共查询到19条相似文献,搜索用时 281 毫秒
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双噁唑啉扩链尼龙1010 总被引:5,自引:0,他引:5
对尼龙 10 10的加成型化学扩链做了系统的研究 ,并对 2 ,2′ 双 (2 唑啉 ) (BOZ)和 1,4 双 (2 唑啉基 )苯 (PBO)的偶联效果和扩链产物的性能做了详细的探讨 ,前者的扩链效果较好 .研究结果表明 ,尼龙10 10熔体的转矩随着反应时间的延长显著增加 .但转矩达到极大值后开始缓慢下降 ,表明扩链产物在高温条件下发生热降解 .扩链剂的用量存在最佳值 ,用量不足时偶联反应不充分 ,用量过量时封端反应加剧 .扩链以后尼龙 10 10的端羧基含量大大降低 ,反应温度对反应速率的影响符合阿累尼乌斯关系式 .扩链产物极限粘度大大高于尼龙原料 ,表明分子量显著提高 相似文献
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利用脂肪族二元酸酯与乙醇胺反应容易获得的对称二酰胺二醇,经缩聚合成聚酯酰胺预聚体,并针对端羧基和端羟基同时扩链来提高分子量,获得可生物降解的聚酯酰胺.首先将N,N′-二(2-羟乙基)草酰胺(HEOA)或N,N′-二(2-羟乙基)己二酰胺(HEHA)与己二酸和丁二醇缩聚,制备同时带有端羧基及端羟基的脂肪族聚酯酰胺预聚体,通过1,4-双(2-噁唑啉)苯及己二酰双己内酰胺混合扩链剂扩链,获得高分子量脂肪族聚酯酰胺,并通过红外、1H-NMR、DSC及TGA对其结构和热性能进行了表征.结果表明,预聚体在制备过程发生了一定的酯-酰胺交换反应;扩链后聚合物的熔点、熔融焓和热稳定性有所下降;但热稳定性仍接近或略高于聚己二酸丁二酯. 相似文献
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选用聚乙烯 丙烯酸 (EAA)为接枝母体 ,首先摸索出 2 乙基 2 唑啉阳离子开环聚合的规律 ,得到高转化率端基为活性离子的聚 ( 2 乙基 2 唑啉 ) (PEOX) ,再与EAA羟基侧基进行接枝反应 ,考察了开环聚合条件及接枝反应条件对接枝率的影响 ,在一定的条件下得到了接枝率 >2 5%的聚乙烯 丙烯酸与聚 ( 2 乙基 2 唑啉 )的接枝共聚物 (EAA g PEOX) .该接枝物用于聚对苯二甲酸丁二醇酯 /聚丙烯 (PBT/PP)共混体系中作相容剂 ,可提高两者的相容性 . 相似文献
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含噁二唑单元共轭聚合物合成与性质研究 总被引:12,自引:0,他引:12
单体 2 ,5 双 (4 溴苯 ) 1,3,4 二唑 (M Ⅰ )与 1,4 二乙烯基 2 ,5 二正丁氧基苯 (M Ⅱ ) ,在钯催化下通过Heck偶合反应合成得到共轭聚合物 ;单体和聚合物进行了1 H NMR ,1 3C NMR、质谱、FT IR、UV、荧光光谱、GPC、元素分析、热分析等测试 ;二唑 (OXD)基团是一种很好的生色团 ,对氧和热特别稳定 ,二唑环的亲电子性能使其特别适合于作为电子传输层 ,聚合物能发射很强的绿色荧光 ,它将是一类潜在的光电高分子材料 相似文献
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MDI与TDI封端聚酯预聚物和扩链剂间反应速率的研究 总被引:8,自引:1,他引:8
用FTIR法系统地研究了不同硬段结构对聚酯型聚氨酯扩链反应动力学的影响,结果显示:不同类二异氰酸酯MDI和TDI形成的NCO封端的聚酯预聚体与二元胺(MOCA)和三元醇(TMP)的扩链反应均为二级反应,由MDI形成NCO封端的聚酯预聚体与胺或醇的扩链反应速度比TDI类的要快,MOCA扩链比TMP扩链反应活化能低,从基团反应活性不同体系扩链反速度的差别进行了讨论。 相似文献
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采用Kolinski等建立的类蛋白质分子的格点模型,通过计算类蛋白质分子的末端距分布函数P(r)来研究类蛋白质分子形成紧密接触对的速率k .发现不同的氨基酸序列,其分布函数P(r)不同.对于序列(H) x和(P) x,分布函数P(r)有二个峰值;而对于序列(HP) x,分布函数P(r)只有一个峰值.对于类蛋白质分子形成紧密接触对的速率k ,当链长N <11,随着N的增加而增加;当N >11,形成紧密接触对的速率k随着N的增加而减少,这个趋势与实验结果一致,并存在关系k~N-α(N >11) ,系数α与氨基酸序列有关.这些研究能够帮助我们加深对蛋白质结构形成的了解. 相似文献
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用红外光谱法、电导法和化学分析对双(2,3-环氧环戊基)醚(W-95)与4,4′-二氨基二苯甲烷(MDA)的反应速度进行了测定,并和双酚A环氧树脂(E-54)与MDA的反应进行了比较。两个反应体系的表现反应活化能的测定结果接近相等。若W-95的环氧基与MDA的Ⅰ级胺和Ⅱ级胺的反应速度为k_1′和k_′,而E-54的为k_1和k_2,则它们的相对反应速度为:k_1:k_2:k_1′:k_2′=200:22:20:1。本文对W-95和E-54混合体系的固化机理也作了探讨。 相似文献
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On the basis of the recently developed optimized Rouse-Zimm theory of chain polymers with excluded volume interactions, we calculate the long-time first-order rate constant k(1) for end-to-end cyclization of linear chain polymers. We first find that the optimized Rouse-Zimm theory provides the longest chain relaxation times tau(1) of excluded volume chains that are in excellent agreement with the available Brownian dynamics simulation results. In the free-draining limit, the cyclization rate is diffusion-controlled and k(1) is inversely proportional to tau(1), and the k(1) values calculated using the Wilemski-Fixman