Gel permeation chromatography on branched polymers

In gel permeation chromatography on long-chain branched polymers, calibration with linear samples leads to incorrect results. There are, however, several ways in which the data can be treated correctly. All of them call for the use of extra experimental information, such as viscosity or light scattering data of the whole polymer or the GPC eluent. The Drott—Mendelson method, using [η] of the whole polymer and GPC data, has been employed for analysing three low density polyethylene samples. The potentialities of viscometry and light-scattering measurements in the GPC effluent have also been examined. From [η], M_w and GPC data the long-chain branching index g′ can be derived in three ways, although it should be stated that the average g′-values so found for polydisperse samples are different.     

Application of multimethod procedure for characterization of branched polydisperse polymers

The multimethod procedure for characterization of branched polydisperse polymers, including gel permeation chromatography, solution viscometry, melt viscometry, and differential scanning calorimetry, is described. An equation relating the average branching degree g¯_x and the average number of branch points n?_bx has been derived and compared with the theoretical Zimm–Stockmayer equation. It has been found that both equations can be consistent for theta solvent and for the branching degree exponent b=1.5. Experimental data are given for trifunctionally branched bisphenol A polycarbonate.     

电镀废水中总氰化物测定的新方法

研究了用丘氏气提定氰器测定电镀废水中总氰化物的条件和方法。实验结果表明，与蒸馏法相比，该法简便安全、分析准确可靠、节电90％以上。     

Synthesis and characterization of well-defined comb-like branched polymers

Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, ¹H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved.     

Synthesis and characterization of well-defined comb-like branched polymers

Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, ¹H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved. __________ Translated from Acta Polymerica Sinica (China), 2007, (3): 203–208 [译自: 高分子学报]     

New method for the synthesis and purification of branched mPEG2lys

Branched PEG structures are particularly useful for the pegylation of different biomaterials. In this regard, the branched structure bearing a lysine core and two mPEG chains linked by urethane bonds (mPEG₂lys) has been used for the pegylation of several important biomolecules. In this work we describe the preparation of a new functionalized mPEG featuring an alkoxy-carbonylimidazolium iodide reactive group that can be used for the urethane bonds formation required in mPEG₂lys (20 kDa). The procedure for the preparation of the mPEG-alkoxy-carbonylimidazolium iodide involves the initial reaction of mPEG with N,N′-carbonylbismidazole (CDI) as phosgene equivalent, followed by alkylation with methyl iodide. The functionalized mPEG was reacted with a silylated lysine derivative affording mPEG₂lys in a single step. Therefore, harmful reagents (like phosgene derivatives) are not employed, making the process safe and straightforward. A 2-step purification procedure of mPEG₂lys is also presented. It is noteworthy that by following this method pure mPEG₂lys was obtained with 41% isolated yield. The mPEG₂lys was further converted to the N-hydroxysuccinimidyl ester by diimide activation and successfully used in the pegylation of interferon α-2a.     

New FTIR method for the determination of FFA in oils

A rapid, practical, and accurate FTIR method for the determination of FFA in edible oils was developed. Analogous to the AOCS titration procedure, the FTIR FFA determination is effected by an acid/base reaction but directly measures the product formed rather than utilizing an end point based on an electrode potential or color change. A suspension of a weak base, potassium phthalimide (K-phthal) in 1-propanol (1-PrOH), is used to convert the FFA present in oils to their carboxylate salt without causing oil saponification, and differential spectroscopy is used to circumvent matrix effects. Samples are first diluted with 1-PrOH, then split, with one-half treated with the K-phthal reagent and the other half with 1-PrOH (blank reagent), their spectra collected, and differential spectra obtained to ratio out the invariant spectral contributions from the oil sample. Quantification of the percentage of FFA in the oil, expressed as %oleic acid, based on measurement of the peak height of the ν (COO⁻) absorption of the FFA salt formed, yielded a calibration with an SE of <0.020% FFA over the range of 0–4%. The method was validated by standard addition and the analysis of Smalley check samples, the results indicating that the analytical performance of the FTIR procedure is as good as or better than that of the standard titrimetric procedure. As structured, the FTIR procedure is a primary method, as calibration is not dependent on reference values provided by another method, and has performance criteria that could lead to its consideration as an instrumental AOCS procedure for FFA determination. The FTIR portion of the analysis is automatable, and a system capable of analyzing ∼60 samples/h was developed that could be of benefit to laboratories that carry out a large number of FFA analyses per day.     

Reversible melt flow rate increase of branched acetal polymers

Continued shearing of molten long-chain branched acetal polymers raises their melt flow rates manyfold. The increase is not due to molecular degradation, as evidenced by constancy of inherent viscosity, and by the ability to reverse the increase by dissolving and reprecipitating the polymer. Shearing was found to have only a relatively small effect upon the melt viscosity but a very large effect upon the entrance correction for capillary flow. It is suggested that crystallization of branched polymers from solution creates an exceptionally strong entanglement network, and that the observed rheological changes reflect the disruption by shear of this network.     

