三氟化硼引发四氢呋喃聚合的研究——Ⅱ. 水的影响

<正> 分子量在3000以下的四氢呋喃聚合产物-聚丁二醇(PTMG)是重要的工业原料。前报中我们已证明用BF_3-环氧氯丙烷(ECH)引发四氢呋喃(THF)聚合时引发效率较高,在这一基础上有希望通过在聚合体系中加水以达到控制产物分子量的目的。 文献上对水在BF_3-ECH引发THF聚合反应中作用的研究不多,Kyzaeb等人     

三氟化硼引发四氢呋喃聚合的研究——以环氧氯丙烷为促进剂

<正> 四氢呋喃(THF)通过正离子开环聚合而制得的聚丁二醇(PTMG)是生产嵌段聚醚聚氨酯及嵌段聚醚聚酯弹性材料的重要原料。目前制备PTMG所采用的引发剂都是强酸型的,如高氯酸、氟磺酸或发烟硫酸等,对设备腐蚀严重。用酸性较弱的三氟化硼引发聚合在文献上也有一些研究报道,但尚难以采用,其主要困难在于实际应用的     

三氟化硼引发四氢呋喃聚合的研究——Ⅳ.1,4-丁二醇的影响

前报中已证明用三氟化硼-环氧氯丙烷(ECH)引发四氢呋喃(THF)聚合具有较高的引发效率,并对在Ac_2O、水和无水存在下的聚合反应进行了研究。本文报道1,4-丁二醇(BG)对BF_3引发THF聚合反应的影响。通常认为在BG存在下,BF_3是不能引发THF聚合的,但本工作证明BG是有效的分子量调节剂,制备分子量在     

四氢呋喃与环氧氯丙烷共聚合的研究

<正> 晃玉等曾以BF_3-二元醇(DO)引发四氢呋喃(THF)与环氧氯丙烷(ECH)共聚合,用所得共聚醚制成嵌段聚醚聚氨酯,与用THF均聚醚或THF-环氧丙烷(PO)共聚醚为软段的聚氨酯相比,分别在低温性能及强度上有明显改进.且由于引入氯甲基侧基可作进一步接枝共聚改性。但用BF_3-DO为引发剂很难制得不含环聚体的共聚醚,     

嵌有长聚醚软段液晶共聚酯的合成

本文用对苯二甲酰氯、对苯二酚、己二醇及分子量为1000或2000的聚丁二醇醚,经溶液缩聚制备了嵌段聚醚聚酯,其介晶单元含量只为21.2重量％(或37.5mol％)即可在宽的温度范围内呈现明显的液晶性.~1H-NMR谱表明,产物的聚酯段呈嵌段微观序列分布.     

聚酯-聚酯多嵌段共聚物的合成及其动态力学性能

聚酯-聚醚多嵌段共聚物的动态力学性能谱上有两个T_8,不宜做阻尼材料。本文报道聚对苯二甲酸乙二醇酯(PET)-端羟基聚己二酸乙二醇酯(PEA)共聚物(简称嵌段共聚酯),比聚醚-聚酯多嵌段共聚物有更好的相容性。我们研究了PEA的分子量,间苯二甲酸的用量对嵌段共聚酯的结晶度,以及结晶度对嵌段共聚酯的动态力学性能的影响。     

ABA型两亲嵌段共聚物的合成及表征

以α ,α′ 二溴代二甲苯为引发剂 ,CuBr/2 ,2′ 联吡啶为催化体系 ,制备了双溴端基的分子量分布窄的聚苯乙烯 (MWD =1 18) .再以此作为大分子引发剂 ,实现了甲基丙烯酸对硝基苯酯的原子转移自由基聚合 ,制得了分子量可控且分子量分布窄的ABA型嵌段共聚物 ,再经水解、酸化 ,得到了聚甲基丙烯酸 b 聚苯乙烯 b 聚甲基丙烯酸ABA型两亲嵌段共聚物     

