Advances in single-sided NMR of polymer and cultural heritage science

• Fortschritte mit unilateraler NMR von Polymeren und Kulturgütern

Marchi Netto, Antonio; Blümich, Bernhard (Thesis advisor); Liauw, Marcel (Thesis advisor)

Aachen : Shaker (2015, 2015)
Book, Dissertation / PhD Thesis

In: Berichte aus der Chemie
Page(s)/Article-Nr.: XI, 125 S. : Ill., graph. Darst.

Zugl.: Aachen, Techn. Hochsch., Diss., 2015

Abstract

The advent of mobile and single-sided NMR enabled performance of non-destructive and non-invasive analysis, boosting NMR experiments in polymer and cultural heritage sciences. Relying on arrangements of permanent magnets, this technology is not as expensive as conventional NMR and supports possibilities of measuring different parts of a heterogeneous sample. The available techniques for assessment of recrystallization as evidence of thermal fusion in joints of PE pipes or the evaluation of polymer cross-link density heretofore required sample destruction or expensive methodology in order to generate accurate conclusions; unilateral NMR can easily provide good results. The depth-dependent monomer mobility in a photo-curing reaction could also be explored with single-sided sensors to probe the reaction kinetics with spatial resolution. Many studies in the field of cultural heritage, such as the evaluation of damaged stone arti- facts, must be carried out in situ, which is possible using single-sided NMR devices. Analysis of the degradation state of ancient paper and parchment, as well evaluations of canvas conditions from easel paintings and studies of ancient pottery, require fully non-invasive methodology. This work proposes innovative utilization of a single-sided sensor, the NMR-MOUSE, to ascertain crystallization, cross-linking and real-time curing observations of polymers and to evaluate a new self-developed inorganic dispersion solution for restoring degraded stones, to detect elementary composition in old pottery, to characterize the damage level of parchments and handmade Chinese paper and, finally, to characterize techniques for canvas reinforcement. It was possible to detect the increase of crystallization generated by a cold-fusion process and the increase in cross-link density of polyethylene created by absorption of β radiation, and also understanding spatiotemporally the photo-curing process of dental resins. Another result indicates changes in porosity of stones due to consolidation and helps to identify the optimum treatment. Furthermore, the transverse magnetization decay in ancient pot- tery showed excellent correlation with the iron quantity and good correlation with the carbon content. Experiments with damaged parchment revealed details of aging, partic- ularly through the use of an innovative two-dimensional NMR experiment. Through a relaxation experiment, it was noted that ancient hemp paper is the kind of paper least sensitive to aging, followed by rice paper and bamboo paper, the most aging-sensitive. Several analyses were made with the help of multivariate data analysis, mainly partial least square (PLS), a robust method that reduces the number of variables. In sum, this thesis explores the NMR-MOUSE sensor as a tool for studying spin relaxation of polymer and cultural heritage samples and supports the feasibility of data processing by exponential curve-fitting, inverse Laplace transformation and multivariate data analysis.