PMMA对聚氧乙烯β转变的影响

对半结晶聚氧乙烯（PEO)/PMMA共混体系的DSC及动态力学行为研究表明：PEO在和PMMA形成半结晶PEO/PMMA共混体系后，其β转变的峰温没有明显移动；β峰只出现在淬炎的半结晶PEO/PMMA共混体系中，而在完全非晶的相容性共混体系以及退火的半结晶共混体系不出现；在β转变区，对应的模量反常地增大，对应的DSC曲线有明显阶跃。可见，半结晶PEO的β转变并不象通常所认为的源于PEO非晶区的玻璃化转变。在接受半结晶PEO及半结晶PEO/PMMA共混体系的PEO结晶区存在结晶-非晶中间相观点的基础上，认为β转变源于PEO结晶区结晶-非晶中间相的玻璃化转变过程。     

聚环氧乙烷(PE0)与聚双酚A羟基醚(PBHE)共混体系的研究

用偏光显微镜(PLM)、扭辫(TBA)、IR及WAXD对PEO/PBHE共混体系结晶形态进行了研究。结果表明,PEO含量在50％以上的共混体系,几乎完全被PEO球晶充满,非晶态PBHE作为微区分散在大球晶之间或球晶之中。PEO含量为40％和30％的照片上呈现树枝晶。PEO含量为20％以下时照片中不再看到结晶出现,PEO与PBHE形成单一非晶相。PEO/PBHE共混体系的组分之间存在着氢键相互作用,这种作用强于PBHE分子间的氢键作用。共混体系的结晶度及T_g随PBHE组分含量的增加,前者减小后者增加并符合FOX方程揭示的规律。PEO与PBHE具有很好的相容性。     

聚环氧乙烷(PE0)与聚双酚A羟基醚(PBHE)共混体系的研究

 用偏光显微镜(PLM)、扭辫(TBA)、IR及WAXD对PEO/PBHE共混体系结晶形态进行了研究。结果表明,PEO含量在50％以上的共混体系,几乎完全被PEO球晶充满,非晶态PBHE作为微区分散在大球晶之间或球晶之中。PEO含量为40％和30％的照片上呈现树枝晶。PEO含量为20％以下时照片中不再看到结晶出现,PEO与PBHE形成单一非晶相。PEO/PBHE共混体系的组分之间存在着氢键相互作用,这种作用强于PBHE分子间的氢键作用。共混体系的结晶度及T_g随PBHE组分含量的增加,前者减小后者增加并符合FOX方程揭示的规律。PEO与PBHE具有很好的相容性。     

聚己内酯和聚氧化乙烯共混体系中的两类片晶相间堆砌

对聚(ε-己内酯)(PCL)/聚氧化乙烯(PEO)共混物的相差显微镜、广角X-射线衍射(WAXD)、小角X-射线散射(SAXS)及示差扫描量热计(DSC)等的研究表明,只有当共混物中PCL(或PEO)的含量低于20％时,两组份是相容的.当PCL含量低于20％时,在共混物中形成了PEO片晶和PCL片晶相间堆砌的结晶形态,当PEO含量不超过20％时,PEO则完全以非晶形式混入PCL的非晶区,同时阻碍了PCL的结晶.可见在结晶过程中,相容的两组份对共混体系形态结构的影响却不尽相同.     

高氯酸锂对PEO结晶结构和结晶行为的影响

利用配备热台的偏光显微镜(POM)、红外光谱仪(FTIR)和示差扫描量热器(DSC)等实验方法研究了高氯酸锂(LiClO4)与聚氧化乙烯(PEO)之间的络合作用对PEO结晶行为和结晶形态的影响.DSC测试结果表明在LiClO4/PEO二元共混体系中,PEO的熔融温度、结晶温度随着锂盐含量的增加出现先增加后降低的现象;而结晶度则是先不变后降低.FTIR结果表明LiClO4影响聚合物结晶性能的原因是Li+能和PEO中的醚基的络合作用.POM观察结果发现LiClO4/PEO共混体系中存在聚合物的球晶,共混体系中聚合物的球晶生长速率都随着结晶温度的升高而下降,并且球晶生长速率还随着体系中随LiClO4含量的增加而减小.     

