聚乳酸-聚乙二醇嵌段共聚物晶行为研究

用1H NMR, SEC, XRD和DSC对聚乳酸(PLLA)-聚乙二醇(PEG)二嵌段共聚物进行了表征. 由于共聚物中两种组分比例的不同, 表现出某组分单独结晶或两种组分共同结晶. 用DSC和POM方法, 对两组分含量相当的共聚物进行了熔体结晶行为研究, 并采用Avrami方程进行了结晶动力学计算. 用Lauritzen-Hoffmann理论对PLLA-PEG结晶机理进行了分析. 在70~94 ℃范围内, 得到成核参数Kg(POM)=5.23×105 K2. 共聚物的Kg和链折叠自由能σe都比均聚物的文献报道值高, 表明PEG链段的存在影响了PLLA的结晶, 使得其成核较均聚物困难.     

聚乙二醇-聚L-丙交酯嵌段共聚物结晶形貌研究

用偏光显微镜和原子力显微镜对比研究了PEG-PLLA嵌段共聚物在110℃或120℃等温结晶后的结晶形貌.发现在110℃时只有PEG5000-PLLA2300和PEG5000-PLLA6300在偏光显微镜下呈现环带球晶形貌,在原子力显微镜高度图中显示明显的环带,并具有交替凸凹起伏形貌.而PEG5000-PLLA12000球晶中没有出现环带形貌而是生成了规则的环线.在120℃时,PEG5000-PLLA12000的球晶中才生成了规则的环带图案,原子力显微镜也显示了其球晶具有明显的交替凸凹起伏形貌,说明过冷度直接影响环带球晶的生成.产生周期性凸凹起伏和明暗交替消光是由片晶沿着球晶的半径方向周期性扭转造成的,片晶在凸起部分是Edge-on取向,在凹下部分是Flat-on取向.     

聚丙烯酰胺-聚乙二醇-水体系相图及丙烯酰胺单体在两相中的分配

聚丙烯酰胺(PAAm)和聚乙二醇(PEG)两种水溶液混合时能形成双水相体系,其中上层为PEG富集相,下层为PAAm和PEG的混合相.用凝胶渗透色谱(GPC)法和浊度滴定法研究了PAAm-PEG-H₂O双水相体系的相图,结果表明,随着PEG分子量的升高,体系的分相浓度下降.在PAAm-PEG20000-H₂O体系中,随着体系温度升高,分相浓度先下降后升高,55℃时分相浓度最低.丙烯酰胺(AAm)单体能在两相中发生相分配,分配系数随着PAAm浓度和平衡温度的增加而增大,随着PEG浓度的增加而下降.     

基于聚乙二醇结构调控高分子量聚乳酸立构复合体系的结晶行为

设计合成了梳形聚(聚乙二醇甲醚丙烯酸酯)(PPEGA)及其与聚乙二醇(PEG)的嵌段共聚物(PEG-b-PPEGA).通过与高分子量左旋聚乳酸(PLLA)和右旋聚乳酸(PDLA)共混探究了PEG不同的结构对PLA立构复合体系(sc-PLA)结晶的影响.结果 表明线形PEGA和PEG能与sc-PLA完全相容,两者均能促进...     

The Synthesis of Poly(ethylene oxide)-Block-Polybutylacrylate

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Sodium Chloride Molar Conductance in Different Poly(ethylene glycol)–Water Mixed Solvents

The molar conductivities of NaCl in several poly(ethylene glycol)(PEG)–water “mixed solvents” are presented as a function of the PEG content in solution. Three different PEG samples, a monodispersed one and two polydispersed ones, have been used. The comparison between the molar conductivity values in the mixed solvents and the corresponding ones in pure water shows that the only effect of PEG on the ions’ motions is an obstruction effect despite the variation of the macroscopic dielectric constant induced by PEG itself. A comparison between the molar conductivities and the corresponding mutual main diffusion coefficients shows a tight correlation between the two quantities. This correlation is possible only in the absence of electrostatic effects due to the presence of PEG.     

New architectures of poly(ethylene glycol) and poly(methylthiirane) in block copolymers

Two synthetic ways were experimented to prepare new architectures of block copolymers made of poly(ethylene glycol) (PEG) and poly(methylthiirane). The coupling of both blocks conveniently end-capped as well as anionic polymerization of methylthiirane initiated by PEG-thiols gave readily the copolymers. Their characterization by ¹H NMR, SEC and IR confirmed the expected structures.     

Characterization of UV-curable Poly(ethylene glycol)Diacrylate Based Hydrogels

Poly(ethylene glycol) diacrylate/polyvinyl alcohol(PEGDA/PVA) hydrogels were prepared from PEGDA and PVA as precurors by means of single UV radiation(UV ra.), UV radiation followed by high energy electron beam irradiation(Irra.), UV radiation followed by freeze-thawing(FT) or UV ra. and Irra. followed by FT, respectively. 2-Hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone(Irgacure 2959) was used as a photoinitiator. The effects of the various methods on the swelling and mechanical properties of the hydrogels were investigated. The results show that hydrogels made by UV ra. plus high energy electron beam irradiation followed by FT showed a higher crosslinking density and a larger tensile strength than those made by the other methods.     

