Estimation of the contribution of tube renewal in the terminal relaxation of linear polybutadiene

A set of low-molecular-weight (low-MW) entangled linear polybutadienes with molecular weights between 1.1 × 10⁴ and 2.5 × 10⁵ have been dilutedly embedded in a high-molecular-weight linear polybutadiene (M_w = 7.6 · 10⁵) matrix. The viscoelastic properties of these blends with 9.1% low-MW polymer have been measured. The loss moduli-frequency master curves, G^″ (Щ), contain contributions from both polymers. The contribution of the low-MW polymer is obtained by subtracting the contribution of the matrix. The maximum in G^″, G^″_m, due to the low-MW polymer occurs at a lower frequency (0.3 to 0.5 log units) than in the homopolymer. This result indicates that the longest relaxation time of the entangled linear polymer embedded in a high-molecular-weight matrix is increased by a factor of 2.0 to 3.0 because tube renewal normally operating in the homopolymer is almost completely absent in the matrix. The longest relaxation time of the polymers in the matrix depends on M^3.3₀. This is only slightly less than the dependence found in linear polymer melts (M^3.3₇). This indicates that reptation and chain-end fluctuation together contribute to the relaxation of linear polymers in permanent networks.     

Effect of the wall Nusselt number on the simulation of catalytic fixed bed reactors

Literature correlations for the apparent wall heat transfer coefficient (h_w) in fixed bed catalytic reactors are compared. At low to moderate values of the Reynolds number (Re), different correlations can produce estimates of the dimensionless wall Nusselt number (Nu_w = h_wd_p/k_f) that differ by an order of magnitude or more. Some correlations give Nu_w as a function of Re only, others allow for the effects of tube-to-particle diameter ratio and particle and fluid thermal conductivities. The value of Nu_w that is used in a simulation of a fixed bed catalytic reactor can have a strong effect on the predicted behavior. Two examples of fixed bed reactors are simulated and show that the more general correlations for Nu_w are to be preferred.     

超重力精馏回收果胶沉淀溶剂的应用

同时应用超重力精馏连续与间歇操作分离回收果胶沉淀溶剂中的乙醇,并以不锈钢波纹丝网为填料,在原料乙醇质量分数x_f=55%、回流比R=4、超重力因子β=63.16～252.67、原料流量F=15～50L/h、1.01×10⁵Pa和室温进料下操作,研究了四级超重机在连续精馏过程中的传质性能;并在β=161.71、R=2.5～7及1.01×10⁵Pa操作条件下,考察了间歇精馏过程中不同回流比R对塔顶和塔底乙醇浓度x_d和x_w的影响.结果表明,在连续精馏过程中,理论塔板数N_T随β和F的增大而增加,设备的等板高度HETP为41.12～58.21mm,x_d=93%,x_w=35%;在间歇精馏过程中,x_d随着R的增大先增高后降低,x_w随着R和t的增大而下降,所得产品x_d为92.5%,x_w为1.05%;乙醇分离回收效果良好,回收率为91.28%,单位回收乙醇产品成本为0.644元/L,充分表现出超重力精馏工艺应用于果胶沉淀溶剂的回收再利用的优势.     

氯化1-{2-[双(2-氨基乙基)氨基]乙基}吡啶离子液体的合成及在ATRP反应中的应用

采用N-烷基化方法将二乙烯三胺（DETA）接枝到氯化1-氯乙基吡啶离子液体[CePy]Cl上,合成了离子液体氯化1-{2-[双（2-氨基乙基）氨基]乙基}吡啶（[N₃Py]Cl）,通过FTIR、¹H NMR和MS等测试手段对合成离子液体的结构进行了表征。采用循环伏安法对离子液体配合物[N₃Py]Cl/CuBr和有机配合物PMDETA/CuBr的氧化还原电位（E_1/2）进行测试,结果表明：合成的离子液体[N₃Py]Cl和CuBr形成配合物的氧化还原电势为E_1/2=-0.541V,比常用的有机配合物PMDETA/CuBr（E_1/2=-0.142V）具有更低的氧化还原电势。将离子液体[N₃Py]Cl与CuBr配位形成催化体系,在离子液体[AMIM]Cl中催化甲基丙烯酸甲酯（MMA）的原子转移自由基聚合（ATRP）反应。结果表明,当配体、催化剂和溶剂的用量分别为n（CuBr）=0.19mmol、n（[N₃Py]Cl）=1.13mmol、n（[AMIM]Cl）=0.02mol,反应温度60℃,反应时间4h时,单体转化率高达75%,分子量分布较窄（M_w/M_n=1.24）,ATRP反应具有明显的可控性能。     

