PA1212-b-PEG嵌段共聚物的组成对结晶和熔融行为的影响

研究以双端羧基尼龙1212为硬段,以双端氨基聚乙二醇为软段的聚酰胺-聚醚分嵌段共聚物的结晶行为。用偏光显微镜、差示扫描量热法研究了不同组成共聚物的结晶形态、熔融结晶温度的影响。PLM观察到共聚物的结晶形态随硬段分子量的增大趋于完善,软硬段相容性随软硬段分子量增大而变差;DSC扫描表明共聚物的熔融温度随着硬段分子量增大而增大,软硬段分子量较大时软硬段相容性较差。     

一步法制备聚酰胺聚醚弹性体及其在抗静电ABS材料中的应用

采用一步原位缩聚法成功制备了聚酰胺6-聚乙二醇嵌段共聚物(PA6-b-PEG),将其与丙烯腈-丁二烯-苯乙烯三元共聚物(ABS)熔融共混制备了永久抗静电ABS,研究了不同软硬比PA6-b-PEG对永久抗静电ABS性能的影响。傅里叶变换红外光谱测试结果表明PA6与PEG发生了共聚反应,成功制备了PA6-b-PEG。抗静电性能测试结果表明添加共聚物(PA6-b-PEG)的ABS材料表面和体内的电阻率均下降,符合抗静电要求;耐水洗性测试说明,添加共聚物(PA6-b-PEG)的ABS材料中软硬比为50/50的抗静电ABS材料,其耐水洗性和抗静电性最好;熔融指数测试表明添加共聚物(PA6-b-PEG)的ABS材料要比纯的ABS材料具有更好的加工流动性;力学性能测试结果显示,添加共聚物(PA6-b-PEG)的ABS材料,其拉伸强度、弯曲强度均不如纯的ABS材料。     

聚酰胺—聚醚多嵌段共聚物的合成,表征及性能

聚酰胺-聚醚多嵌段共聚物是以结晶型饱和脂肪聚酰胺为硬链段(PA)和无定型脂肪聚醚(PTMG)为软链段的一种尼龙多嵌段共聚物。采用双端羧基尼龙1010预聚体和双端羟基聚四亚甲基醚预聚体经高温熔融缩聚制得了不同软硬段分子量和含量的PA-PTMG多嵌段共聚物,并通过分子量测定,溶剂萃取,红外光谱和~(18)C-NMR测量等对产物进行表征。同时,研究了软硬段分子量和含量对嵌段共聚物力学性能的影响,结果表明硬段分子量太小和软段分子量太大都不利于材料的力学性能。     

光敏性咖啡酸基三元聚酯的制备与自组装

采用熔融缩聚方法合成了3,4-二羟基肉桂酸(DHCA,咖啡酸)、石胆酸(LCA)和聚乙二醇(PEG)的三元类嵌段共聚物P(DHCA-co-LCA)-b-PEG,用傅里叶红外变换(FTIR)光谱、核磁共振氢谱(1H-NMR)和凝胶渗透色谱(GPC)对该聚酯的结构与分子量进行分析.所合成的聚酯结构,其分子量在2.0×104...     

端氨基聚乙二醇-聚乳酸嵌段共聚物的合成及表征

以聚乙二醇为原料,采用四步反应,合成了二碳酸二叔丁酯单保护的氨基聚乙二醇(BOC-PEG-NH2);并以DOe-PEG-NH2为引发剂,引发丙交酯开环聚合,得到了叔丁氧基酰胺基聚乙二醇-聚乳酸嵌段共聚物(BOC-PEG-PLA).在三氟乙酸二氯甲烷溶液中,脱去保护基团,得到了端氨基聚乙二醇-聚乳酸嵌段共聚物(NH2-PEG-PLA).采用核磁共振氢谱(1H-NMR)、紫外光度仪(UV)表征各聚合物的结构,由凝胶色谱仪(GPC)测定嵌段共聚物的分子量以及分子量分布.结果表明:合成的氨基引发在无催化剂条件下能够引发丙交酯开环聚合,制得分子量高、分子量分布窄的双亲性共聚物.通过三氟乙酸脱保护得到了端氨基聚乙二醇-一聚乳酸(NH2-PEG-PLA),且对分子量没有影响.     