高分子量立构复合结晶的三枝化PPO-PDLA-PLLA嵌段共聚物

以三枝化低不饱和度聚环氧丙烷(PPO)引发D-丙交酯(D-LA)逐步开环聚合, 合成了三枝化聚环氧丙烷-聚右旋乳酸(PPO-PDLA)共聚物. 用辛酸亚锡Sn(Oct)₂与PPO-PDLA端羟基反应进行Sn(Oct)封端, 制备了三枝化PPO-PDLA-Sn(Oct)预聚物. 再于130 ℃下, 以其作为大分子引发剂与L-丙交酯(L-LA)开环聚合, 合成了分子量>10⁵的三枝化PPO-PDLA-PLLA嵌段共聚物. 活性端基的引入, 降低了聚合反应温度, 从而降低了聚合中的酯交换或热降解反应发生的概率. 实现了高分子量PPO-PDLA-PLLA嵌段共聚物的合成. 结构测试结果表明, 合成的嵌段共聚物具有分子结构易控及立构规整度高等特点. 在结晶-熔融-再结晶重复热处理下, 三枝化PPO-PDLA-PLLA嵌段共聚物仅发生立构复合聚乳酸结晶, 且结晶能力稳定.     

化学酶法合成五嵌段聚合物及其自组装行为的研究

用酶促开环聚合与ATRP方法相结合,制备了聚甲基丙烯酸六氟丁酯-聚己内酯-聚乙二醇-聚己内酯-聚甲基丙烯酸六氟丁酯(PHFMA-b-PCL-b-PEG-b-PCL-b-PHFMA)五嵌段聚合物.首先用Novozym e 435作为催化剂合成了聚己内酯-聚乙二醇-聚己内酯三嵌段聚合物,然后通过端基官能化法合成了大分子引发剂,并用其引发甲基丙烯酸六氟丁酯(HFMA)的ATRP反应,合成了五嵌段聚合物.通过核磁和GPC证明了大分子引发剂和五嵌段共聚物的结构,五嵌段共聚物的GPC分析表明这种合成方法的可行.共聚物胶束的直径和大小通过动态光散射方法和原子力显微镜测试,五嵌段共聚物在水中的的自组装行为也被研究.结果证明胶束是球形,其平均直径为77 nm.聚合物在四氢呋喃中的浓度对聚合物的聚集形貌有很大的影响.     

自组装制备聚(丙烯酸叔丁酯-b-甲基丙烯酸二甲胺基乙酯)壳交联胶束

以1-氯代乙苯为引发剂、氯化亚铜/N,N,N′,N″,N″-五甲基二乙撑三胺(PMDETA)为催化体系、丁酮-异丙醇为混合溶剂,通过原子转移自由基聚合法制备不同分子量的大分子引发剂聚丙烯酸叔丁酯(1-PECl)及不同嵌段比的两亲性嵌段共聚物聚(丙烯酸叔丁酯-b-甲基丙烯酸二甲胺基乙酯)(P(tBA-b-DMAEMA))。通过1H-NMR表征了P(tBA-b-DMAEMA)的结构,GPC测试了其分子量及分子量分布。P(tBA-b-DMAEMA)在选择性溶剂中自组装形成核-壳结构的胶束,引用了乙烯基乙二醇二碘醚(BIEE)为交联剂与链段PDMAEMA发生化学交联反应从而得到稳定的壳交联胶束结构,并通过马尔文粒径仪研究了自组装所得胶束的温度及pH敏感性。     

New synthetic route of polyoxytetramethyleneglycol by use of heteropolyacids as catalyst

Polyoxytetramethyleneglycol (PTMG) can be directly prepared from tetrahydrofuran (THF) and water in the presence of heteropolyacids (HPA), without the hydrolysis step. The reaction is carried out by mixing two liquid phases: the THF phase and a heteropolyacid catalyst phase. In this reaction the molar ratio of water to a heteropolyacid (H₂O/HPA) in the catalyst phase plays an important role in the THF polymerization activity and the molecular weight of PTMG. IR spectrometric studies revealed that THF is coordinated to a heteropolyanion through either a water molecule or a proton in the catalyst phase. The latter type of coordination bings about the activation of THF capable of initiating the ring-opening polymerization even in the presence of water at a lower acid strength. The PTMG prepared by this method has a narrow molecular weight distribution (M?_w/M?_n = 1.5 or less) and a number average molecular weight of 500–2000 which are requisite for the production of polyurethane elastomers. A new polymerization mechanism named “Phase Transfer Polymerization” is proposed for elucidating a narrow molecular weight distribution.     

