Tethered diblock copolymer chains on platelets prepared by semicrystalline ABC triblock copolymers in toluene with trace amounts of water

Lamellar platelets of triblock copolymers grown in dilute toluene solution with trace amounts of water can be used as templates for tethered diblock copolymer chain preparation and analysis. Polystyrene-bpoly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) with two different block fractions were used as model templates to generate tethered P2VP-b-PS chains on the platelet basal surfaces. In toluene solution the aggregation states of PS-b-P2VP-b-PEO were sensitive to the water content in the solution. For toluene with trace amount of water, spherical micelles were formed in the early stage and large square platelets would gradually grow from these spherical micelles. The hydrogen bonding between water and EO units was responsible for the formation of micelles and subsequent square platelets in the solution. Tethered P2VP-b-PS chains on basal surface of PEO platelets could be regarded as diblock copolymer brushes and the density (or: 0.086-0.36) and height (d: 3.5-14.3 nm) of these tethered chains could be easily modulated by changing the crystallization condition and/ or the molecular weight of each block. The tethered P2VP-b-PS chains were responsive to different solvent vapor.

Synthesis and crystallization behaviors of poly(styrene-b-isoprene-b-epsilon-caprolactone) triblock copolymers

The triblock copolymers, poly(styrene-b-isoprene-b-epsilon-caprolactone)s (PS-b-PI-b-PCL) have been synthesized successfully by combination of anionic polymerization and ring-opening polymerization. Diblock copolymer capped with hydroxyl group, PS-b-PI-OH was synthesized by sequential- anionic polymerization of styrene and isoprene and following end-capping reaction of EO, and then it was used as macro initiator in the ring-opening polymerization of CL. The results of DSC and WAXD show big effect of amorphous PS-b-PI on the thermal behaviors of PCL block in the triblock copolymers and the lower degree of crystalline in the triblock copolymer with higher molecular weight of PS-b-PI was observed. The real-time observation on the polarized optical microscopy shows the spherulite growth rates of PCL27, PCL328 and PS-b-PI-b-PCL344 are 0.71, 0.46 and 0.07 mu m s(-1), respectively. The atomic force microscopy (AFM) images of the PS90-b-PI66-b-PCL-(28) show the columns morphology formed by it's self-assembling.

马来酸酐封端聚碳酸亚丙酯的大分子偶联反应

自从 1 969年井上祥平[1] 发现二氧化碳 (CO2 )可以同环氧化合物直接共聚合成脂肪族聚碳酸酯(APC)以来 ,这一学科领域受到科学家的广泛关注[2～ 8] .这是因为CO2 所产生的温室效应 ,成为使全球变暖的主要因素[9,10 ] .已经确定CO2 使气侯变暖占诸多因素中的 66% .目前大气中CO2 的体积浓度为 345ppmv,由于人类的各类活动每年以 1ppmv的速度递增 .因此 ,降低CO2 排放量已成为全人类共同关注的热点之一 .另一方面 ,CO2 的固定化以及消耗、利用显然是一个应积极鼓励的研究课题 .目前人们已经将CO2 同环氧乙烷 (EO)、环氧丙烷 (PO)、环氧环己烷 (CHO)等环氧化合物实现共聚 ,制得一类脂肪族碳酸酯新材料 .特别是自从人们发现戊二酸锌等高效催化剂可以得到具有高分子量的APC以来 ,APC做为一种新的塑料材料使用已具有现实意义 .由于APC的加工热稳定性较差 ,在高温条件下 ,很容易产生大分子主链的断裂及从端基开始的解拉链式降解 ,因此 ,研究其物理特性及提高其热稳定性的方法具有重要的科学意义和实际应用价值 .本文采用熔体反应的办法 ,实现了马来酸酐(MA...

Thermodynamical study on pressure-induced compatibility in UCST polymer-containing mixtures

The present calculations were performed on the basis of the Sanchez-Lacombe lattice fluid theory and the new combinatorial rules for block copolymer according to the experimental results on the pressure-induced compatibility in poly(ethylene oxide) (PEO) and poly(ethylene oxide-b-dimethylsiloxane) (P(EO-b-DMS)) mixtures with UCST behavior. The study on enthalpy, combinatorial entropy, vacancy entropy and Gibbs energy upon mixture shows that Sanchez-Lacombe fluid theory and the new combinatorial rules could describe the pressure-induced compatibility (PIC) of polymer mixtures with UCST behavior well.