端羧基聚苯乙烯的合成及室温缩聚

采用链式聚合方法,用4,4'-偶氮-二(4-氰基戊酸)为引发剂引发苯乙烯的自由基聚合,合成了两端带有羧基基团的功能化聚苯乙烯。研究了单体、引发剂、溶剂之间的配比及聚合温度对合成端羧基聚苯乙烯的影响。并用合成得到的端羧基聚苯乙烯与聚乙二醇在室温、常压等十分温和的条件下进行酯化缩聚反应,得到聚苯乙烯/聚乙二醇两亲性嵌段共聚物。红外分析(FT-IR)和核磁共振(~1H-NMR)测试结果证实成功合成了端羧基聚苯乙烯和聚苯乙烯/聚乙二醇嵌段共聚物;凝胶渗透色谱(GPC)和差热分析(DSC)测试结果分别表明合成得到的端羧基聚苯乙烯的分子量较大、分子量分布比较均匀,并且随着分子量的增加,端羧基聚苯乙烯的玻璃化转变温度逐渐升高。     

尼龙1010—聚四氢呋喃多嵌段共聚物的聚集态结构研究

用缩聚法制成尼龙1010-聚四氢呋喃多嵌段共聚物(简称PA-PTMG)。经元素分析、抽提分析、红外光谱(IR)1H-NMR等实验,结果表明所得共聚物的嵌段比和投料比吻合,嵌段效果好。应用广角X射线衍射(WAXD)(常温和变温)发现这种共聚物在常温时不是通常人们所认为的由一相晶相一相非晶相所构成,而是除结晶区以外有两种非晶区,即PA晶区、PA非晶区和PTMG非晶区。升温以后两非晶峰逐渐形成统一的非晶散射峰。给出了嵌段共聚物的形态示意图,探讨了温度对结构的影响以及分子量对结构和力学性能的影响。     

PEG改性聚乳酸嵌段共聚物降解性能研究

辛酸亚锡催化下开环聚合制备聚乳酸(DL-PLA)-聚乙二醇(PEG)-聚乳酸三嵌段共聚物.用GPC、DSC、1 H-NMR、质量损失、静态接触角等方法在pH=7.4磷酸盐缓冲液中,37℃下研究了分子量Mn=400、1000和4000的PEG改性DL-PLA的降解行为.结果表明,PEG嵌段增强了共聚物的亲水性,降低了共聚物Tg,加速了共聚物降解,随着PEG分子量增加及两端DL-PLA链段增长,共聚物分子量下降速率加快.由研究结果得出,共聚物降解期间DL-PLA链段中的酯键随机断裂,PEG两端DL-PLA链段逐渐变短;降解后期DL-PLA链段进一步变短,并有短链DL-PLA均聚物产生,当PEG两端DL-PLA链段足够短时,共聚物在介质中溶解.     

星形聚乙二醇-聚乳酸嵌段共聚物的合成与表征

以不同臂数和分子量的星型聚乙二醇(sPEG)和L-丙交酯为原料,采用开环聚合法合成了以星型聚乙二醇为内部嵌段、聚L-乳酸为外部嵌段的多臂星形聚乙二醇-聚乳酸嵌段共聚物(sPEG-b-PLLA)。研究了sPEG的臂数、分子量及L-丙交酯/sPEG投料比等参数对产物结构与性能的影响。并分别用红外光谱(FT-IR)、核磁共振(1H-NMR)、凝胶渗透色谱(GPC)、差示扫描量热(DSC)对产物进行了表征,证实所合成的嵌段共聚物具有预期的结构。结果表明,sPEG-b-PLLA为结晶性聚合物,且表现出与PLLA相似的晶型,随着PLLA链段的增加,产物的结晶度也呈增大的趋势;与PLLA相比,sPEG-b-PLLA的接触角随着PEG链段的增多而增大,表明其亲水性明显改善。     

聚乙二醇改性聚乳酸嵌段共聚物的合成与亲水性研究

以DL-丙交酯和分子量Mn=400、1000和2000聚乙二醇(PEG)为原料,在辛酸亚锡催化下开环聚合制备了聚乳酸(PLA)-聚乙二醇-聚乳酸三嵌段共聚物(PLEG)。考察了催化剂用量、反应时间对产率和[η]的影响。用FT-IR、1 H-NMR、GPC、DSC、XRD、静态水接触角等对共聚物进行了表征和性能测试。结果表明,催化剂用量为0.2%、反应时间分别为PLEG400共聚物2～4h、PLEG1000共聚物4～8h和PLEG2000共聚物8～12h较宜;共聚物组成比与投料比较一致,共聚物的数均分子量与理论计算值较一致;共聚物为无定形态,PEG的引入使共聚物Tg明显低于PLA均聚物,且随PEG的Mn减小,共聚物的Tg随之降低;而且PEG的引入明显提高了PLA的亲水性,PEG的Mn越小,PLA亲水性的提高程度越大。通过控制催化剂用量和反应时间,150℃可以得到分子量符合投料组成比要求、亲水性有明显提高的PLA-PEG-PLA三嵌段共聚物。     

