N-异丙基丙烯酰胺温度敏感性水凝胶相转变动力学研究及其应用

研究指出表观二级动力学方程可以很好地描述N-异丙基丙烯酰胺水凝胶的溶胀和消溶胀动力学.即溶胀动力学方程为dR/dt=k_1(R_e-R)~2,消溶胀动力学方程为-dR/dt=k_c(R-R_e)~2.把这种水凝胶用于分离高分子水溶液时可引入“单位溶张比分离循环的合理时耗”这样一个参量.它根据溶胀和消溶胀过程中的起始溶胀比、平衡溶胀比、表观溶胀动力学常数和表观消溶胀动力学常数求出.具体公式为△t_1(T_s,T_c)=2/[R_c(T_s)-R_0(T_s)]~2k_s(T_s)+15/[R_0(T_c)- R_s(T_c)]~2k_c(T_c)~(1/2)在理想情况下,分离过程的“总合理时耗”与△t_1成正比,比例系数为分离过程中的除水总量与干凝胶用量的比值,即△t_r=W_W/W_G·△t_1.当根据二个动力学方程求得的总时耗计算值处于(0.9△t_r,1.1△t_r)范围内时,表明所选干凝胶用量和循环溶胀比区段均合适.     

三代碳硅烷光致变色液晶树状物的光化学研究——端基含108个4-丁氧基偶氮苯介晶基元

报道了新化合物含108个丁氧基偶氮基元端基的三代(D3)碳硅烷光致变色液晶树状物在各溶液中的反-顺光异构化(光致变色)反应速率常数k_p, 光化学回复异构化正/逆反应速率常数k_t和k_c, 热回复异构化反应速率常数k_H, 光化学回复异构化反应平衡常数k_t/k_c, 活化能E, 异构化转换率及热回复异构化反应中的反-顺异构体组分比. D3的光致变色反应速率常数为10^－1 s^－1, 而含偶氮基元的光致变色液晶聚硅氧烷的光致变色反应速率常数为10^－8 s^－1, 因此, D3的光响应速度比后者快10⁷倍.     

从DSC曲线数据计算/确定含能材料自催化分解反应动力学参数和热爆炸临界温升速率的方法

为应用热爆炸临界温升速率(dT/dt)_Tb评价含能材料(EMs)的热安全性, 得到计算(dT/dt)_Tb值的基本数据, 用合理的假设, 由Semenov的热爆炸理论和9 个自催化反应速率方程[dα/dt=Aexp(-E/RT)α(1-α) (I), dα/dt=Aexp(-E/RT)(1-α)ⁿ(1+K_catα) (II), dα/dt=Aexp(-E/RT)[α^a-(1-α)ⁿ)] (III), dα/dt=A₁exp(-E_a1/RT)(1-α)+A₂exp(-E_a2/RT)α(1-α) (IV), dα/dt=A₁exp(-E_a1/RT)(1-α)^m+A₂exp(-E_a2/RT)αⁿ(1-α)^p (V), dα/dt=Aexp(-E/RT)(1-α) (VI), dα/dt=Aexp(-E/RT)(1-α)ⁿ (VII), dα/dt=A₁exp(-E_a1/RT)+A₂exp(-E_a2/RT)(1-α) (VII), dα/dt=A₁exp(-E_a1/RT)+A₂exp(-E_a2/RT)α(1-α) (IX)]导出了计算(dT/dt)_Tb值的9 个表达式. 提出了从不同恒速升温速率(β)条件下的差示扫描量热(DSC)曲线数据计算/确定EMs自催化分解反应的动力学参数和自催化分解转向热爆炸时的(dT/dt)_Tb的方法. 由DSC曲线数据的分析得到了用于计算(dT/dt)_Tb值的β→0 时的onset 温度(T_e0),热爆炸临界温度(T_b)和相应于T_b时的转化率(α_b). 分别用线性最小二乘法和信赖域方法得到方程(I)和(VI)及方程(II)-(V)和方程(VII)-(IX)中的自催化分解反应动力学参数. 用上述基础数据得到了EMs的(dT/dt)_Tb值. 结果表明: (1) 在非等温DSC条件下硝化棉(NC, 13.54% N)分解反应可用表观经验级数自催化反应速率方程dα/dt=10^15.82exp(-170020/RT)(1-α)^1.11+10^15.82exp(-157140/RT)α^1.51(1-α)^2.51描述; (2) NC (13.54% N)自催化分解转向热爆炸时的(dT/dt)_Tb值为0.103 K·s^-1.     

