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Glass transitions in peat: Their relevance and the impact of water

机译：泥炭中的玻璃化转变：其相关性和水的影响

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This contribution aims to expand the macromolecular view of fractionated natural organic matter(NOM)to organic matter in whole soils. It focuses on glass transition behavior of whole soil organic matter (SOM) and its interrelation with water through use of differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). Three processes of structural relaxation related to macromolecular mobility were distinguished. Process I occurs in thermally pretreated and very low water-content samples and corresponds to classic glass transition behavior. Process II occurs in water-containing samples, where water is believed to act as an antiplasticizing agent in the peat at water contents below 12%, causing decreased macromolecular mobility and increased glass transition temperature. We suggest the formation of hydrogen bond-based cross-links being responsible for this antiplasticizing effect. Process III represents a slow swelling process induced by water uptake with a time constant of swelling in the order of days, with water acting as a plasticizing agent. Results from this work are of particular importance for environmental systems as changes in environmental conditions (e.g., water content, temperature) may induce slow structural relaxation processes in NOM over periods of time ranging from days to weeks. These influences on NOM macromolecular mobility lead to continuous changes in physicochemical properties that may greatly influence sorbate-sorbent interactions in surface and subsurface environments.
机译：该贡献旨在将分馏的天然有机物（NOM）分解为整个土壤中有机物的大分子观点。它通过使用差示扫描量热法（DSC）和热力学分析（TMA）着眼于整个土壤有机质（SOM）的玻璃化转变行为及其与水的相互关系。区分了与大分子迁移率有关的结构弛豫的三个过程。方法I发生在经过热处理和含水量很低的样品中，并且与经典的玻璃化转变行为相对应。方法II发生在含水样品中，据信水在泥煤中的含水量低于12％时会充当抗增塑剂，从而导致大分子迁移率降低和玻璃化转变温度升高。我们建议基于氢键的交联的形成负责这种抗塑化作用。方法III代表由吸水引起的缓慢溶胀过程，溶胀的时间常数为数天左右，其中水起增塑剂的作用。这项工作的结果对环境系统尤为重要，因为环境条件（例如，水含量，温度）的变化可能会导致NOM在数天至数周的时间内缓慢出现结构松弛过程。这些对NOM大分子迁移率的影响导致物理化学性质的连续变化，这可能会极大地影响表面和地下环境中的吸附物-吸附剂相互作用。

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