气相法聚乙烯高效催化剂的进展

综述了国内外气相法聚乙烯高效催化剂研究进展概况,以及各种新型高效催化剂制备技术和性能,并对开发我国新型高效推化剂提出了看法。     

Synthesis of polyethylene oxide end‐capped with perfluoroalkyl groups/polystyrene prototype brushes

Polystyrene (PS)/poly(ethylene oxide) (PEO) prototype brushes were prepared by alternating free‐radical copolymerization of methacryloyl‐terminated PS and α‐vinylbenzyl‐ω‐hydroxy or α‐vinylbenzyl‐ω‐perfluoroalkyl (R_f) PEO macromonomers with the addition of Lewis acid (SnCl₄). It was found from their dilute‐solution properties that PS/PEO end‐capped with R_f (PBR_f), and PS/PEO having OH groups at terminal ends (PBOH) prototype brushes formed a single molecule in benzene and aggregates in chloroform, respectively. However, the brush PBOH formed a single molecule in N,N‐dimethylformamide. Such aggregation behaviors seemed to be caused by the interaction between hydroxy groups of PEO chain ends. The brush PBOH was also converted into PBR_f‐type brush by chemical modification, using corresponding acid chloride. The substitution of R_f groups was ～70% due to slipping of terminal hydroxy groups into PEO internal domains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 772–778, 2006     

Lewis酸存在下的自由基共聚合——Ⅰ.GeCl_4与BCl_3存在下的乙酸乙烯酯与丙烯酸交替共聚

乙酸乙烯酯(VAc)与丙烯酸(AA)在GeCl_4及BCl_3存在下通过自由基聚合可得到交替共聚物。对GeCl_4体系,聚合反应速率正比于[引发剂]~(0.5)。当VAc/AA=1:1(mol比)时有最大反应速率。CCl_4对本聚合反应无链转移作用。通过紫外光谱分析可证实VAc及AA均与GeC\(?)生成络合物;ESR分析表明,络合AA自由基较未络合AA有较强的阳离子特性,交替共聚的原因可能与络合AA自由基及活化单体络合物二者有关。     

Rheological study of poly(ethylene glycol)/poly(N‐isopropylacrylamide‐co‐2‐acrylamido‐2‐methylpropanesulphonic acid) semiinterpenetrating network formation

The formation of a series of semiinterpenetrating network (SIPN) hydrogels made by free‐radical copolymerization of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) with varying comonomer mole ratios, crosslinked with N,N′‐methylene‐bisacrylamide (MBAA) in the presence of poly(ethylene glycol) (PEG) with average molecular weight 6,000 g mol^?1 was studied via determination of complex viscosity, η*, using plate–plate rheometry. The isothermal time dependence of η* at various temperatures or the variation of η* with temperature of pregel solutions was utilized to detect the onset of gelation. The SIPN systems were compared with the corresponding gels made under the same conditions in the absence of PEG. The copolymer mainchain composition has a major effect on the time or temperature for onset of gelation and in particular gelation appears to be inhibited to some extent by MBAA when the AMPS/NIPA mole ratio in the pregel solution exceeds 0.5. The presence or absence of PEG in pregel solutions has a lesser effect on gelation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2083–2087, 2004     

Kinetic study of the curing behavior of bismaleimide modified with diallylbisphenol A

The curing kinetics of bismaleimide modified with diallylbisphenol A were investigated for different ratios of 1,1′‐(methylene di‐4,1‐phenylene) bismaleimide and diallylbisphenol A with differential scanning calorimetry. Multiheating‐rate and isothermal methods were used to study the kinetics of the curing process. The results indicated that the activation energy changed with the extent of conversion. The activation energy obtained by the multiheating‐rate method was higher than that obtained by the isothermal method. Two kinetic models (autocatalytic and nth‐order) were successfully used to model the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2229–2240, 2003     

Synthesis and chain extension of nitroxide‐terminated styrene–maleimide copolymers

