Barrère Caroline, Rejaibi Majed, Curat Aurélien, Hubert-Roux Marie, Lavanant Hélène, Afonso Carlos, Kebir Nasreddine, Desilles Nicolas, Lecamp Laurence, Burel Fabrice, Loutelier-Bourhis Corinne
Normandie Université, COBRA, UMR 6014 and FR3038, Université de Rouen; INSA de Rouen; CNRS, IRCOF, 1 rue Tesnière, 76821, Mont-Saint-Aignan Cedex, France.
Rapid Commun Mass Spectrom. 2014 Aug 15;28(15):1697-704. doi: 10.1002/rcm.6939.
Polyamides (PA) are among the most used classes of polymers because of their attractive properties. Depending on the nature and proportion of the co-monomers used for their synthesis, they can exhibit a very large range of melting temperatures (Tm ). This study aims at the correlation of data from mass spectrometry (MS) with differential scanning calorimetry (DSC) and X-ray diffraction analyses to relate molecular structure to physical properties such as melting temperature, enthalpy change and crystallinity rate.
Six different PA copolymers with molecular weights around 3500 g mol(-1) were synthesized with varying proportions of different co-monomers (amino-acid AB/di-amine AA/di-acid BB). Their melting temperature, enthalpy change and crystallinity rate were measured by DSC and X-ray diffraction. Their structural characterization was carried out by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Because of the poor solubility of PA, a solvent-free sample preparation strategy was used with 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix and sodium iodide as the cationizing agent.
The different proportions of the repeating unit types led to the formation of PA with melting temperatures ranging from 115°C to 185°C. The structural characterization of these samples by MALDI-TOF-MS revealed a collection of different ion distributions with different sequences of repeating units (AA, BB; AB/AA, BB and AB) in different proportions according to the mixture of monomers used in the synthesis. The relative intensities of these ion distributions were related to sample complexity and structure. They were correlated to DSC and X-ray results, to explain the observed physical properties.
The structural information obtained by MALDI-TOF-MS provided a better understanding of the variation of the PA melting temperature and established a structure-properties relationship. This work will allow future PA designs to be monitored.
聚酰胺（PA）因其具有吸引人的特性而成为使用最为广泛的聚合物类别之一。根据用于合成的共聚单体的性质和比例，它们可以表现出非常大的熔点范围（Tm）。本研究旨在将质谱（MS）数据与差示扫描量热法（DSC）和X射线衍射分析的数据相关联，以将分子结构与诸如熔点、焓变和结晶速率等物理性质联系起来。
合成了六种分子量约为3500 g mol⁻¹的不同PA共聚物，其具有不同比例的不同共聚单体（氨基酸AB/二胺AA/二酸BB）。通过DSC和X射线衍射测量它们的熔点、焓变和结晶速率。通过基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF-MS）对其进行结构表征。由于PA的溶解性较差，采用了无溶剂样品制备策略，以2,5-二羟基苯甲酸（2,5-DHB）为基质，碘化钠为阳离子化剂。
重复单元类型的不同比例导致形成熔点范围为115°C至185°C的PA。通过MALDI-TOF-MS对这些样品进行结构表征，揭示了根据合成中使用的单体混合物，具有不同比例的不同重复单元序列（AA、BB；AB/AA、BB和AB）的不同离子分布集合。这些离子分布的相对强度与样品复杂性和结构相关。它们与DSC和X射线结果相关，以解释观察到 的物理性质。
通过MALDI-TOF-MS获得的结构信息更好地理解了PA熔点的变化，并建立了结构-性质关系。这项工作将有助于监测未来的PA设计。