rate theory are in good agreement with Brownian dynamics simulation results. However, when hydrodynamic interactions are included, noticeable deviations are found. The main sources of errors are fluctuating hydrodynamic interaction and correlation hole effects as well as the non-Markovian reaction dynamic effect. The physical natures of these factors are discussed, and estimates for the magnitudes of required corrections are given. When the corrections are included, the present theory allows the prediction of accurate k(1) values for the cyclization of finite-length chains in good solvents as well as the correct scaling exponent in the long-chain limit. 相似文献
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本文研究了在HgCl2-BiCl3复合催化剂作用下,乙炔氢氯化制氯乙烯均相催化反应的动力学,获得该反应速率方程为:r=(k+k'[BiCl3]/[H+])[HgCl2]·[H+]3[CH≡CH].在25℃时k=0.00239,k'=0.0269,根据实验结果,提出了由两个复杂的连串反应组成的平行反应机理,相应的表观活化能为13.4Kcal/mol及14.8Kcal/mol. 相似文献
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Chain‐Growth Click Polymerization of AB2 Monomers for the Formation of Hyperbranched Polymers with Low Polydispersities in a One‐Pot Process
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Yi Shi Robert W. Graff Xiaosong Cao Xiaofeng Wang Haifeng Gao 《Angewandte Chemie (International ed. in English)》2015,54(26):7631-7635
Hyperbranched polymers are important soft nanomaterials but robust synthetic methods with which the polymer structures can be easily controlled have rarely been reported. For the first time, we present a one‐pot one‐batch synthesis of polytriazole‐based hyperbranched polymers with both low polydispersity and a high degree of branching (DB) using a copper‐catalyzed azide–alkyne cycloaddition (CuAAC) polymerization. The use of a trifunctional AB2 monomer that contains one alkyne and two azide groups ensures that all Cu catalysts are bound to polytriazole polymers at low monomer conversion. Subsequent CuAAC polymerization displayed the features of a “living” chain‐growth mechanism with a linear increase in molecular weight with conversion and clean chain extension for repeated monomer additions. Furthermore, the triazole group in a linear (L) monomer unit complexed CuI, which catalyzed a faster reaction of the second azide group to quickly convert the L unit into a dendritic unit, producing hyperbranched polymers with DB=0.83. 相似文献
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A kinetic study is reported for nucleophilic substitution reactions of 2,4-dinitro-1-fluorobenzene (DNFB) with a series of secondary amines in MeCN and H2O at 25.0 degrees C. The reaction in MeCN results in an upward curvature in the plot of k(obsd) vs [amine], indicating that the reaction proceeds through a rate-limiting proton transfer (RLPT) mechanism. On the contrary, the corresponding plot for the reaction in H2O is linear, implying that general base catalysis is absent. The ratios of the microscopic rate constants for the reactions in MeCN are consistent with the proposed mechanism, e.g., the facts that