showing 17 related works from this author
Infrared spectroscopy on new multiphase thermoplastic elastomers based on hydrogen bond complexes - temperature dependence and orientation behaviour
1991
The structure and deformation behaviour of a new class of thermoplastic elastomers is studied by temperature dependent infrared (IR) spectroscopy and by IR - dichroism spectroscopy. The thermoplastic elastomer is based on polybutadiene with statistically distributed side groups which form an anisotropic supramolecular structure via hydrogen bonds. Changes in the IR spectra at elevated temperatures are related to the melting of the ordered structure. The uniaxial deformation behaviour is studied by linear dichroism Fourier-transform (FT)-IR spectroscopy. A deformation model is developed which accounts for the major experimental results: while the polybutadiene segments behave as flexible cha…
Artifacts in Light Scattering Experiments Using Opaque Scattering Screens on the Example of Spinodal Decomposition
1996
Synthesis of a polystyrene-arm-polybutadiene-arm-poly(methyl methacrylate) triarm star copolymer
1996
The straightforward synthesis of a polystyrene-arm-polybutadiene-arm-poly(methyl methacrylate) triarm star copolymer has been successfully realized by a sequence of reactions which involves the sequential addition of a living polybutadienyllithium to a polystyrene macromonomer with a terminal 1,1-diphenylethylene unit and subsequent polymerization of methyl methacrylate. The high-molecular-weight polystyrene-arm-polybutadiene-arm-poly(methyl methacrylate) star copolymer shows microphase separation into three phases.
The glass transition of mixtures of polystyrene with alkyl-terminated oligostyrene — experimental evidence for microphase separation in a polymer ble…
1995
Mixtures of high molecular weight polystyrene (P n = 961.5 ; T g = 373 K) and sec-butyl-terminated oligostyrene (P n = 10.6 ; T g = 302 K) show a dependence of the glass transition on the composition (i.e., number-average molecular weight) which cannot be described by the classic equations of Fox & Flory or Kanig & Ueberreiter. Addition of small amounts of the oligostyrene strongly decreases the glass transition, and above an oligomer content of 40 wt.-% the glass transition remains constant within experimental error. This behavior can be attributed to the unfavorable interactions between the alkyl-terminated oligomer and the high molecular weight PS. As a result the oligomer is a bad solve…
Infrared linear dichroism spectroscopy by a double modulation technique
1990
A linear IR dichroism experiment has been devised using a FTIR instrument in combination with a photoelastic modulator. Based on the Mueller-Stokes calculus, a method to directly obtain the absorbance spectra Av parallel and Av perpendicular from the modulated interferogram is developped, which allows the sensitive evaluation of the dichroic ratio. The photoelastic modulator, in combination with a FTIR instrument, offers high sensitivity, high speed, excellent signal to noise ratio and a broad spectral range from 3300 to 850 cm-1. First experimental results obstained from SBS block copolymer are reported.
Indication of an order-order-transition by a partial disordering in ABC-triblock copolymers
1996
Poly(ethylene-alt-propylene)-block-polyethylethylene-block-polystyrene (PEP-b-PEE-b-PS) triblock copolymers were synthesized by anionic polymerization and subsequent hydrogenation of poly-1,4-isoprene-block-poly-1,2-butadiene-block-polystyrene triblock copolymers (1,4PI-b-1,2PB-b-PS). Differential scanning calorimetry and dynamic mechanical spectroscopy reveal an order-order transition which is induced by the mixing of PEP and PEE above their respective order-disorder transition (ODT).
ABC and BAC triblock copolymers - morphological engineering by variation of the block sequence
1997
Different morphologies and phase transitions of ternary triblock copolymers with different block sequences (ABC and BAC) are discussed qualitatively. The interplay between interfacial energies and elastic energies of the different blocks leads to various morphologies and enhances or prevents mixing of different blocks, depending on composition and topology.
Orientation of polybutadiene chains in a thermoplastic elastomer
1996
The orientation of polybutadiene chains in thermoplastic elastomers based on hydrogen bonding complexes is investigated under uniaxial deformation by two-dimensional small-angle neutron scattering (SANS), deuteron magnetic resonance spectroscopy (2H-NMR), optical birefringence and infrared dichroism spectroscopy (FTIR-D). While SANS probes orientation on the length scale of the radius of gyration,2H-NMR, birefringence and FTIR-D monitor orientation on a segmental scale. The deformation of the elastomer chains appears to be affine on the different length scales.
