The present manuscript investigates the solution coordinative chain transfer polymerization (CCTP) of isoprene initiated by the ternary Ziegler‐Natta catalyst system composed by neodymium versatate (NdV3), diisobutylaluminum (DIBAH), and dimethyldichlorosilane. A kinetic mechanism is proposed and the kinetic parameters are estimated to allow the appropriate description of dynamic trajectories of average molecular weights and isoprene conversions obtained in solution CCTP polymerizations for the first time. A data reconciliation strategy is applied to evaluate the amount of DIBAH used as a chain transfer agent, as this very active compound can be consumed by undesired side reactions. Additionally, the impacts of key operation variables on the control of the average molecular weights and monomer conversion are evaluated to elucidate the living nature of the polymerization. As observed experimentally, the temperature effect on the course of the polymerization is not so pronounced as the effect of NdV3, isoprene, and DIBAH initial concentrations. The kinetic mechanism is described better and kinetic constants are estimated more precisely when the dynamic trajectories of average molecular weights are fitted during the whole batch. In this case, the proposed model is able to predict well the experimental trajectories of average molecular weights of the produced polymer and monomer conversion.
The monomer β‐myrcene, a renewable resource, was polymerized in cyclohexane using two different Ziegler‐Natta catalyst systems based on neodymium Nd(Oi‐Pr)3 and NdV3. The Nd(Oi‐Pr)3 was combined with [HNMe2Ph][B(C6F5)4] (or [CPh3][B(C6F5)4]) and Al(i‐Bu)3 (or Al(i‐Bu)2H). Next, the NdV3 was activated using Al(i‐Bu)3 and AlEt2Cl. Both catalyst systems exhibited high polymer yields near 100 % in the established reaction time, high polymer molecular masses, and broad molecular mass distributions. The catalyst systems gave an effective and stereospecific polymerization reaction of β‐myrcene providing high cis selectivity of 1,4‐polymyrcenes (> 92 %) with a glass transition temperature between −66 and −62 °C. The above‐mentioned features of resulting elastomers in conjunction with the polymer's molecular masses and molecular mass distributions proved to be sensitive to borane and alkylaluminum compounds molar ratios, [B]/[Nd] and [Al]/[Nd] using Nd(Oi‐Pr)3 and [Cl]/[Nd] and [Al]/[Nd] with NdV3.
Organoboron compounds of nonionic and ionic nature, tris(pentafluorophenyl)borane, and N,N-dimethylanilinium tetra(pentafluorophenyl)borate were evaluated to act in conjunction with MAO as activators on ethylene polymerization by using the catalyst Cp2ZrCl2. A decrease on the catalytic activity was observed in both cases in relation with a reference polyethylene which was synthesized in absence of any organoboron compound. An increase on the crystallinity degree and molecular weight, as well as an improvement in thermal and dynamic-mechanical properties, was observed in polyethylenes synthetized in presence of tris(pentafluorophenyl)borane. A low density polyethylene with improved thermal stability was obtained when N,N-dimethylanilinium tetra(pentafluorophenyl)borate was employed as activator.
Titanium dioxide doped silver (nTiO 2 /Ag) nanoparticles were surface-modified by microwave-assisted polymerization of 2-bis-(hydroxyethyl) terephthalate (BHET). The modified and unmodified nanoparticles were analyzed by FTIR, XRD, TGA, and TEM. A thin layer of grafted PET on the surface of the nanoparticles was observed and quantified by TGA giving a value of 40 wt-%. XRD and electron diffraction analyses showed traces of AgO 2 after the modification. The bactericide activity of modified and unmodified nanoparticles was evaluated; the presence of the thin layer of grafted-PET on the nTiO 2 /Ag did not change significantly the bactericide activity, showing an excellent performance similar to unmodified nanoparticles.
Composites based on low-density polyethylene (LDPE) were prepared withAgavefiber powder (AFP) that was coated by plasma polymerization process using ethylene gas. Treated and pristine AFP were analyzed by infrared spectroscopy, scanning electron microscopy, and contact water angle for the assessment of surface properties. The polymer composites were prepared by melt mixing using 0, 5, 10, and 20 wt% of AFP and their mechanical and thermal properties were measured. Dispersion evaluation in water confirmed that the AFP treated changed from hydrophilic to hydrophobic behavior and it was also corroborated with water contact angle tests. The addition of treated and untreated AFP (200 mesh) at 20 wt% promotes an increase of Young’s modulus of the composites of up to 60% and 32%, respectively, in relation to the neat matrix. Also, an increase of crystallinity of LDPE was observed by the addition of treated and untreated AFP; however no significant effect on the crystallization temperature was observed in LDPE containing AFP.
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