k2/k(-1) < 1 and k3/k2 > 10(2) suggest that formation of a Meisenheimer complex occurs before the rate-limiting step and the deprotonation by a second amine molecule becomes dominant when [amine] > 0.01 M, respectively. The Br?nsted-type plots for k1k2/k(-1) and k1k3/k(-1) are linear with betanuc values of 0.82 and 0.84, respectively, which supports the proposed mechanism. The Br?nsted-type plot for the reactions in H2O is also linear with betanuc = 0.52 which has been interpreted to indicate that the reaction proceeds through rate-limiting formation of a Meisenheimer complex. DNFB is more reactive toward secondary amines in MeCN than in H2O. The enhanced basicity of amines as well as the increased stability of the intermediate whose charges are delocalized through resonance are responsible for the enhanced reactivity in the aprotic solvent. 相似文献
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It has been shown that the rate of symmetrical hydride transfer reaction varies with the hydride affinity of the (identical) donor and acceptor. In that case, Marcus theory of atom and group transfer predicts that the Br?nsted alpha depends on the location of the substituent, whether it is in the donor or the acceptor, and the tightness of the critical configuration, as well as the resemblance of the critical configuration to reactants or products. This prediction has now been confirmed for hydride transfer reactions between heterocyclic, nitrogen-containing cations, which can be regarded as analogues of the enzyme cofactor, nicotinamide adenine dinucleotide (NAD+). A series of reactions with substituents in the donor gives Br?nsted alpha of 0.67 +/- 0.03 and a tightness parameter, tau, of 0.64 +/- 0.06. With substituents in the acceptor alpha = 0.32 +/- 0.03 and tau = 0.68 +/- 0.08. The reactions are all spontaneous, with equilibrium constants between 0.4 and 3 x 10(4), and the two sets span about the same range of equilibrium constants. The two tau values are essentially identical with an average value of 0.66 +/- 0.05. These results can be semiquantitatively mimicked by rate constants calculated for a linear, triatomic model of the reaction. Variational transition state theory and a physically motivated but empirically calibrated potential function were used. The computed rate constants generate an alpha value of 0.56 if the hydride affinity of the acceptor is varied and an alpha of 0.44 if the hydride affinity of the donor is varied. The calculated kinetic isotope effects are similar to the measured values. A previous error in the Born charging term of the potential function has been corrected. Marcus theory can be successfully fitted to both the experimental and computed rate constants, and appears to be the most compact way to express and compare them. The success of the linear triatomic model in qualitatively reproducing these results encourages the continued use of this easily conceptualized model to think about group, ion, and atom transfer reactions. 相似文献