【作者】 王猛；

【导师】 王静康； 郝红勋； 刘松强；

【作者基本信息】 天津大学 ， 工程硕士（专业学位）， 2023， 硕士

【摘要】 晶体成核过程作为液固相转化的开始,直接决定了最终晶体的结构、形貌以及粒度分布等理化性质。然而,目前成核动力学及成核机理相关研究仍不完善,从分子聚集体角度探究晶体成核机理的研究有待补充。基于此,为避免复杂的构象变换,更加专注地研究分子聚集体形式,本文以刚性有机分子3,5-二硝基苯甲酸为模型化合物,系统研究了其在不同溶剂中的溶液热力学、晶体成核动力学以及分子聚集形式,并探究了成核动力学与分子聚集形式的关系以及相应的成核机理,具体内容如下:首先,使用静态法测定了3,5-二硝基苯甲酸在13种不同溶剂中的溶解度,并采用修正的Apelblat方程、λh方程、vant’Hoff方程和NRTL方程对溶解度数据进行拟合;在此基础上,根据NRTL方程进一步计算了3,5-二硝基苯甲酸在不同溶剂中的混合热力学性质,为后续研究奠定热力学基础。其次,使用非随机性方法测定了3,5-二硝基苯甲酸在9种不同溶剂中的成核诱导期,并基于经典成核理论计算得到了包括γ和f₀C₀在内的成核动力学参数。研究发现,界面能γ越大,成核速率越慢,而成核速率与成核动力学参数附着频率f₀C₀没有明显的对应关系,说明成核过程主要受热力学控制。再次,对成核过程聚集体存在形式及其结构演变机制进行研究。通过粉末X射线衍射（PXRD）研究了3,5-二硝基苯甲酸在不同溶剂中的结晶形式,并结合红外反射光谱（FTIR）、液体核磁（NMR）、高分辨质谱（MS）探究溶质在不同溶剂中的聚集形式,结果表明,3,5-二硝基苯甲酸在不同溶液中不同的分子聚集形式对成核动力学有决定性影响。最后,采用分子模拟技术对成核过程机理进行分析。基于3,5-二硝基苯甲酸晶体结构计算了分子表面静电势分布特征,并选取3个位点进行1:1溶质-溶剂结合能计算;对不同溶液中成核过程进行了分子动力学模拟,得到了体现溶质-溶剂相互作用的溶剂化自由能和径向分布函数（RDF）;比较了1:1溶质-溶剂结合能、溶剂化自由能等影响成核速率的因素,并最终提出了3,5-二硝基苯甲酸在不同溶液中的成核机理。更多还原

【Abstract】 The nucleation process,as the beginning of the liquid-solid phase transformation,directly determines the structure,morphology and particle size distribution of the final crystal.However,the research on nucleation kinetics and nucleation mechanism is still incomplete,and the research on the nucleation mechanism of crystals from the perspective of molecular aggregates needs to be supplemented.Based on this,in order to avoid complex conformational transformations and to focus more on the molecular aggregation forms,this dissertation systematically investigated the solution thermodynamics,crystal nucleation kinetics and molecular aggregation forms of 3,5-dinitrobenzoic acid in different solvents,and investigated the relationship between nucleation kinetics and molecular aggregation forms as well as the corresponding nucleation mechanism,as follows:Firstly,the solubility of 3,5-dinitrobenzoic acid in 13 different solvents was determined using the static method,and the solubility data were fitted with the modified Apelblat equation,λh equation,vant’Hoff equation and NRTL equation;based on this,the thermodynamic properties of 3,5-dinitrobenzoic acid in different solvents were further calculated based on the NRTL equation,which laid the thermodynamic foundation for the subsequent study.Secondly,the nucleation induction periods of 3,5-dinitrobenzoic acid in nine different solvents were determined using a non-random method,and the nucleation kinetic parameters includingγand f₀C₀ were calculated based on the classical nucleation theory.It was found that the larger the interfacial energyγ,the slower the nucleation rate,while there was no obvious correspondence between the nucleation rate and the attachment frequency f₀C₀of the nucleation kinetic parameters,indicating that the nucleation process was mainly controlled by thermodynamics.Again,the nucleation process was investigated in terms of the existence of aggregates and their structural evolution mechanisms.The crystalline forms of 3,5-dinitrobenzoic acid in different solvents were investigated by powder X-ray diffraction（PXRD）,and the aggregation forms of solutes in different solvents were explored by combining Fourier transform infrared（FTIR）,nuclear magnetic resonance（NMR）,and high-resolution mass spectrometry（HRMS）,and the results showed that the different molecular aggregation forms of 3,5-dinitrobenzoic acid in different solutions have a decisive influence on the nucleation kinetics.Finally,molecular simulation was used to analyze the mechanism of nucleation process.Based on the crystal structure of 3,5-dinitrobenzoic acid,the distribution characteristics of the electrostatic potential on the molecular surface were calculated,and three sites were selected for 1:1 solute-solvent binding energy calculation;molecular dynamics simulations were performed in different solutions to obtain the solvation free energy and radial distribution function（RDF）reflecting the solute-solvent interaction.The factors affecting the nucleation rate such as 1:1 solute-solvent binding energy and solvation free energy were compared,and finally the nucleation mechanism of 3,5-dinitrobenzoic acid in different solutions was proposed.更多还原