共查询到20条相似文献,搜索用时 31 毫秒
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聚对苯硫醚[poly(pphenylenesulfide),简称pPPS]的分子链是由对苯撑基和硫原子交替连接构成而使制品抗冲击能力差[1](有些研究者用共聚或共混的方法在pPPS中引入间位结构来达到减少其结晶度,增强韧性的目的)。余自力等[2]用硫磺溶液法合成了mPPS、pPPS及其共聚物,认为在pP... 相似文献
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1991年Decher等将带相反电荷的聚电解质 ,于水溶液中交替沉积在片基上 ,制备了多层超薄膜[1] ,这种制膜方法现称为静电自组装 .它操作简单 ,无需专用设备 ;一般在水体系进行 ,对环境友好 ;静电力比范德华力强 ,使它比LB膜稳定 ,所以近年来有很大发展[2 ] .现在自组装成膜驱动力已从静电力扩展到氢键力、电荷转移相互作用、疏水相互作用等 ,用于组装的组分也从聚电解质扩展到多官能团小分子、胶体粒子、无机纳米颗粒 ,DNA、蛋白质等生物大分子等[3~ 11] .虽然自组装膜比LB膜稳定 ,但它也不耐极性溶剂、电解质水溶液等侵蚀 .如… 相似文献
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IR spectral shifts of carbonyl vibrational absorption for ethyl acetate, which acts analogically as the structural unit of poly(methyl methacrylate), in cyclohexane, chloroform, chlorinated paraffins, poly(vinyl chloride) and chlorinated poly(vinyl chloride) were measured. The results suggest that there are specific interactions between the carbonyl groups and the chlorinated hydrocarbons which could be responsible for the apparent compatibility of poly(vinyl chloride)—poly(methyl methacrylate) and chlorinated poly(vinyl chloride)—poly(methyl methacrylate) blends. Additionally, the effects of the preparation mode of blend films on phase separation and observed compatibility are discussed. 相似文献
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聚(L-丙交酯)/聚(DL-丙交酯)的结晶性能及相溶性 总被引:2,自引:0,他引:2
用共溶液沉淀法制备了聚 (L 丙交酯 ) 聚 (DL 丙交酯 )共混物 (PLLA PDLLA) ,然后用成纤模压法压制成3 2mm的棒材 .用差示扫描量热法研究了共混物的结晶性能和相溶性 .结果表明 ,PLLA组分在共溶液沉淀过程中可生成结晶 ,共混物中PDLLA含量直到 30 %时 ,PLLA组分的结晶熔融温度和结晶度与纯PLLA相同 ,但PDLLA含量为 5 0 %时 ,PLLA组分的结晶熔融温度和结晶度明显下降 .由于加工成型条件的不一致性 ,共混物棒材中的PLLA组分的结晶熔融温度和结晶度呈较大的分散性 .共混物从熔体降温 ,在其后的升温DSC扫描中出现分别相应于PDLLA和PLLA的玻璃化转变 ,表明PDLLA与未结晶的PLLA形成的非晶相是不相溶的 相似文献
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Measurements of the steady-state fluorescence spectrum and anisotropy, r, of the alternating polynucleotide poly(dA-dT).poly(dA-dT) were carried out in order to characterize its photophysical properties at room temperature. The shape of the fluorescence spectrum depends on the excitation wavelength, namely, the relative fluorescence intensity of the short-wavelength peak decreases for excitation at short wavelengths. When monitoring the emission at short wavelengths, r is 0.18 and independent of the excitation wavelength. When monitoring the emission at long wavelengths, however, r is very low, about 0.03. These results suggest that: (i) the short-wavelength emission stems from thymine; and (ii) the long-wavelength emission stems from an excited-state complex (excimer), with the same one being formed regardless of whether thymine or adenine is excited. The corresponding fluorescence spectra have been resolved. The occurrence of transfer of electronic energy is discussed. 相似文献
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用DSC、WAXD和SAXS研究了聚乙烯醇(PVAl)/聚乙烯基吡咯烷酮(PVP)共混体系的结晶行为.PVAl的结晶度随PVP含量增加而减少,并存在结晶度为零的组成(PVAl)的重量分数约为50%.与纯PVAl相比,共混物的温度区间T_m-T_g减小,表明PVP对PVAl的结晶起抑制作用.共混物中PVAl的结晶速度下降,具体表现为PVAl过冷区随PVP含量增加而扩大,动力学速度常数减小,球晶增长速度下降.纯PVAl和共混体系的等温结晶速率均遵循Avrami方程.退火样品的长周期、片晶厚度和过渡层厚度大于相同组成未退火样品.两者长周期随PVP含量增长加显著增大,片晶厚度增长次之,过渡层厚度变化不大. 相似文献
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基于改进的旋转异构态方法,推导了对称双取代基高分子链的均方回转半径和均方偶极矩公式,用于研究聚四氟乙烯(PTFE)、聚二甲基硅烷(PDMS)和聚乙烯(PE)链构象依赖的性质.计算得到长链聚四氟乙烯PTFE4(四态模型)和PDMS的构型参数值分别为0.44·mol0.5·g-0.5和0.43·mol0.5·g-0.5,PDMS链的相应温度系数值-7.32×10-3K-1,它与PTFE和PE的值(约-1.00×10-3K-1)相差较大.得到长链PTFE和PDMS的均方电偶极矩特征比结果都很小,如PDMS链的特征比为0.27,说明虽然PTFE和PDMS的侧基键C—F和Si—CH3都有强极性,但其聚合物却是非极性的电介质,具有较好的电绝缘性能,可见高分子链的构象和结构也对聚合物极性和电学性质有很大的影响.得到短链PTFE和PDMS(重复单元x10)均方偶极矩表现出明显的端点效应,特征比随x的改变而呈现明显的波动,这与Flory等的计算结果一致. 相似文献
