties and molecular weight of cellulose. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 347–353, 2004     

Molecular dimensions and melt rheology of an all‐aromatic liquid crystalline polymer

The molecular dimensions and melt rheology of a thermotropic all‐aromatic liquid crystalline polyester (TLCP) composed of p‐hydroxy benzoic acid, hydroquinone, terephthalic acid, and 2,4‐naphthalenedicarboxylic acid is examined. The Mark–Houwink exponent (α) of 0.95 is estimated for the TLCP. The persistence length estimated from molecular weight (M) and intrinsic viscosity ([η]) data using the Bohdanecky–Bushin equation is about 95 Å, whereas that estimated from light scattering data is 117 Å. These persistence lengths and the observed α value, both higher than those for flexible polymers, suggest that the present TLCP is a semirigid polymer. The zero shear melt viscosity (η₀) varies with approximately M⁶ for molecular weight M > 3 × 10⁴ g/mol; below this molecular weight, η₀ varies almost linearly with M. Widely different entanglement molecular weights (M_e) are predicted, depending on the method used; the plateau modulus estimates M_e of about 8 × 10⁵ g/mol, whereas the ratio of mean square end‐to‐end distance and molecular weight (〈R²〉₀/M) predicts M_e's either too small (0.33 g/mol) or too large (2.5 × 10⁶ g/mol), depending on the theory used. Although the change in the molecular weight dependency of melt viscosity appears to be associated with the onset of entanglement coupling of the semirigid molecules, its origin needs further investigation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2378–2389, 2001     

Anodic Stripping Voltammetric Determination of Lead（Ⅱ） Using Glassy Carbon Electrode Modified with Novel Calix[4] arene

A new glassy carbon electrode modified with novel calix[4]‐arene derivative was prepared and then applied to the selective recognition of lead ion in aqueous media by cyclic and square wave voltammetry. A new anodic stripping peak at ? 0.92 V (vs. Ag/Ag⁺) in square wave voltammogram can be obtained by scanning the potential from ? 1.5 to ? 0.6 V, of which the peak current is proportional to the concentration of Pb²⁺. The modified electrode in 0.1 mol/L HNO₃ solution showed a linear voltammetric response in the range of 2.0 × 10–⁸–1.0 × 10–⁶ mol/L and a detection limit of 6.1 × 10–⁹ mol/L. In the modified glassy carbon electrode no significant interference occurred from alkali, alkaline and transition metal ions except Hg²⁺, Ag⁺ and Cu²⁺ ions, which can be eliminated by the addition of KSCN. The proposed method was successfully applied to determine lead in aqueous samples.     

LIGHT SCATTERING OF POLYSACCHARIDE FROM LACQUER IN AQUEOUS SOLUTION

The polysaccharide having weight-average molecular weight M_w=1. 09×10~5, isolated from the sap of lac trees (Vietnam), was separated into 12 fractions by aqueous-phase preparative gel permeation chromatography. The molecular weights and molecular weight distributions of the fractions were measured in aqueous 0.08M KCl/0.01 M NaAc and 0.4M KCl/0.05M NaAc at pH =7. 6 by light scattering, viscometry and gel permeation chromatography. The Mark-Houwink equation in aqueous 0.08M KCl/0.01M NaAc at 30℃was found to be [η]= 2.28×10~(-2) M_w~(0.52) (cm~3/g), which indicated the polysaccharide chain in the aqueous solution to be a spherical random coil.     

Counterion mixing effects on the conformational transitions of polyelectrolytes. I. Volume phase transition and coil‐globule transition of alkali metal poly(acrylate)s

Counterion mixing effects on the volume phase transition and the coil‐globule transition of alkali metal poly(acrylate)s (PAAM) in aqueous organic solvents were investigated by observing the swelling behavior of PAAM gel and by measuring the solution viscosity and the conductivity as a function of the counterion mixing ratio. Marked transitions to the collapsed states were induced only for Li⁺/Cs⁺ system in most solvent systems; namely, PAA gel significantly collapsed in the presence of Li⁺ and Cs⁺ counterions irrespective of the solvent species employed, while only a slight deswelling was observed for Li⁺/K⁺ system in some aqueous organic solvents. Corresponding specific decrements in the solution viscosity and conductivity were also confirmed for the combination of Li⁺ and Cs⁺ in aqueous dimethyl sulfoxide (DMSO) system. A simple analysis of the conductivity decrement observed for Li⁺/Cs⁺ system in 60 vol % DMSO suggested that only Cs⁺ is tightly bound upon addition of Li⁺ while no restriction is induced for Li⁺ upon mixing with Cs⁺. A working hypothesis is proposed for the apparently intriguing behaviors of the counterions in the mixed system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2122–2131, 2009