~(13)C-NMR研究稀土催化聚戊二烯-1,3的末端链结构

用~(13)C-NMR方法研究了稀土催化聚戊二烯-1,3的末端链结构及聚合温度对聚合物微观结构的影响。结果指出,聚合物的末端活性增长链是以头-尾或尾-头加成生成的anti-和syn-四种 π-烯丙基。聚合温度降低时,顺-1,4含量增加,这可解释为由于 anti-和 syn-异构化的作用。同时解释了反-1,2结构形成的过程。     

~(13)C-NMR研究3,4-聚异戊二烯的序列分布

Fe(acac)_3-Phen-AlEt_3 催化体系可使异戊二烯聚合成以 3,4-链节为主具有一定结晶性能的聚异戊二烯。本文对该聚合物的~(13)C-NMR 谱进行了全分析,研究了序列分布、微观结构。结果表明不同方法求得的微观结构含量很好地一致,说明对~(13)C-NMR 谱峰归属的正确性。并指出顺-1,4/3,4-序列中存在着头-头,尾-尾的连接方式,3,4-嵌段链节不足够长及存在反节可能是结晶度不太高的主要原因。     

聚丁二烯~(13)C-NMR谱图中一个新的共振吸收峰(T_4)

<正> 最近解析锂系和铁系含乙烯基聚丁二烯的~(13)C-NMR谱图,发现并确认了一个新的共振吸收峰。即聚丁二烯反式1,4-序列的第四峰,简称T_4峰。 Furukawa等对钼系和章哲彦等对铁系等二元聚顺-1,4-1,2-丁二烯的研究都指出在聚丁二烯的~(13)C-NMR谱图上,有四个谱峰属于顺1,4-序列。本文给出其化学位     

~(13)C-NMR研究聚丁二烯的序列结构

本文采用~13C-NMR方法研究了不同催化体系制备的聚丁二烯。经分析指出,聚丁二烯分子链的三种序列(顺-1,4-序列、反-1,4-序列和1,2-序列)和十七类脂碳碳核为~13C-NNR谱贡献了十六个谱峰。经数据的解析,得到一组计算聚丁二烯脂碳部分各谱峰化学位移的经验参数。在本文条件下,应用该组参数得到的计算值与实验值符合较好。本文确认了聚丁二烯反-1,4-序列第四峰(T_4)的存在。初步研究了聚丁二烯~13℃-NMR谱图的定量处理问题。     

钼催化体系制备的聚1,2-丁二烯链结构

本文利用红外光谱、~(13)C-NMR和线膨胀等方法研究了钼体系聚1,2-丁二烯的链结构,并研究了链结构的调节方法。发现烯丙基卤等极性添加剂既可以调节1,2-链节含量,又可以调节链节的立体构型。最后,利用统计理论估计了1,2-链节的各种异构体的平均序列长度。     

~(13)C核磁共振研究稀土催化剂聚合双烯的机理

用~(13)C-NMR 方法测定了稀土顺丁二烯和聚异戊二烯链端结构及序列结构,从链端结构推测的聚合活性链端结构与前文是一致的。在聚异戊二烯中存在着“头-头”和“尾-尾”结构,这种结构引起活性链端甲基位置的改变,从而解释了稀土异戊二烯中3,4-链节的形成。测定了不同聚合温度对聚合物中顺、反结构含量的影响,可用活性链端的 anti-syn异构化加以解释。     

用~(13)C-NMR研究 1,2-聚丁二烯的分子运动——1,2-聚丁二烯分子运动对微观结构的依赖性

本工作用200兆赫脉冲傅里叶变换 NMR 波谱仪测定了一系列1,2-聚丁二烯样品在溶液中~13C核自旋-晶格弛豫时间(T_1)和核Overhauser效应(NOE)。较系统地研究了1,2-聚丁二烯的分子运动与化学结构、序列结构和大分子链节构成的关系,分析了乙烯基的内旋转运动。实验结果表明,顺1,4-链节中各碳的nT_1值比1,2-链节中相应各碳的nT_1值长1倍左右;对于相同的链节,当其两旁由1,2-链节变为顺1,4-链节时,其各类碳的nT_1值都大大增加;随着1,2-链节增加,各类碳的nT_1值都明显缩短。乙烯基叔碳的nT_1值大于端碳,经计算表明,引起乙烯基叔、端碳的nT_1值不相等的主要因素是乙烯基在垂直于主链的平面上的摆动。     

