NMR proton relaxation and porosity study of Baltic amber

Korneva I.P., Sinyavsky N.Ya., Kostrikova N.A. NMR proton relaxation and porosity study of Baltic amber. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2026, vol. 26, no. 4, pp. 717–723 (in Russian). doi: 10.17586/2226-1494-2026-26-4-717-723

Baltic amber possesses exceptional optical properties and transparency, making it considered one of the most valuable materials. Analysis of its structural features allows one to assess the purity and authenticity of amber. This study aims to understand the fundamental processes within the amber polymer matrix. The development of new, more reliable criteria for amber authentication and classification, as well as a fundamental understanding of the relationship between molecular dynamics and the macroscopic properties of natural polymers, is relevant. This paper presents the results of a study of molecular dynamics in amber and its interaction with water. Currently, there are no published values for the T₁ and T₂ nuclear magnetic resonance (NMR) relaxation times in amber which is a complex amorphous natural polymer with variable composition and structure. The aim of this study was to systematize existing scientific papers on the application of nuclear magnetic resonance to amber samples, identify gaps in current knowledge, and substantiate the relevance of new, more sophisticated techniques, such as 2D T₁-T₂ NMR relaxometry, for studying the complex structure of the polymer. An analysis of the relationships between relaxation characteristics, porosity, and water saturation of amber was conducted. The use of 2D T₁-T₂ relaxometry method enabled a transition from a phenomenological description to a mechanistic understanding of the structure and properties of amber at the molecular level. It has been established that there are two types of pores in amber, the sizes of which differ by two orders of magnitude. It is shown that water treatment leads to the appearance of new components with dynamics different from the original matrix, which is interpreted as the filling of micropores with water and a change in the flexibility of polymer chains. Information about the pores is of interest from the point of view of amber processing technology, since the size of the pores determines its fragility and cracking ability. The work established a correlation between relaxation times and the degree of saturation of Baltic amber with water. Fused amber has shorter T₂ times, which is probably due to a decrease in molecular mobility due to the formation of additional cross-links in the polymer matrix. Conversely, the T₁ time may exhibit more complex behavior related to the efficiency of cross-relaxation. The method enables selective identification of components: separating signals from a rigid polymer network (long T₁, short T₂ — high T₁/T₂ ratio), mobile molecular fragments (moderate T₁ and T₂), and possible liquid inclusions (short T₁, long T₂ — low T₁/T₂ ratio). The implementation of 2D T₁-T₂ relaxometry method is a relevant and promising direction in studying the structure and properties of complex polymers.

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