Ring-opening polymerization of epsilon-caprolactone and L-lactide using organic amino calcium catalyst

Poly (6-caprolactone) (PCL) and poly (L-lactide) (PLA) were prepared by ring-opening Polymerization catalyzed by organic amino calcium catalysts (Ca/PO and Ca/EO) which were prepared by reacting calcium ammoniate Ca(NH3)(6) with propylene oxide and ethylene oxide, respectively. The catalysts exhibited high activity and the ring-opening polymerization behaved a quasi-living characteristic. Based on the Fr-IR spectra and the calcium contents of the catalysts, and based on the H-1 NMR end-group analysis of the low molecular weight PCL prepared using catalysts Ca/PO and Ca/EO, it was proposed that the catalysts have the structure of NH2-Ca-O-CH(CH3)(2) and NH2-CaO-CH2CH3 for Ca/PO and Ca/EO, respectively. The ring-opening polymerization of CL and LA follows a coordination-insertion mechanism and the active site is the Ca-O bond.

Nonisothermal crystallization kinetics of ethylene terephthalate-ethylene oxide segmented copolymers with two crystallizing segments

The nonisothermal crystallization behavior of ethylene terephthalate-ethylene oxide segmented copolymers has been studied by means of differential scanning calorimetry (DSC). The kinetics of ET-EO segmented copolymer under nonisothermal crystallization conditions has been analyzed by the Ozawa equation. During the crystallization of the high-T-m segments (PET), the low-T-m segments (PEO) act as a noncrystalline diluent, the crystallization behavior of PET obeys the Ozawa theory. When the PEO segments begin to crystallize, the PET phase is always partially solidified and the presence of the spherulitic microstructure of PET profoundly influences the crystallization behavior, which results in that the overall crystallization process does not obey the Ozawa equation. (C) 2000 Elsevier Science Ltd. All rights reserved.

Nonisothermal crystallization kinetics of PEO in ethylene terephthalate-ethylene oxide segmented copolymers

The nonisothermal crystallization behavior of Ethylene Terephthalate-Ethylene Oxide (ET-EO) segmented copolymers has been studied with the use of differential scanning calorimetry (DSC). The kinetics of PEO in ET-EO segmented copolymer under nonisothermal crystallization conditions has been analyzed with the Ozawa equation. The results show that there is no agreement with Ozawa's theoretical predictions in the whole crystallization process owing to the constraint of ET segments imposed on the EO segments. A distinct two-crystallization process has been investigated by using the Avrami equation modified by Jeziorny to deal with the nonisothermal crystallization data. The value of the Avrami exponent n is independent of the length of soft segments. However, the crystallization rate is sensitive to the length of soft segments. The longer the soft segments, the faster the crystallization will be.

Spectrometric investigation on the thermooxidative degradation of ethylene oxide and tetra-hydrofuran co-polyether

The thermooxidative degradtion of ethylene oxide and tetra-hydrofuran (EO-THF) co-polyether has been studied by electron spin resonance (ESR), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The initial degradation site was found to be at the a-carbon of the ether bond. Two free radicals which derived from dehydrogenation and oxygen addition were successfully detected by spin-trapping technique which used alpha -phenyl-N-tert-butyl nitrone(PBN) as spin trap. Both FT-IR and NMR have been used to follow structural changes of the copolyether during degradation. Nearly 20 product fragments including formate, carbonate, methyl, alcohol, methylene-dioxy, hydroperoxide and semiformal have been characterized by D-1 and D-2 NMR. The thermooxidtion of co-polyether preferred to occur on the THF units especially at the alternating linkage of EO and THF. Antioxidant (BHT) not only retarded the thermooxidation but also modified the degradation products with less ester and methylene-dioxy groups hut more hydroxyl and methyl groups.

多种谱学方法研究环氧乙烷/四氢呋喃共聚醚的热氧降解

采用电子自旋共振 (ESR)、傅里叶变换红外光谱 (FT IR)和多种核磁共振 (NMR)技术研究了环氧乙烷 /四氢呋喃共聚醚的热氧降解 ,表征了近 2 0种产物结构碎片 ,并对EO���THF两种链节的降解作了定量讨论。共聚醚的氧化降解发生在醚键氧碳上 ,遵循自由基氧化机理 ,最后形成大量的甲酸酯、碳酸酯等酯类以及甲基、亚甲二氧基和醇 ,此外还检测到过氧化氢和半缩甲醛结构。分析表明共聚醚中THF链节的降解程度明显大于EO���节 ,而且降解容易发生在两种链节交替连接处。抗氧剂 2 ,6 二叔丁基 4 甲基酚 (BHT)不仅降低了共聚醚的氧化降解程度 ,还改变了降解产物的结构分布 ,显著抑制了碳酸酯和亚甲二氧基结构的生成 ,相对增加了羟基和端甲基结构