原位构建富氟SEI的凝胶电解质用于金属锂二次电池

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质,同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface,SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后,锂负极表面没有明显的锂枝晶和被损毁的形貌出现;XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下,稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中,促进了LiPF₆分解反应平衡的正向移动,在锂负极表面形成稳定的富含LiF的SEI,能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。     

商业正渗透膜的改性及其用于处理焦化废水的研究

正渗透技术是一种新兴的膜分离技术,在处理有机废水方面具有广阔的应用前景。分别对Poten以及HTI商业正渗透膜进行改性,并用于对焦化废水中难降解毒性小分子(吲哚和吡啶)的截留测试。探究了水相单体PIP浓度、膜朝向、汲取液浓度对改性前后两种膜水通量、J_s/J_w比值、有机物截留率的影响,以及改性前后两膜特征参数的变化。结果表明：对Poten膜和HTI膜进行界面聚合改性后,膜水通量以及J_s/J_w比值都不同程度地降低;改性后的两正渗透膜水渗透系数A、盐渗透系数B均降低,而膜结构参数S以及对NaCl和有机物的截留率均提高;其中HTI-IP复合膜对有机物的截留率(81%)明显高于IP-2(改性Poten膜)复合膜;与FO模式相比,IP-2复合膜在PRO模式下(汲取液面向活性层)具有更高的水通量及反向盐通量。此外,在两种膜朝向下,水通量及反向盐通量都随汲取液浓度的增大而增大,但是在FO模式下(料液面向活性层),通量呈现非线性增长。     

原位构建富氟SEI的凝胶电解质用于金属锂二次电池

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质,同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface,SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后,锂负极表面没有明显的锂枝晶和被损毁的形貌出现;XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下,稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中,促进了LiPF₆分解反应平衡的正向移动,在锂负极表面形成稳定的富含LiF的SEI,能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。     

Solubility of polyethylene in n-pentane at high pressures

The high pressure solubility of polyethylene standards (M_w = 2100, 16400, 108000 and 420000 and M_w/M_n = 1.14, 1.16, 1.32 and 2.66, respectively) in n-pentane has been studied. Concentrations of up to 15 wt% polymer have been investigated. For each polymer sample and concentration, pressures that are required to achieve single-phase solutions have been determined over a range of temperatures. The solutions are found to all show lower critical solution temperatures. Demixing pressures are observed to depend strongly on the molecular weight of the polymer.     

Homogeneous reverse atom transfer radical polymerization of glycidyl methacrylate and ring-opening reaction of the pendant oxirane ring

The homogeneous reverse atom transfer radical polymerization (reverse ATRP) of glycidyl methacrylate (GMA) was carried out in bulk, using 2,2′-azobisisobutyronitrile (AIBN) as the initiator and N,N-n-butyldithiocarbamate copper (Cu(SC(S)N(C₄H₉)₂)₂) as the catalyst. The polymerization showed typical controlled/‘living’ polymerization behavior, i.e. first-order kinetics, well-controlled molecular weight (M_n) and narrow molecular weight distribution (M_w/M_n). ¹H NMR and IR spectra showed that the pendant epoxy groups in PGMA polymer remained intact throughout the polymerization of GMA. A phosphorated PGMA (PPGMA) polymer was obtained by phosphonation reaction of the pendant epoxy groups in PGMA with diphenylphosphinic chloride (DPPC). Thermal behavior of the PPGMA was studied by TG and DTG. A major DTG peak at 340 °C was observed for the PPGMA.     

Critical extent of reaction of a polydimethylsiloxane polymer network

A direct rheological technique was used to measure the critical time for gelation, t_c, of a well characterized polydimethylsiloxane (PDMS) polymer network. This technique is based on the observation that the gel point of crosslinking systems occurs at the instant at which the viscoelastic behaviour reduces to power-law relaxation (critical state described by the gel equation). The extent of reaction, p(t), was measured by a Fourier-transform infra-red method. The measured value of the critical extent of reaction, p_c = p(t_c) = 0.57 ± 0.01, agrees extremely well with the value predicted by mean-field theory. This agreement is an independent confirmation of the observation that power-law relaxation is a property of the polymer at the gel point.     

