Universal Relationships in Hyperbranched Polymer Architecture for Batch and Continuous Step Growth Polymerization of AB2-Type Monomers

Tobita Tobita

doi:10.3390/pr7040220

Abstract

Design and control of hyperbranched (HB) polymer architecture by way of reactor operation is key to a successful production of higher-valued HB polymers, and it is essential in order to clarify the fundamental structural characteristics formed in representative types of reactors. In this article, the irreversible step growth polymerization of AB2 type monomer is investigated by a Monte Carlo simulation method, and the calculation was conducted for a batch and a continuous stirred-tank reactor (CSTR). In a CSTR, a highly branched core region consisting of units with large residence times is formed to give much more compact architecture, compared to batch polymerization. The universal relationships, unchanged by the conversion levels and/or the reactivity ratio, are found for the mean-square radius of gyration Rg2, and the maximum span length LMS. For batch polymerization, the g-ratio of Rg2 of the HB molecule to that for a linear molecule conforms to that for the random branched polymers represented by the Zimm-Stockmayer equation. A single linear equation represents the relationship between Rg2 and LMS, both for batch and CSTR. Appropriate process control in combination with the chemical control of the reactivity of the second B-group promises to produce tailor-made HB polymer architecture.

Highlights

Hyperbranched (HB) polymers are specialty polymeric materials, possessing compact architecture, a vast number of end groups that can be functionalized, and specific space inside the molecule.A wide variety of potential applications have been and are being developed [1]
For a continuous stirred-tank reactor (CSTR), the cases with ξ = ξUL are shown in the figure, while xA = 0.95 for batch polymerization
For a CSTR, the largest cluster size PLC increases with P, and a very large tri-branched cluster exists in a large polymer molecule

Summary

Introduction

Hyperbranched (HB) polymers are specialty polymeric materials, possessing compact architecture, a vast number of end groups that can be functionalized, and specific space inside the molecule.A wide variety of potential applications have been and are being developed [1]. The HB polymers are macromolecules in between deterministic linear chains and dendrimer structures [2], and their properties are influenced significantly by their detailed branched architecture. The prediction and control of HB architecture is essential to produce higher quality polymers, which opens up a challenging field for the chemical engineers to develop novel production processes. Basic chemical reaction engineering textbooks emphasize the importance in clarifying the fundamental chemical behavior in three representative reactor types; batch reactor, plug flow reactor (PFR), and continuous stirred-tank reactor (CSTR) [3]. A PFR is equivalent to a batch reactor by changing the reaction time to the residence time. The differences in branched architecture formed in a batch reactor and a CSTR are considered

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