~(13)C-NMR研究聚丁二烯长支链支化

本文研究了用不同催化体系制备的聚丁二烯和加氢的聚丁二烯的~(13)C-NMR谱图。结合GPC测定支化度的数据,提出了二种可能的支化结构。以Ni及Co催化体系聚合的试样,支化点可能位于顺-1,4主链双键的α-次甲基上;而由Ni+Mo催化体系聚合的试样,可能为1,2-乙烯基的双键打开接长支链。     

铁体系催化丁二烯聚合的研究—Ⅳ.聚丁二烯的序列结构

在聚合温度为-30°～50°范围内,用FeCl₃-(i-C₄H₉)₃Al-phen催化体系合成出(顺1,4-1,2)等二元聚丁二烯,用臭氧解和¹³C-NMR方法研究了它们的序列结构。结果表明,这些聚合物的顺-1,4和1,2-链节都是非交替的。聚合温度高的样品比较接近Bernou-lli无规分布,而聚合温度低的样品的序列排布偏离无规分布。讨论了聚合机理。     

共轭双烯与丙烯酸甲酯交替共聚物的~(13)C-NMR谱研究

用~(13)C-NMR方法研究了丁二烯(BD)-丙烯酸甲酯(MA)、异戊二烯(IP)-MA和氯丁二烯(CP)-MA交替共聚物(分别简称为PBM、PIM和PCM)的联接方式和微观结构。在PBM中,BD单元以反-1,4-结构存在,并有少量的顺-1,4-和1,2-结构,其比例为88:7:5;在PIM和PCM中,IP与CP单元也主要以反-1,4-结构存在,与MA以“头-头”方式相连接。在PCM中还有少量CP-CP相连接的结构,交替度较低,而PBM和PIM则完全是交替结构。     

~(13)C-NMR研究铁系聚丁二烯(顺1,4-1,2)的链结构

前已报道,以高活性铁催化剂可以制得性能良好的含顺-1,4-1,2结构的等二元聚丁二烯。文献已有用~(13)C-NMR研究以钴,钼催化剂合成的这种等二元聚合物的报导。本工作用~(13)C-NMR进行了研究,得到的聚合物的~(13)C-NMR图谱表明,聚合物的脂碳部分共有十一个共振峰,烯碳部分有九个峰。通过改进Furukawa的经验参数,并应用Randall的方法,这些共振峰的归属得到了令人满意的结果。确认该聚合物是双烯和单烯的无规共聚物,但偏离Bernoulli分布,趋向于一级Markov分布。     

~(13)C-NMR STUDY ON THE EQUIBINARY (cis-1,4;1,2) POLYBUTADIENE POLYMERIZED WITH IRON CATALYST

The (cis-1,4 and 1,2) polybutadiene polymerized with iron catalyst was investigated by ~(13)C-NMR. Assignments have been made on the spectra for all peaks of the aliphatic and olefinic carbons using chemical shift corrective terms together with Furukawa parameters. The relative intensities of peaks were calculated from the Bernoulli distribution of cis-1,4 and 1,2 units.Quantification of cis-1,4 and 1,2 contents, sequence distribution, alternation pattern of cis-1,4 and 1,2 units, and the chain propagation mechanism were discussed as a result of the detailed study of the spectra.     

