Adsorption of polyamides and polyamide–silane mixtures at glass surfaces

The individual and combined adsorption behavior of polyamides and two different silanes to multicomponent glass surfaces was probed with a combination of x‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and static contact angle measurements. Samples were analyzed with and without solvent rinsing to separate the weakly bound (physisorbed) and more strongly bound (chemisorbed) species. High‐resolution XPS on N 1s revealed that the polyamides adsorb to the glass surfaces via protonated amine species at the acidic (OH) sites on the glass surface. Angle‐resolved XPS confirmed this by showing that the alkyl portion of the polymer is oriented away from the glass interface. In competitive coadsorption studies it was found that amino‐terminated silanes preferentially adsorb to the glass surface, relegating the polyamide to a physisorbed outer layer. When mercaptoterminated silanes were competitively coadsorbed the polyamide was preferentially adsorbed even when present at a concentration twenty times less than that of the silane. Altogether, this work reveals the strong interaction between surface silanols and amino‐functionalized organics. Copyright © 2003 John Wiley & Sons, Ltd.     

Highly tilted antiferroelectric (R) enantiomers useful for the formulation of eutectic mixtures

ABSTRACT

Novel chiral three-ring (R) enantiomers were synthesised using optically active (R)-(?)-2-octanol. Properties, such as the sequence of phases, the transition temperatures and enthalpies, were tested by a polarising optical microscope and differential scanning calorimeter. An antiferroelectric smectic phase (SmC_A*) with a direct transition from the antiferroelectric to the isotropic phase (SmC_A*-Iso) was observed for three esters with an achiral C₃F₇CH₂O(CH₂)₃O– terminal chain. Bi- and multicomponent mixtures with a broad temperature range of the antiferroelectric phase and good electro-optical properties were formulated. Helical pitch of pure esters and mixtures was measured by spectrophotometry method.     

Microphase separation of PEG-modified urethane acrylate and the swelling behavior of its gels

The viscosity of PEG-modified urethane acrylate (PMUA) showed peculiar behavior in the course of soap-free emulsification. Moreover, the viscosity change with added amounts of water was influenced by the reaction molar ratio of polyethylene glycol (PEG). The rate of increase in viscosity slowed and the ratio of increase in viscosity increased as the reaction molar ratio of PEG increased. This peculiar viscosity behavior was due to the microphase separation between hydrophilic and hydrophobic segments of PMUA, and the orientation of polyoxyethylene groups at O/W interface which influenced droplet size of the soap-free PMUA emulsion. The location of polyoxyethylene groups of this resin at O/W interface was confirmed using the adsorption isotherm measurement of PMUA molecules containing polyoxyethylene groups at water/benzene interface. The microphase separation behavior of PMUA between hydrophilic and hydrophobic segments could apply to the preparation of the PMUA gels containing peculiar structure. PMUA gels were prepared using dioxane (UAG) and the swelling behavior of these gels were compared to that of gels prepared using water (UAHG) in the same medium. In the same medium, the swelling behavior of UAHG gels differed from that of UAG gels because of the difference in the microstructure of gel due to the microphase separation between hydrophilic and hydrophobic segments. This phase separation in the course of gelation in water could be confirmed using contact angle measurement.     

Controlling electron delocalisation in constrained N,N′-dimethyl-4,4′-bipyridinium dications

The synthesis is described of two N,N′-dimethyl-4,4′-bipyridinium salts for which the two pyridinium rings are connected via varying length alkoxy chains attached at the 3,3′-locations.     

含氮给体结构对丙烯腈电荷转移光聚合的影响

<正> 对于正性烯类单体,主要是乙烯基咔唑的电荷转移聚合,诚田已作过详细综述。负性烯类单体的电荷转移聚合主要研究的单体是丙烯腈(AN)及甲基丙烯酸甲酯(MMA)。Barton等研究了芳烃为引发剂的MMA光聚合。我们研究了芳胺为引发剂的光聚合。 芳胺,尤其是芳叔胺,是较强的电子给体,与负性单体在光照下经激基复合物而引发聚合,我们的实验表明,吡啶及其同系物(喹啉与吖啶)并不象吡咯及其同系物(吲哚与咔唑)那样有效地引发AN等负性单体的光聚合(见表1)。从图1所示的结构看,它们有     

