Elimination of undesirable water layers in solid-contact polymeric ion-selective electrodes

This study aimed to develop a novel approach for the production of analytically robust and miniaturized polymeric ion sensors that are vitally important in modern analytical chemistry (e.g., clinical chemistry using single blood droplets, modern biosensors measuring clouds of ions released from nanoparticle-tagged biomolecules, laboratory-on-a-chip applications, etc.). This research has shown that the use of a water-repellent poly(methyl methacrylate)/poly(decyl methacrylate) (PMMA/PDMA) copolymer as the ion-sensing membrane, along with a hydrophobic poly(3-octylthiophene 2,5-diyl) (POT) solid contact as the ion-to-electron transducer, is an excellent strategy for avoiding the detrimental water layer formed at the buried interface of solid-contact ion-selective electrodes (ISEs). Accordingly, it has been necessary to implement a rigorous surface analysis scheme employing electrochemical impedance spectroscopy (EIS), in situ neutron reflectometry/EIS (NR/EIS), secondary ion mass spectrometry (SIMS), and small-angle neutron scattering (SANS) to probe structurally the solid-contact/membrane interface, so as to identify the conditions that eliminate the undesirable water layer in all solid-state polymeric ion sensors. In this work, we provide the first experimental evidence that the PMMA/PDMA copolymer system is susceptible to water "pooling" at the interface in areas surrounding physical imperfections in the solid contact, with the exposure time for such an event in a PMMA/PDMA copolymer ISE taking nearly 20 times longer than that for a plasticized poly(vinyl chloride) (PVC) ISE, and the simultaneous use of a hydrophobic POT solid contact with a PMMA/PDMA membrane can eliminate totally this water layer problem.     

Fabrication of high yield and highly crystalline poly(2,5-dimethoxyanline) nanoplates using various organic sulfonic acids as the dopant agents and soft-templates

This paper demonstrates a simple and effective approach to fabricate highly crystalline poly(2,5-dimethoxyaniline) (PDMA) nanoplates using various organic sulfonic acids including Dodecyl benzenesulfonic acid (DBSA), Camphorsulfonic acid (CSA) and p-Toluenesulfonic Acid (p-TSA) as the dopant agents. The structures and morphologies of PDMA nanoplates were characterized using Fourier transform infrared spectrometer, Raman spectrometer, X-ray diffraction, Atom force microscope and Electron microscope. The results show that the PDMA nanoplates possess high crystallinity and layered nanoplate aggregation structure. The estimated degree of crystallinity is higher than 95 %. With different organic sulfonic acids used, the aggregation structures of PDMA nanoplates vary from triclinic hexahedron to cuboid and rod shape. Through adjusting the dopant agent/monomer molar ratio, the yield of PDMA nanoplates can be as high as 53 %.     

Optimizing hydrogen-bonding miscible binary polymer blends made by concentrated emulsion polymerization

Polystyrene/poly (n-butyl methacrylate) blends were prepared by concentrated emulsion polymerization using (2-hydroxy ethyl) methacrylate and n-butyl methacrylate as hydrogen-bond donor and acceptor respectively. Two concentrated emulsions of styrene/(2-hydroxy ethyl) methacrylate and n-butyl methacrylate monomers were prepared separately, and mixed mechanically after partial polymerization. The products thus obtained consisted of compact particles. The specific formation of hydrogen bond between poly [styrene-co- (2-hydroxy ethyl) methacrylate] with poly (n-butyl methacrylate) were studied by transmission electron microscope and dynamic mechanical thermal analysis. The results showed that the miscibility is induced via hydrogen bonding between the hydroxyl group and the carbonyl groups and that hydrogen bonding plays an important role in the compatibilization of the PS/PBMA blends. The TEM micrographs also showed that the PS/PBMA blends are partially inhomogeneous on a scale of 50 nm, and only a single glass transition temperature was found by DMTA for the PS/PBMA blends containing more than 3.0 ml of (2-hydroxy) methacrylate /100 ml styrene.     

