This work proposes a new model for particle nucleation, in addition to particle growth, in the process of stabilizer-free dispersion copolymerization of styrene and maleic anhydride in organic solvents. This paper provides the first contribution to the modeling and simulation of the nucleation step in this process. The model considers that (1) polymerization takes place in both the continuous phase and the polymer particles; (2) radicals in the continuous phase that exceed the size J_crit precipitate and form aggregates; (3) the coagulation between aggregates forms new particles; (4) the radicals in the continuous phase can also enter into the polymer particles, reducing the nucleation rate; and (5) the termination step inside the particles is diffusion-controlled. The model is able to correctly predict the time evolution of the monomer conversion, particle number, and particle size and was successfully validated against data obtained experimentally and from the literature. Different from the existing models, the proposed model does not require previous information regarding the particle size or number to initialize the model. The radical entry parameter and the radical solubility are important parameters that affect the nucleation step.

中文翻译：

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苯乙烯和马来酸酐的无稳定剂分散共聚：成核的数学模型

这项工作提出了一种新的粒子成核模型，除了粒子生长之外，在苯乙烯和马来酸酐在有机溶剂中的无稳定剂分散共聚过程中。本文为该过程中成核步骤的建模和模拟提供了第一个贡献。该模型认为（1）聚合发生在连续相和聚合物颗粒中；(2) 连续相中超过尺寸J _{crit 的}自由基沉淀并形成聚集体；(3)聚集体之间的凝聚形成新的颗粒；(4)连续相中的自由基也可以进入聚合物颗粒中，降低成核率；(5)粒子内部的终止步骤是扩散控制的。该模型能够正确预测单体转化率、颗粒数和颗粒尺寸的时间演变，并成功地根据实验和文献中获得的数据进行了验证。与现有模型不同，所提出的模型不需要有关粒子大小或数量的先前信息来初始化模型。自由基进入参数和自由基溶解度是影响成核步骤的重要参数。