Studies on molecular weight distribution of carbon fiber polymer precursors synthesized using mixed solvents

The molecular weight distributions were estimated for carbon fiber polymer precursors such as poly（acrylonitrile-co -itaconic acid） synthesized by semi batch solution polymerization in mixed solvents media with the azonitrile compounds as initiator under the different ratios of solvent and non solvent from 0.75 to 2.5 in weight.The copolymer was characterized by using Fourier transform infrared spectroscopy（FTIR） and nuclear magnetic resonance（¹H-NMR） analyses.The molecular weight distributions were evaluated by M_v/M_n ratios estimated from viscosity and osmotic measurements,and M_w/M_n estimated from size exclusion chromatography.The molecular weight distributions of these polymers as determined from M_v/M_n and M_w/M_n are 2.9 to 3.2 and 2.0 to 2.5 respectively.The molecular distributions were close to a narrow distribution of 2.0 when the solvent/non-solvent ratio was varied between 1.4 and 2.0.Intrinsic viscosity[?]as a function of molecular weight of poly（acrylonitrile-co-itaconic acid） was evaluated by means of low angle laser light scattering with size exclusion chromatography（SEC-LALLS） and viscometry with SEC（SEC-VISCO）.The relationship between[?]and M_w for poly（acrylonitrile-co-itaconic acid） in DMF at 50℃was[?]= 1.1×10^-5M_w^0.79,where[?]is obtained in dL/g.     

富勒烯(C60/70)-丙烯酸的自由基共聚

富勒烯及其衍生物在超导、光电、磁学等领域展现出奇特性能[1],富勒烯的化学修饰成为化学工作者们关注的热点之一,而其中合成含富勒烯的新型聚合物是一个非常重要的方面.     

Thermal Stability and Thermal Behavior of Nanoparticle a-Fe2O3-stearate Alternating Langmuir-BIodgett Multilayer

Thermal stability and thermal behavior of nanoparticulate α-Fe₂O₃-stearate alternating Langmuir-Blodgett multilayer have been studied through temperature dependent FTIR spectroscopy. The results show that this multilayer has an excellent thermal stability. From 60℃ to 150℃,the alkyl chains in the multilayer can keep "all trans" configuration and the Fe₂O₃ nanopar-ticle multilayer film structure still remains an order structure. From 200℃ to 220℃, the film undergoes a phase transition from solid to liquid. Tins high melting point is due to the high molecular weight (at least 105 atomic weight units for one nanoparticle) and the stearate ions are chemically bonded to it.     

稀土化合物催化内酯开环聚合(Ⅲ)──氯化钕-环氧化合物体系催化ε

Bulk polymerization of ε-caprolactone(CL) with neodymium chloride-epoxide sys tem has been studied. It was found that the addition of epoxide can greatly increase the catalytic activity of neodymium chloride. The catalytic activity sequence of NdCl₃ combined with epoxide is: NdCl₃-ethylene oxide > NdCl₃-proplene oxide > NdCl₃-epichlorohydrin≈NdCl₃-allyl glycidyl ether. The catalytic activity of NdCl₃-proplene oxide system increases,but molecular weight of resulting polycaprolactone(PCL) decreases at higher proplene oxide/ neodymium chloride molar ratio.The molecular weight of PCL can be controlled by catalyst concentration. Higher polymerization temperature can greatly increase the catalytic efficien cy. At 30℃, PCLwith molecular weight as high as 28. 9×10⁴can be prepared easily with an activity of 44×10⁴g PCLper molar neodymium, and at 60℃, the molecular weight of PCLand catalytic efficiency increased to 42×10⁴and 10⁶g PCL/mole Nd respectively.     

C60-苯乙烯-顺丁烯二酸酐的三元自由基共聚

自从研制出克量的Ｃ6 0 [1],其在超导光、电、磁、生物等领域的研究迅速发展 .由于Ｃ6 0 只溶于几种非极性溶剂中 ,其使用受到限制 ,从而制备Ｃ6 0 的高分子衍生物一直被认为是Ｃ6 0 材料化的重要途径[2 6 ].文献 [39]报道 ,富勒烯与含双键的单体如苯乙烯、甲基丙烯酸甲酯等可很方便地进行自由基共聚 ,得到富勒烯与烯类单体的共聚物 ,产物可溶于四氢呋喃等有机溶剂 .但迄今为止 ,可溶于水或其它强极性溶剂中的Ｃ6 0 聚合物研究的很少[10 ,11],而Ｃ6 0 的三元共聚物的制备几乎未见报道 ,为此 ,我们采用自由基共聚制备了Ｃ6 0 苯乙烯 顺丁烯…     

