Determining kinetic parameters for copolymerizations including depropagation and transesterification reactions is complicated by the impracticality of a complete deterministic model. Stochastic simulations are uniquely appropriate for reversible copolymerization with simultaneous transesterification and have been used to describe theoretical reversible copolymerizations, but parameter estimation on experimental data using stochastic models has not been attempted in a copolymerization context. Here, we advance the method of stochastic model regression (SMR) for fitting a stochastic simulation algorithm to experimental data. Conversion versus time data were fit to a stochastic model for five initial compositions of glycolide (f_G) in rac-lactide/glycolide copolymerization resulting in poly(lactide-co-glycolide) (PLGA) and five initial compositions of rac-lactide (f_L) in rac-lactide/ε-caprolactone copolymerization resulting in poly(lactide-co-ε-caprolactone) (PLCL). We determined reactivity ratios of r_G = 4.4, r_L = 0.34 for PLGA and r_L = 12.3 and r_C = 0.07 for PLCL, which establish an initial compositional gradient that is counteracted by random transesterification. Complete kinetic parameters including depropagation and transesterification rate constants resulted from our analysis by SMR and are needed for a complete description of repeat unit sequencing and the time evolution of composition (f_G or f_L).

中文翻译：

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随机模型回归分析同时可逆性共聚和酯交换反应

由于完整的确定性模型不切实际，确定共聚反应（包括去传播和酯交换反应）的动力学参数变得复杂。随机模拟特别适合同时酯交换的可逆共聚，并已用于描述理论上的可逆共聚，但尚未在共聚环境中尝试使用随机模型对实验数据进行参数估计。在这里，我们提出了随机模型回归（SMR）方法，用于将随机模拟算法拟合到实验数据。将转化率与时间数据拟合为外消旋丙交酯/乙交酯共聚中乙交酯（ f _G ）的五种初始组合物的随机模型，产生聚（丙交酯-共-乙交酯）（PLGA）和外消旋丙交酯（f G ）的五种初始组合物_L )在外消旋-丙交酯/ε-己内酯共聚中产生聚(丙交酯-共-ε-己内酯)(PLCL)。我们确定了PLGA的反应性比为r _G = 4.4、r _{L = 0.34，PLCL 的反应性比为}r _L = 12.3 和r _C = 0.07，这建立了由随机酯交换反应抵消的初始组成梯度。完整的动力学参数（包括去传播和酯交换速率常数）是我们通过 SMR 分析得出的，是重复单元测序和组成（ f _G或f _L）的时间演化的完整描述所需要的。