异山梨醇与碳酸二甲酯两步法合成聚碳酸酯的工艺

研究了以碳酸铷（Rb₂CO₃）和乙酰丙酮锂（LiAcac）为催化剂,异山梨醇（IS）和碳酸二甲酯（DMC）为原料合成聚碳酸酯（PC）的工艺过程。优化了酯交换反应催化剂用量、原料配比、缩聚反应催化剂用量、缩聚反应温度以及缩聚反应停留时间,并对酯交换产物和聚碳酸酯产品进行了红外光谱、核磁氢谱、核磁碳谱和热重分析,得到较优工艺条件为：Rb₂CO₃用量1×10^-3mol/mol_IS、原料配比n(DMC)/n(IS)=14、LiAcac用量2×10^-3mol/mol_IS、缩聚温度225℃、缩聚停留时间4h,所得的PC产品特性黏数可达36.55mL/g,数均分子量（M_n）为30659,重均分子量（M_w）为42551,M_w/M_n为1.39,色差为6.92,玻璃化转变温度（T_g）为155.6℃。     

聚合植物油脂表面活性剂的制备及其结构与性能

采用环氧大豆油(ESO)为原料,乙酸乙酯为溶剂,四氯化锡为催化剂,通过环氧大豆油的开环自聚,制备聚合环氧大豆油(PESO);再将PESO在碱性条件下水解,洗涤纯化后得到水解聚合环氧大豆油(HPESO)。通过傅里叶红外光谱(FTIR)、核磁共振氢谱(¹H NMR)和凝胶渗透色谱(GPC)对HPESO的结构及分子量分布进行了表征,并对得到的水解聚合环氧大豆油脂肪酸钾盐表面活性剂(HPESO-K)的临界胶束浓度cmc及其表面张力(γ_cmc)、Krafft点(KP)、液体石蜡/水体系的乳化能力(EP)与抑泡及消泡能力(FP)进行了研究。结果表明:HPESO的数均分子量范围为1056～1156g/mol,重均分子量范围为1255～1374g/mol。在水溶液pH值为9～12条件下,HPESO-K的cmc值为0.13～0.41g/L,γ_cmc值为25.6～31.2mN/m。在水溶液pH=9条件下测得HPESO-K的Krafft点为37℃,液体石蜡/水体系中分出10mL水的时间为130s,亲水亲油平衡(HLB)值范围为10～11。     

玉米芯木聚糖的提取及其相对分子质量分布研究

通过碱性过氧化氢溶液提取玉米芯半纤维素，单因素试验结果表明：在1% H₂O₂、5% NaOH的碱性过氧化氢溶液中，反应温度50℃、反应时间16 h、液固比为20：1（mL：g），木聚糖得率可达83.15%。采用梯度乙醇分级沉淀法进行半纤维素的分离实验，考察了真空冷冻和烘干方式对产物性能的影响。采用高效离子色谱测定半纤维素单糖组成，并用FT-IR、TG、¹H NMR、¹³C NMR和GPC对半纤维素进行分析与表征。结果表明：各级分由木糖、葡萄糖、阿拉伯糖等组成，玉米芯中半纤维素主要由L-阿拉伯糖-（4-O-甲基-D-葡萄糖醛酸）木聚糖构成；支化度（w（阿拉伯糖）/w（木糖））为0.17~0.52，且随着乙醇体积分数的增加而变大。干燥方式对产物的相对分子质量影响很大，真空冷冻干燥的木聚糖重均相对分子质量（M_w）为108 533~197 752，真空干燥的M_w为41 231~47 242；2种干燥方式所得12种级分中，分散系数为1.172~1.517，其中11种产物分散系数小于1.5，为分布均一的低分散度木聚糖。     

Effect of swirling addition on the liquid mixing performance in a T-jets mixer

Swirling addition to the stream is beneficial for the fluid mixing. This work aims to study the mixing process intensification in a conventional T-jets mixer by the swirling addition. After experimental verification by the planar laser-induced fluorescence technique, large eddy simulation with the dynamic kinetic energy sub-grid stress model is used to predict how the swirling strength (in terms of swirling number, S_w) and swirling directions affect the mixing performance, e.g. the tracer concentration distribution, mixing time, and turbulent characteristics in the T-jets mixers. Predictions show that the swirling strength is the key factor affecting the mixing efficiency of the process. The overall mixing time, τ₉₀, can be significantly reduced by increasing S_w. Vortex analysis shows that more turbulent eddies appear in the collision zone and the turbulent kinetic energy dissipation rate increases obviously with the swirling addition. When S_w is kept constant, the mixing process can be accelerated and intensified by adding swirling to only one stream, to both streams with the opposite swirling directions, or to both streams with the same swirling directions. Amplification of the mixing process by enlarging the mixer size or increasing the flow rates is also optimized. Thus, this work provides a new strategy to improve the mixing performance of the traditional T-jets mixers by the swirling addition.     