用正电子研究CuCl2在NaY上的扩散

用正电子湮没谱学研究了机械混合CuCl₂与NaY中CuCl₂在NaY沸石中的扩散.分别测量了不同质量比的CuCl₂-NaY(0～0.03)沸石分子筛经140℃烘烤1h;CuCl₂-NaY(0～0.05)经450℃烘烤4h;CuCl₂-NaY(0.01)经不同温度烘烤1h以及经300℃下烘烤烘不同时间后的正电子寿命谱.所有谱中都出现了5(或4)个寿命分量,其第3,4,5寿命分量分别与β笼、超笼及沸石微粒界面空间的大小和数量相关.实验表明,正电子湮没谱学可敏感地探测出少量CuCl₂在NaY沸石中的扩散变化.而对于只含少量氯化铜(0.01)的情况,虽经高温长时间烘烤,但仍有相当数量的氯化铜存在于NaY外表面.     

SEC with UV and ELSD detection for analysis of gamma-irradiated PS-radiation-grafted P(VDF/HFP) films

Summary Thin poly(vinylidene fluoride/hexafluoropropylene) (P(VDF/HFP)) films ahve been irradiated with gammarays to induce the initiation of styrene grafting by the indirect method. To obtain a better understanding of the radiation-grafting process we have used size exclusion chromatography (SEC) to study the effect of irradiation of this polymer and the evolution of the molecular weights of the polystyrene (PS) grafted chains as a function of the grafting time. Pristine, irradiated and PS radiation-grafted samples have been compared. We present evidence that the gamma irradiation induces both scission and crosslinking of the P(VDF/HFP) chains. We show that the average molecular weights of the PS grafted chains increase with grafting time and that the asymmetry of the chromatographic peak increases also. These grafted chains have molecular weights much higher than those of pristine P(VDF/HFP) and they cannot be confused with PS homopolymer chains, which have higher molecular weights as both, pristine and radiation-grafted P (VDF/HFP). Reversed-phase high-performance liquid chromatography (RPHPLC) has shown the absence of additives in pristine P(VDF/HFP) and has provided evidence of the presence of oligomers.     

基于二氧化碳共聚物的紫外光固化高分子材料的制备与性能

普通低分子量的二氧化碳共聚物由于预聚体中含有较多的亲水性端羟基, 在紫外光辐照下不能交联而降低材料的耐水性. 为降低亲水性端羟基对材料耐水性的影响, 本文利用锌钴双金属氰化物(Zn-Co DMC)催化剂实现了CO₂与4-乙烯基环氧环己烷、 环氧环己烷的三元无规共聚, 制备出分子量在40000以上, 含C=C双键的脂环族聚碳酸酯; 采用四(3-巯基丙酸)季戊四醇酯为固化剂, 基于紫外光诱导的双键-巯基点击反应制备了紫外光固化高分子材料. 研究发现, 在5.0 mJ/cm²的紫外光辐照剂量下即可制备出高透明硬化涂层, 在可见光(400~750 nm)波段内透光率达到97.5%, 铅笔硬度达到3H, 对马口铁等基体附着力达到0级. 值得指出的是, 该紫外光固化薄膜的玻璃化转变温度超过110 ℃, 与双酚A型环氧树脂相当, 而且不含苯环等结构, 具有更优异的耐紫外光老化性能.     

麦草半纤维素的快速热裂解实验研究

采用管式炉反应器在550℃~850℃进行了半纤维素的高温快速热裂解实验,以了解其热裂解产物分布及热解规律。结果表明,半纤维素热解三相产物中,气体产物产率最大且随着温度的升高而增加,其主要成分为H₂、CO、CO₂、CH₄ 以及小分子烃类。液相产物中主要是酸类、醇类、呋喃、环戊烯酮类化合物,以及苯酚等芳香化合物,其产率随着温度的升高无明显变化。而焦炭产率则随着温度的升高而降低,且其中残留有大量的有机化合物如醇类、酮类及脱水糖等。     

