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1.
<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  相似文献   

2.
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。  相似文献   

3.
The chain structure of 1,2-polybutadienes prepared with molybdenum catalyst systems has been studied by IR, ~(13)C-NMR and T_g method, and the method to regulate the chain structure investigated. It was found that some polar additives, e. g., allyl halides, are able to regulate not only the content of 1,2-units in the polymer, but also its configuration and sequence distribution. Attempt has been made to estimate the sequence length of stereo-isomers of 1,2-units by statistical theory.  相似文献   

4.
The structure of stereoregular polymers of 1,3-pentadiene was determined by 13C-NMR spectroscopy at 22.6 MHz. Not only was it possible to distinguish between cis-1,4 and trans-1,4 but also between isotactic and syndiotactic cis-1,4 structures. Triad effects were detected in the trans-1,2 syndiotactic polypentadiene; 1,4–1,2 as well as 1,4–4,1 linkages were observed.  相似文献   

5.
Stereoblock polybutadiene (PBD) composed of amorphous equibinary cis?1,4/1,2 PBD (e‐PBD, soft) and crystalline syndiotactic 1,2‐PBD (s‐1,2‐PBD, hard) segments is synthesized through one‐pot sequential polymerization with iron(III)2‐ethylhexanoate/triisobutylaluminum/diethyl phosphate [Fe(2‐EHA)3/Al(i‐Bu)3/DEP] catalyst system. The first‐stage polymerization of 1,3‐butadiene (BD) is carried out at a low [Al]/[Fe] ratio to give amorphous e‐PBD block, and sequentially, the in situ addition of excessive Al(i‐Bu)3 and BD to the living polymerization system give rise to a second crystalline s‐1,2‐PBD block. The length of each block is controllable by adjusting cocatalyst and monomer feed ratio. The syndiotactic pentad content is in the range of 63.8–76.6% and increases with the length of s‐1,2‐PBD block. The copolymer exhibits glass transition temperature (Tg) around ?40 °C and melting point (Tm) around 168 °C originating from e‐PBD and s‐1,2‐PBD blocks, respectively. The incompatibility between s‐1,2‐PBD and e‐PBD blocks as well as the crystallization of s‐1,2‐PBD block induce the microphase separation in stereoblock PBD. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1182–1188  相似文献   

6.
The microstructure of stereoregular 1,4-trans-and 1,4-cis-polypiperylenes, as well as polymers prepared from the trans-and cis-piperylene isomers via cationic polymerization in the presence of TiCl4, was studied by high-resolution 13C NMR spectroscopy. Polypiperylene synthesized through the cationic polymerization of the cis isomer had a more diversified morphology of the macromolecular chain, i.e., had higher relative amounts of 1,2-cis-units and combinations of irregular-addition 1,4-trans-units. It was shown that 13C NMR spectra give the most comprehensive and independent information on the details of structure of the piperylene macromolecular chain.  相似文献   

7.
High-resolution 1H and 13C NMR spectroscopy, including two-dimensional heteronuclear experiments, has been used to study the microstructure of polyisoprene produced by cationic polymerization. It is shown that macromolecules resulting from both regular and inverse additions are predominantly composed of trans-1,4-units, while 1,2- and 3,4-units are present in small amounts. NMR spectra demonstrate the absence of cis-1,4-units in the polymer, whereas broad signals (pedestals) are related to the presence of saturated structures. It is proposed to determine the content of trans-1,4-, 1,2-, and 3,4-units in cationic polyisoprene via the combined measurements of intensities of signals in the olefinic regions of 1H and 13C NMR spectra.  相似文献   

8.
Proton decoupled, partially relaxed, Fourier-transform 50.3 MHz carbon-13 NMR in naturalabundance was used to determine spin-lattice times (T_1) and nuclear Overhauser enhancement fac-tors (NOE) of individual carbon of a serics of 1,2-polybutadienes with different structures in solutionin CDCl_2 The structure dependence of molecular metion and the internal motion of vinyl group in1,2-polybutadiene have been studied by nT_1 and NOE values. The nT_1 values of the carbons in cis-1,4-units are the highest and those of the carbons in 1.2-units are the lowest in three types of units in1,2-polybutadiene. The nT_1 values of carbons in the same unit become greater when the adjacent1,2-units are replaced by 1,4-units, and nT_1 values of the carbons in all units decrease sharply withthe increase of content of 1,2-units in the polymers. The fact that nT_1 values of --CH=are larger than those of=CH_2 in vinyl group impliesthat there are complex internal motions of vinyl group. It is shown by calculation that the dominantfactor causing the difference in nT_1 of--CH=and=CH_2 in vinyl group is a swing of vinyl group ina plane peopndicular to the chain backbone.  相似文献   