尼龙1212/SEBS-g-MA/DIDP/BSBA共混体系的结晶行为

用W AXD、PLM及DSC研究了尼龙1212/SEBS-g-M A/D IDP/BSBA共混体系的结晶行为。W AXD结果显示,增韧剂的加入改变了尼龙1212的晶型。PLM观察表明共混体系中由于M A与尼龙之间的相互作用,增韧剂充当了成核剂,使得尼龙1212球晶向细晶化发展。用修正A vram i方程的Jez iorny法研究共混体系的非等温结晶动力学,发现共混体系的半结晶时间t1/2缩短,增韧剂对尼龙1212有明显的异相成核作用。     

Reinforcing polyamide 1212 with graphene oxide via a two-step melt compounding process

In this study, graphene oxide (GO) was synthesized from graphite powders via Hummers’ method. Polyamide 1212 (PA1212)/GO composites were prepared via a two-step melt compounding process. First, GO concentrates were prepared via solution coagulation. In this method, a GO solution was mixed with an ethanol-soluble polyamide solution. The resulting product was melt-compounded with a PA1212 matrix. This method enabled GO nanosheets to be well-dispersed in a PA1212 matrix. GO, which functioned as a nucleation template, exhibited heterogeneous nucleation effect in the PA1212 matrix because of its large specific surface area. The mechanical properties of the oriented PA1212/GO composites improved efficiently compared with those of pure PA1212. Crystal orientation degree and crystallinity in the composites increased slightly when GO was added after drawing. The composites’ reinforcing effect was mainly attributed to GO nanosheet alignment. These nanonsheets functioned as the nuclei to reinforce the entire oriented crystals.     

Reinforcing polyamide 1212 nanocomposites with aligned carbon nanofibers

In this study, the mechanical properties and structure orientation of pure polyamide 1212 (PA1212) were compared with those of PA1212–carbon nanofibers (CNFs) nanocomposites. The tensile strength of the composite containing 0.3 wt.% modified CNFs was improved from 328 MPa (pure PA1212) to 373 MPa after drawing. The reinforcing effect was investigated in terms of crystallization behavior, crystal morphology, alignment of CNFs, and crystal orientation degree. Spherulites developed into oriented crystals after drawing, and the CNFs aligned along the drawing direction. The heterogeneous nucleation effect of the aligned CNFs improved the crystal orientation degree, which produced the reinforcing effect. The oriented fibril structures with rigid nanofibers acting as nuclei reinforced the entire oriented crystals in the composites.     

柔韧性石油发酵尼龙1212等速降温结晶动力学研究

将等温Avrami方程推广应用于等速降温的非等温结晶过程，用DSC法研究了柔韧性PFPA1212的等速降温结晶行为和结晶动力学。结果表明，柔韧性PFPA1212中增韧剂使基体的结晶温度有一定的提高，结果温度范围变窄。其结晶行为的动力学参数n,k,t1/2等结果与同类高聚物的文献报道的有相似之处，但由于增韧剂不同而使结晶行为动力学参数的处理结果更为复杂，总的结果是增韧剂具有诱导结晶作用，使PFPA1212的结晶速率常数增大，半衰期减小。     

The gelation behaviors of the reactive blends of nylon1212 and functional elastomer

Studies on the gelation behaviors of the reactive blends of nylon1212 and functional elastomer were carried out. The results show that the curves of the storage modulus(G′)–frequency (ω) exhibit a gel plateau in the low ω region, and the transition from liquid-like to solid-like viscoelastic behaviors emerges with the concentration of SEBS-g-MA increasing. There exist the gelation behaviors in the blending process similar to those of crosslinking polymer. Based on Winter’s method, the gel point of blends is determined to be, φ_g = 17.45 wt%, and the corresponding value of tanδ is 1.44. The gel index n calculated is 0.61 and the gel strength S _g is 1.08 × 10⁴ Pa s^0.61. However, the non-reactive blends of nylon1212 and elastomer have no emergence of gelation behaviors. The morphology analysis shows that the gel point for the reactive blends is a threshold of cocontinuous morphology, and morphology analysis can also be a method to determine the gel point.     