由乙烯高效催化聚合而得的超高分子量聚乙烯的研究

本工作系研究以高效催化聚合获得的超高分子量聚乙烯的结构和性能。用扫描电子显微镜观察了高效催化剂及初生聚乙烯的形态。透射电子显微镜观察了初生聚乙烯粉未,发现毛遂边缘的超分子原纤维状织态结构。用偏光显微镜观察了不同分子量聚乙烯粉末的熔融和冷却结晶过程,生成的球晶随分子量增大而增大。用X-射线衍射、差热分析、倒换气相色谱测定了初生聚乙烯的结晶度随分子量而增大;用X-射线衍射、差热分析及密度梯度法测定经退火或热压制的聚乙烯样品的结晶度均随分子量增大而下降。X-射线衍射测定其晶粒尺寸亦随分子量增大而减小。差热分析和倒换气相色谱测定超高分子量聚乙烯粉末的结晶熔点温度(T_m)要比普通分子量聚乙烯高8-12℃。不同分子量聚乙烯的热形变曲线表明,超高分子量聚乙烯在熔融温度后出现明显的橡胶态。此外,还用差热与热重分析研究了超高分子量聚乙烯的热老化行为。测定了超高分子量聚乙烯的优异抗冲强度和沙浆磨耗量。并用扫描电镜对比观察了常规分子量和超高分子量聚乙烯试样的冲击断面的织态结构。     

不同有机胺修饰MCM-41的CO2吸附性能和热稳定性

将乙二胺(EDA,60 g/mol)、四乙烯五胺(TEPA,189 g/mol)和两种聚乙烯亚胺600(PEI600g/mol; PEI1800g/mol)分别负载在MCM-41上制备氨基功能化介孔材料,研究其对CO₂的吸附性能和热稳定性.结果表明,除了EDA-MCM41,其他三种材料随着胺分子量增大CO₂吸附性能下降,但是热稳定性却有所提高,其中,TEPA-MCM41的吸附容量最大,达到2.7 mmol/g.同时发现,乙二胺在制备过程中随溶剂挥发而难以完全负载在MCM-41上.在纯N₂气氛和再生温度100 ℃条件下,经10次循环实验后,TEPA-MCM41的吸附能力下降了7.4%,而PEI600-MCM41和PEI1800-MCM41吸附能力保持不变,且质量变化在1%以内,表现出良好的再生稳定性.采用80%CO₂/20%N₂对吸附饱和的材料进行再生,四种材料的再生温度将提高到160 ℃以上,高分子量PEI600-MCM41和PEI1800-MCM41相比于TEPA-MCM41具有更好的热稳定性.     

茂金属聚乙烯的非等温结晶行为及其动力学研究

为探索分子量和支链含量对聚乙烯非等温结晶过程的影响,选用3组样品:(1)不同分子量的无支链线形聚乙烯;(2)低分子量的支链含量不同的试样;(3)高分子量的支链含量不同的试样.用DSC研究了这3组样品的非等温结晶动力学.结果表明:(1)与支链含量相比,分子量大小对结晶的影响是次要的,但高分子量样品的结晶度比低分子量样品低;(2)支链对聚乙烯的非等温结晶有重要影响,在支化聚乙烯中起决定作用;(3)无论是高分子量试样还是低分子量试样,支化含量增加,聚乙烯的结晶温度、结晶度、结晶动力学以及晶体的熔点等显著降低.     

等规聚丙烯/聚丁烯-1釜内合金的结构与性能

高分子材料的组成、 组分分布及链结构与宏观性能紧密相关. 因此, 分析多组分釜内合金材料的链结构特点与性能之间的关系至关重要. 采用升温淋洗分级的方法对两种采用序贯两段聚合原位合成的等规聚丙烯/聚丁烯-1(iPP/iPB)釜内合金在-30 ℃~140 ℃温度范围进行分级, 采用核磁共振波谱仪、 傅里叶变换红外光谱仪、 差示扫描量热仪和凝胶渗透色谱仪等表征了级分的链结构及序列分布、 热行为、 分子量(M_w)及分子量分布(M_w/M_n)等. 结果表明iPP/iPB合金主要由5种级分组成, 高等规聚丁烯(iPB)为主要组分, 同时含有少量的丁烯-丙烯嵌段共聚物(PB-b-PP)和等规聚丙烯(iPP)等. 随淋洗温度升高, PB-b-PP级分中PP嵌段长度逐渐增加, PB嵌段长度逐渐减小; 在相同的淋洗温度, 合金B的嵌段共聚物级分中PP嵌段较长且结晶较完善; 合金B中iPB组分及嵌段共聚物组分含量较高, 使得合金B具有较高的拉伸强度、 弯曲强度、 优异的抗冲击性能、 较高的维卡软化温度及较快的晶型转变速率.     