用钛系载体高效催化剂进行乙烯-丙烯-1-丁烯三元共聚合的研究 Ⅰ.聚合条件对共聚合反应的影响

 用多组份改性钛系载体催化剂TiCl₄,Ti(OBu)₄/MgCl₂/Ethylbenzeate(EB)/φ₂SiCl₂/AlEt₃进行了乙烯-丙烯-1-丁烯三元共聚合的研究。考察了单体进料比、聚合温度,烷基铝浓度和催化剂浓度等条件对共聚合的影响。发现本催化剂对乙丙丁三元共聚合有极高的催化效率,聚合1h达8.6×10⁴g共聚物/g-Ti。共聚合速率衰减符合动力学方程:R_s=R_s+(R₀—R_s)_e^βs。     

联合处理电位法和极谱法得到的实验数据确定金属配合物稳定常数(英)

The cadmium(Ⅱ)-glycinamide system was modeled and its stability constants were calculated by a unified mathematical treatment for experimental data obtained from ion selective electrode (ISE) and differential pulse polarography (DPP). It has been shown that very much the same experimental complex formation curve (ECFC) and theoretical complex formation curve (TCFC) could be given from both experimental techniques for the same experimental conditions, such as the same total ligand c(L_T) and metal ion c(M_T) concentrations. The combination of the two techniques is of many advantages as ISE can be performed at low a c(L_T)∶c(M_T) ratio and significantly higher c(M_T), whereas DPP could be used well at larger the c(L_T)∶c(M_T) ratio and very low c(M_T). This makes it possible to study a metal-ligand system in much broader range of experimental conditions that, in turn, provides us more data and information about the metal-ligand system of interest. Application of the unified mathematical treatment to the cadmium-glycinamide system in this paper, three new complexes MHL, ML₃ and ML₃(OH) as well as two complexes ML and ML₂, reported in literatures, could be modeled and all their stability constants have been refined.     

蝎型铜配合物：Cu2[ μ-pz]2[HB(pz)3]2和Cu[B(pz)4]2的合成、结构及热分解动力学性质

本文设计合成了两种以聚吡唑硼酸盐、吡唑为配体的铜配合物Cu₂[ μ-pz]₂[HB(pz)₃]₂(1)和Cu[B(pz)₄]₂(2)(pz：吡唑(C₃H₄N₂))。运用元素分析、红外光谱对配合物进行了表征，并用X-ray衍射测定了它们的晶体结构。非等温热分解动力学研究表明：配合物1的热分解反应分两步，配合物2的热分解反应一步进行。通过计算，配合物1热分解的第一步反应的可能机理为成核与生长，n=1/4；第二步反应的可能机理为化学反应。其非等温动力学方程分别为：dα/dT=A/β e^-E/RT·1/4(1-α)[-ln(1-α)]^-3和dα/dT=A/β e^-E/RT·(1-α)²。分解反应的表观活化能分别是520.37 kJ·mol^-1和149.65 kJ·mol^-1；指前因子lnA分别是118.06 s^-1和28.10 s^-1。配合物2热分解的可能机理为化学反应。其非等温动力学方程为：dα/dT=A/β e^-E/RT·(1-α)²。分解反应的表观活化能是111.41 kJ·mol^-1；指前因子lnA是21.20 s^-1。     