Preparation of RuEu-1212 and RuEu-1222 Large Single-Crystalline Grains by Partial Melting

Journal of Superconductivity and Novel Magnetism - Single-crystal growth of rutheno-cuprate materials EuSr2RuCu2O8?δ (RuEu-1212) and (Eu, Ce)2Sr2RuCu2O10?δ (RuEu-1222), where...     

The Study of Hole Distribution in High-Tc Tl- and Hg-based 1212 Type Cuprates via High-Resolution X-Ray Absorption Near Edge Structure

High resolution O K-edge and Cu L₃-edge X-ray absorption near-edge-structure (XANES) spectra of the high-T_c cuprates of (Tl_0.5Pb_0.5)Sr₂(Ca_1?xY_x)Cu₂O₇ (Tl-1212) and (Hg_0.5Pb_0.5)Sr₂(Ca_1?xY_x)Cu₂O₇ (Hg-1212) in powder form were measured using a bulk sensitive total-fluorescence-yield technique. Near the O 1s edge, the pre-edge peak with maxima at ～ 528.3 eV is ascribed to the transitions to O 2p holes located in the CuO₂ planes. The intensity of this pre-edge peak increases with increasing doping level of Ca²⁺ into the Y³⁺ sites in Tl-1212 and Hg-1212. In the Cu L-edge absorption spectra, high-energy shoulders at around 933 eV are attributed to the transitions to the Cu(2p_3/2)^?13d¹⁰L states in the CuO₂ layers, where L denotes the O 2p ligand hole. The behavior of these shoulders in Tl-1212 and Hg-1212 correlates with that of the pre-edge peak at ～ 528.3 eV in the O K-edge absorption spectra. The results can lead us to understand the hole distribution in high-T_c cuprates which will give a direction to find new high-T_c materials.     

Superconducting properties of 1212 phase in (Tl, M) Sr2(Ca1-xCrx)Cu2O7 (M=Zr and Ce)

Samples with nominal starting compositions (Tl0.8M0.2)Sr2(Ca1-xCrx)Cu2O7 (1212) where M=Ce and Zr have been prepared and investigated by the d.c. electrical resistance method and powder X-ray diffraction analyses. Most of the samples showed the 1212 as the major phase and 1201 as the minor phase. Both series of samples showed the highest superconducting onset temperature (Tc) at x=0.2. Ce was found to be more favourable for the formation of the 1212 phase compared to Zr. The valence state of Zr, estimated by employing previous results of optimum average Cu valence for superconductivity in the 1212 superconductors, is 4+. The importance of ionic radius of the substituted elements and the effect of starting composition on Tc and phase formation are discussed. © 1998 Chapman & Hall     

The Study of Hole Distribution in High-Tc Tl- and Hg-based 1212 Type Cuprates via High-Resolution X-Ray Absorption Near Edge Structure

High resolution O K-edge and Cu L₃-edge X-ray absorption near-edge-structure (XANES) spectra of the high-T_c cuprates of (Tl_0.5Pb_0.5)Sr₂(Ca_1–xY_x)Cu₂O₇ (Tl-1212) and (Hg_0.5Pb_0.5)Sr₂(Ca_1–xY_x)Cu₂O₇ (Hg-1212) in powder form were measured using a bulk sensitive total-fluorescence-yield technique. Near the O 1s edge, the pre-edge peak with maxima at 528.3 eV is ascribed to the transitions to O 2p holes located in the CuO₂ planes. The intensity of this pre-edge peak increases with increasing doping level of Ca²⁺ into the Y³⁺ sites in Tl-1212 and Hg-1212. In the Cu L-edge absorption spectra, high-energy shoulders at around 933 eV are attributed to the transitions to the Cu(2p_3/2)^–13d¹⁰L states in the CuO₂ layers, where L denotes the O 2p ligand hole. The behavior of these shoulders in Tl-1212 and Hg-1212 correlates with that of the pre-edge peak at 528.3 eV in the O K-edge absorption spectra. The results can lead us to understand the hole distribution in high-T_c cuprates which will give a direction to find new high-T_c materials.