Direct Correlation Between Adhesion Promotion and Coupling Reaction at Immiscible Polymer-Polymer Interfaces

Hugh Brown has shown that interfacial entanglements govern adhesion between two polymers. We demonstrate this for three systems by adding interfacial chains via chemical coupling. The adhesion between polypropylene (PP)/amorphous polyamide (aPA) was reinforced by the coupling reaction of maleic anhydride grafted PP (PP-g-MA) and the primary amine groups on aPA; huge increases in adhesion were observed. A good correlation between critical fracture toughness, G_c, and PP-g-MA concentration squared follows Brown's crazing mechanism. For a polystyrene (PS)/aPA interface reinforced by the coupling reaction of poly(styrene-r-maleic anhydride) (PS-r-MA)/aPA only modest adhesion increases in G_c were observed through the whole PS-r-MA concentration range. This different behavior of G_c vs. functional polymer concentration is believed to be caused by segregation of the formed graft copolymers at the interface. The relationship between G_c and the extent of coupling was studied quantitatively with a model PS/PMMA system. The interface was reinforced by the coupling reaction of 0-10% PS-NH₂/PMMA-anh. G_c was measured with the asymmetric dual cantilever beam test (ADCB) and the amount of copolymer formed at the interface was determined by a fluorescence labeling technique. G_c is low and is linear in block copolymer interfacial coverage (Σ), indicating a chain scission mechanism. Reasonable agreement was achieved between experiment and theoretical prediction based on the energy to break C-C bonds.     

Polymers of carbonic acid: 13. Polymerization of cyclotrimethylenecarbonate with tin tetrahalides

Polymerizations of cyclotrimethylenecarbonate (TMC) with SnCl₄, SnBr₄ were and SnI₄ were conducted in bulk. The reaction time, the temperature and the monomer/initiator (M/I) ratio were varied, and the influence of these parameters on yields and molecular weights was investigated. Yields above 90% were obtained with all these initiators, but the highest molecular weights (M_w ≈ 1.5 × 10⁵) resulted from SnI₄-initiated polymerizations. SnI₄ has the additional advantage that the polycarbonates were free of ether groups when prepared at moderate temperatures (e.g. 60°C). In contrast, SnCl₄ and SnBr₄ cause partial decarboxylation even at 60°C, and at higher temperatures up to 20 mol% of the carbonate groups may be replaced by ether linkages. Furthermore, mechanistic studies were conducted. SnCl₄ and SnBr₄ form solid 1:2 complexes with TMC at 20–25°C. Infra-red, ¹H and ¹³C nuclear magnetic resonance (n.m.r.) spectroscopies indicate complexation at the carbonyl oxygen. Kinetic measurements of polymerizations in solvents of different polarity suggest cationic polymerization mechanisms. In addition to CH₂---OH, CH₂Cl and CH₂Br end groups were detected by ¹H n.m.r. spectroscopy. The endgroup analyses of reaction mixtures and isolated poly(TMC) support the assumption of a cationic polymerization mechanism.     

Polymerization of norbornene using novel palladium carboxylate/boron trifluoride etherate catalyst system

The vinyl polymerization of norbornene with Pd(carboxylate)₂/BF₃OEt₂ catalyst system has been investigated by varying the molar cocatalyst/metal ratio, the norbornene/metal ratio, the metal concentration and the reaction temperature. The effects on the catalyst activity were explained on the basis of complexation equilibrium for the active homogeneous complex. A “particular” activity of 154 100 kg NB per mole Pd for an hour has been achieved at B/Pd = 25 and 25 °C. The molecular weights M_w from 77 700 to 293 800 g/mol and glass transition temperatures T_g from 240 to 262 °C were observed for the representative samples of polynorbornene. The molar mass distribution indicates a single-site, highly homogeneous character of the active catalyst species. Catalytic activity and polymer molecular weight can be controlled by varying the reaction parameters over a wide range. NMR and IR spectroscopic studies of the polymer showed 2,3-enchained repeating units of polymer backbone with low diisotacticity. The simplicity of catalyst system composition might be of industrial importance.     