Application of generalized two-dimensional infrared correlation spectroscopy to the study of a hydrogen-bonded blend

In the preceding studies in this series, generalized two-dimensional (2D) infrared correlation spectroscopy has been applied to the study of polymer blends with relatively weak intermolecular interactions. In this paper, a miscible system with strong intermolecular interactions, hydrogen-bonded blends of poly(4-vinyl phenol) (PVPh) and poly(methyl methacrylate) (PMMA), is considered. It has been found that band positions in 2D plots are dependent on the data sets used, due to large peak shifts and/or bandwidth changes. This observation complements our preceding studies, in which it was found that new features correspond to maxima, minima, or points of inflection in the difference spectra used to generate the 2D plots and are not normal modes of vibration of specific functional groups. Great care needs to be taken in order not to interpret artifacts of the procedure in terms of new spectroscopic features.     

Interaction of crazes with pre-existing shear bands in glassy polymers

Shear bands have been grown in bulk specimens of P₃O(poly 2,6 diphenyl 1,4 phenylene oxide) and in thin films of two blends of polystyrene with poly(xylenyl ether). The subsequent interaction of crazes with these shear bands has been characterized by transmission electron microscopy. For the case of shear bands grown under the plane stress conditions of thin films, it is found that the bands act as preferential sites for craze nucleation. A fairly regularly-spaced array of short crazes grows within the shear bands and these crazes may thicken sufficiently to coalesce. When the crazes reach the end of the shear band they emerge and propagate into the unoriented polymer matrix. Within the shear band the craze growth direction does not lie normal to the tensile axis, but is rotated due to the molecular orientation of the shear band. The direction of craze growth is also affected under the plane strain conditions of bulk specimens. In this case the craze is diverted along the shear band before re-emerging into the matrix. Measurements of the craze fibril extension ratio, , within the shear band show an increase over typical values obtained outside the shear band in the same polymer. This high value of leads to an increased likelihood of craze break-down and crack nucleation within the shear band.     

Evaluation of photochemically immobilized poly(2-ethyl-2-oxazoline) thin films as protein-resistant surfaces

Poly(2-ethyl-2-oxazoline) (PEOX) of various molecular weights were covalently immobilized on silicon wafers and gold slides to form protein-resistant surfaces via a fast and general photocoupling chemistry based on the CH insertion reaction of light-activated perfluorophenyl azide (PFPA). The thicknesses of the immobilized PEOX films ranged from 23 to 80 ? for molecular weight of 5000 to 500,000, and the grafting density reached 3.2 × 10(-3) ?(-2) for PEOX 5000. The protein-resistant property of the films was studied using bovine serum albumin (BSA) by fluorescence imaging, ellipsometry, and surface plasmon resonance imaging (SPRi). The fluorescence imaging and ellipsometry studies showed the largest amount of BSA adsorbed on PEOX 5000 and the smallest on PEOX 500,000. This was consistent with the kinetic analysis of BSA adsorption by SPRi showing that PEOX 5000 exhibited the fastest association rate and the slowest dissociation rate whereas PEOX 500,000 had the slowest association rate and the fastest dissociation rate. The PEOX film was then applied in the fabrication of carbohydrate microarrays to reduce the nonspecific adsorption of lectins and thus the background noises. Results showed that the microarray signals were significantly enhanced when the PEOX film was used.     

Impulse-induced compression rheo-optics study of polymers using attenuated total reflection based step-scan Fourier transform infrared time-resolved spectroscopy

An impulse-induced attenuated total reflection (ATR) based dynamic compression step-scan time-resolved Fourier transform rheo-optical system has been developed. This system was used to observe different viscoelastic properties of poly(ethylene terephthalate) (PET), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx), and carbon-black-filled polyester-polyamide blend. In the case of PET, almost no viscoelastic response extending beyond 15 ms was observed in the dynamic absorbance difference time domain spectrum. In contrast, PHBHx showed apparently different viscoelastic responses in the dynamic absorbance difference spectrum, especially in the C=O stretching band region. A long relaxation tail of the 1723 cm(-1) band lasting about 2.7 milliseconds was clearly seen. The tail corresponds to the structural or morphological reorganization of a less ordered crystalline form (Type II) under compressive perturbation. The carbon-black-filled polyester-polyamide blend film also shows different viscoelastic response tails. In this case, the amide C=O stretching vibration band does not show distinct viscoelastic responses, suggesting that the polyamide component does not contribute much to the viscoelastic properties. The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, copolymers, and semicrystalline polymers.     

