查询词典 chain reaction

The invention uses the method of the fusion and direct polymerization to prepare the carboxyl-terminated lactic acid prepolymer and then copolymerize with the aliphatic polycarbonate; then the reaction is done in the twin-screw extruder to screw out the extension chain and the good polylactic acid copolymer is made.

本发明采用熔融直接缩聚的方法制备出羧基封端的乳酸预聚物，接着再与脂肪族聚碳酸酯二元醇进行共聚，然后再在双螺杆挤出机中进行反应挤出扩链，制备性能良好的聚乳酸共聚物。

The preparation method comprises the following steps in sequence:(1) metric acetonitrile is added into a dual-bottleneck distilling flask that is provided with a refluxing and condensing tube, and simultaneously, long-chain dialkyl methyl tertiary amine and relevant saturated dihalide are added thereof;(2) nitrogen is pumped for 10 to 20 minutes for deoxidizing;(3) a magnetic mixing reaction is carried through for 10 to 15 hours under the condition of 78 to 83 DEG C.

其制备方法依次包括以下步骤：(1)在装有回流冷凝管的二颈蒸流烧瓶中，加入计量的乙腈，同时按一定比例加入二长链烷基甲基叔胺与相应的二卤代烷；(2)通氮气10-20分钟，排除氧气；(3)在78-83℃条件下磁力搅拌反应10～15h。

A method for the preparation of microcellular elastomeric polyurethane foams from a reaction mixture comprising a polyisocyanate component containing at least 85% by weight of 4,4'-diphenylmethane diisocyanate or a variant thereof, a polyol composition comprising at least one polyoxyalkylene polyol having an average nominal hydroxyl functionality of from 2 to 6, an average hydroxyl equivalent weight of at least 1300 and an average oxyethylene content of between 50 and 85% by weight, water, a chain extender having an average hydroxyl equivalent weight of from 15 to 250 and optionally a crosslinking agent, the hardblock-content being more than 45% by weight.

本发明是有关一种制备微孔弹性聚氨基甲酸酯泡沫体的方法，其反应混合物包括：一种含至少85重量％的4，4′－二苯甲烷二异氰酸酯或其变体的聚异氰酸酯组分，一种多元醇组合物，其包含至少一种平均标称羟基官能度从2至6、平均羟基当量至少1300且平均氧乙烯含量介于50至85重量％之间的聚氧亚烷基多元醇，水，一种平均羟基当量为15至250之增链剂，以及视需要使用的交联剂，该硬性嵌段－含量（hardblock-content）大于45重量％。

In the case of radical-initial polymerization, the chain-transferring reaction occurred in the blends of PMMA and PV Ac, and there was a dramatical increase in gel content when PV Ac concentration come to a critical value of 30 wt%.

研究结果表明在PMMA/PV Ac共混体系中，链转移反应导致了凝胶产物的形成，并且凝胶含量的增加与共混组成的变化存在一临界现象，即当PV Ac含量超过30wt%，体系中的PMMA-PV Ac凝胶含量急剧增加。

With the self-emulsifying aqueous polyurethane containing polymeric double bond in the lateral chain acted as macromolecular emulsor and reactant for acrylate monomer polymerization, controlling the reaction amount of polymeric double bond so that adjusting the chemical bond linkage degree between polyurethane and acrylate, core-shell type interpenetrating polymer network structural aqueous acrylate polyurethane hybrid dispersion was synthesized, which is now a new type molecular composite technology for aqueous polyurethane.

利用侧链含可聚双键的自乳化聚氨酯水分散体作为丙烯酸酯单体聚合反应的高分子乳化剂和反应物，通过控制聚氨酯水分散体侧链上参与共聚的双键数目，调节聚氨酯和丙烯酸酯的化学键合程度，制备得到核壳型互穿网络结构丙烯酸聚氨酯杂合水分散体是一种新颖的复合改性技术。

Carotene can transform into fluorene series and the reaction of sulphur with chain organic compounds can form more abundant fluorene series.

而硫和链状化合物反应可以形成更为丰富的芴系列化合物。

In this study, we first synthesize a conducting polymer, P3HT, via Grignard metathesis method. And we functionalize the polymer chain end of P3HT into vinyl group. After characterize from 1H NMR spectroscopy, we use the end functionalized P3HT to proceed coupling reaction with P2VP anion.

为了达到这个研究目的，我们先利用格林纳置换法合成导电高分子P3HT，并将其尾端乙烯化，在经核磁共振仪确定结构后，利用此尾端乙烯化之P3HT与P2VP阴离子反应进行接合。

The reactions of 〓with bptz generate a cyclic tetranuclear and a 1-D helical chain 〓 complexes with thehydrolysis reaction products: 2,5-di(4-pyridyl)-l,3,4-oxadiazole and N,N'-bis(α-hydroxyl-2-pyridyl)ketazine.

本文利用〓在不同的环境中与bptz反应得到两个水解产物形成的配合物并解析了其晶体结构，一个为一维链状配合物，另一个为一个四核环状结构。

A one-pot chemoselective reduction and lactonization of(4S,5R)-hemiesters was carried out to afford high-yielding(3aS,6aR)-lactone,a key chiral building block for the biotin synthesis. One-step introduction of carboxybutyl chain onto(3aS,6aR)-thiolactone was reached upon treatment of zinc reagent 25 in the presence of nanopalladium via an improved Fukuyama coupling under mild reaction conditions.

在侧链引入过程中，采用纳米钯LDH-Pd~0为催化剂以改进的Fukuyama偶联反应一步高效地引入-生物素五碳羧酸侧链，紧接着创造性地以离子氢化的方式建立了-生物素的第三个手性中心。

In this thesis, the process of side-chain alkenylation and cyclization reaction have been studied. NaK eutectic mixture is seldom used as acatalyst, not to mention the sonochemical treatment of it in a catalytic system.

本研究通过烯基化反应合成OTP并对其进行环化反应合成1，5-DMT，同时对反应催化剂进行表征并对反应机理进行探讨。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。