铝交联皂石的合成和表征及催化性能

用XRD、化学分析、IR、MASNMR、TPD等手段表征了合成皂石及其铝交联物的结构。结果表明:皂石的交联密度与四面体层电荷和交联条件(Al/土比)有关。在乙醇氨化反应中,交联皂石显示了较好的催化活性和选择性。皂石的交联密度与液相产物分布的关系表明层柱材料对此反应具有择形催化作用。醇氨化反应可能是在吸附态NH_3和气相醇分子间进行的。     

Solid state extrusion of thermoplastic elastomers 4

A solid state extrusion technique is applied as to produce oriented block copoly(ether ester) under various physical conditions. The morphology of the extruded samples is characterized in relation to the extrusion parameters and hard segment compositions of the polymer, using thermal analysis and X-ray methods. The lateral dimensions of the crystalline domains are found to be approximately 150 Å depending on the extrusion conditions. The statistics of the long range periodicity of the structure along the extrusion direction is in agreement with a one-dimensional two phase model, the crystalline portion of which does not vary much in thickness (35 – 45 Å). The unexpected increase in the long period and the thermal shrinkage suggest the existence of strained interlamellar amorphous chains (tie molecules). The observed variations in tensile properties are interpreted under the assumption that both the number of such tie molecules and their fully extended lengths are determined by the hard segment composition and the extrusion conditions. It is also argued that the increase in the glass transition temperature is not only a function of the composition of hard segments in the amorphous phase but also of the number of strained tie molecules.Herrn Dr. Dr. h. c. H. Hellmann zum 70. Geburtstag gewidmet.Part 3 cf. lit [11]     

Surface modification of low density polyethylene (LDPE) film by low pressure O2 plasma treatment

In this work, low pressure glow discharge O₂ plasma has been used to increase wettability in a LDPE film in order to improve adhesion properties and make it useful for technical applications. Surface energy values have been estimated using contact angle measurements for different exposure times and different test liquids. In addition, plasma-treated samples have been subjected to an aging process to determine the durability of the plasma treatment. Characterization of the surface changes due to the plasma treatment has been carried out by means of Fourier transformed infrared spectroscopy (FTIR) to determine the presence of polar species such as carbonyl, carboxyl and hydroxyl groups. In addition to this, atomic force microscopy (AFM) analysis has been used to evaluate changes in surface morphology and roughness. Furthermore, and considering the semicrystalline nature of the LDPE film, a calorimetric study using differential scanning calorimetry (DSC) has been carried out to determine changes in crystallinity and degradation temperatures induced by the plasma treatment. The results show that low pressure O₂ plasma improves wettability in LDPE films and no significant changes can be observed at longer exposure times. Nevertheless, we can observe that short exposure times to low pressure O₂ plasma promote the formation of some polar species on the exposed surface and longer exposure times cause slight abrasion on LDPE films as observed by the little increase in surface roughness.     

Influence of drawing and heat treatment on surface free energies of polyethylene terephthalate fibers

The surface free energies of polyethylene terepthalate fibers with different draw ratios were experimentally determined by contact angle measurements inn-alkane/water systems. The dispersive component of the surface free energy increased with increasing draw ratio, whereas the nondispersive one remained almost constant. After heat treatment, the dispersive surface free energy increased, but was reduced above 140°C. The nondispersive component increased by heat treatment at 190°C. The increases in the density and birefringence of the fibres due to the drawing and heat treatment suggested that the increase in the dispersive surface free energy was caused by the increase in the atomic density at the fiber surface due to drawing and heat treatment. ESCA results indicated that the increment in the nondispersive surface free energy due to heat treatment was caused by the addition of functional groups to the fiber surface due to heat treatment.     

Determination of dispersive and nondispersive components of the surface free energy of glass fibers

The dispersive component _s ^d of the surface free energy of glass fibers and its interaction energy with alkanes, benzene, 1-nitropropane, ethyleneglycol, glycerol, formamide, and water were quantitatively determined by the tensiometric method within two liquids. The values of nondispersive interaction energy I _SL ^p were found to be a linear function of the square root of the nondispersive component of the surface free energy of liquids. This suggests that the nondispersive interaction energy may be represented by the geometric mean of the nondispersive component of the surface free energy of a solid and a liquid. The slope gave the nondispersive component _s ^p of the surface free energy. The _s ^p values are 33 and 14 mJ/m² for the untreated and aminosilane-treated fibers, respectively, suggesting that organophilic character has developed on the surface after aminosilane treatment. The _s ^p value was almost similar after the treatment, probably because of the polar characteristics of amino groups.