9.
The barium salt of the dimeric dianion of 1,1-diphenylethylene (Ba-DPhE) initiates polymerization and copolymerization of monomers capable of anionic polymerization (butadiene, isoprene, styrene) in ethereal and hydrocarbon solvents. Ba-DPhE is more stereospecific in butadiene polymerization (up to 70% of cis-1, 4-units in hydrocarbon medium) than initiators based on other metals of Groups I and II. The relative reactivity of monomers in copolymerization processes in THF decreases in an order typical for anionic polymerization: styrene > butadiene > isoprene. The most interesting feature of organobarium initiators is their ability to form random butadiene-styrene copolymers with high cis-1,4-butadiene unit content when copolymerization proceeds in a hydrocarbon medium.

A new phenomenon in anionic polymerization, the dependence of diene units structure on copolymer composition, was observed. Thus an increase of styrene content in butadienestyrene copolymer leads to conversion of cis-1,4-butadiene units into trans-1,4-units (in benzene) or to conversion of 1,4-units to 1,2-units (in THF). Similarly, an increase of butadiene content in its copolymer with isoprene (in benzene) leads to conversion of cis-1,4-isoprene units into trans-1,4-units.

Spectrophotometric, conductometric, and viscometric methods were used to study organobarium active centers. Certain anomalies connected with the formation of specific aggregates due to coupling of bifunctional hydrocarbon chains with bivalent counterions were observed.  相似文献   

10.
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.  相似文献   

11.
This study deals with cationic polymerization of the cis- and trans-isomers of 1,3-pentadiene. The microstructure of the polymer chains is studied by 1H-NMR, 13C-NMR and IR spectroscopies. It is shown that the trans-diene gives strictly trans-1,4 and trans-1,2 residual linear insaturations, whereas the cis-isomer yields also cis-1,4, cis-1,2 and 3,4-units whose overall content can reach 10 mol-%. According to the cyclization degree of the macromolecules, ranging from 30 to 70 mol-%, the number of trans-(1,2+1,4) units varies between 33 to 65 mol-% and that of trans-1,2 units between 4 and 20 mol-%. An analytical method is proposed to evaluate the average number of rings present in the polycyclic sequences. It is found that the cyclic fragments of the polymer chains consist of bi- or tri-cyclohexane fused rings containing α tetrasubstituted double bond.  相似文献   

12.
The ~(13)C-NMR spectra of alternating copolymers of conjugated dienes, butadiene (BD), isoprene(IP) and chloroprene (CP), with methyl acrylate (MA) were studied. It is proved that they are allalternating copolymers. The BD units in Poly (BD-alt-MA) are joined to MA mainly in the formof trans 1,4-structure. The contents of trans 1,4-, cis 1,4-and 1,2-structure are 88, 7 and 5%, res-pectively. The IP and CP units in Poly(IP-alt-MA) and Poly(CP-alt-MA) exist essentially as trans1,4-configuration and connect with MA units in "head to head" arrangement predominantly, whileCP-CP units present in Poly(CP-alt-MA) in a small quantity.  相似文献   

13.
High molecular weight carboxylated polybutadienes (cPBDs) with number-average molecular weight (Mn) from 98,000 to 200,000 and carboxylic acid (COOH) contents of 0.5–10 mol % were successfully synthesized through hydrocarboxylation of polybutadienes (PBDs) at temperatures of 140–150°C using PdCl2(PPh3)2 and SnCl2 · 2H2O catalysts. At low extents of hydrocarboxylation (COOH < 6 mol %), glass transition temperatures (Tg's) of the resulting cPBDs did not change considerably (<10°C). Significant chain scission and crosslinking was not detected during the chemical modification process. Characterization of the microstructures of cPBDs by FTIR, 13C-NMR, and Raman spectroscopy showed that the carboxylic groups were incorporated on the pendant (1,2) PBD double bonds as well as the backbone (1,4) double bonds, indicating the hydrocarboxylation reaction did not solely occur at the terminal carbons of the pendant double bonds. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3129–3138, 1999  相似文献   

14.
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.  相似文献   

15.
The mode of formation of isotactic and syndiotactic polymers from 1,3-dienes is examined in the light of the most recent results. An interpretation is given for the formation of trans-1,4 isotactic polymers from CH2=CH-CH=CHR (R = Me, Et, Pr, etc.) type monomers with heterogeneous VCl3-based catalysts. Evidence is reported showing that stereoregular 1,2 or cis-1,4 polymers derive from a growing polymer chain anti-η3-bonded to the transition metal and a cis-η4 coordinated monomer. The influence on stereoselectivity of the substituents at the central carbon atoms of the monomer is discussed. The peculiar behavior of (Z)-1,3-pentadiene and 4-methyl-1,3-pentadiene, which give 1,2 polymers with catalysts that give 1,4 polymers from other monomers, is attributable to the fact that they can coordinate trans-η2, in addition to cis-η4.  相似文献   