纳米结晶体Ni0.5Zn0.5Fe2O4对高氯酸铵热行为及分解反应动力学的影响

采用差示扫描量热法(DSC)、热重和微分热重(TG-DTG)及固相原位反应池/快速扫描傅立叶变换红外联用技术(hyphenated in situ thermolysis/RSFTIR)研究了纳米结晶体Ni_0.5Zn_0.5Fe₂O₄与高氯酸铵(AP)组成的混合物的热行为和分解反应动力学。结果表明：Ni_0.5Zn_0.5Fe₂O₄使得AP的低、高温分解放热峰温分别提前17.44 K和27.74 K,并使得对应的分解热分别增加3.7 J·g^-1和193.7 J·g^-1。Ni_0.5Zn_0.5Fe₂O₄并不影响AP的晶转温度和晶转热。Ni_0.5Zn_0.5Fe₂O₄使得AP的TG曲线出现3个阶段,并使得后2个失重阶段的初始和终止温度都有所提前。凝聚相分解产物分析表明Ni_0.5Zn_0.5Fe₂O₄加速了凝聚相AP的分解及氨气的释放。含Ni_0.5Zn_0.5Fe₂O₄的AP的高温分解反应的动力学参数E_a=238.88 kJ·mol^-1,A=1018.59 s^-1,动力学方程可表示为dα/dt=10^18.99(1-α)[-ln(1-α)]^3/5e^-2.87×104T。始点温度(T_e)和峰顶温度(T_p)计算得出AP的热爆炸临界温度值分别为:574.83 K和595.41 K。分解反应的活化熵(ΔS^≠)、活化焓(ΔH^≠)和活化能(ΔG^≠)分别为:109.61 J·mol^-1·K^-1、236.49 kJ·mol^-1及172.58 kJ·mol^-1。     

New hexanuclear antiferromagnetic heterospin iron complex

Precise oxidation of Fe^II ₄(μ₃-OH)₂(OOCBu^t)₆(EtOH)₆ afforded the mixed-valent hexanuclear complex [Fe^II ₄Fe^III ₂(μ₄-O)₂(μ₃-OOCBu^t)₄(μ-OOCBu^t)₆(HOOCBu^t)₃(EtOH)]· ·HOOCBu^t. The structure of the latter was established by X-ray diffraction. The magnetic properties of the new complex were studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 900–903, May, 2006.     

1,3,3-三硝基氮杂环丁烷的热安全性

借助不同加热速率(β)的非等温DSC曲线离开基线的初始温度(T₀)、onset温度(T_e)和峰顶温度(T_p), Kissinger法和Ozawa法求得的热分解反应的表观活化能(E_k和E_O)和指前因子(A_k), Hu-Zhao-Gao方程ln β_i＝ln[A₀/(b_{e0 or p0}G(α))]＋   b_{e0 or p0}T_{ei or pi}求得的b_{e0 or p0}, Zhao-Hu-Gao方程ln β_i＝ln[A₀/((a_{e0 or p0}＋1)G(α))]＋(a_{e0 or p0}＋1) ln T_{ei or pi}求得的a_{e0 or p0}, 微热量法确定的比热容(C_p), 以及密度(ρ)、热导率(λ)和分解热(Q_d, 取爆热之半)数据, Zhang-Hu-Xie-Li公式、Hu-Yang-Liang-Xie公式、Hu-Zhao-Gao公式、Zhao-Hu-Gao公式、Smith方程、Friedman公式和Bruckman-Guillet公式, 计算了TNAZ在β→0时的T₀, T_e和T_p值(T₀₀, T_eo和T_p0)、热爆炸临界温度(T_be和T_bp)、绝热至爆时间(t_Tlad)、撞击感度50%落高(H₅₀)和热点起爆临界温度(T_cr), 得到了评价TNAZ热安全性的结果: T_SADT＝T_e0＝485.81 K, T_p0＝497.38 K, T_beo＝499.50 K, T_bp0＝513.45 K, t_Tlad＝8.90 s (n＝0), t_Tlad＝8.96 s (n＝1), t_Tlad＝9.01 s (n＝2), H₅₀＝28.88 cm, T_cr＝641.46 K (T_room＝293.15 K), T_cr＝658.89 K (T_room＝300 K), 表明: (1) TNAZ对热是稳定的; (2)撞击感度好于环三亚甲基三硝胺(RDX); (3)热点起爆临界温度高于RDX, 而界于1,3,5-三氨基-2,4,6-三硝基苯(TATB)和六硝基茋(HNS)之间.     

