Click construction of spiro- and bridged-quatrefoil polymer topologies with kyklo-telechelics having an azide group.
Unprecedented tetracyclic polymer topologies with spiro- and a bridged-type quatrefoil forms are effectively constructed through an alkyne-azide, click-linking reaction by employing a kyklo-telechelic poly(tetrahydrofuran), poly(THF), precursor having an azide group, obtained through an electrostatic self-assembly and covalent fixation (ESA-CF) process, and complementary tetrafunctional alkyne reagents of either a pentaerythritol derivative or a four-armed star telechelic polymer precursor.
Designing 8-Shaped Polymer Topology by Metathesis Condensation with Cyclic Poly(THF) Precursors Having Allyl Groups
A metathesis condensation process was applied for the synthesis of double cyclic, 8-shaped poly(THF)s. Thus, first, a cyclic poly(THF) having an allyl group, 1, was subjected to the intermolecular metathesis condensation. The bimolecular condensation reaction was found to proceed in the presence of a Grubbs catalyst, while with noticeable concurrent reactions. Alternatively, a twin-tailed tadpole, i.e., “a ring with two branches” structure, poly(THF) having tail-end allyl groups, 2, and a kyklo-telechelic poly(THF) having two allyl groups at opposite positions, 3, were prepared for the intramolecular metathesis condensation. The unimolecular reactions proceeded effectively even under dilution of the polymer concentration at 0.2 g/L to produce the corresponding 8-shaped poly(THF)s. These products were unequivocally characterized by means of 1H NMR, SEC, and MALDI−TOF MASS techniques.
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.