P（MMA—MAA）／PEO氢键复合物的增容效应

本文研究了P(MMA-MAA)/PEO氢键复合物对一些聚合物共混体系的增容效应。首次用机械共混方法制备了P(MMA-MAA)/PEO氢键复合物。该复合物不能被甲醇革取,其热失重行为不是其组分聚合物的加和,表明此复合物不是简单的共混物。实验结果证实,该复合物可以改进PMMA/PEO体系的相容性,改善PVC共混体系的力学性能和加工性能。     

聚β-羟基丁酸酯/聚氧化乙烯共混体系力学性能研究

本文详细研究了可完全生物降解的聚 β 羟基丁酸酯 (PHB)与水溶性聚氧化乙烯 (PEO)两元共混体系的拉伸力学性能 .讨论了PEO分子量、共混组成及热处理条件对共混体系力学性能的影响 .其中 ,PHB与超高分子量PEO(重均分子量 5× 10 6)共混 ,两组分力学上具有相容性 ,共混物的拉伸强度、断裂伸长率及模量都有明显的正的协同效应 .共混改性效果显著PHB的力学性能得到很大改善 ,尤其PHB的脆性缺陷 .并且 ,共混物在经过适当温度退火处理之后 ,共混物性能还可进一步改善     

结晶-非晶共混体系的结晶行为研究——PEO/PMMA与PEO/PVA共混物

用DSC和傅里叶红外(FTIR)光谱表征PEO/PMMA和PEO/PVA共混体系的结晶行为。发现PEO/PVA体系的结晶度与其组成的变化是一致的;而PEO/PMMA体系的结晶度随非晶组分增加而下降的速度,从与组成变化一致到比后者快,但又随时间而改变。对此结晶/非晶共混体系的结晶度随组成和时间而变化的现象,可用体系的玻璃化转变温度(T_g)来解释。     

聚左旋乳酸/聚氧化乙烯共混物的拉伸行为及结构转变

采用熔融共混方法制备了聚左旋乳酸(PLLA)和超高分子量聚氧化乙烯(PEO)共混物, 通过差示扫描量热(DSC)、 扫描电子显微镜(SEM)和二维广角X射线散射(2D-WAXS)等方法系统研究了PEO的加入对不同温度下PLLA拉伸行为及拉伸过程中微观结构变化的影响. 结果表明, PLLA/PEO共混物为非均相体系, PEO粒子均匀分布在PLLA中形成两相结构. PEO的加入能够显著降低PLLA的玻璃化转变温度(T_g), 在25～60 ℃范围内显著提高PLLA的拉伸性能. 在60 ℃拉伸时, PEO的加入提高了PLLA在拉伸过程中的结晶和形变能力. 在80 ℃拉伸时, 共混物的拉伸断裂伸长率下降, 但共混物的结晶速度仍高于纯PLLA样品.     

PEO／PBHE共混体系X射线散射研究

在聚环氧乙烷(PEO)/聚双酚A羟基醚(PBHE)共混体系中PEO是一个强质子受体,而PBHE是一个强质子给体,两者极易形成氢键,十分有利于形成互容对。笔者研究了PEO/PBHE共混体系的相容性,等温及非等温结晶动力学,本文根据Vonk提出的一维电子密度相关函数,分析了PEO/PBHE的SAXS现象,求得了共混体系的结晶度,片晶层厚度,过渡层厚度及长周期等结构参数。     

PEO/PVAc共混体系辐射交联反应中溶胶分数与辐照剂量间的关系

交联度对由聚合物共混物辐射交联而制备出的材料的性能影响很大,研究共混体系的辐射交联度和交联行为是十分重要的。通常,用溶胶分数与辐照剂量间的关系表征聚合物的交联度和交联行为。文献[2]发现线性聚合物的溶胶分数与辐照剂量间的关系与高分子链结构参数有关。本文试图考察共混体系的辐射交联行为是否也与高分子链结构有关,并将线性聚合物的关系式(1)推广应用到PEO/PVAc共混体系中。目前,有关这方面的研究工作还未曾见文献详细报道。     