PVC／LLDPE共混体系形态结构的控制

采用氢化聚丁二烯－ｂ－甲基丙烯酸甲酯（ＰＢＤ－ｂ－ＰＭＭＡ）共聚物作为聚氯乙烯／线性低密度聚乙烯（ＰＶＣ／ＬＬＤＰＥ）共混体系的增容剂，用扫描电子微镜（ＳＥＭ）和透射电子显微镜（ＴＥＭ）对共混体系的冲击缺口断面和相结构进行了研究。并用小角激光菜射技术了ＬＬＤＰＥ在共混物中的结晶行为，发现增容剂对共混体系的形态结构会产生极大的影响。     

聚丙烯酸丁酯接枝共聚物的可控合成及作为相容剂的应用

结合电子转移再生催化剂原子转移自由基聚合(ARGET ATRP)和普通自由基聚合,制备了一系列聚丙烯酸丁酯接枝共聚物,详细研究了其作为苯乙烯-丙烯腈共聚物树脂/丙烯酸酯橡胶(SAN/ACM)共混体系的相容剂,在制备丙烯腈-苯乙烯-丙烯酸酯树脂(ASA树脂)时,不同主链结构、侧链相对分子质量、接枝密度及用量对增容效果的影响。通过傅里叶变换红外光谱仪和凝胶渗透色谱仪对聚合物结构进行测试和表征;采用动态力学分析仪(DMA)和冲击试验机研究了共混物的力学性能。结果表明,成功制备了不同结构的聚丙烯酸丁酯接枝共聚物,以苯乙烯-丙烯腈共聚物(SAN)作为主链比聚丙烯酸丁酯(PBA)作为主链的接枝共聚物具有更好的增容效果。此外,侧链PBA的相对分子质量较小时,侧链与主链摩尔比为3∶1及相容剂用量为3%(质量分数)时,接枝共聚物的增容效果最佳。DMA分析表明添加接枝共聚物后SAN和ACM两组分的玻璃化转变温度相互靠近,聚丙烯酸丁酯接枝共聚物起到了明显的增容作用。     

Mechanical and three-body abrasive wear behaviour of PMMA/TPU blends

The blends of poly(methyl methacrlate) (PMMA) and thermoplastic polyurethane (TPU) were prepared by a Brabender co-twin screw extruder. The mechanical and three-body abrasive wear behaviour of PMMA/TPU blends has been studied. Three-body abrasive wear tests were conducted using rubber wheel abrasion tester (RWAT) under different abrading distances at 200 rpm and 22 N load. A significant reduction in tensile strength and tensile modulus with an increase in TPU content in the blend formulation was observed. Three-body abrasive wear results indicate that the wear volume increases with increase in abrading distance for all the samples studied. However, neat PMMA showed better wear resistance as compared to PMMA/TPU blends. The worn surface features, as examined through scanning electron microscope (SEM), show matrix cracking and deep furrows in PMMA/TPU blends.     

Phase behaviour and mechanical properties of poly(ether ether ketone)-poly(ether sulphone) blends

The phase behaviour and the mechanical properties of binary blends composed of poly(ether ether ketone) and poly(ether sulphone) have been studied both in the amorphous state and after crystallization of poly(ether ether ketone).Differential scanning calorimetry and dynamical mechanical analysis clearly show the existence of phase separation in the blends. Density measurements confirm the absence of strong interactions between the blend components, as well as the slight effect of PES on the crystallization of PEEK.The mechanical properties of the quenched, amorphous blends remain surprisingly good in spite of the observed immiscibility, however, slowly cooled, crystalline blends appear as brittle materials.     

Thermal degradation of polyethylene oxide blended with novolac type phenolic resin

The miscibility and thermal degradation of poly(ethylene oxide) (PEO) toughened novolac type phenolic resin were investigated. Differential scanning calorimetry (DSC) results confirmed that phenolic resin/PEO blend was blended completely. Infrared spectra show that hydrogen bonding existed in the blends. Thermal degradation of poly(ethylene oxide) blended with novolac type phenolic resin has been studied utilizing a dynamic thermogravimetric technique in a flowing nitrogen atmosphere at several heating rates (i.e. 5, 10, 20, 40°C/min). Thermal degradation of phenolic resin/PEO blends takes place in multiple steps. Chemical structure and components of blends affected thermal degradation, which coincided with the data from thermal degradation of novolac type phenolic resin/PEO blends by thermogravimetric analysis (TGA).     

