Generation Of Polymer Networks Research Articles

Probing Rubber Cross-Linking Generation of Industrial Polymer Networks at Nanometer Scale.

We present improved analyses of rheometric torque measurements as well as (1)H double-quantum (DQ) nuclear magnetic resonance (NMR) buildup data on polymer networks of industrial compounds. This latter DQ NMR analysis allows finding the distribution of an orientation order parameter (Dres) resulting from the noncomplete averaging of proton dipole-dipole couplings within the cross-linked polymer chains. We investigate the influence of the formulation (filler and vulcanization systems) as well as the process (curing temperature) ending to the final polymer network. We show that DQ NMR follows the generation of the polymer network during the vulcanization process from a heterogeneous network to a very homogeneous one. The time variations of microscopic Dres and macroscopic rheometric torques present power-law behaviors above a threshold time scale with characteristic exponents of the percolation theory. We observe also a very good linear correlation between the kinetics of Dres and rheometric data routinely performed in industry. All these observations confirm the description of the polymer network generation as a critical phenomenon. On the basis of all these results, we believe that DQ NMR could become a valuable tool for investigating in situ the cross-linking of industrial polymer networks at the nanometer scale.

Poly‐α,β‐unsaturated aldehydes derived from castor oil via ADMET polymerization

Abstract10‐Undecenal, derived by pyrolysis and reduction from castor oil, was almost quantitatively transformed into the corresponding aldol condensation product under basic conditions. This α,ω‐diene monomer was polymerized using acyclic diene metathesis (ADMET) polymerization. In a catalyst screening, four of nine different ruthenium‐based metathesis catalysts showed good reactivity under neat conditions at 80°C in the presence of 1,4‐benzoquinone and polymers with molecular weights up to 11 kDa were formed. Furthermore, the 1H NMR spectra showed that the metathesis catalysts tolerate the α,β‐unsaturated aldehyde function and due to the addition of benzoquinone, the degree of double bond isomerization was low. Further experiments investigating reduced catalyst amounts (down to 0.2 mol%) and the temperature dependence of these ADMET polymerizations gave also satisfying results for the formation of poly‐α,β‐unsaturated aldehydes. Moreover, ADMET polymerizations with different amounts of methyl 10‐undecenoate as chain‐stopper were performed and the integrals of the corresponding 1H NMR spectra allowed the determination of an absolute degree of polymerization. Finally, a reduction of a poly‐α,β‐unsaturated aldehyde with sodium borohydride was accomplished. The resulting poly‐(allyl alcohol) could be a useful compound in the generation of polymer networks like polyesters, polyurethanes, and polycarbonates and thus be of high interest in materials research.