PEO/PVAc共混体系辐射交联反应中溶胶分数与辐照剂量间的关系

In this paper, the relationship between T_m and composition of PEO/PVAc blend were studied and the Flory-Huggins parameter of the blend system were calculated. The experimental results show that this blend system is compatible and have only one glass transition temperature (T_g), so we can extend the relationship between sol fraction (S) and radiation dose (R) of linear polymer to the PEO/PVAc system. The Bb value of PEO/PVAc system were calculated, which is in good agreement with the experimental value.     

SiO2纳米颗粒与聚氧乙烯对Pickering乳液的协同稳定作用简

研究了聚氧乙烯(PEO)与SiO2纳米颗粒对水/二甲苯体系Pickering乳液的协同稳定作用. 实验发现,PEO的存在减小了乳液液滴的平均直径,抑制了乳液的相反转,有效阻止了乳液的熟化,使乳液具有更好的稳定性. 进一步对纳米颗粒膜的流变性质进行研究,结果表明,PEO高分子促进了纳米颗粒形成更大尺寸的聚集结构,提高了其在界面上的吸附性,增强了颗粒膜的力学性能,在较小颗粒用量条件下使得Gibbs稳定性判据得到满足.     

A Study of the Compatibilizing Effect of High-speed Stirring on the Poly-(Ethylene Oxide)/Polyacrylamide System

The compatibility of the poly(ethylene oxide) (PEO)/polyacrylamide (PAM) system and the compatibilizing effect of PEO-PAM block copolymer formed during high-speed stirring of the PEO/PAM mixture in aqueous solution were studied. Thermodynamics predicts that PEO/PAM is incompatible; contrast microscopy, TEM, SAXS, and stress-strain behavior testing verify this. It is found that PEO-PAM block copolymer is an effective compatibilizer, which decreases the dimension of the domains, reduces the heterogeneity of the system, increases the thickness of the boundary layer, and improves the mechanical properties of the polyblend.     

Electrospinning of cyclodextrin functionalized polyethylene oxide (PEO) nanofibers

By means of the electrospinning technique we have successfully synthesized cyclodextrin (CD) functionalized polyethylene oxide (PEO) nanofibers (PEO/CD) with the ultimate goal to develop functional nanowebs. Three different types of CDs; α-CD, β-CD and γ-CD are incorporated individually in electrospun PEO nanofibers. The aqueous solutions containing different amount of PEO (3%, 3.5% and 4% (w/v), with respect to solvent) and CDs (25% and 50% (w/w), with respect to PEO) are electrospun and bead-free nanofibers are obtained. The presence of the CDs in the PEO solutions is found to facilitate the electrospinning of bead-free nanofibers from the lower polymer concentrations and this behavior is attributed to the high conductivity and viscosity of the PEO/CD solutions. The presence of CDs in the electrospun PEO nanofibers is confirmed by Fourier transform infrared (FTIR) spectroscopy studies. The 2-D X-ray diffraction (XRD) spectra of PEO/CD nanowebs did not show any significant diffraction peaks for CDs indicating that the CD molecules are distributed within the polymer matrix without any phase separated crystalline aggregates.     