Effect of oxygen plasma asher on poly(methylphenylsiloxane)-polyimide blends

Variable concentrations of low molecular weight poly(methylphenylsiloxane) were added to polyimide at its precursor poly(amic acid) stage to produce blends of different compositions. Ultimately cured poly(methylphenylsiloxane)/polyimide blends (PMSI) were exposed to radio frequency oxygen plasma. The stability of the blends to the oxygen plasma was assessed by monitoring the weight loss of the films as a function of exposure time. After 24 h exposure blends exhibited weight losses that were much lower than neat polyimide. The effect of oxygen plasma on polyimide and its blends has been analyzed by scanning electron microscopy and changes in surface chemistry of the exposed films were subsequently examined using X-ray photoelectron spectroscopy. The mechanical properties of oxygen plasma exposed and unexposed neat polyimide and its blends have been evaluated.     

可全生物降解PLA/PBAT/PHBV共混材料的结构与性能

为了得到刚性与韧性平衡的聚乳酸（PLA）基可生物降解共混材料,通过熔融共混挤出法制备了不同质量比的PLA/己二酸-对苯二甲酸-丁二酯共聚物（PBAT）/聚（3-羟基丁酸-co-羟基戊酸共聚酯（PHBV）可全生物降解共混材料,采用SEM、TG、DSC、毛细管流变仪和万能材料试验机对PLA/PBAT/PHBV共混材料的形态结构、热性能、流变性能和力学性能进行了研究。结果表明:PLA/PBAT/PHBV共混材料的热失重起始分解温度相对纯PHBV提高了45 ℃,热稳定性提高;共混体系中各组分的玻璃化转变温度与单一体系相比几乎无变化,PLA/PBAT/PHBV共混体系为完全不相容体系,同时PBAT和PHBV的加入阻碍了PLA的冷结晶;PLA/PBAT/PHBV 共混体系的共混形态呈“海-岛”分布,PBAT和PHBV均匀地分散于PLA基体中,相界面分明;随着PBAT含量增加,PLA/PBAT/PHBV共混材料熔体的流动性增加,温度变化对黏度的影响变大;PLA/PBAT/PHBV质量比为70/20/10的共混材料可在保留纯PLA 60%拉伸应力的同时,拉伸应变提高到纯PLA的2.6倍,韧性得到改善。所得结论表明PLA/PBAT/PHBV质量比为70/20/10的共混材料的综合力学性能较纯PLA好。      

Compatibility studies of natural rubber/poly(methyl methacrylate) blends by viscometry and phase separation techniques

The compatibility of binary blends of natural rubber (NR) and poly(methyl methacrylate) (PMMA) has been analysed from the viscosity behaviour. For this, the equations developed by both Krighbaum and Wall, and their modified forms by Williamson and Wright, were used. The interaction between polymers in solution has been interpreted qualitatively based on the heat of mixing (ΔH) and interaction parameter (X1). Viscometry and spectroscopy studies and calculation of the heat of mixing and the interaction parameter indicated the heterogeneous nature of NR/PMMA blends. The effects of graft copolymer of natural rubber and poly(methyl methacrylate) (NR-g-PMMA) as an emulsifying agent on the interfacial properties of NR/PMMA blends were studied based on the phase separation behaviour. The demixing behaviour is found to be a function of graft copolymer concentration, mode of mixing, nature of solvent and molecular weight of homopolymers and graft copolymers. The demixing behaviour has been studied by noting the phase separation time and volume of the phase separated region. The addition of graft copolymer decreases the demixing behaviour of the blends. This revised version was published online in November 2006 with corrections to the Cover Date.     

FTIR investigation of structural modifications during low-temperature ageing of polycarbonate

Conformational changes are sought during low-temperature ageing of solution-cast films of BPA-polycarbonate, by observing the conformationally sensitive IR aromatic breathing band at 1600 cm^–1. Preliminary results using the carbonyl band at 1775 cm^–1 had shown some indication of ageing-induced changes in the distribution of conformations. The present results obtained on the 1600 cm^–1 band show no indication whatever of conformational rearrangements. This result, at variance with observations of conformational rearrangements accompanying sub-T _g annealing, lends support to the concept that sub-T _g annealing and low temperature ageing are two distinct processes.     

