双烯类聚合物的热分析——Ⅱ.不同含1,2-含量无规聚丁二烯热(氧化)的研究

不同1,2-含量无规聚丁二烯的研究表明,与侧链乙烯基相比,主链双键更易于发生热氧化反应,这可能因其含有较多的a-氢。根据热氧化温度和动力学参数活化能E,钴系高1,2-含量间规聚丁二烯比之钼(或锂)系聚丁二烯更为稳定,前者E值高达150kJ/mol以上,后者为100kJ/mol左右。热交联表观活化能分别为181、166kJ/mol。它们热氧化稳定性的差别,是由于通常钴系聚合物为晶态,锂(或钼)系为非晶态。     

双烯类聚合物的热分析Ⅱ.不同含1,2-含量无规聚丁二烯热(氧化)的研究

不同1,2-含量无规聚丁二烯的研究表明,与侧链乙烯基相比,主链双键更易于发生热氧化反应,这可能因其含有较多的α-氢。根据热氧化温度和动力学参数活化能E,钴系高1,2-含量间规聚丁二烯比之钼(或锂)系聚丁二烯更为稳定,前者E值高达150kJ/mol以上,后者为100kJ/mol左右。热交联表观活化能分别为181、166kJ/mol。它们热氧化稳定性的差别,是由于通常钴系聚合物为晶态,锂(或钼)系为非晶态。     

含反式-1,4和间规-1,2链节的聚丁二烯X-射线衍射谱分析

<正> 近年来陆续出现在顺式-1,4聚丁二烯分子链中引入室温下可结晶的反式-1,4及间规-1,2聚丁二烯链节,以期改善顺丁橡胶的抗撕裂性和抗弯曲性等。有关这方面的结构表征工作尚很少报道。本工作用广角X-射线衍射(WAXD)方法,对钒、钴催化体系合成的含反式-1,4及钴催化体系合成的含间规-1,2的顺丁橡胶进行了结构表征。     

1,2-聚丁二烯分子链的结构和内旋转运动

实验订定了1,2-链节含量分别为8％,30％和90％的1,2-聚丁二烯在30℃甲苯溶液中的Mark-Houwink方程[η]=KM~(?)。发现不同样品的α值基本相同,而K值确实随1,2-链节含量的增加而减小,说明溶液中分子链线团变得紧密了。用线膨胀法和Stockmayer-Fixman方程及分子链的统计力学方法,分别得到了样品的玻璃化温度T_g,和它们的分子链内旋转空间位阻因子σ。它们二者符合T_g=A(σ—b),其中A=174(K),b=0.68。反映了1,2-链节对分子链内旋转的阻碍作用。进一步的研究表明,低1,2-链节含量对应着较低的分子链内旋转势垒和内旋转异构化能。     

聚丁二烯1,2-结构含量和SBS中聚丁二烯段1,2-结构含量的调节

以正丁基锂为引发剂,环己烷为溶剂,研究了四氢呋喃(THF)对聚丁二烯1,2-结构和丁苯嵌段共聚物SBS中聚丁二烯段1,2-结构含量的影响,指出在一定温度下,聚丁二烯1,2-结构含量与体系中THF的浓度有指数关系。控制体系中THF的浓度和聚合反应温度,可调节聚合产物中聚丁二烯1,2-结构含量。     

1,2-聚丁二烯分子运动的~(13)C-NMR研究——Ⅱ.分子运动的温度依赖性

本文用200MHz脉冲傅利叶变换波谱仪测定了1,2-聚丁二烯样品在不同温度下的~(13)C-T_(19)NOE,线宽和化学位移等~(13)G自旋弛豫参数,研究了1,2-聚丁二烯分子运动的温度依赖性.结果发现,在-10—-30℃之间,样品中各碳核的NOE和谱线宽度随温度变化的曲线斜率增加,表明此时长程链运动冻结;各碳核nT_1随温度的变化均在-45℃左右出现极小值.     

