Synthesis of ethylene/1‐octene copolymers with controlled block structures by semibatch living copolymerization

Abstract

A kinetic model was developed for the living copolymerization of ethylene/1-octene using the fluorinated FI-Ti catalyst system, bis[N-(3-methylsalicylidene)-2,3,4,5,6-pentafluoroanilinato] TiCl 2 /dried methylaluminoxane is presented. The model was first validated by batch polymerization experiments. Kinetic parameters were estimated from the model correlations with online ethylene consumption rates and end-of-batch copolymer molecular weight. The model was then used to calculate the microstructural properties of ethylene/1-octene copolymers with controlled composition profiles (uniform, diblock, and step triblock), which were synthesized using sequential comonomer feeding policies in semibatch copolymerization. The synthesized block copolymers had the exact composition distributions and molecular weights as the model simulated. It was demonstrated that the polymer chain microstructure in the living copolymerization of olefins could be precisely regulated by using semibatch comonomer feeding policies.Scheme 2. Schematic illustration of chain structure of diblock (a) and (b) step triblock copolymers.

Understanding the Microstructure of Living Ethylene/1‐Octene Block Copolymers with Dynamic Monte Carlo Simulation

“…The reaction mechanism for living ethylene/α‐olefin copolymerization consists of four elementary reactions: initiation, propagation, chain transfer to cocatalyst, and deactivation (Table ) . We adopted the following modeling assumptions: (1) polymerization takes place in a semibatch well‐mixed reactor, where solvent, catalysts, and cocatalysts are fed into the reactor at the beginning of the polymerization, while ethylene is fed continuously to keep the pressure constant throughout the polymerization, and (2) all reaction rate constants are independent of chain length.…”

“…During 0– t 1 min, f 2 = f 2,stage 1 to start making living random copolymer chains; the comonomer fraction in the reactor is increased to f 2,stage 2 from t 1 to t 2 min to produce diblock chains, and to f 2,stage 3 from t 2 to t 3 min to make triblock chains. Comonomer fractions in each stage were considered to be approximately constant as reported by the experiment performed with three injection steps and later verified by the method of moment . The chain segments produced during the first, second, and third stages will be referred to as B 1 (thick solid line), B 2 (dotted thin line), and B 3 (thin solid line), respectively.…”

“…Table summarizes the kinetic parameters and operation conditions for simulating the LBCs investigated in this work . The initial number of ethylene molecules in the control volume was 1 × 10 9 ; the number of molecules of the other reactants were calculated based on this information.…”

“…Polymerization models for living ethylene/1‐octene copolymerization were recently developed using the method of moments to predict the microstructure of LBCs, including number average molecular weight (), polydispersity index (PDI), and comonomer fraction ( F 2 ) . These models generate useful guidelines for tailor‐making the overall chain microstructural characteristics of LBCs, but they do not provide any detailed information on the microstructure of LBC blocks, including their distributions, as a function of polymerization time.…”

The molecular structure control of butyl methacrylate/acrylamide (co)polymers

“…The prepolymerization temperature greatly influenced the polymerization reaction rate constant and half-life of the initiator [20][21], which would greatly influence the distribution of the chain segment of the copolymer and the resulting properties of the copolymer foam [22]. The distribution of the chain segment and the conversion ratio of the monomer were also greatly influenced by feeding method of the monomer, which would reduce the implosion possibility of bulk polymerization [23][24][25][26]. Different feeding methods were employed to adjust the conversion ratio of the monomer and further adjust the composition of the copolymer in this study.…”