聚甲基丙烯酸甲酯/星形聚乙二醇半互穿聚合物网络的形状记忆性能和分子机理

采用非共价复合方法,设计并合成了具有星形结构的聚甲基丙烯酸甲酯/星形聚乙二醇半互穿聚合物网络(PMMA/SPEG)和聚甲基丙烯酸甲酯/线性聚乙二醇半互穿聚合物网络(PMMA/LPEG).研究了PEG分子量对PMMA/SPEG和PMMA/LPEG的热性能、机械性能、动态机械性能和形状记忆性能的影响.结果表明,与PMMA/LPEG相比,星形结构的嵌入显著提高了PMMA/SPEG复合物的机械性能、形状回复率和回复速度.采用Edwards管道模型理论对其形状记忆效应的分子机理进行了阐释,利用材料的应力松弛特性对机理分析进行了验证.     

Determination of poly(ethylene glycol)s by both normal-phase and reversed-phase modes of high-performance liquid chromatography

A normal-phase HPLC system using an amino column has been developed to characterise oligomers of poly(ethylene glycol)s (PEGs) of average M_r 400 to 2000 with derivatisation by dinitrobenzoate. Normal-phase HPLC with gradient elution using ternary solvents of hexane, dichloromethane and methanol has produced a baseline resolution for oligomers of PEG 400, 600 and 1000, while PEG 1000 and 2000 were analysed by using binary solvents of acetonitrile and water. Mixtures of PEGs have been determined by these HPLC systems. PEG 400 in a textile finish has also been determined with satisfactory recovery. It has been found that the hydroxyl group of solvents in normal-phase HPLC plays an important role in resolution and retention of PEG oligomers. Derivatisation efficiency for PEGs by dinitrobenzoyl chloride and quantitative determination of derivatised PEGs by HPLC have been studied. A reversed-phase (RP) mode of HPLC was examined for determination of PEG 400 oligomers. The normal-phase system provided greater resolution for oligomers of PEGs.     

Stereoselective Synthesis of Polysubstituted Cyclopropanes from Poly(ethylene glycol)Supported Pyridinium Ylide

Polysubstituted cyclopropanes were efficiently prepared with poly(ethylene glycol)(PEG) as soluble support. The reaction of PEG-supported pyridinium ylide with arylidenemalononitrile(R=CN) or ethyl arylidenecyanoacetate(R=COOEt) in the presence of triethylamine(TEA) afforded PEG-supported cyclopropanecarboxylates, which were cleaved by 1% KCN/EtOH to obtain polysubstituted cyclopropanes with exclusive trans-selectivity and good yields.     

聚二甲基丙烯酸乙二醇酯壁材微胶囊的制备及其表征

采用界面自由基聚合的方法,制备了以聚二甲基丙烯酸乙二醇酯(PEGDMA)为壁材,薄荷素油(DPO)与石蜡或者三辛癸酸甘油酯(GTCC)的混合物为芯材的微胶囊.微胶囊壁材是二甲基丙烯酸乙二醇酯(EGDMA)单体通过界面自由基聚合形成的高聚物PEGDMA.提出了该界面自由基聚合形成PEGDMA的机理过程.利用光学显微镜和扫描电镜探究了乳化剂类型、芯材组成和固化温度对微胶囊形貌的影响.用傅里叶红外光谱对微胶囊的化学结构进行了表征.利用紫外分光光度计测出了未被微胶囊包埋的芯材占总芯材的百分比(free oil).并用热重分析仪分析了微胶囊的热稳定性能,讨论了固化时间对微胶囊热性能的影响.结果表明,采用阿拉伯树胶为乳化剂,芯材组成为质量比M_(DPO)/M_(GTCC)=1∶1,在60℃下固化1 h,制备出的微胶囊为饱满的球形状,表面光滑.同时测得该体系中芯材的free oil为26.5 wt%.PEGDMA微胶囊在60℃固化温度下反应3 h,具有很好热稳定性,且固化温度升高能提高微胶囊的热稳定性.所制备的微胶囊无毒,在个人护理品和医药领域具有广泛的应用前景.     

Poly(ethylene glycol) enhances the surface activity of a pulmonary surfactant

The primary role of lung surfactant is to reduce surface tension at the air–liquid interface of alveoli during respiration. Axisymmetric drop shape analysis (ADSA) was used to study the effect of poly(ethylene glycol) (PEG) on the rate of surface film formation of a bovine lipid extract surfactant (BLES), a therapeutic lung surfactant preparation. PEG of molecular weights 3350; 8000; 10,000; 35,000; and 300,000 in combination with a BLES mixture of 0.5 mg/mL was studied. The adsorption rate of BLES alone at 0.5 mg/mL was much slower than that of a natural lung surfactant at the same concentration; more than 200 s are required to reach the equilibrium surface tension of 25 mJ/m². PEG, while not surface active itself, enhances the adsorption of BLES to an extent depending on its concentration and molecular weight. These findings suggest that depletion attraction induced by higher molecular weight PEG (in the range of 8000 to 35,000) may be responsible for increasing the adsorption rate of BLES at low concentration. The results provide a basis for using PEG as an additive to BLES to reduce its required concentration in clinical treatment, thus reducing the cost for surfactant replacement therapy.     