丁二烯在 Co(acac)_3-Al(i-Bu)_3-含硫化合物催化体系中的定向聚合及其聚合机理

在 Co(acac)_3—Al(i-Bu)_3—含硫化合物催化体系中合成了含量在97%以上的高结晶性1,2-结构的间同1,2-聚丁二烯.研究了几种含硫化合物、催化剂的组成及配比对聚合的影响.初步探讨了丁二烯间同1,2-聚合的机理.     

间同立构1,2-聚丁二烯的合成和形态结构研究

间同立构 1 ,2 -聚丁二烯自 1 955年问世以来 ,引起人们的广泛关注 ,但绝大多数研究工作集中在聚合物的合成方面[1～ 3] ,对其形态结构方面的研究却很少报道[4 ] ,原因是该聚合物分子侧链含有大量双链 ,在较高温度下 (>1 50℃ )很容易产生热交联 ,这给结构研究造成了很大困难 .间同立构 1 ,2 -聚丁二烯的性能取决于间规度 ,低间规度聚合物呈现弹性体特征 ,而高间规度聚合物则是一种半结晶性塑料 ,其结晶为平面锯齿链正交堆砌 ,Pacm空间群[4 ] .本文采用一种新的催化体系 ,使合成的 1 ,2 -聚丁二烯间规度可以调控 .同时首次报道了结晶性间规…     

分子结构对1,2-聚丁二烯橡胶性能的影响

本文研究了分子链结构、分子量及其分布对钼催化聚合1,2-聚丁二烯(1,2-PB)的加工工艺性能及硫化胶性能的影响.实验发现,1,2-PB的加工工艺行为随分子量降低和分子量分布加宽而得以改善,其抗湿滑性能随分子链中1,2-结构含量增加而提高,而1,2-结构的空间规整性—间同含量的增加则导致1,2-PB应变诱导结晶、降低硫化胶的弹性和增加生热值。     

W-Al体系在合成1,2-聚丁二烯中的催化活性

WCl_6是优良的开环聚合催化剂,但只有一篇专利中提到用WCl_6催化丁二烯的聚合得到非顺式1,4-聚丁二烯,而且活性很低.用钨化合物催化丁二烯聚合为高1,2-链节含量的聚丁二烯,则尚未有报道.我们的工作发现,WCl_4(OR)_2-(i-Bu)_2AlOPh体系可使丁二烯在加氢汽油中聚合成1,2-链节含量在80％左右,1,2-链节的全同立构体含量达60％以上的聚丁二烯.为合成1,2-聚丁二烯橡胶开辟了一个新的催化体系.但是,初步研究结果表明:催化活性和聚合物分子量均较低.因此,本文试图探索提高催化活性和聚合物分子量的方法.     

Considering factors on determination of microstructures of SBR vulcanizates using pyrolytic analysis

Properties of styrene-butadiene rubbers (SBRs) are depending on their microstructures (contents of 1,4-unit, 1,2-unit, and styrene), but it is hard to determine the microstructures of SBR vulcanizates. Pyrolytic method such as pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been used for microstructures of cured rubbers without pretreatment. Microstructure of SBRs can be estimated using the major pyrolysis products (butadiene, 4-vinylcyclohexene (VCH), and styrene). In this study, considering factors for determination of microstructures of SBR vulcanizates using Py-GC/MS were investigated. The principal considering factors were found to be change of the major pyrolysis products due to radicals formed in carbon backbone and sulfur by dissociation of sulfide crosslinks in SBR vulcanizates. Relative abundances of the major pyrolysis products of raw and cured SBRs were different due to rearrangements of the radicals. Influencing factors on pyrolysis behaviors of SBR vulcanizates were found to be 1,2-unit block, alternating sequence of 1,4- and 1,2-units, styrene-1,4-unit and styrene-1,2-unit sequences, and location of the radicals. Especially, the 1,2-unit block influenced on change of the VCH/butadiene ratio, while the styrene-1,2-unit sequence affected change of the styrene/(butadiene + VCH) one.     

