Polymer dispersions from catalytic polymerization in aqueous systems

By contrast to traditional free radical emulsion polymerization, catalytic polymerization allows for polymer microstructure control. In terms of polymerizable monomers, both techniques are largely complementary. Since the beginning of this decade, an increasing number of reports on polyolefin, polybutadiene, polyalkenamer, polynorbornene, polyketone, and polyacetylene dispersions prepared by catalytic polymerization in disperse aqueous systems has appeared. This contribution reviews the preparation of these dispersions, their colloidal properties, particle formation mechanisms, particle morphologies, and polymer microstructures.     

Isothermal-crystallization kinetics and spherulite growth of aliphatic polyketone/polyamide-6 blends

In this research,the morphologies,isothermal-crystallization kinetics,and spherulite growth of aliphatic polyketone/polyamide-6 blends were studied.A single glass-transition temperature (Tg) was determined,and the composition dependence of Tg for these blends was well described by the Kwei equation.The strong intermolecular interaction between the two polymer components was confirmed by melting-point depression.The isothermal-crystallization kinetics were analyzed on the basis of the Avrami approach.A linear increase in the radii of the spherulites with time was observed for all compositions.All the spherulites continued to grow at nearly identical growth rates.With increasing polyamide-6 content,the size of the spherulites in the polyketone/polyamide-6 blends gradually decreased,and the number of spherulites in the blends increased.     

钯催化CO/乙烯共聚配体和阴离子效应

由ＣＯ与乙烯共聚制备的聚酮高分子,属新型功能高分子材料,由于其具有良好的光降解性,避免了传统非降解材料对生态环境造成的白色污染,同时由价廉的ＣＯ代替５０ %的乙烯直接制备高附加值的聚酮高分子,节约了石油资源,合理精细的利用了煤资源和其它化学过程中副产的ＣＯ,符合近代化工对环保和资源的要求,因而在近二十年来得到了快速发展,目前Ｓｈｅｌｌ公司已有万吨级的工业化装置,并有少量产品上市．制备聚酮的关键技术是高效钯 (Ⅱ )催化剂,该催化剂一般以三元组合物的形式加入到聚合釜中［１］,(１)醋酸钯,(２)双膦配体 (Ｌ…     

Effects of the chain microstructure on the properties of polyketones terpolymers characterized by scanning force microscopy

A new approach is described to tailor properties of polyketones based on the controlled modification of the block structure by varying the polymerization process. Ethylene-propylene-CO (ECOPCO) terblock copolymers with similar composition but different chain microstructures have been synthesized using either preset polymerization (PSP) or pulsed-feed polymerization (PFP), respectively. Whereas by PSP an ABC-triblock structure is obtained, the PFP results in [AB]_n-multiblock structure. In this paper we investigate the influence of the chain microstructure on the mechanical behavior and the surface properties.SFM phase images display a phase-separated bulk morphology where triblock polymers due to the larger block lengths form coarser structures than the multiblock samples. If the ECO content is above 50%, partially crystalline lamellar structures can be found, which in case of the multiblock sample form a continuous network of lamellar-like ECO rich domains. All ECOPCO terpolymers reveal elastomeric behavior with an elastic recovery of at least 82% but tensile strength and elongation vary with the block length of the chain microstructures. Differences in elasticity are explained by the formation of different amounts of cross-links consisting of blocks of parallel-aligned ECO chain segments or crystalline lamellae. It can be shown that the surface morphology differs from bulk morphology, mainly by the point that no distinct phase separation appears but ECO rich domains can be detected. Surface tension measurements enable to correlate the surface energy with surface composition and surface morphology.     