Thermal radical copolymerization of styrene (S) and maleimide (MI) at 125°C in diglyme in the presence of 2,2,6,6‐tetramethylpiperidin‐1‐yloxyl radical (TEMPO) was studied. Mole fractions of maleimide in the feed, F_MI, varied in the range 0.1–0.9. A quasiliving reaction process proceeded yielding copolymers with a low polydispersity (M_w/M_n = 1.17–1.41). The found azeotropic composition, (F_MI)_A = 0.46, did not differ substantially from that (0.5) in the conventional radical S‐MI copolymerization. At a higher conversion or MI content in the feed, deactivation of the copolymer chains occurred. The obtained TEMPO‐terminated S‐MI copolymers readily initiated polymerization of styrene; chain extension of the macroinitiators took place, giving poly(S‐co‐MI)‐block‐poly(S) diblock copolymers. The synthesized copolymers containing S and MI units were characterized by elemental analysis, NMR spectroscopy, size‐exclusion chromatography, and differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1863–1868, 2004     

八甲基环四硅氧烷与氨取代基有机硅单体的共聚动力学Ⅱ模型考核与结果讨论

对前文 (I)的共聚动力学模型进行了分析与简化 ,并分别通过对各影响因素的单因素实验和多因素相互作用实验对模型进行了进一步的考核 ,确定了模型参数并通过模型对聚合动力学行为作了说明     

改性淀粉与丙烯酸接枝共聚物的合成及应用性能

研究经过热处理的改性淀粉与丙烯酸的接枝共聚反应。接枝共聚产物在 790cm-1、85 0cm-1(物理改性淀粉的特征吸收峰 )和 172 0cm-1(聚丙烯酸的特征吸收峰 )处的红外光谱验证了接枝共聚反应的发生。探讨了引发剂过硫酸铵浓度、丙烯酸浓度、反应温度和反应时间等因素对接枝率和接枝效率的影响。当 ρ(淀粉 ) =70 g/L、t =6 0℃、反应时间为 3h、c〔(NH4) 2 S2 O8〕 =3 0× 10 -3 mol/L、c(丙烯酸 ) =0 4 2mol/L时 ,合成胶粘剂的初粘力为 10 0 % ,吸水率为 15 0 14 % ,吸油率为 2 0 6 % ,其压制的纸板冲击强度为 3 2 5kN/m ,拉伸强度为 3 75MPa ,与纯淀粉粘接剂相比较 ,所压制纸板的应用性能得到较大的改善。     

Effects of poly(acrylic acid) and poly(ethylene oxide) adsorption on the stability of alumina suspension

The effect of adsorbed polymer on the stability of alumina suspension was investigated. Poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA) and similar kinds of polymer salts were used as a dispersant. The amount of polymer adsorbed on alumina surface and the suspension stability was measured. The pH, molecular weight, and concentration were considered as experimental parameters. PEO shows low affinity on the alumina surface while PAA has high affinity. In the case of PAA adsorption, the surface charge change by polymer adsorption influences suspension stability strongly, but not in the case of PEO adsorption. In simultaneous adsorption of PEO and PAA, the PAA concentration was fixed and PEO concentration was varied. The stability of suspension increased with increasing PEO concentration, and this is partly due to the steric stabilization by adsorption of PAA-PEO complex or adsorption of PEO through pre-adsorbed PAA and the depletion effect of non-adsorbed polymer. Suspension adsorbing sodium salts of PAA and poly(methacrylic acid) (PMA) each showed similar stability. But, when the PEO and these kinds of salts were added together to the suspension, the one with PAA sodium salt could keep a higher stability even with lower molecular weights of PEO compared with suspension with PMA sodium salt.     

改性SBS胶粘剂的研制

以丙烯酸酯类混合单体对SBS热塑性弹性体在混合溶剂中接枝共聚，添加混合型增粘树脂，研制成接枝改性的SBS胶粘剂，具有较高的初粘力和终强度。探讨了单体比例、引发剂用量、反应温度、反应时间、增粘树脂对胶液性能的影响。