异戊二烯/甲基丙烯酸甲酯嵌段共聚物的合成与微结构研究

用稀土催化剂ＲＥ（Ｐ２０４）３ （ｉ Ｂｕ）３Ａｌ ＢｒＣＨ２ＣＨ２Ｂｒ（ＲＥ＝Ｎｄ,Ｐｒ,Ｙ等）合成嵌段共聚物Ｐ（ＩＰ ｂ ＭＭＡ）．系统考察了共聚合反应特征,以ＤＳＣ,１Ｈ ＮＭＲ,１３Ｃ ＮＭＲ技术研究了该嵌段共聚物的微结构．发现以二溴乙烷为添加剂的稀土催化体系是制备Ｐ（ＩＰ ｂ ＭＭＡ）的良好催化剂,共聚物含２个玻璃化转变温度,分别为－７５６℃和１２９℃,嵌段共聚物的结构规整,（ＩＰ）ｍ段以ｃｉｓ １,４结构为主,其含量为９７％左右,３,４ 结构为３％左右,链节间以头 尾方式连接．（ＭＭＡ）ｎ段以间同立构为主,其含量达７４％．     

Initiator‐fragment incorporation radical copolymerization of vinyl acetate and 1,2‐polybutadiene as a multivinyl monomer

The copolymerization of vinyl acetate (VAc) with 1,2‐polybutadiene (1,2‐PB; 85.5% 1,2‐units and 14.5% 1,4‐units) as a multivinyl monomer was carried out at 80 °C in dioxane with dimethyl 2,2′‐azobisisobutyrate (MAIB) at high concentrations (0.10–0.50 mol/L) as an initiator. The copolymerization of 1,2‐PB [0.80 mol/L (monomer unit)] and VAc (1.20 mol/L) with MAIB (0.30 mol/L) for 4 h proceeded homogeneously without gelation to yield a soluble copolymer. The resulting copolymer was divided into methanol‐ and n‐hexane‐insoluble parts, of which the yields based on the total weight of the comonomers and initiator were 46 and 20%, respectively. The methanol‐insoluble part consisted of the fractions of the 1,2‐PB units with (9 mol %) and without (39 mol %) an intact double bond, the 1,4‐PB unit (8 mol %), the VAc unit (32 mol %), and the methoxycarbonylpropyl group (12 mol %) as the MAIB fragment, whereas the hexane‐insoluble one was composed of the fraction of the 1,2‐PB units with (4 mol %) and without (17 mol %) a double bond, the 1,4‐PB unit (4 mol %), the VAc unit (60 mol %), and the methoxycarbonylpropyl group (15 mol %). The use of higher concentrations of 1,2‐PB and VAc and lower concentrations of MAIB resulted in gelation. The cast film from a chloroform solution of the methanol‐insoluble part contained spherical pores organized in a hexagonal way with a monodisperse pore size of 3 μm. The copolymer molecules seemed to be arranged in an ordered way on the surface layer of the pores, as shown by an optical microscopy image under crossed polarizers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2328–2337, 2006     

Crystallizable elastomers by chemical modification of transtactic polydiolefins. Hydrochlorination

Solutions of crystalline, high-melting trans-1,4 polybutadiene (trans-PB), trans-1,4 mix 1,2 butadiene-piperylene copolymer (BPC, low piperylene content), and isotactic trans-1,4 piperylene (trans-PP) were partly hydrochlorinated under mild conditions with gaseous HCl. Glass transition and melting temperatures were strongly affected by the addition of HCl. Several hydrochlorinated trans-PB and -BPC were semicrystalline or amorphous elastomers, susceptible to reversible crystallization when stretched. The straininduced crystallinity was similar to that shown by trans-polybutadiene sequences, particularly in the form that is unstable in bulk at room temperature (form II). The addition of HCl to the asymmetric double bond in trans-PP occurs in a stereoselective way, according to ¹³C-NMR. under the experimental conditions of the present study the occurrence of side reactions was observed; these reactions decrease the polymer unsaturation to a lower level than that calculated by the amount of HCl added to the polymer.     