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《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1037-1051
Poly(methylene terephthalate) (PMT) and poly(ethylene terephthalate) (PET) were synthesized by triethylamine-mediated reactions of terephthalic acid and dihalomethanes or 1,2-dihaloethanes, respectively. Reactions with chloro compounds required longer reaction times and higher temper-atures than those with bromo. Copolymers were synthesized by using proportionate amounts of dihalomethane/1,2-dihaloethane mixtures. Copolymer compositions were determined by inte-grations of relative areas of methylene and ethylene 1H NMR peaks. Mn values were determined from 1H NMR end group signals. Mole fraction feed is linearly related to CH2/CH2CH2 incorporation into copolymer products. Mechanisms are proposed to explain results. 相似文献
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聚乙烯醇/聚乙烯基吡咯烷酮共混体系相容性研究 总被引:1,自引:1,他引:1
用DSC、FTIR、SAXS和测定Flory-Huggins相互作用参数等方法对聚乙二醇(PVA1)/聚乙烯基吡咯烷酮(PVP)共混体系的研究。结果表明,该体系具有完全互容的性质。共混物只有一个玻璃化转变温度。用DMSO作溶剂浇铸的膜光学透明。PVA1的长周期和片晶厚度均随PVP含量增加而增大,但后者增大的幅度比前者小得多,表明PVP和PVA1的非晶部分形成均相并夹入到球晶内部。共混物中PVP羰基吸收峰和PVA1的羟基吸收峰与相应均聚物相比,在红外光谱图中皆向低频方向迁移,迁移波数随第二组分含量的增加而增大。表明二者间有氢键生成。用平衡熔点计算的Flory-Huggins相互作用参数为-0.88。 相似文献
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Jordi Contreras J. Idris Jones 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):67-68
Abstract Various sulfides are easily oxidized selectively to the corresponding sulfoxides in quantitative yields by iodosylarene (ArIO) catalyzed by metalloporphyrin (TPPM(III)Cl (M [dbnd] Fe, Mn)). The oxidation system is demonstrated to be a possible model for monooxygenase in the study of the stereochemistry of these sulfoxides. Metalloporphyrin-iodosylarene can initially equilibrate with the oxometalloporphyrin (TPPM(V)=O·Cl) formed in situ. The initial process may involve one-electron transfer from the sulfide to the intermediate oxometalloporphyrin followed by coupling of two resulting charged products, and/or nucleophilic attack of sulfide on oxometalloporphyrin oxygen. The overall reactions are depicted by paths with different electron demands from the results of Hammett plots. 相似文献
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聚β-羟基丁酸酯和聚ε-己内酯的酯交换反应 总被引:5,自引:0,他引:5
以辛酸亚锡为催化剂 ,研究了聚 β 羟基丁酸酯 (PHB)与聚ε 己内酯 (PCL)在液相条件下的酯交换反应 .讨论了反应时间 ,反应温度和催化剂浓度对酯交换反应的影响 .采用1 3C NMR ,FTIR ,DSC ,WAXD和TGA等方法对PHB和PCL共聚酯 (PHB co PCL)的结构进行了表征 ,并对其结晶行为、晶体结构和热稳定性进行了研究 .结果表明 ,通过酯交换反应 ,所得到的共聚酯为嵌段共聚物 .提高反应温度和延长反应时间有利于酯交换反应的发生 .随着酯交换量的增加 ,PHB co PCL的结晶行为发生很大的变化 .但是 ,PHB co PCL晶体结构并没有因为PCL链段的引入而发生变化 ,而且它的热稳定性在空气气氛中略有提高 相似文献
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The ultrasonic degradation of poly(ethylene oxide) and poly(vinyl acetate) in benzene solution, and grafting reaction of poly(vinyl acetate) with poly(ethylene oxide) were studied. It is found that the chain-scission reactions follow the course suggested by D. W. Ovenall. The structure of the copolymer was identified by IR, NMR and DTA, showing that the copolymer prepared is a graft copolymer mainly. The copolymer formed by irradiating 1% PEO/PVAc solution (PEO/PVAc:1/1 by weight) for a period of 10 rain at 18.2 kHZ, with 2.0 A input current on reversed main circuit, amounts to 10.5%. 相似文献