Prediction of the Oligomer Distribution after Degradation of (Co)Polymers with Inserted Break Points

Abstract

Introduction of some weaker break points in otherwise all carbon backbone polymers produced via chain growth polymerizations can facilitate easy recycling and/or biodegradability. The break points are used to generate oligomers that then can be purified from additives and reconstituted into the circular polymers. In some cases, the oligomers can be biodegradable. For both purposes, predicting and controlling the oligomer length is of great importance. The authors look at chain growth polymerizations and compare the oligomer distributions obtained via Kinetic Monte Carlo (KMC) simulations by using the more easily accessible analytical solutions (AS). Before hydrolysis, the authors talk about the sequence length distribution; after hydrolysis, the resulting oligomer length distributions are dealt with. It turns out that for the targeted small oligomers, the AS approach is a fast alternative for the time‐consuming KMC simulations. To account for termination to occur during long sequences being formed, a correction factor is successfully introduced. The correction is based on the average degree of polymerization. With the AS method it is then shown that applying optimal monomer addition profiles narrows down the width of the oligomer distributions, optimizes the use of the weak‐bond‐inserting monomers, and brings the oligomer length in the right desired range.

Mechanism and Kinetics of Prothioconazole Photodegradation in Aqueous Solution

“…Simultaneously, chemical bonds with a greater length are generally more unstable, making them easier to break . Accordingly, the C–O, C–Cl, and C–S bonds of prothioconazole were determined to break more readily owing to their large bond lengths, as calculated at the DFT/B3LYP/6-311G (2d,2p) level of theory (Table S4), which verified the analysis results for the photoproducts of prothioconazole.…”

Kinetic Modeling of Ring Opening Polymerization of Lactones under Microwave Irradiation

“…This behavior is modeled by using conversion-dependent effective kinetic rate coefficients, k i . [37] Herein, a semi-empirical model based on Bueche's free volume theory of is used to modify all the intrinsic kinetic rate coefficients, k i,0 , according to Equations ( 13) and (14). V f0 in these equations is fractional free volume at initial conditions; V f is fractional free volume at time t; and 𝛽 i is a free volume parameter.…”

“…[11] Recent theoretical studies have highlighted the effect of reactivity ratios on cumulative copolymer composition, [11] appropriate re-estimation of reactivity ratios by using non-linear least squares methods, [12] and predictions of molar mass distributions (MMDs) before and after degradation by hydrolysis. [13,14] The mechanism of ROP of 𝜖-CL and LAs catalyzed by Sn(Oct) 2 has been investigated widely in the literature. [15][16][17] Although different mechanisms were proposed in the past in order to account for the role of Sn(Oct) 2 , it seems to be accepted that the active species are tin(II) alkoxides formed in situ by reaction of Sn(Oct) 2 with either adventitious water and hydroxy acids, or with an alcohol co-initiator.…”

“…[ 11 ] Recent theoretical studies have highlighted the effect of reactivity ratios on cumulative copolymer composition, [ 11 ] appropriate re‐estimation of reactivity ratios by using non‐linear least squares methods, [ 12 ] and predictions of molar mass distributions (MMDs) before and after degradation by hydrolysis. [ 13,14 ]…”

Kinetic Monte Carlo Tool for Kinetic Modeling of Linear Step‐Growth Polymerization: Insight into Recycling of Polyurethanes

“…[35] First developed by Gillespie in the context of well-mixed gas phase chemical reactions, kMC has since been applied to systems ranging from vacancy diffusion to thin film growth to free radical polymerization. [35][36][37][38][39][40][41][42][43][44] A fundamental assumption of kMC is that the system is well-mixed, which is most likely to be violated by polymer entanglement at high molecular weight. [36,41] That is, in the limit of very high conversion, the process may no longer be kinetically limited and therefore the predictions of the kinetic model may need to be coupled with a model of physical phenomena like diffusion to be accurate.…”