We introduce a theoretical model based upon the kinetic Monte Carlo (KMC) simulation approach capable of quantifying chain shuttling copolymerization (CSP) of ethylene and 1-octene in a semibatch operation. To make a deeper understanding of kinetics and evolution of microstructure, the reversible transfer reaction is first investigated by applying each of the individual catalysts to the reaction media, and the competences and shortcomings of a qualified set of CSP catalysts are discussed based on coordinative chain transfer copolymerization (CCTP) requirements. A detailed simulation study is also provided, which reflects and compares the contributions of chain transfer reversibility and other chain breaking reactions in controlling distribution fashion of molecular weight and chemical composition. The developed computer code is executed to capture developments in dead chain concentration and time-driven composition drift during CCTP. Also, the effect of chain shuttling agent (CSA) on the copolymerization kinetics is theoretically studied by simultaneous activation of both catalysts. In this way, it is attempted to make control over comonomer incorporation in the course of copolymerization. The molecular-level criteria reflecting copolymer properties, i.e., ethylene sequence length distribution and longest ethylene sequence length, as the signature of CSA performance, are virtually simulated in the presence and absence of hydrogen to capture an image on gradient copolymers in CCTP and blocks with gradually changing composition in CSP.

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Traditional characterization methods are still unable to reveal the block structure of olefin block copolymers (OBCs). Therefore, extending the predictability of our well-developed computer code (Mohammadi et al., Macromolecules, 2014, 47, 4778-4789); the blocky nature of OBCs is modeled and characterized. The expanded model could produce diversity of macromolecules varying the concentration of chain-shuttling agent, catalyst ratio, and monomer composition, as key processing variables. The OBCs were screened and distinguished in view of chain related specifics i.e., chain length and chemical composition distribution as well as block related characteristics i.e., number, length and chemical composition of hard and soft blocks. A detailed picture of blockiness was captured and visualized tracing transitions in the microstructure of copolymers, from the case corresponding to blend copolymer (without any shuttling) to OBC (with considerable shuttling) and then to random copolymers, reflecting the significance of the chosen parameters in determining the blockiness of OBCs.

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Herein, a multifunctional filler, a dye (organic)–clay (inorganic) hybrid nanopigment (DCNP), was embedded into polylactic acid (PLA) to fabricate a colored biodegradable/biocompatible film, which is explored as a high thermomechanical resistant as well as a superior light and mass transport barrier for food packaging applications. In this respect, the DCNP was synthesized through a wet chemical process with a reaction yield of 76% and incorporated into a PLA matrix at various concentrations using a solution casting method. The morphological characterizations revealed partially intercalated/exfoliated structure for PLA–DCNP films. The samples filled with DCNP showed up to 20% and 12 °C improvements in storage modulus (E′) and glass transition temperature (Tg), respectively, compared to those with neat PLA. Incorporation of a small amount of DCNP into the PLA matrix significantly declined the water vapor and gas permeability of PLA by 36 and 54%, respectively. The optical property investigations indicated remarkable color characteristics and light protection performance of the samples containing DCNP. The results also showed better performance of the PLA–DCNP film compared to that of the PLA–Cloisite 20A sample at an identical filler loading. In conclusion, the desirable properties of the resulting films highlighted the potential application of such nanocomposite films as a promising option for food packaging materials.