Rheological changes for urethane polymerizations in bulk and in solution

Viscosity rise and extent of reaction were followed during the step growth polymerization of linear and branched urethanes in bulk and in solution. Results indicate that intra-molecular reaction may exist in both linear and branched systems. Adding solvent increases the extent of intra-molecular reaction. The system viscosity was found to correlate with CgM_w, where C is polymer concentration, g is the ratio of branched to linear polymer radii of gyration, and M_w is the weight-average molecular weight.     

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.     

Morphology and structure of poly(p-phenylene terephthalamide) crystallized from dilute organic solution

The high-temperature crystallization of poly(p-phenylene terephthalamide) (PPTA) from dilute organic solutions was achieved through the introduction of a non-solvent, or precipitating agent, at the desired crystallization temperature. The morphology and crystal structure were examined for crystals produced from PPTA polymer with two different molecular weights (M_w = 46000 and 3430 g mol⁻¹), using transmission electron microscopy. For the high-molecular-weight polymer, ribbon-like crystals were produced, while the low-molecular-weight polymer yielded small needles or platelets. In both cases, electron diffraction showed that the Northolt allomorph was obtained. For the high-molecular-weight polymer, the molecular axes were parallel to the ribbon axes in a chain-extended type structure. A hypothesis for the orientation of the low-molecular-weight PPTA in the small platelets, is also given.     

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℃。     

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.     

制备条件对壳聚糖/胶原蛋白海绵敷料性能的影响

为了改善壳聚糖/胶蛋白复合海绵辅料的性能,研究了壳聚糖相对分子质量、壳聚糖/胶原蛋白配比、交联剂用量的影响,并得出最佳条件.优化后的制备条件为壳聚糖相对分子质量为1.5×105Da、壳聚糖与胶原蛋白质量比为2:3,戊二醛添加量为1.5%,得到的复合海绵的各项性能都较好.扫描电镜观察复合海绵的孔径大小为100～150μm...     

Rosin derivatives: novel film forming materials for controlled drug delivery

Two new rosin derivatives (RD-1 and RD-2) were synthesized in the laboratory and evaluated for physicochemical properties, molecular weight (M_w), polydispersity (M_w/M_n) and glass transition temperature (T_g). Plasticizer free films of the derivatives were produced by casting/solvent evaporation method. The surface morphology (SEM), water vapour transmission and mechanical properties (tensile strength, percent elongation and modulus of elasticity) of the films were investigated. The derivatives were further evaluated for pharmaceutical film coating by characterizing the release of a model drug (diclofenac sodium) from non-pariel seeds (pellets) coated with the derivatives. Pellet film coating could be achieved without agglomeration of the pellets within a reasonable operation time. Drug release from the coated pellets was sustained up to 10 h with the two rosin derivatives. These findings suggest the possible application of rosin derivatives (RD-1 and RD-2) for film coating.     

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.     

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.     

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。     

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.     

Introduction of long-chain branches in linear polyethylene by light cross-linking with 1,3-benzenedisulfonyl azide

Metallocene synthesised HDPE with M_w=82,000 and M_n=40,000 was modified with small amounts of 1,3-benzenedisulfonyl azide by reactive extrusion at 200 °C with the purpose to form long-chain branches. At the processing temperature the two azide groups decompose to nitrenes that work as cross-linkers for PE. Cross-linking occurs primarily by insertion of singlet nitrenes into CH bonds. Size exclusion chromatography revealed that the modification resulted in the formation of a long-chain branched (LCB) high molecular weight fraction. The LCB was detectable with SEC for concentrations above 100 ppm corresponding to approximately 0.03–0.04 branch points pr 10⁴ carbon. No signs of the formation of low molecular species due to chain scission were observed. Dynamical mechanical analysis and shear creep test showed sign of long chain branching at concentrations down to the same limit as SEC (100 ppm). These signs were thermorheological complexity, increased zero shear viscosity, increased shear thinning and increased recovery compliance. The cross-linking efficiency of 1,3-BDSA were estimated to 40–60% from comparison of SEC data with random cross-linking theory and traditional SEC-LCB analyses.     

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。     

Temperature dependence of dynamics of solutions of triblock copolymer in a selective solvent

The temperature dependence of dynamic properties of solutions of a triblock copolymer with polystyrene outer blocks and a middle block of fully hydrogenated polybutadiene (M_w=7.0×10⁴ gmol⁻¹, mass fraction of PS 0.28) was studied in a selective solvent for the middle block, n-heptane. In dilute solutions, a gradual decomposition of the flower-like micelles was observed on heating. A more complex behavior was observed in semidilute solutions of the copolymer where three dynamic processes can be reliably extracted from the correlation functions. The fast mode corresponds to the collective diffusion mode of physically interconnected micelles, the broad middle mode is probably due to the tracer diffusion of polydispersed clusters (animal-like structures) formed by random association of the triblock copolymer and the slow mode is probably related to the diffusion of aggregates of insoluble polystyrene impurities. The crossover from relaxational to diffusive behavior was found for samples with c>5.5% (w/v). The scattered light intensity measurements revealed a phase transition for the solution with the concentration 4% (w/v) at a temperature of 79±2°C, which was related to the phase separation of polystyrene homopolymer present in a small amount in the copolymer used.     