The problem of correction for ohmic potential drop in linear potential sweep experiments and the derivation of s0 values for electrode surface processes

Rate constants or exchange current densities of electrode surface processes involving adatom arrays are conveniently evaluated by determining that sweep rate, s₀ (the reversibility parameter), in a linear potential sweep (LPS) experiment, below which the process just remains kinetically reversible, ie its overpotential is sensibly zero. Transition to irreversibility is characterized by peak potentials, E_p, becoming linear in the log of the sweep rate, s, following a region of independence of s for < s₀. A suitable extrapolation procedure enables s₀ to be evaluated. However, if s₀ is large and/or the resistivity of the solution is appreciable, the IR_u drop associated with uncompensated resistance in the measurement system can be comparable with the increase of E_p with log s, when s > s₀, rendering evaluation of s₀ inaccurate. While compensation or empirical correction for this may be made, it is desirable that the nature of the IR_u effect of the LPS I vs E profiles be understood in a more fundamental way. It is the purpose of this communication to provide such a treatment of this effect through evaluation of the actual time-dependent potential that becomes applied to the electrode, and to propose criteria based on the product of s₀, R_u and the reaction pseudocapacitance, C_φ for indicating the anticipated extent of the IR_u effect in the evaluation of s₀. While the transition in the E_p vs log s plot may be due to IR_u effects as well as to kinetic irreversibility, when the former are appreciable, it is shown that the corresponding transition in the value of C_φ with increasing log s can usually allow spurious IR_u and significant irreversibility effects to be distinguished.     

Correlation between equation of state and temperature and pressure dependence of self-diffusion coefficient of polymers and simple liquids

Correlation between the equation of state and the temperature dependence of the self-diffusion coefficient D for polymers such as polystyrene (PS) and polydimethyl siloxane (PDMS) and simple liquids such as argon, methane and benzene and the pressure dependence of D for oligomers such as dimethyl siloxane (DMS) and simple liquids such as cyclohexane and methanol has been examined based on the equation of state derived previously. The experimental data used were published by Antonietti et al. and McCall et al. for polymers, by McCall for linear dimethylsiloxanes and by Jonas et al. and Woolf et al. for simple liquids. The expression for D in this work is given by

where A₁(M) is a function of molecular weight M_w, C₁(T) and P₁(T) are functions of temperature and B₁, n₁ and m₁ are constants determined experimentally. For simple liquids, the values of n₁ obtained range from 0.3 to 1.2, with an average , and m₁ is in the range 0.5–1.2, with . For polymers, values of n₁ are in the range 2.5–7.0 for PS and 0.5–1.3 for PDMS and m₁ for DMS is in the range 0.8–1.0. The relation Dη/T = f(M) is found to be useful for simple liquids over a wide range of temperature including the critical region and for pressures up to ≈5 kbar

1 kbar = 100 MPa There is a close correlation between ln(D/T) and _p and β_T through ln(D/T)ln D_c−⁻¹_p−β⁻¹_T, where D_c is D at the critical temperature and _p and β_T are the thermal expansion coefficient and compressibility, respectively. The molecular weight dependence of D for polymers and simple liquids is discussed based on the experimental data and recent theory of Doi and Edwards. A new model for the mechanism of self-diffusion in the liquid state is proposed.     

螺环二醇改性PET共聚酯的合成及性能

为了扩大聚对苯二甲酸乙二醇酯（PET）的应用范围,常通过引入第三单体来改变其性能。本研究以螺环二醇（SPG）为原料,采用酯交换法熔融缩聚合成了一系列不同单体含量的共聚酯。采用超高效聚合物色谱-多角度激光光散射仪（APC-MALLS）联用分析了共聚酯的分子量与分子量分布,利用核磁氢谱（¹H NMR）、傅里叶红外光谱（FTIR）研究了共聚酯的化学结构,同时采用差示扫描量热仪（DSC）、热重分析仪（TGA）和X射线衍射仪（XRD）研究了共聚酯的热性能以及结晶性能,测试了共聚酯的拉伸性能。结果表明,成功合成了符合纤维级聚酯数均分子量（M_n）和重均分子量（M_w）要求的共聚酯,分子量分布较窄,随着第三单体含量的增加,玻璃化转变温度从77℃提升至85℃,而熔融温度从255℃降低至222℃,热分解温度无明显变化,结晶性能下降。