Ag(Ⅰ)、Pd(Ⅱ)异核金属簇合物的制备和晶体结构研究

The complexes of [Ag₂Pd₂(μ-dppm)₂(μ-S₂CNC₄H₈)₂(μ₃-S₂CNC₄H₈)₂](SbF₆)₂·Et₂O (1) and [AgPd(S₂CN C₄H₈)(μ-dppm)₂](SbF₆)·H₂O (2)were synthesized and their single crystal structures were determined by X-ray diffraction. The complex 1 is monoclinic system, space group P2₁/c with a=1.14370(3)nm, b=1.39025(4)nm, c=2.93579(8)nm, β=95.173(1)°, V=4.6490(2)nm³, Z=4, D_c=1.716g·cm^-3, μ(Mo Kα)=1682cm^-1, F(000)=2384, M_r=2401.98, R=0.0662, wR=0.1302. The complex 2 is monoclinic system, space group Cc with a=2.74136(6)nm, b=1.04317(2)nm, c=2.523990(10)nm, β=95.173(1)°, V=4.6490(2)nm³, Z=4, D_c=1.716g·cm^-3, μ(Mo Kα)=1682cm^-1, F(000)=2384, M_r=2401.98, R=0.0662, wR=0.1302. CCDC: 1, 213613; 2, 213612.     

HPAN/SPI水凝胶纤维的PH刺激响应性能

探索了聚丙烯腈(PAN)和大豆分离蛋白(SPI)在NaOH水溶液中进行PAN碱解,然后挤到凝固浴中凝固、交联,制备水解聚丙烯腈(HPAN)／SPI水凝胶纤维的方法。通过测定凝胶纤维的平衡溶胀伸长率和溶胀伸长率,观察到HPAN／SPI水凝胶纤维的滞后和可逆的伸长／收缩行为,同时在不同组成的凝胶纤维中,随着PAN含量的逐渐增大,水凝胶纤维的响应速率呈现由小到大然后减小的变化规律,当mPAN／mspt=6／4时有最好的响应性能。     

P(AA-DAC)两性聚电解质水凝胶的合成及性质

以丙烯酸(AA)和丙烯酰氧乙基三甲基氯化铵(DAC)为单体, 采用水溶液聚合法制备了P(AA-DAC)聚电解质水凝胶. 采用红外光谱和核磁共振等方法对其结构进行了表征. 研究了不同组成比的聚电解质水凝胶在去离子水、不同pH值溶液以及不同离子强度盐溶液中的溶胀行为. 研究结果表明, 摩尔比为1∶1的聚电解质水凝胶表现出典型的两性聚电解质凝胶的溶胀行为. 离子强度对其溶胀行为有着显著影响, 在溶液离子强度较高时, 凝胶网络的溶胀主要受溶剂向凝胶内部扩散所控制, 满足Fick型扩散规律n≤0.5, 随着溶液离子强度的增加, 凝胶网络平衡含水量增加, 扩散系数增大.     

聚乙烯醇/丙烯酸共聚物水凝胶的制备及溶胀性

制备了具有pH敏感性的聚乙烯醇(PVA)/丙烯酸(AA)共聚物水凝胶,研究了PVA与AA之间配比、交联剂、引发剂用量对凝胶转化率的影响,对水凝胶的溶胀行为和pH敏感性也进行了详细研究.实验表明PVA与AA的质量比为(1∶9)~(3∶7)之间时,引发剂和交联剂分别为PVA和AA总量的0.2%和0.3%时,凝胶转化率高.随着水溶液pH值从3增加到9,凝胶的溶胀比也相应的增加,表现出明显的pH敏感性.     