Surface morphology control of immiscible polymer-blend thin films

The effects of the molecular weights (molecular weight of polystyrene, M_w,PS, varying from 2.9 to 129 k) on the surface morphologies of spin-coated and annealed polystyrene/poly (methyl methacrylate) (PS/PMMA=50/50, w/w) blend films were investigated by atomic force microscopy and X-ray photoelectron spectroscopy. For the spin-coated films, when the M_w,PS varied from 2.9 to 129 k, three different kinds of surface morphologies (a nanophase-separated morphology, a PMMA cellular or network-like morphology whose meshes filled with PS, a sea-island like morphology) were observed and their formation mechanisms are discussed, respectively. Upon annealing, two different morphology-evolution processes were observed. It is found that a upper PS-rich phase layer is formed when M_w,PS<4 k, and this behavior is mainly attributed to the low interfacial tension between PS and PMMA component. When M_w,PS>4 k, the PS-rich phase forms droplets on top of the PMMA-rich phase layer which wets the SiO_x substrate. These results indicate that the surface morphology of the polymer blend films can be controlled by the polymer molecular weight and annealing conditions.     

Synthesis of hydrophilic poly(vinyl ether)s and their application for separation media design

Poly(2-acetoxyethyl vinyl ether (AcOVE)) and poly(2-acetoxyethyl vinyl ether-co-2-vinyloxyethyl phthalimide) were synthesized by traditional cationic polymerization, typically at −20°C in toluene with BF₃O(C₂H₅)₂ as initiator, to give polymers with degrees of polymerization (Dp) in the range of 600–1100. In addition, poly(AcOVE) was polymerized by controlled cationic polymerization at 0°C with molecular weights in a predetermined fashion. The Dp's were calculated from Dp = [M]₀/[I]₀ and typical values were 5, 10, 100 and 200. The molecular weight values obtained for a theoretical Dp = 200, were for poly(2-acetoxyethyl vinyl ether), M_n = 19,200, M_w = 22,700 and POLYDISPERSITY = 1.2, as determined by GPC. The deprotected hydrophilic polymers, poly(2-hydroxyethyl vinyl ether) and poly(2-hydroxyethyl vinyl ether-co-2-aminoethyl vinyl ether), were used for the preparation of novel gel filtration media as well as new anion exchangers. In the case of gel filtration, poly(2-hydroxyethyl vinyl ether) was attached to a beaded agarose matrix (34 μm), i.e. Sepharose® HP. It was shown that the attachment of the poly(vinyl ether) affected the selectivity. In gel filtration of selected biomolecules, the poly(vinyl ether) modified agarose matrix showed performance characteristics comparable to the reference used, i.e. Superdex® 30 prep grade. In addition the poly(vinyl ether)s were shown to be stable in a wide pH-range. The stability was confirmed by the conclusion that no changes in molecular weight were observed after treatment with 0.1 M HCl (pH = 1) or 0.01 M NaOH (pH = 12) for six weeks at 40°C. For the preparation of anion-exchanger media, the beads containing poly(2-hydroxyethyl vinyl ether) was further modified with a quaternary ammonium group, to produce a separation media having a high dynamic binding capacity for bovine serum albumin (BSA).     

Multiobjective dynamic optimization of a semi-batch epoxy polymerization process

Multiobjective Pareto optimal solutions for epoxy semi-batch polymerization process are obtained by adapting nondominated sorting genetic algorithm II (NSGA II). The objective is to produce polymer of maximum possible number average molecular weight (M_n) with a specified value of polydispersity index (PDI) and number average molecular weight in minimum possible time. The M_n and reaction time are, therefore, taken as two objectives where the first one is maximized and the second one is minimized. The decision variables are addition profiles of various reactants and the reaction time itself and PDI is treated as a constraint. In another optimization study, the time intervals are also been changed from hourly addition assumptions to equal interval additions for an optimized time frame. Additionally, similar analysis has been performed with a new addition strategy with total additions of reactants very close to available experimental conditions. Sensitivity analysis for estimated kinetic parameters and analysis for stabilization of products are also studied. A validated model, taking care of required physico-chemical aspects of the proposed reaction mechanism, is a prerequisite for this kind of study.     

(CH3CH[NH3]CH2NH3)1/2·ZnPO4, a zincophosphate analogue of aluminosilicate zeolite thomsonite

The synthesis and structure of (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, an organically templated zincophosphate (ZnPO) analogue of aluminosilicate zeolite thomsonite (THO), are described. The ZnPO framework is built up from an alternating, vertex-sharing, network of ZnO₄ and PO₄ groups (d_av(Zn–O)=1.944 (8) Å, d_av(P–O)=1.535 (9) Å, θ_av(Zn–O–P)=130.5°) involving distinctive 4=1 secondary building units. The 1,2-diammonium propane cations are highly disordered in the [0 0 1] 8-ring channels. Crystal data: (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, M_r=198.42, orthorhombic, space group Pncn (no. 52), a=14.119 (6) Å, b=14.136 (5) Å, c=12.985 (5) Å, V=2591 (3) ų, Z=10, R(F)=0.057, R_w(F)=0.061 (for a twinned crystal).     

Polymers in mixed solvents: application of the new representation of viscosity data as a function of molecular weight

The relation proposed between the intrinsic viscosity and the molecular weight of a polymer^1,2 (1/[η]versus 1/M^1/2), has been applied in this paper in cases when the polymer is dissolved in a binary solvent mixture. We have then shown that even in this case we can calculate in a very accurate way the molecular weight of the polymer from its intrinsic viscosity, especially in the molecular weight range where the Mark-Houwink-Sakurada equation is the least applicable (M_w < 150 000).     

Preparation of high viscosity thermoplastic phenol formaldehyde polymers for application in reactive extrusion

This work deals with the synthesis of high molecular weight, thermoplastic phenol formaldehyde (PF) resins for the application in the synthesis of polypropylene–PF compatibilizers by reactive extrusion. Phenol formaldehyde of high molecular weight is required in reactive extrusion with most polypropylene grades to meet the viscosity ratio (λ) requirement for best mixing. Special lab-grades of PF were therefore developed. The polymers synthesized were highly linear and in the M_w range of 10–30 000 g mole⁻¹.