Stable syndiotactic polystyrene (s-PS) co-crystals with highly polar guests have been prepared by sorption
in δ or in co-crystalline phases of molecules dissolved in suitable solvent carriers. These co-crystals are
clathrates, that is, isolated molecules are imprisoned as a guest into cavities formed between layers of
polymer helices, and the maximum guest molecular volume is close to 0.25 nm3. Infrared linear dichroism
measurements show that molecules included in s-PS molecular complexes are oriented nearly perpendicular
to the chain axes of the polymeric crystalline phase. These new materials present in their crystalline
phases an ordered three-dimensional arrangement of highly polar molecules with large first-order
hyperpolarizability.
The possible formation of molecular-complex phases of s-PS with styrene dimers has been investigated by their sorption in amorphous and nanoporous δ-form films. X-ray diffraction, 13 C solid state NMR, and FTIR analyses have shown that only 1,3-diphenylbutane (dpb), but not 1,4-diphenylbutane, forms a highly stable molecular-complex with s-PS. Preliminary structural considerations indicate that this s-PS/dpb molecularcomplex phase presents an intercalate structure, with host-monomer-unit/guest stoichiometric ratio of 4/1 and with a guest conformation with anti C2-C3 bond. Guest conformational behavior has allowed to discriminate, for the first time by a NMR technique, between guest molecules located in crystalline and amorphous s-PS phases. Presently dpb is the s-PS guest with maximum volume (≈0.36 nm 3 ) and maximum number of non-hydrogen atoms (n ) 16).
The effect of electron density at the incoming metal-carbon bond on the regiochemistry of styrene insertion into the zirconium-carbon bond is eVidenced through experimental results and computational studies.
The solution structure of AlMe F and its reactivity with a prototypical ansa-metallocene have been investigated by advanced NMR techniques, in an attempt to indirectly shed some light on the structure and working principles of methylalumoxane (MAO) mixtures in olefin polymerization. In solution, AlMe F gives rise to a complex equilibrium of oligomeric species, including a heterocubane [(Me Al) F ] tetramer, resembling the behavior of MAO. This complex mixture reacts with (ETH)ZrMe (ETH=rac-[ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]) to afford [(ETH)ZrMe (μ-F)(AlMe F) AlMe ] inner-sphere ion pairs through successive insertions/deinsertions of AlMe F units into the Zr⋅⋅⋅(μ-F) bond.
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