聚合物电解质的玻璃化转变温度与离子解离的关系

采用动态力学和数学拟合相结合的方法 ,研究了聚环氧乙烷环氧丙烷—LiClO4 体系的离子解离与缔合。结果表明 :Tg的增加依赖于盐浓度和环氧乙烷 (EO)与环氧丙烷 (PO)的比例 ,并且玻璃化转变温度 (Tg)的增加可以用一个简单的溶解平衡解释 ,进而得出平衡常数K和离解度α

环氧乙烷/四氢呋喃共聚醚聚氨酯的热氧降解

采用FT-IR和13CNMR、1HNMR技术研究羟基环氧乙烷/四氢 呋喃共聚醚(EO/THF)聚氨酯在90℃空气中降解产物的结构．结果表明，聚醚聚氨酯的热氧降解既有软段的氧化降解，又有硬段的解缩聚过程，同时还存在重聚合反应；并且软、硬段互有影响，硬段中的交联结构和氢键增加了软段的热氧稳定性，而软段降解产生的醇的含量和结构影响硬段的解缩聚和重聚合过程．90℃下聚氨酯 的热氧降解并不发生硬段的氧化反应，也不存在碳化二亚胺和假脲醚结构.

Ion-conducting polymers based on modified alternating maleic anhydride copolymer with oligo(oxyethylene) side chains

Comb-like polymers (CPs) based on modified alternating methyl vinyl ether/maleic anhydride copolymer with oligo(oxyethylene) side chains of the type -O(CH2CH2O)(n)CH3 were synthesized and characterized, and complexed with lithium salts to form amorphous polymer electrolytes. Maximum conductivity close to 1.38 x 10(-4) S/cm was achieved at room temperature and at a [Li]/[EO] ratio (EO = ethylene oxide) of about 0.066. The temperature dependence of ionic conductivity suggested that the ion transport was controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel-Tammann-Fulcher plots. The ionic conductivity maximum moved to a higher salt concentration as the temperature increased, indicating that a larger number of charge carriers can be transferred through polymer chains, of which free volume is increased at higher temperature. IR results indicated that the ester in CPs might decompose at 140 degrees C and reproduce the maleic anhydride ring.

梳状高分子固体电解质的二级玻璃化转变及离子传输研究

研究了交替马来酸酐共聚物多缩乙二醇酯(CP350)-LiSCN配合物的热行为及离子传输特性.实验表明:CP350/LiSCN配合物在所研究[Li]/[EO]配比范围呈均相无定形并具有二级玻璃化转变.两种玻璃化转变温度均随盐含量的增加而上升.离子电导率随盐浓度的变化而出现一极大值,室温电导率最大可达2.19×10~(-5)S/cm.导电行为符合VTF方程.

Studies on the two class glass transition and the typical VTF behaviour of an amorphous comb polymer electrolyte

A comb polymer (CP350) with oligo-oxyethylene side chains of the type -(CH2CH2O)(7)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly(ethylene glycol) methyl ether. The polymer can dissolve LiNO3 salt to form homogeneous amorphous polymer electrolyte. This electrolyte system was first found to have two class glass transitions, and the two T(g)s were observed to increase with increasing salt content. The ionic conduction was measured by using the complex impedance method, and conductivities were investigated as functions of temperature and salt concentration. At 25 degrees C, the ionic conductivity maximum of this system can get to 3.72 X 10(-5) S/cm at the [Li]/ [EO] ratio of 0.057. The appearance of the conductivity maximum has been interpreted as being due to the effect of T-g and the so called physical crosslinks. The temperature dependence of the ionic conductivity displaying non-Arrhenius behaviour can be analyzed using the Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model.

Study of ion solvation and ion association in polymer gel electrolyte with polyethylene oxide-co-polypropylene oxide as a plasticizer

Using a molal conductance method, ion solvation and ion association in polytriethylene glycol dimethacrylate (PTREGD)-LiClO4 gel electrolytes with amorphous ethylene oxide-co-propylene oxide (EO-co-PO, <(M)over bar (n)>, = 1750) as the plasticizer were investigated. It was found that the fraction of solute existing as single ions (alpha(i)) and ion pairs (alpha(p)) decreases, while that of triple ions (alpha(t)) increases linearly with increasing salt concentration. The dependence of these fractions on molecular weight of plasticizer was also examined. It was shown that alpha(i) and alpha(t) increase and alpha(p) decreases with increasing molecular weight. The result of temperature dependence of these fractions was very interesting: when the temperature is lower than 55 degrees C, alpha(i) increases while alpha(p) and alpha(t) decrease with increasing temperature; however, when the temperature is higher than 55 degrees C, the reverse is true.