Effect of Substituent on Titanocene/MMAO Catalyst for Ethylene/1-Hexene Copolymerization
Copolymerization of ethylene with 1-hexene was carried out using two ansa-fluorenyl titanium derivative complexes. The substituent effect on the catalytic activity, monomer reactivity ratio and polymer property was investigated. It was found that the presence of t-Bu groups on fluorenyl ring exhibited remarkable catalytic activity and produced polymer with high molecular weight. However, these catalysts produce polymer with narrow molecular weight distribution, indicating the characteristic of single-site metallocene catalyst. Based on C NMR, we can observe that monomer reactivity ratio was affected by catalyst structure. The rH values of complex 2 were lower than that of complex 1 which might be result from the higher steric hindrance leading to a reduction of 1hexene insertion step. Keywords—Constrained geometry catalyst, linear low density polyethylene, copolymerization, reactivity ratio
Copolymerization of olefins with Kaminsky‐Sinn‐type catalysts
Copolymerizations of ethylene with propene, ethylene with 1-hexene and propene with 1-hexene were performed at 40°C under atmospheric using three kinds of Kaminsky-Sinn-type catalysts which differ in stereospecificity: Cp2ZrCl2-methylaluminoxane (MAO) (aspecific); Et[IndH4]2 ZrCl2-MAO (isopecific); i-Pr(Cp)(Flu)ZrCl2-MAO (syndiospecific). 
 
The 13C NMR analysis of copolymers showed that the incorporation of higher olefins decreases in the following order: i -Pr(Cp)(Flu)ZrCl2-MAO > Et[IndH4]2ZrCl2-MAO > Cp2ZrCl2-MAO, and that stereospecificity is retained even in the copolymerization. 
 
The product of monomer reactivity ratios (r1 · r2) indicates that poly(propene-co-1-hexene) is a statistically random copolymer whereas both poly(ethylene-co-propene) and poly(ethylene-co-1-hexene) have somewhat alternating character regardless of catalyst stereospecificity.
Dating of Historical Manuscripts Using Spectrometric Methods: A Mini-Review
An overview is provided of spectrometric methods useful for age estimation of historical manuscripts (medieval ones in particular), in order to confirm their authenticity. Individual methods (infrared and Raman spectroscopy, mass spectrometry, atomic emission spectroscopy, X-ray spectroscopy, and electron scanning microscopy) are discussed and examples of their application described. The following general strategy can be recommended for dating and/or authenticating of historical manuscripts. First of all, the pigment analysis should be carried out using Raman spectroscopy (distinguishing the period and modern pigments), followed by PIXE ink analysis (solving the question of ink homogeneity). Finally, the radiocarbon dating of the writing support, potentially supplemented by the ink dating using scanning Auger microscopy should be performed.