钯(Ⅱ)催化CO/乙烯交替共聚溶剂效应的研究

利用小釜实验考察了在多种新溶剂中钯（Ⅱ）催化ＣＯ／乙烯共聚制备聚酮高分子的反应，并利用高分辨核磁共振１Ｈ ＮＭＲ、１３Ｃ ＮＭＲ技术对在不同溶剂中制得产品的主链和端基进行了分析，实验结果表明除甲醇外，在丙酮、丙醛、Ｎ，Ｎ 二甲基甲酰胺、Ｎ，Ｎ 二甲基乙酰胺、冰乙酸、二甲基亚砜等溶剂中，钯（Ⅱ） 双膦催化剂仍具有较好的催化活性，尤其以冰乙酸为溶剂，在没有强酸阴离子存在的条件下，催化反应亦可顺利进行．实验结果同时表明适宜的溶剂除作为稀释剂外，还对中心金属钯（Ⅱ）具有适宜的稳定作用．产品端基分析结果表明在非醇类溶剂中共聚反应由乙烯插入Ｐｄ Ｈ键引发，在醇类溶剂中共聚反应主要由ＣＯ插入Ｐｄ ＯＲ键引发．     

An efficient organic additive to control the crystallization rate of aliphatic polyketone: A non-isothermal crystallization kinetics study

Three types of organic compounds—two carboxylic acids and an anhydride, were used as additives for polyketone(PK). The effect of the additive structure and their feed ratios on the melting temperature, crystallization temperature, and crystallization rate of PK were studied. We found that the crystallization temperature could be reduced significantly by introducing a small quantity of organic additive, in particular, an anhydride. On addition of 1 phr of anhydride, the crystallization temperature was reduced by 10.7 ℃. Therefore, the non-isothermal crystallization kinetics of aliphatic PK/anhydride blends with various feed ratios was investigated using DSC. The results were analyzed by various theoretical models, such as Avrami, Ozawa and combined Avrami-Ozawa models.     

A DFT investigation of the mechanism for alternating copolymerization of styrene with carbon monoxide catalyzed by Pd(II) complexes

Density functional theory has been employed to study the homogeneous catalytic copolymerization of styrene with carbon monoxide.The copolymerization reaction is catalyzed by Pd（Ⅱ） coordinated with 2,2’-bipyridine,a conventional nitrogen-containing bidentate ligand with achiral C_2vsymmetry.The chain propagation mechanism for the alternating copolymerization as well as the side reactions,including multiple insertions of CO and homopolymerization of styrene,has been investigated.This study focused exclusively on regioisomerism and stereoisomerism.We have demonstrated that the strictly alternating copolymerization is kinetically and thermodynamically favored over the side reactions（i.e.,multiple insertions of CO and homopolymerization of styrene）.The regiochemistry study indicates the 2,1 type.Furthermore,the stereochemistry study shows that the syndiotactic conformation is preferred over the isotactic or atactic conformations.     

Diphenylphosphino(phenyl pyridin-2-yl methylene)amine palladium(II) complexes: Chemoselective alkene hydrocarboxylation initiators

The heteroditopic, P-N-chelating ligand diphenylphosphino(phenyl pyridin-2-yl methylene)amine (1) has been synthesised via a simple ‘one-pot’ procedure and its donor characteristics assessed. The neutral [MX(Y)(1-κ²-P-N)] (3, M = Rh, X = Cl, Y = CO; 4, M = Pd, X = Y = Cl; 5, M = Pd, X = Cl, Y = Me; 6, M = Pt, X = Y = Cl; 7, M = Pt, X = Cl, Y = Me; 8, M = Pt, X = Y = Me) and cationic [Pd(Me)(MeCN)(1-κ²-P-N)][Z] (9, Z = B{3,5-(CF₃)₂-C₆H₃}4; 10, Z = PF₆) complexes of 1 have been prepared and characterised. The solid-state structures of complexes 3, 4, 6 and 7 have been established by X-ray crystallography. Reactions of [PdCl(Me)(1-κ²-P-N)] towards CO and ^tBuNC have been investigated, affording the corresponding η¹-acyl (12) and -iminoacyl (14) complexes, respectively. Similar insertion chemistry is observed for the cationic derivative 9. Treatment of the acyl complex 12 with ethene at elevated pressure establishes an equilibrium between the starting material and the product resulting from insertion, 13. Under catalytic conditions, combination of palladium(II) with 1 in MeOH affords a selective initiator for the formation of 4-oxo-hexanoic acid methyl ester (15) from CO/ethene (38 bar, 90 °C).