13C-Nuclear Magnetic Resonance Analysis of Some Essentially Random Copolymers of Methyl Methacrylate and Butadiene

20 MHz ¹³C-NMR (nuclear magnetic resonance) spectroscopy has been used to determine the relative concentrations of certain methacrylate and butadiene containing monomer sequence fractions in some essentially random free-radical copolymers of methyl methacrylate and butadiene. Several of the results are in good agreement with those obtained in an earlier ¹H-NMR study and confirm, within experimental error, that the copolymeriza-tion obeys first-order Markov statistics. The patterns of olefinic carbon resonances reveal that the progressive introduction of methacrylate units into the polymers slightly increases the trans-1,4- to cis-1,4 ratios of the butadiene units relative to that found for a pure polybutadiene prepared under similar conditions.     

STUDY ON SEQUENCE DISTRIBUTION OF 3, 4-POLYISOPRENE BY ~(13)C-NMR

Isoprene can be plymerized with Fe(acac)_3-phen-AlEt_3 catalyst system into a polymer mainly containg 3, 4-unit and capable of crystallizing to some extent. The ~(13)C-NMR spectra of 3, 4-polyisoprene synthesized: with Fe-catalyst system were investigated, and the: sequence distribution of cis-1, 4, trons-1, 4 and 3, 4-units and the amount of head-to-head and tail-to-tail linkages of 1, 4 and 3, 4-units were discussed. Results showed that the contents of cis-1, 4, trans-1, 4 and 3, 4-unit calculated from different carbon types were satisfactorily identical, indicating correct assignments of these peaks.     

A NEW PEAK (T_4) IN THE ~(13)C-NMR SPECTRUM OF POLYBUTADIENE

A new peak at 39.0 ppm in the ~(13)C-NMR spectrum of polybutadiene (PBD) was discovered. This peak is assigned to the fourth peak (T_4) of trans-1,4-sequence marked with an asterisk as shown in Fig. 3 in the text.The occurrence of T_4 carbon nuclei is strongly affected by their neighboring 1,2-units. So long as both contents of trans-1,4- and 1,2-units attain their proper amounts the peak (T_4) with appear in the ~(13)C-NMR spectrum of PBD.     

2-丁基-四氢噻吩亚砜13C-NMR的理论研究

在RHF/6-31G和B3LYP/6-31G水平上对顺式(Cis-)与反式(Trans-)2-丁基-四氢噻吩亚砜(BTHTO)进行几何优化,应用规范不变原子轨道法(GIAO)在6-31G、6-31+G、6-31++G和6-31+G(2d,p)水平上计算了Cis-和Trans-BTHTO的13C-NMR,对13C-NMR谱进行了归属。结果表明,BTHTO噻吩五元环的稳定构象呈半椅式,Cis-和Trans-BTHTO中与硫原子直接碳原子13C-NMR的显著差异主要是由于空间构型不同引起分子的静电势场对相应碳原子的屏蔽作用不同所致。     

溶聚丁苯链化学结构的NMR研究

溶聚丁苯链化学结构的NMR研究;溶聚丁苯; 链化学结构; 相容性     

Synthesis and 13C-NMR spectroscopic investigations of rhamnobioses

A convenient method has been developed for the synthesis of all mono- and di-O-benzyl ethers of methyl α-L-rhamnopyranoside applying a new stereoselective method for the hydrogenolytic ring-cleavage of benzylidene acetals. Using the prepared dibenzyl ethers as aglycones, the (1→2)-, (1→3)- and (l→4)-linked rhamnosyl-rhamnose derivatives (13–15) were synthesised. Hydrogenolysis of the latter compounds and subsequent acetylation gave the pentaacetates (16–18) of methyl dirhamnosides, which on saponification furnished the free methyl dirhamnosides (19–21). Acetolysis of 16–18 gave the corresponding dirhamnose-hexaacetates which were transformed into the three disaccharides by saponification. The structure of each product was investigated by ¹³C-NMR spectroscopy, and for the purpose of ¹³C-NMR studies the mono-O-methyl ethers of methyl α-L-rhamnopyranoside, the diacetates and di-O-benzyl ethers of the latter compounds, and, also the diacetates of methyl α-L-rhamnopyranoside were synthesised.It has been established that, for ¹³C-NMR investigations of oligosaccharides, the benzyl ethers of monosaccharides are more suitable model compounds than the currently used monosaccharide methyl ethers.