Styrolux and Styroflex are styrene and butadiene based block copolymers prepared by butyllithium initiated anionic polymerization. Styrolux is a transparent, tough and stiff thermoplastic material for high speed processing. Its specially designed molecular structure allows homogeneous mixing with general purpose polystyrene maintaining the transparency. Styroflex is a newly commercialized product with the mechanical behavior of a thermoplastic elastomer, e.g. low modulus and yield strength, high elongation and excellent recovery. High transparency and thermal stability give the competitive edge over conventional styrene‐butadiene elastomers. Styroflex, Styrolux and general purpose polystyrene form a unit construction system e.g. for transparent film materials and injection molded parts with fine‐tunable hardness and toughness.

Donor-acceptor substituted linear polyenes: Chain length dependent electronic structure of anthrylpolyenes J. Chem. Phys. 98, 7969 (1993); 10.1063/1.464551 Resonant Raman scattering of controlled molecular weight polyacetyleneWe have measured the solid state Raman scattering spectra of a homologous series of linear polyenes, with the number of alternated double bonds varying from 3 to 12. While we find a linear dependence of the Raman shifts of resonantly coupled modes with inverse conjugation length, we have also followed the suggestion of previous work in examining the inverse square product of the several Raman frequencies as a function of the logarithm of the measured energy gap of the molecule. This provides a linear relationship, as found for transpoly acetylene, a result which is qualitatively consistent with the amplitude mode model of Horovitz and co-workers. We also find, consistent with previous work on polyacetylene, a monotonic decrease in the ratios of oscillator strengths of the two strongest bands with conjugation length, as recently predicted by a series of molecular dynamics calculations. Suggested interpretations of a number of qualitative observations, including splitting of modes for shorter conjugation length, are offered, and the implications for the structure of transpolyacetylene are discussed. The present work confirms that the previously measured dispersion in the Raman spectra of trans-polyacetylene is due to a distribution of conjugation lengths and brings into question some of the quantitative aspects of the amplitude mode model.

No abstract

Dibenzylbarium is prepared in yields of 80-90% by reaction of the tetramethyl ethylenediamine adduct of benzyllithium with the bis-THF adduct of barium bis(bis-trimethylsilylamide) or with barium bis(2,4,6-tri-tert-butyl phenolate). It is converted, by reaction with diphenylmethane in THF, to bis(diphenylmethyl)barium in 90% yield and, by reaction with 1,1-diphenylethene in THF, to bis(1,1,3-triphenylpropyl)barium in essentially quantitative yield. The latter is soluble also in hydrocarbon solvents, while dibenzylbarium and bis(diphenylmethyl)barium are soluble only in THF. Reaction of the bis-chelate complex (C 5 Me 4 SiMe 2 C 6 H 5 ) 2 Ba, the phenyl residues of which are coordinated to the Ba center, with each of the bis(arylalkyl)barium species generates heteroleptic barium complexes with one chelate and one reactive arylalkyl ligand. Homoleptic and heteroleptic triphenylpropylbarium complexes both induce, in cyclohexane solution, living polymerization of styrene to atactic polystyrene.

Lamellae-forming styrene/butadiene star block copolymers are studied to investigate the influence of morphology on micromechanical deformation mechanisms and mechanical properties by using transmission electron microscopy and tensile testing. A large homogeneous plastic deformation of polystyrene (PS) lamellae is found in styrene/butadiene star block copolymers on the basis of the new mechanism called thin-layer yielding. This mechanism depends strongly on the thickness of the PS lamellae. At a critical thickness of PS lamellae of about 20 nm, a transition from thin-layer yielding mechanism to a crazelike deformation was observed. These new deformation zones are similar to crazes with respect to their propagation perpendicular to direction of external stress and similar to shear bands with respect to an internal shear deformation component of the lamellae in the deformation zones. As a result of our investigations, the mechanical properties of star block copolymers can be understood in correlation with morphology and micromechanical deformation mechanisms.