四氢呋喃开环聚合的研究

四氢呋喃(THF)通过正离子开环聚合制得的聚丁二醇(PTMG)是生产聚氨酯及聚酯弹性材料的重要原料。对PTMG的一般要求是平均分子量在600—3000之间,两个端基为羟基。一般用下列三类催化剂制备的:醋酸酐-高氯酸,氟磺酸及发烟硫酸,用醋酸酐-高氯酸为催化剂制得的聚四氢呋喃,是以醋酸酯基(—OAC)为端基,尚需进一步水解反应,使端基变为羟基。用氟磺酸为催化剂,虽然产物的端基为羟     

Preparation and characterization of a new class of poly(ether‐block‐amide)s via solvent free reactive processing

Novel poly(ether‐co‐amide) block copolymers (PEA) with polyamide‐6 as hard segments and different polyether (polyoxytetramethylene glycol [PTMG]/polyethylene glycol [PEG]) as soft segments were prepared via reactive processing. The chemical structure, crystalline properties, mechanical properties, water resistance, and thermal stability of as‐prepared PEAs were extensively studied by Fourier transform infrared spectroscopy, X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, tensile testing, water contact angle, water absorption, and thermal gravity analysis. Fourier transform infrared spectroscopy confirmed the chemical structure and composition of PEAs. The X‐ray diffraction and differential scanning calorimetry showed that PEAs consist of obvious crystalline polyamide‐6 hard segments and that the crystalline structure of PEG will be significantly changed with the addition of PTMG. Dynamic mechanical analysis and tensile testing showed that the obtained PEAs exhibit classical elastomeric rubber plateau and tensile behavior. Meanwhile, the introduction of PTMG will improve the mechanical properties of PEAs. PEA with PEG as soft segments exhibited extremely surface hydrophilicity and high water absorption of 127%; the increasing of PTMG content in soft segments will reduce the surface hydrophilicity and improve the water resistance. In addition, the obtained PEAs exhibited good thermal stability, which will meet requirement of multiple processing.     

Studies on thermotropic main chain liquid crystalline segmented polyurethanes I. Synthesis and properties of polyurethanes from high aspect ratio mesogenic diol as chain extender

Thermotropic main chain liquid crystalline polyurethanes were prepared from 4-{[4-(6-hydroxyhexyloxy)phenylimino]methyl}benzoic acid 4-{[4-(6-hydroxyhexyloxy)phenylimino]methyl}phenyl ester (mesogenic diol) and 1,6-hexamethylene di-isocyanate. The effects of partial replacement of the mesogenic diol by 20-50 mol% of poly(tetramethylene oxide)glycol (PTMG) of varying molecular mass (M _n =650, 1000, 2000) on the liquid crystalline properties were studied. Structural characterization was carried out by FTIR spectroscopy and the molecular mass distribution was determined by GPC. Differential scanning calorimetry and hot stage polarizing optical microscopy were used to study the mesomorphic properties. It was observed that the partial replacement of the mesogenic diol by PTMG of varying molecular masses influenced the phase transitions and the occurrence of mesophase textures. When the molecular mass of PTMG was enhanced, a higher content of mesogenic agent was needed to obtain liquid crystalline properties.     