聚合物共混物的超高效液相色谱-空间排阻色谱在线联用分离与表征

黏合剂和涂料行业中, 聚合物共混物表征是分析的难题, 分离技术的研究一直备受关注. 本文设计并搭建了超高效液相色谱-空间排阻色谱在线联用系统(UHPLC-SEC), 采用羟基聚丁二烯(HTPB)考察了二维色谱系统的溶剂兼容性及正交性, 以苯乙烯-丁二烯嵌段共聚物(SBS)、 苯乙烯-异戊二烯嵌段共聚物(SIS)和聚甲基丙烯酸酯(PMMA)共混物研究了二维色谱系统的适用性. 结果表明, HTPB分子量及分布的UHPLC-SEC测定结果与SEC测定结果一致, 峰尖分子量(M_p)为3407 Da, 重均分子量(M_w)为6573 Da, 分散系数(PDI)为2.36, 相对标准偏差(RSD)均小于5.7%, 系统的溶剂兼容性和正交性良好. UHPLC-SEC法测得聚合物共混物中PMMA, SBS和SIS的M_p, M_w和PDI与单个聚合物的SEC测定结果的相对误差均小于7.1%. PMMA, SBS和SIS共混物在200 °C加热3 h后, PMMA 稳定不变, SBS和SIS组分明显降解. UHPLC-SEC在线联用方法对聚合物共混物的表征结果准确、 重复性好, 为聚合物配方产品的失效分析提供了一种重要且有效的手段.     

三种不同碳桥联双核茂钛配合物的合成及催化乙烯聚合研究

合成了3种不同结构的CnH₂n桥联双核茂钛配合物(CH₃)₂C[(C₅H₄)TiCl₂(C₅H₅)]₂(3),(CH₂)_n[(C₅H₄)TiCl₂(C₅H₅)]₂(6,n=3;7,n=4),并用1HNMR进行了表征.发现以甲苯为溶剂时,不仅提高了产率,而且有效地避免了副产物Cp₂TiCl₂的生成.研究了化合物7/MAO(甲基铝氧烷)催化乙烯聚合的反应,考察了反应条件对催化体系的影响.结果表明,催化活性随着n(Al)/n(Cat.)比的增大而提高,聚乙烯的分子量在n(Al)/n(Cat.)=500和50℃时达到最高值9.0102×10⁴;随着聚合时间的延长,催化活性下降,而产物分子量不断升高;随着温度的上升,50℃时催化活性和聚乙烯的分子量最高,分别为2.4074×10⁵gPE/(molTi·h)和6.8679×10⁴.随着桥联双核茂钛配合物碳桥的增长,催化活性增加,所得聚乙烯的分子量降低.     

具有GPX活力的抗体片段Fv的制备和性质

具有谷胱甘肽(GSH)结合部位的鼠抗体3H₄(IgM)经胃蛋白酶水解,产生分子量为25000的抗体Fv片段,用荧光滴定法测定了它与GSH的亲和常数K_a=1.17×10₇L/mol.该片段经苯甲基磺酰氟活化,再经NaHSe作用,其结合部位的丝氨酸被突变为谷胱甘肽过氧化物酶(GPX)的催化基团硒代半胱氨酸.突变后的Fv片段表现出很高的GPX活性,其活力高达2500U/μmol,称为Fv抗体酶.动力学分析表明,Fv酶的最适温度为55℃,最适pH为7.0,催化机制为乒乓机制,米氏常数分别为:K_m(GSH)=4.16×10^-3mol/L,K_m(H₂O₂)=2.8×10^-4mol/L.     

鲨鱼软骨血管形成抑制因子的分离纯化及其活性的初步研究

以广东阳江鲨鱼软骨为原料,研究了鲨鱼软骨新生血管形成抑制因子的分离纯化方法,并对其生物学活性进行了初步研究.采用盐酸胍抽提、膜超滤、丙酮分级沉淀、SephadexG-75柱层析和C₄反相高效液相色谱等步骤,分离纯化出一种新的鲨鱼软骨血管生成抑制因子-a(SharkCartilageAngiogenesisInhibitor-a,SCAI-a),分子量为12600,能显著抑制鸡胚绒毛尿囊膜血管的形成.     