聚乙二醇稳定的RuB非晶态纳米催化剂对吡啶及其衍生物加氢反应

制备了聚乙二醇(PEG)稳定的RuB非晶态纳米催化剂, 采用X射线衍射(XRD)、X射线光电子能谱(XPS)和透射电镜(TEM)对催化剂进行表征. 结果表明, RuB以高分散态存在, 其平均粒径为2.4 nm. 该催化剂体系对吡啶及其衍生物显示了优异的催化活性和选择性. 在100 ℃、氢气压力3.0 MPa, 催化剂与底物的摩尔比为1/670的条件下, 反应60 min, 催化吡啶加氢的转化率大于99.0%, 生成哌啶的选择性为100%. 对含不同取代基的底物的加氢反应活性顺序如下: 2-甲基吡啶>2,6-二甲基吡啶>吡啶.     

聚乙二醇和叶酸对层状双金属氢氧化物颗粒的表面修饰

以具有伪装隐形作用的聚乙二醇(PEG)和具有靶向作用的叶酸(FA)为修饰剂, 以氨丙基三甲氧基硅烷(APTMS)为连接剂, 对Mg₃Al-NO₃层状双金属氢氧化物(LDH)进行了表面修饰, 制备了LDH-PEG-FA纳米颗粒, 并通过X射线衍射(XRD)、 透射电子显微镜(TEM)、 紫外-可见光谱(UV-Vis)、 傅里叶变换红外光谱(FTIR)、 粒度分布分析和元素分析等技术对其结构进行了表征. 结果表明, PEG和FA的修饰量可由其原料配比调控, 修饰后的产物具有良好的水再分散性, 这主要源于修饰层的空间位阻效应. 预期LDH-PEG-FA同时具有伪装隐形性和靶向性, 可用于药物载体等领域.     

光固化聚乙二醇水凝胶及其固定化枯草杆菌的研究

制备了一系列光固化聚乙二醇水凝胶固定化载体，研究了该水凝胶的结构、性能及其固定化枯草杆菌发酵产出α－淀粉酶的特性。结果表明，用水凝胶作载体制备的固定化枯草杆菌具有强度高、对温度和酸碱度变化的适应性强、贮存及重复使用性能好等优点。而且其产出α－淀粉酶的活力比相应的游离细胞高出２０％　以上。固定化细胞半连续发酵１７批，历时３７天，产酶活力仅下降２０％。基本能达到实际应用的要求。     

Structural analysis of poly(amidoamine) dendrimer immobilized in crosslinked poly(ethylene glycol)

Polymeric membranes comprised of poly(amidoamine) (PAMAM) dendrimer immobilized in a poly(ethylene glycol) (PEG) network exhibit an excellent CO₂ separation selectivity over H₂. The CO₂ permeability increases with PAMAM dendrimer concentration in the polymeric membrane and becomes 500 times greater than H₂ permeability when the dendrimer content was 50 wt % at ambient conditions (5 kPa of CO₂ partial pressure). However, the detailed morphology of the membrane has not been discussed. The immiscibility of PAMAM dendrimer and PEG matrix results in phase separation, which takes place in a couple of microns scale. Especially, laser scanning confocal microscope captures a 3D morphology of the polymeric blend. The obtained 3D reconstructions demonstrate a bicontinuous structure of PAMAM dendrimer‐rich and PEG‐rich phases, which indicates the presence of PAMAM dendrimer channel penetrating the polymeric membrane, and CO₂ will preferentially pass through the dendrimer channel. In addition, Fourier transform of the 3D reconstructions indicates the presence of a periodic structure. An average size of the dendrimer domain calculated is 2–4 μm in proportion to PAMAM dendrimer concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide),PEG-b-(PNIPAM)_2,were successfully synthesized through atom transfer radical polymerization(ATRP).A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether(PEG).The copolymers were obtained via the ATRP of N-isopropylacrylamide(NIPAM) at 30℃with CuCl/Me_6TREN as a catalyst system and DMF/H_2O(v/v = 3:1) mixture as solvent.The resulting copo...     

Poly（L—lactide）—Poly（ethylene glycol） Multiblock Copolymers：Synthesis and Properties

Poly (L-lactide)-poly (ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. These copolymers presented special properties, such as better miscibility between the two components, low crystallinity and better hydrophilicity, which can be modulated by adjusting the block lengths of the two components.     

Synthesis of oligo(ethylene glycol) methacrylate polymer brushes

Here we report a study into controlling the polymerization of mono-hydroxy and mono-methoxy terminated oligo(ethylene glycol) methacrylates (HOEGMA and MeOEGMA, respectively) from functionalised, planar surfaces via atom transfer radical polymerization (ATRP). The effects of initiator structure, initiator density, temperature, and monomer ratios have been investigated for these polymerizations. The polymer brushes grown in this way were found to convey protein resistance to the underlying inorganic substrates, prone to facile protein adsorption in their native state.