EFFECT OF MOLECULAR WEIGHT OF PEO ON THE STRUCTURE AND PROPERTIES OF PDMAEMA/PEO HYDROGELS

A new kind of binary hydrogels composed of poly(dimethylaminoethylmethacrylate) (PDMAEMA) and poly(ethylene oxide) (PEO) with varying weight average molecular weights ((M)w = 5 × 104, 1 × 105 and 2.5 × 106) were prepared by y-irradiation technology. The properties of PDMAEMA/PEO hydrogels obtained were evaluated in terms of gel fraction, gel strength, thermal characterization and swelling behavior. The gel strength and swelling degree of the hydrogels could be improved obviously after adding PEO into the PDMAEMA system, while the degree of improvement decreased with increasing (M)w of PEO. The temperature sensitivity of PDMAEMA/PEO was retained only in the sample with PEO of (M)w = 5 × 104, and the pH sensitivity was retained in samples with PEO of (M)w = 5 × 104 and 1 × 105. When DMAEMA/PEO mixtures containing PEO of (M)w = 5 × 104 were irradiated, the main reaction could be the cross-linking of DMAEMA, and the linear PEO molecular chains could penetrate into the cross-linked network of PDMAEMA. With increasing Mw of PEO, some side reactions were induced, such as grafting of DMAEMA onto PEO molecules, the scission or cross-linking of PEO.     

Universal drag reduction characteristics of saline water-soluble poly(ethylene oxide) in a rotating disk apparatus

 Polymer-induced turbulent drag reduction in a rotating disk apparatus was investigated using nonionic poly(ethylene oxide) (PEO) in a synthetic saline solution with novel application to ocean thermal energy conversion technology. A maximum total (skin friction plus form) drag reduction of 30% was obtained with 50 wppm of PEO with molecular weight 5.0 × 10⁶. The concentration dependence of the percentage drag reduction for the PEO/saline solution system is found to fit Virk's empirical correlation, and a universal correlation for various molecular weights and Reynolds numbers is also presented. Furthermore, hydrodynamic volume fraction was introduced to correlate drag reduction efficiency with molecular parameters in this PEO/saline solution system. Received: 28 December 1999/Accepted: 17 February 2000     

Crystallization behavior of disproportionately high and low molecular weight PEO blends

The crystallization behavior of PEOs with molecular weight of 1 Ok and 200k as well as their blends was studied in details. The results show that the lower molecular weight PEO crystallizes with faster crystallization rate as judged from a shorter time for completing the crystallization. On the other hand, the higher molecular weight PEO crystallizes at relatively higher temperature, indicating an early start of crystallization compared with the lower molecular weight one. The blends of these two PEOs with different blend ratios always cocrystallize during the cooling processes. It is confirmed that mixing of the 10k PEO with the 200k one is in favor of the crystallization of the system. This is not only demonstrated by the early start of the crystallization at higher crystallization temperature, and also a faster crystal growth of the blend with respect to the 200k PEO. The crystallization of the blends at higher temperature is caused by an early start of nucleation and an increment of nucleus density. This may originate from the density fluctuation of the blend and a reduction in energy barrier for nucleation. Moreover, it is found that the crystallinity of the 1 Ok PEO rich blends increases with increasing concentration of the 10k PEO. This is caused by the solvent effect of the 10k PEO toward the 200k PEO. On the other hand, the crystallinity of the 30/70 （10k/200k） PEO blend is decreased a little bit. This may be a balanced result of the improved crystallization of the 200k PEO at the expense of the high crystallization ability of the 1 Ok PEO.     

Towards microphase separation in epoxy systems containing PEO/PPO/PEO block copolymers by controlling cure conditions and molar ratios between blocks. Part 2. Structural characterization

The influence of addition of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO–PPO–PEO) copolymers on final morphologies of modified epoxy matrices has been investigated as a function of PEO:PPO molar ratio and cure conditions by comparison with the cured epoxy blends only containing poly(ethylene oxide) (PEO) or poly(propylene oxide) (PPO) homopolymers. Atomic force microscopy (AFM) has been used to characterize structural features of blends. Whilst diglycidyl ether of bisphenol-A (DGEBA)/4,4’-diaminodiphenylmethane (DDM)/PPO system macrophase separates, the interactions between PEO and cured epoxy are responsible for miscibility of DGEBA/DDM/PEO system. Depending on PEO:PPO molar ratio, micro- or macrophase separated morphologies have been obtained for block copolymer modified epoxy matrices. Moreover, the influence of both copolymer content and cure temperature on final morphologies has also been investigated by both experimental and theoretical analysis.