Polyurethanes containing sulfur. III. New thermoplastic HDI-based segmented polyurethanes with diphenylmethane unit in their structure

Three series of new thermoplastic, high molecular weight, segmented thiopolyurethanes were synthesized by a one-step melt polymerization from newly obtained thiodiols, including bis[4-(2-hydroxyethyl)thiomethylphenyl]methane, bis[4-(3-hydroxypropyl)thiomethylphenyl]methane, and bis[4-(6-hydroxyhexyl)thiomethylphenyl]methane (BHHM), as chain extenders; hexamethylene diisocyanate; and 20–80 mol % poly(oxytetramethylene) glycol (PTMG; number-average molecular weight = 1000) as the soft segment. Solution polymerization with the chain extender BHHM gave considerably lower molecular weight polymers. The structures of all the polyurethanes were determined with Fourier transform infrared and X-ray diffraction analysis. The thermal properties of the polyurethanes were examined with differential scanning calorimetry and thermogravimetric analysis. Shore A/D hardness and tensile properties were also determined. All the polyurethanes showed partially crystalline structures; those obtained with 40–80 mol % PTMG were elastomers. An increase in the PTMG content decreased hardness, modulus of elasticity, and tensile strength, whereas elongation at break increased. BHHM-based polyurethanes obtained in the melt showed the best tensile properties. The polyurethanes exhibited definite glass transitions (−70 to −59 °C) that were nearly independent of the hard-segment content up to about 50 wt % (40–80 mol % PTMG), indicating the existence of mainly microphase-separated soft and hard segments. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1733–1742, 2001     

Effect of Organoclays on Silicate Layer Structures and Thermal Stabilities of in-situ Polymerized Poly(D-lactide)/Clay Nanocomposites

Six kinds of organoclays were prepared through three kinds of polyols (PTMG, PEA and PCL) to investigate the effects of molecular weight and the chemical structure of organifiers. PTMG based organoclays showed higher ion-exchanged fraction than other organoclays and long chain organifier showed better efficiency in ion-exchanged fraction in the case of PTMG based organifiers. From WAXD and TEM analysis, it was confirmed that PTMG based organoclays formed partially exfoliated or fully exfoliated silicate layer structures. PDLA/clay nanocomposites were prepared by in-situ ring-opening polymerization of D-lactide with PTMG based organoclays as macro-initiators in the presence of equimolar Sn(Oct)₂/PPh₃ complex catalysts. The molecular weight of PDLA/clay nanocomposite decreased as increasing the feeding amount of organoclay because organoclay had hydroxyl terminal groups which can initiate the ring-opening polymerization of D-lactide. From TGA analysis, thermal stabilities of PDLA/clay nanocomposites improved with increasing organoclay content. From WAXD and TEM analysis, organoclay which was prepared by high molecular weight of PTMG based organifier was effective on the exfoliation of silicate layers in the in-situ polymerized PDLA/clay nanocomposite.     

Energy-efficient manufacturing of polymers with tunable mechanical properties by frontal ring-opening metathesis polymerization

Frontal polymerization (FP) is a process in which the heat generated by the self-reaction transforms monomers to cured polymers. Here, in order to improve the flexibility of polydicyclopentadiene, comonomers (norbornene-terminated polyether, ND-230,400,2000) are designed and synthesized, which can copolymerize with dicyclopentadiene (DCPD) by FP. The polymers (ND) prepared by ND-2000 and DCPD have tunable mechanical properties, from thermosets to elastomers. Specifically, the breaking elongation of the polymers can be varied 69-fold, from 6.1% to 423.4% by controlling the proportion of ND-2000. Among them, ND polymer with 50 wt% ND-2000 has good elastic behavior without yield. And, the reaction mixture solutions of DCPD and ND-2000 have the characteristics of controllable gel time and shear thinning, which make it have the potential of application in additive manufacturing.     

Synthesis and characterization of novel degradable photocrosslinked poly(ether‐anhydride) networks

New degradable poly(ether‐anhydride) networks were synthesized by UV photopolymerization. Dicarboxylated poly(ethylene glycol) (PEG) or poly(tetramethylene glycol) (PTMG) was reacted with an excess of methacrylic anhydride to form dimethacrylated macromers containing anhydride linkages. The percent of conversion for the macromer formation was more than 80% at 60 °C after 24 h. ¹H NMR and IR spectroscopies show the presence of anhydride linkages in the macromer. In vitro degradation studies were carried out at 37 °C in PBS with crosslinked polymer networks formed by UV irradiation. All PEG‐based polymers degraded within 2 days, while PTMG‐based polymers degraded by 50% of the initial weight after 14 days. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1277–1282, 2000