Design of a rate- and time-programming drug release device using a hydrogel: pulsatile drug release from kappa-carrageenan hydrogel device by surface erosion of the hydrogel

We have found that a repetitive pulsatile drug release with a certain time interval is observed from a monolithic hydrogel device by surface erosion of the hydrogel. As a model system of pulsatile drug release, dibucaine hydrochloride and kappa-carrageenan hydrogel were chosen as a drug and a device, respectively. Electrostatic interactions between dibucaine hydrochloride and kappa-carrageenan polymer segments are strong, since dibucaine hydrochloride is positively charged and each disaccharide repeating unit of kappa-carrageenan chains has one sulfate group. Dibucaine hydrochloride was loaded into the hydrogel by immersing dry kappa-carrageenan hydrogel disks in a dibucaine hydrochloride solution for 24 h. The pulsed release of dibucaine hydrochloride from the device was observed every 50 min between 30 and 250 min after the release starts. The weight of kappa-carrageenan hydrogel decreases in an oscillatory manner with time in distilled water. The oscillatory changes observed in the hydrogel weight in distilled water are considered to be caused by influx and efflux of water molecules into and from the surface and core of the hydrogel and by polymer liberation from the hydrogel. This phenomenon was well explained by our kinetic model [Colloids and Surfaces B 8 (1996) 93-100]. The time interval between pulses observed in drug release coincides with that observed in the oscillatory weight change of the hydrogel. From these, it was concluded that the pulsatile release of dibucaine hydrochloride from the device was caused by the pulsatile liberation of swollen kappa-carrageenan hydrogel from the surface of the device.     

Zymomonas mobilis as catalyst for the biotechnological production of sorbitol and gluconic acid

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free (CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/L (glucose plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 U/L. The concentration of the products varied hyperbolically with time according to the equations (GA)=t(GA)(max)/(W(GA) +t), (SOR)=t (SOR)(max)/(W(Sor)+t), v(GA)=[W(GA) (GA)(max)]/(W(GA)+t)(2) and V(SOR)=[W(SOR) (SOR)(max)]/(W(SOR)+t)(2). Taking the test carried out with free CTAB-treated cells as an example, the constant parameters were (GA)(max)= 541 g/L, (SOR)(max)=552 g/L, W(GA)=4.8h, W(SOR)=4.9h, upsilon(GA)=112.7 g/L. and upsilon(SOR)=112.7 g/L.     

Preparation and characterization of a novel IPN hydrogel memberane of poly(N-isopropylacrylamide)/carboxymethyl chitosan (PNIPAAM/CMCS)

A novel type of interpenetrating polymer networks (IPN) hydrogel membrane of poly(N-isopropylacrylamide)/carboxymethyl chitosan (PNIPAAm)/(CMCS) was prepared, and the effects of the feed ratio of components, swelling medium and irradiation dose on the swelling and deswelling properties of the hydrogel was systematically studied. The results showed that the introduction of CMCS did not shift the LCST (at 32 °C), which is similar to the pure PNIPAAm. The lowest swelling ratio was at pH 2. There was little influence of irradiation dose on the thermo- and pH-sensitivity of the IPN hydrogel, increasing dose only decreased the swelling ratio. The PNIPAAm:CMCS=1:4 w/w hydrogel was not thermo-sensitive in distilled water, whereas it showed a discontinuous volume phase transition in pH 2 and a continuous one in pH 8 buffer. Consequently, a combination of pH and temperature can be coupled to control the responsive behavior of these hydrogels.     

ABSORPTION OF METAL IONS AND SWELLING PROPERTIES OF POLY(ACRYLIC ACID-CO-ITACONIC ACID) HYDROGELS

Hydrogels of acrylic acid and itaconic acid has been synthesized with different monomers ratios. The swelling process of the different xerogels immersed in water and salt solutions has been studied. The swelling of hydrogels loaded with metal cations (Cu²⁺, Zn²⁺) was also investigated. The swelling process was monitored by the increase in the weight of hydrogel as a function of time. The absorption properties of metal ions were studied by using the hydrogel, and different concentrations of copper and zinc solutions (prepared from sulphate salts). The influence of pH on the absorption process was studied. For the absorption of metal ions, the amount of ions absorbed within the hydrogel can be calculated from the initial and equilibrium concentrations of the metal ions in aqueous phase, the weight of the hydrogel, and the volume of solution used. Metal absorption increased when pH, salt concentration in external solution and itaconic acid content is levelled.