16.
The results of the search for the à → X? radiative relaxation of haloethylene cations in the gaseous phase are reported. Only in the case of cis-1,2-difloroethylene cation was an emission spectrum detected. It is identified as the à 2A1 → X? 2B 1 band system on the basis of photoelectron spectroscopic measurements. An assignment of the emission bands yields the vibrational frequencies of four of the A1 fundamentals (under C2, symmetry) for the X? state and one for the à state. Well resolved Ne(I) photoelectron spectra of cis- and trans-1,2-difluoroethylene are presented, from which some vibrational frequencies for these cations in the X? and à states are also obtained. The lifetimes of cis-1,2-difluoroethylene cation in the lowest vibrational levels of the à 2A1 state have been measured. The decay of this cation is unusual as these levels are depleted both by, radiative, and pathways leading to fragment ions (C2HF+). The lack of detectable emissions with other fluoro-, chloro- and bromo-ethylene cations is discussed and the likely symmetries of the à states are proposed.  相似文献   

17.
New epoxide and cyanate ester resins with an aromatic ester backbone namely 1,3-[di-(4-glycidyloxy diphenyl-2,2-propane)]-isophthalate (DGDPI) and 1,4-[di-(4-cyanato diphenyl-2,2-propane)]-terephthalate (DCDPT) were synthesized and the intermediates were characterized by IR, 1H-/13C-NMR spectroscopic methods. The cured products from DGDPI and DHDPI exhibited higher Tg compared with standard epoxy system. The increase in the Tg may be due to the cyanate ester and rigid aromatic backbones present in the curing system.  相似文献   

18.
E. Giralt  J. Rizo  E. Pedroso 《Tetrahedron》1984,40(20):4141-4152
The results presented in this article show the general applicability of gel-phase 13C-NMR to monitor solid phase peptide synthesis on the most commonly used polystyrene-based resins. The optimal conditions to acquire gel-phase 13C-NMR spectra of copoly(styrene-l%-divinylbenzene) has been determined. The technique proved to be applicable to characterize polystyrene-based starting supports as well as to the determination of their degree of functionality and purity. The stage-by-stage 13C-NMR characterization of the growing peptide chain during the synthesis of tripeptide H-Asn-(N-Me)Ala-Thr-NH2 on a benzhydrylamine resin is described. The structural information, derived from this technique is relevant for the synthetic process as the spectra can be acquired under similar conditions. The characteristics of the spectra facilitate monitoring of coupling and deprotection reactions.  相似文献   

19.
Highly crystalline syndiotactic 1,2-polybutadiene (s-PB) having melting point (mp) up to 216°C was obtained by using a Co(acac)3-AIEt3-CS2 catalyst. The polymer with mp 208°C was found to have 99.7% 1,2 content and 99.6% syndiotacticity by 1H and 13C-NMR measurements. The s-PB can be molded by addition of a stabilizer such as 2,6-di-t-butyl-4-hydroxymethylphenol into fiber, film, and various shaped articles. The physical properties presented in the present article include stress-strain and dynamic mechanical behavior. The highly crystalline syndiotactic 1,2-polybutadiene was applied to a carbon fiber and UBEPOL VCR (cis-1,4-polybutadiene reinforced by fibrous syndiotactic 1,2-polybutadiene).  相似文献   

20.
13C-NMR spectra of bulk acrylonitrile-butadiene-styrene (ABS) resin are reported. The styrene-co-acrylonitrile (SAN) carbons can be observed selectively by using high-power proton decoupling, cross polarization, and magic angle spinning (MAS). The polybutadiene (PBd) carbons can be observed selectively by using low-power proton decoupling, with or without MAS. Methods and conditions for using 13C-NMR to quantify the amount of PBd in solid ABS resins are developed. The 13C-NMR results and results from iodine monochloride titrations for PBd content are in good agreement. Resonances of PBd in ABS in the solid state are assigned on the basis of triad sequences of cis, trans, and vinyl-1,2 geometric isomers of butadiene. Computational methods are set forth for measuring directly from the 13C-NMR spectra the percent of cis, trans, and vinyl-1,2 isomers in PBd in the ABS resin. The NMR measurement of PBd microstructure appears to be preferable to infrared (IR) determinations. Relaxation parameters (T1 and NOE) are reported for PBd in bulk ABS as a function of temperature and are analyzed in terms of a distribution of rotational correlation times. These relaxation parameters are similar to those of nongrafted PBd and indicate that the local motions in grafted and nongrafted PBd are similar.  相似文献   

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