Interactions of a liquid crystalline polymer with polycarbonate and poly(ethylene terephthalate)

Thermal behaviour of blends of a liquid crystalline copoly(ester amide) (Vectra B950) with two isotropic polymers has been studied by differential scanning calorimetry. One of the isotropic polymers is an amorphous polymer – polycarbonate, the other is a semi-crystalline polymer – poly(ethylene terephthalate). It was found that the glass transition temperature of polycarbonate decreases with increasing Vectra concentration in the blend, suggesting a partial miscibility between the Vectra liquid crystalline polymer (LCP) and polycarbonate. The miscibility is enhanced through heat treatment at elevated temperatures presumably due to a transesterification reaction. Moreover, the presence of the amorphous poly- carbonate hinders the crystallization of the liquid crystalline polymer in the blends. It was also observed that heat treatment of the Vectra LCP and poly(ethylene terephthalate) blends causes a loss in crystallinity and shifts in transition temperatures of poly(ethylene terephthalate), indicating that exchange reactions occur between Vectra B950 and poly(ethylene terephthalate). Based on these results, a new strategy, in situ compatibilization, is proposed to improve the interfacial adhesion between an LCP and an isotropic polymer. This revised version was published online in November 2006 with corrections to the Cover Date.     

In Situ Fourier transform infrared spectroscopic study of the thermal degradation of isotactic poly(propylene)

The conformational change of isotactic poly(propylene) (iPP) during the thermal degradation process has been carefully studied by in situ Fourier transform infrared (FT-IR) spectroscopy. This new method of studying thermal degradation of iPP not only shows the conventional kinetic parameter information of thermal degradation such as the degradation activation energy DeltaE and the degradation factor n, which are in accord with the results of traditional thermogravimetry experiments, but also indicates that many significant molecular structure changes occur during the thermal degradation process that come from some characteristic absorption band changes of in situ FT-IR. A multivariate approach, principal components analysis (PCA), is applied to the analysis of infrared (IR) data, and the results further confirm the multi-step processes of the thermal degradation of iPP. Above all, this is a new application to polymer thermal degradation by in situ FT-IR that connects the intermediate conformational change with final results during thermal degradation.     

Composition-dependent physical properties of poly[(vinylidene fluoride)-co-trifluoroethylene]–poly(ethylene oxide) blends

Polymer blends based on poly(vinylidene fluoride-co-trifluoroethylene) copolymers, P(VDF-TrFE), and poly(ethylene oxide), PEO, with varying compositions have been prepared by solvent casting. In this way, P(VDF-TrFE) crystallizes from the solution while solvent evaporates, while PEO crystallizes from the melt during cooling to room temperature. The surface morphology of the polymer blends indicates the transition from the fibrillar microstructure typical of PVDF-TrFE to the spherulite structure characteristic of PEO. The vibration mode characteristics of P(VDF-TrFE) are not influenced by the presence of PEO in the polymer blend. Confinement of PEO in the P(VDF-TrFE) phase change the conformation of PEO from trans to helix, increasing this transformation for increasing P(VDF-TrFE) content in the polymer blends. Sequential crystallization of the two polymers produce separated amorphous phases whose independent cooperative conformational motions are revealed by two main dynamic-mechanical relaxations. No chemical interaction seems to exist between the polymers within the blend.     

反应增容PA6/PBT共混体系聚集态结构与力学性能

通过熔融共混制备了SMA增容的PA6/PBT共混物,研究了增容剂对PA6/PBT共混体系聚集态结构及力学性能的影响。研究表明,SMA能有效地提高PA6/PBT共混体系两相间的相容性,降低分散相尺寸,使分散相分布均匀,同时有效地提高了共混体系的力学性能。通过对试样进行热处理,探讨了不同热处理温度对PA6/PBT共混合金力学性能的影响。结果表明,热处理能提高共混物的拉伸强度,但导致共混物的缺口冲击强度下降。