一种新的无模型自适应控制模型参数整定方法

无模型自适应控制（MFAC）有四个模型参数,现有研究认为其无关联,且全程守恒。通过虚拟系统在初始时刻的状态,基于第一时刻输出值应与期望值接近的原则,采用遗传算法找到了参数关联,从而将四参数问题转化成单参数问题;并在控制过程中,依系统输出与期望差异自动改变步长因子取值,将其动态化,不但加速了初期计算,还避免了收敛时可能出现的超调或振荡;由此以参数关联和动态化为切入,改进了现有紧格式动态线性化MFAC方法,使其更为简捷和准确。某炼油单元3参数调优案例表明新方法可行,较老方法实现系统最大增益的参数调整次数由33次减少到14次,最大增益由413.4万元/年提高到542.9万元/年。     

Unperturbed dimensions of branched chain,star and ring polymers

A novel Monte Carlo method has been applied to the calculation of the unperturbed dimensions of various monodisperse polymers, e.g. star polymers, branched polymers formed by the crosslinking of linear primary chains, and linear chains with some intramolecular cycles. Where results for the parameters h^?1 and g (representing the effect of branching upon the hydrodynamic radius and the radius of gyration, respectively) were known previously, agreement is good. The method can, however, be applied to furnish other statistical averages for polymers of any arbitrary branched structure, and the effects of polydispersity may also be included.     

Optimized data collection for determination of the MWD from the viscosity data of polymer melts

Numerical differentiation is one source of loss of resolution in the differential transformation of viscosity to MWD. Resolution can be improved by increasing the amount of viscosity data, keeping in mind that optimizing this process is necessary for practical reasons. This problem was approached by finding the minimum point for practical reasons. This problem was approached by finding the minimum point density and coverage required to resolve bimodality. For given point density and range, the higher the superposition between the viscosity data and the “knee” in the viscosity function produced by each mode, the better the resolution. Testing time can be reduced and resolution can still be preserved by placing more points in the “knee” region in the viscosity function and by skipping the unnecessary points at low shear rates.     

Characterization of branched polymers by size exclusion chromatography coupled with multiangle light scattering detector. I. Size exclusion chromatography elution behavior of branched polymers

The elution behavior of branched macromolecules during their separation by size exclusion chromatography (SEC) was studied. The elution behavior of branched polymers was investigated using samples of randomly branched polystyrene and star branched poly(benzyl methacrylate) of different levels of branching by means of a SEC chromatograph coupled with a multiangle light scattering detector. Abnormal SEC elution behavior was found to be typical for highly branched polymers. After a normal elution at small elution volumes the molar mass and root mean square radius of the eluting molecules increased with increasing elution volume. Several SEC experiments were carried out to find explanation for this effect and SEC separation was compared with the separation by thermal field flow fractionation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1588–1594, 2001     

催化反应液中氨基葡萄糖酸的光度法测定

利用氨基葡萄糖酸在强酸性(pH 1.5)条件下形成内酯,并与羟胺碱-三氯化铁显色体系生成红棕色络合物,建立了氨基葡萄糖酸的分光光度检测方法,给出了线性方程。检测波长为500 nm,在1.0×10-5～9.0×10-5 mol/mL范围内呈现良好的线性关系,平均加标回收率为99.28%,相对标准偏差≤4.91%。该方法操作简单、结果稳定、选择性和灵敏度良好,能成功应用于实际样品的检测。     

New synthetic method for soluble starlike C60‐bonding polymers

Novel starlike C₆₀‐bonding polymers were synthesized by using the iniferter technique. The fullerene C₆₀ with pendent N,N‐diethyldithiocarbamate groups (C₆₀–SR) was used as polyfunctional photoiniferter. The effects of UV‐irradiation time and ambient temperature on the molecular weight of polymer were investigated. The photopolymerization with C₆₀–SR proceeded via a living‐radical mechanism, and gave soluble polyfunctional polymers (photoiniferters). Multiple polymer arms were attached to the C₆₀ core and the polymers obtained by C₆₀–SR could also be used as excellent crosslinking agents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1286–1290, 2001     

用燃烧瓶法测定聚合物中氯含量的影响因素

采用GB/T7139-2002《塑料氯乙烯均聚和共聚树脂氯含量的测定》的燃烧瓶法检测含氯聚合物的氯含量,从燃烧过程、称样量、滴定终点控制等方面探讨了造成测定结果产生偏差的因素.     

Studies on the preparation of branched polymers from styrene and divinylbenzene

The self‐condensing vinyl polymerization of styrene and an inimer formed in situ by atom transfer radical addition from divinylbenzene and 2‐bromoisobutyl‐tert‐butyrate using atom transfer radical polymerization technique was studied. To study the polymerization mechanism and achieve high molecular weight polymer in a high polymer yield, the polymerization was carried out in bulk at 80°C. Proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and gel permeation chromatography (GPC) coupled with multiangle laser light scattering (MALLS) were used to monitor the polymerization process and characterize the solid polymers. It is proved that the polymerization shows a “living” polymerization behavior and the crosslinking reaction has been restrained effectively due to the introduction of styrene. Polymers with high molecular weight (M_w.MALLS > 10⁵) can be prepared in high yield (near 80%). Comparison of the apparent molecular weights measured by GPC with the absolute values measured by MALLS indicates the existence of branched structures in the prepared polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007