Filler-polymer interactions in filled polybutadiene compounds

Bound rubber in a filled rubber compound is formed by physical adsorption and chemisorption between the rubber and filler. Polybutadiene (PB) is composed of three components of 1,2-, cis-1,4-, and trans-1,4-units. Filler-polymer interactions in PB compounds filled with carbon black or silica were studied by analyzing microstructures of the bound rubbers with pyrolysis-gas chromatography. Differences in the filler-polymer interactions of the 1,2-, cis-1,4-, and trans-1,4-units were investigated. The filler-polymer interaction of the 1,2-unit is stronger than those of the cis-1,4- and trans-1,4-units. The interaction of the 1,2-unit with silica is stronger than with carbon black. Bound rubber content is decreased by treatment with ammonia. Change of the bound rubber composition after the ammonia treatment was also studied.     

The Origin of Hierarchical Structure Formation in Highly Grafted Symmetric Supramolecular Double‐Comb Diblock Copolymers

Involving supramolecular chemistry in self‐assembling block copolymer systems enables design of complex macromolecular architectures that, in turn, could lead to complex phase behavior. It is an elegant route, as complicated and sensitive synthesis techniques can be avoided. Highly grafted double‐comb diblock copolymers based on symmetric double hydrogen bond accepting poly(4‐vinylpyridine)‐block‐poly(N‐acryloylpiperidine) diblock copolymers and donating 3‐nonadecylphenol amphiphiles are realized and studied systematically by changing the molecular weight of the copolymer. Double perpendicular lamellae‐in‐lamellae are formed in all complexes, independent of the copolymer molecular weight. Temperature‐resolved measurements demonstrate that the supramolecular nature and ability to crystallize are responsible for the formation of such multiblock‐like structures. Because of these driving forces and severe plasticization of the complexes in the liquid crystalline state, this supramolecular approach can be useful for steering self‐assembly of both low‐ and high‐molecular‐weight block copolymer systems.     

完全交替结构乙烯-丙烯共聚物的制备与表征

对顺-1,4含量为100%的高顺式聚异戊二烯(HCPI)进行加氢反应,得到了序列结构高度规整的乙烯-丙烯交替共聚物(alt-EP).所用的HCPI有适当的分子量(Mn=41×104)和极窄的分子量分布(Mw/Mn=1.02).HCPI的加氢反应以环烷酸镍和三异丁基铝为催化剂,在60℃和4.0MPa氢压的条件下反应3h,加氢产物的加氢度为100%.GPC测试结果显示所得乙烯-丙烯交替共聚物保持了窄分布的特点,表明HCPI加氢后未发生交联和降解反应;NMR,FTIR和广角X射线衍射测试结果表明此乙烯-丙烯交替共聚物具有高度规整的序列结构,为完全交替结构的乙烯-丙烯共聚物.并通过TGA和DSC对乙烯-丙烯交替共聚物的热性能进行了表征.     

Dehydrogenation of poly(1,3‐cyclohexadiene)–polystyrene binary block copolymers

The dehydrogenation of poly(1,3‐cyclohexadiene)–polystyrene binary block copolymers obtained by anionic copolymerization with alkyllithium/amine systems was investigated for the first time. The dehydrogenation of the poly(1,3‐cyclohexadiene) block, which was composed of 1,2‐cyclohexadiene (1,2‐CHD) and 1,4‐cyclohexadiene (1,4‐CHD) units, was strongly affected by the polymer chain structure. The existence of 1,2‐CHD units prevented the dehydrogenation of the poly(1,3‐cyclohexadiene) block in the binary block copolymer. The rate of dehydrogenation was fast on a long sequence of 1,4‐CHD units, whereas it was relatively slow for 1,2‐CHD/1,4‐CHD (≈1/1) unit sequences. The bonding of the polystyrene block to the polymer chain effectively improved not only the rate of dehydrogenation of a long sequence of 1,4‐CHD units but also that of the polymer chain with a high content of 1,2‐CHD units. The dehydrogenation of a poly(1,3‐cyclohexadiene) block containing a small number of 1,2‐CHD units progressed via step‐by‐step reactions. The dehydrogenation of a long sequence of 1,4‐CHD units proceeded as the first step. Subsequently, in the second step, the 1,2‐CHD/1,4‐CHD (≈1/1) unit sequences remaining in the polymer chain were dehydrogenated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3526–3537, 2006