Thermodynamically Controlled Morphological Disorder in a Microphase-Separated Cylindrical Block Copolymer
1996
Organometallic ABC-triblock copolymers
1998
The interaction of Fe and Pd complexes with double bonds of the polybutadiene (PB) block in polystyrene-polybutadiene-poly(methyl methacrylate) block copolymers has been studied. The incorporation of Fe(CO)3 fragments into the PB bloc was found to result in an increase in its rigidity. The presence of iron or palladium complexes in the PB block affects strongly the morphology of the triblock copolymers.
Order-disorder-and order-order-transitions in AB and ABC block copolymers: description by a simple model
1996
Based on the description of AB-block copolymers as micellar structures given by Semenov, the phase diagram of AB-diblock copolymers is calculated taking the homogeneously mixed system as a reference state. The predicted value (χN)c = 10.385 for a symmetric AB-diblock copolymer compares very well to the result of the original Random Phase Approximation theory (10.495). The simplicity of the model allows its extension to predict order-order transitions in ABC-triblock copolymers.
Polybutadiene model networks —synthesis, mechanical characterization and comparison with rubber elasticity models
1995
Model networks of defined crosslink density are prepared via nonradical statistical crosslinking of polybutadiene in bulk and concentrated solution using a masked bistriazolinedione as crosslinker. The kinetics of crosslinking is monitored by FT-IR-spectroscopy. The reaction follows pseudo-1st-order reaction kinetics. The activation parameter of the crosslinking reaction is estimated from crosslinking at various temperatures. Networks of deuterated polybutadiene are prepared by this reaction in a wide range of crosslink densities. The stress strain behavior is analyzed according to the Junction Constraint-Theory of rubber elasticity (JCT) and to the approach introduced by Graessley accounti…
Static and dynamic elasticity of some thermotropic liquid-crystalline copolyesters
1997
Two series of thermotropic liquid crystalline copolyesters were studied in static and dynamic tensile deformation. Static loading generally does not lead to any peculiar phenomena: the stress-strain diagrams are linear or convex, except one copolyester fibre, the stress-strain diagram of which is concave at high temperatures. On the contrary, in dynamic loading the elasticity modulus increased during deformation for all the samples investigated. So it can be assumed that formation of a more rigid and stable structure takes place due to the dynamic deformation.
Hydrogen bonds in unpolar matrix — Comparison of complexation in polymeric and low molecular-weight systems
1991
By ene-reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with double bonds, polar 4-phenyl-1,2,4-triazolidine-3,5-dione (phenyl urazole) groups are introduced into unpolar matrices. Hydrogen-bond complexes are formed between two amide-like units. The temperature dependence of complex formation in dilute hydrocarbon medium is obtained from remperature-dependent IR spectra in the region of the C=O stretching vibration. Results obtained for a low molecular-weight model system are compared with modified polybutadienes, where the groups are attached statistically along the polymer backbone. The enthalpy and the entropy of complex formation (ΔH f =−28.6 kJ/mol; ΔS f =−52 J/mol K−1) obtained for the…
Microphase separation in ternary ABC block copolymers: Ordering control in molten diblock AB copolymers by attaching a short strongly interacting C b…
1997
Some specific features of the microphase separation in molten ternary ABC triblock copolymers (in particular, modifications of the molten AB diblock copolymers by attaching a short third block C strongly incompatible with both A and B blocks) are studied rigorously within the framework of the weak segragation approach. It is shown that via such a modification one can control both the stability as to the microphase separation transition (i.e., the corresponding spinodal temparatures) and the smoothness of such a transition. Two modes of such modifications for every composition are studied in detail: (i) those resulting in the minimal spinodal temperatures and (ii) those that result in the s…
Cylindrical morphologies in asymmetric ABC triblock copolymers
1997
In asymmetric ABC triblock copolymers with C being the matrix-forming majority component, the formation of cylindrical morphologies is governed by the sum of the volume fractions of the components A and B (Φ A + Φ B ) as well as by their ratio (Φ B /Φ A ). The paper describes the morphologies of various polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM) and polystyrene-block-poly(ethylene-co-butylene)-block-poly(methyl methacrylate) block copolymers (SEBM) in dependence on these parameters. In addition to previously reported cylinder in cylinder (c i c, core shell) and helical (hel) morphologies, new microphase separated structures as cylinders at cylinder (c a c), undula…
Linear infrared dichroism by a double modulation technique
1991
In the first part of this paper an experimental setup using Fourier-transform infrared spectroscopy (FTIR) in combination with a photoelastic modulator (PEM) for linear dichroism measurements is described. The second part shows the influence of PEM-amplitude and scan-velocity on the sensitivity of the instrument. The third part deals with the fringe-problem in the baselines of absorbance spectra and its influence on the determination of the linear dichroic ratio.