Influence of molecular weight and polydispersity on phase behaviour of polyesters with laterally fixed or cross-shaped mesogens

To supplement previous studies of polyesters with laterally attached and cross-shaped mesogens the influence of molecular weight and molecular weight distribution on the phase behaviour has been investigated. For that purpose two polyesters have been fractionated by preparative gel permeation chromatography under high pressure and observed by polarizing microscopy and DSC measurements. A monotropic nematic polyester with laterally attached mesogens shows changing phase transitions up to a molecular weight of 10 000 (M_w); at higher molecular weight only the clearing transition is still slightly influenced. The molecular weight distribution at an average molecular weight of 15 000 (M_w) has no influence on the melting and clearing temperatures, but does effect recrystallization. The tendency to recrystallize decreases with increasing polydispersity, with increasing aberration from a monomodal molecular weight distribution. The recrystallization and the melting enthalpy are most distinguished at molecular weights around 12 000 (M_w) and crystallization disappears at molecular weights under about 5000 (M_w). In this way, fractions with stable nematic phases are obtained. Additionally, the broadness of the biphasic region shows a distinct dependence on molecular weight. Clearing temperatures show the most significant dependence on the molecular weight of an enantiotropic polyester with crossshaped mesogens dropping significantly below a molecular weight of about 20 000 (M_w). Oligomers with molecular weights below 10 000 (M_w) do not exhibit a mesophase. Polyesters with laterally attached mesogens as well as with crossshaped mesogens show no new liquid-crystalline phases by varying the molecular weight or the molecular weight distribution.     

聚合温度对负载型Ziegler-Natta催化剂催化丁二烯-异戊二烯共聚合的影响

非均相TiCl₄/MgCl₂-AlR₃型Ziegler-Natta(非均相Z-N)催化剂是聚烯烃工业最重要的催化剂,经烷基铝活化的非均相Z-N催化剂具有复杂的活性中心结构,改变聚合温度、聚合时间、烷基铝种类及浓度等均会影响活性中心结构与催化性能.本文研究了不同聚合温度下TiCl₄/MgCl₂-AlEt₃(三乙基铝)催化丁二烯(Bd)和异戊二烯(Ip)的共聚合动力学,研究发现,随着聚合时间的延长,聚合活性先升高然后降低,在50℃聚合活性最高.采用核磁共振波谱(¹H NMR)、紫外荧光定硫仪和凝胶渗透色谱(GPC)研究了共聚物的微观结构、活性中心数和分子量及其分布,发现随着聚合时间的延长及聚合温度的升高,活性中心数、共聚物中反式-1,4-结构、分子量及分子量分布均发生不同规律的变化.本文研究结果可为进一步理解非均相Z-N催化剂在不同聚合温度下催化共轭二烯烃聚合的动力学及其关键影响因素提供参考.     

二氧化碳-氧化环己烯共聚物的合成和热性能研究

采用三元催化剂(Y(Cl3COO)3-ZnEt2-glycerin)催化二氧化碳与氧化环己烯共聚反应,制备了高分子量二氧化碳与氧化环己烯共聚物(PCHC).8 h内催化剂平均活性达到11.8 kg polymer/mol Zn,PCHC主链上碳酸酯单元含量大于95%,数均分子量达到7.0×104.研究了PCHC的玻璃化转变温度和分子量的关系,当PCHC的数均分子量(Mn)低于8.5×104时,玻璃化转变温度(Tg)随Mn增加而升高;Mn高于8.5×104时,Tg对Mn的依赖性不大.当PCHC的分子量充分高时,其玻璃化转变温度可以达到120℃,PCHC的自由体积特征常数K=1.91×105.研究了聚合物分子量对其热稳定性的影响,结果表明提高分子量有利于提高PCHC的热分解温度.通过实施聚合反应和后处理,三元催化剂转化为相应的金属氧化物(主要为氧化锌)残留在聚合物中,采用Kissinger方法得到纯PCHC(除去金属氧化物)的热分解表观活化能约为199.9 kJ/mol,含金属氧化物(Zn含量4400×10-6)PCHC的热分解表观活化能下降为143.9 kJ/mol.因此氧化锌能够促进PCHC的热降解,减少PCHC中氧化锌的含量有利于改善PCHC的耐热性能.