The swelling isotherms which consisted of an initial fast increase levelled off asymptotically to the equilibrium swelling limit. The experimental data clearly suggest that our hydrogels follow a second-order kinetics for both cases (unload and metal loaded). The kinetics rate constant and the equilibrium water content, K, have been calculated for every monomer ratio from the experimental data according to the kinetics equation. Both magnitudes decreased as the itaconic acid content decreases in the xerogels.     

Radiation Synthesis of Superabsorbent Hydrogels Based on Chitosan and Acrylic Acid for Controlled Drug Release

Superabsorbent hydrogels based on the natural polymer chitosan and acrylic acid (CS/AAc) was prepared using ⁶⁰Co gamma radiation as a source of initiation and crosslinking. The factors, which affect the preparation of CS/AAc hydrogels such as irradiation dose, CS/AAc ratios, and acrylic acid monomer concentrations, to get the best optimum conditions, were investigated. The kinetic studies of the swelling of CS/AAc hydrogel showed that it follows a Fickian type of water diffusion. The Fickian constant value ‘n’ was more than 0.5 with a high swelling capacity of 300 g/g as superabsorbent hydrogel. In addition, the suitability of CS/AAc hydrogel as carrier material for the drug Chlortetracycline-HCl has been investigated by adsorption isotherm studies. The performance of drug release from hydrogel systems, influenced by acrylic acid ratio and the effect of pH of the medium was studied.     

Design of a rate- and time-programming drug release device using a hydrogel: pulsatile drug release from κ-carrageenan hydrogel device by surface erosion of the hydrogel

We have found that a repetitive pulsatile drug release with a certain time interval is observed from a monolithic hydrogel device by surface erosion of the hydrogel. As a model system of pulsatile drug release, dibucaine hydrochloride and κ-carrageenan hydrogel were chosen as a drug and a device, respectively. Electrostatic interactions between dibucaine hydrochloride and κ-carrageenan polymer segments are strong, since dibucaine hydrochloride is positively charged and each disaccharide repeating unit of κ-carrageenan chains has one sulfate group. Dibucaine hydrochloride was loaded into the hydrogel by immersing dry κ-carrageenan hydrogel disks in a dibucaine hydrochloride solution for 24 h. The pulsed release of dibucaine hydrochloride from the device was observed every 50 min between 30 and 250 min after the release starts. The weight of κ-carrageenan hydrogel decreases in an oscillatory manner with time in distilled water. The oscillatory changes observed in the hydrogel weight in distilled water are considered to be caused by influx and efflux of water molecules into and from the surface and core of the hydrogel and by polymer liberation from the hydrogel. This phenomenon was well explained by our kinetic model [Colloids and Surfaces B 8 (1996) 93–100]. The time interval between pulses observed in drug release coincides with that observed in the oscillatory weight change of the hydrogel. From these, it was concluded that the pulsatile release of dibucaine hydrochloride from the device was caused by the pulsatile liberation of swollen κ-carrageenan hydrogel from the surface of the device.     

PVA/PAA thermo-crosslinking hydrogel fiber: preparation and pH-sensitive properties in electrolyte solution

The preparation of thermo-crosslinking hydrogel fibers composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was presented. The hydrogel fiber was prepared by extruding the spinning dope from in situ polymerization of acrylic acid in the presence of PVA into coagulating bath of saturated ammonium sulfate aqueous solution. The network was formed by thermally heating the dried fibers under vacuum. The final hydrogel fibers exhibit pH-sensitive behavior and show hysteresis loop in the pH range from 2.5 to 12.5. The pH value at which the swelling ratio of the fiber had a jump shifted to lower value with increasing the PAA content within the network. Increasing the heating temperature and time for the fibers, the swelling ratio decreased and the jump point pH shifted to higher pH value. The oscillatory swelling/contracting behavior of the hydrogel fiber exhibited a well reversible pH-responsive property.