Polystyrene Chain Growth Initiated from Dialkylzinc for Synthesis of Polyolefin-Polystyrene BlockCopolymers.

Tae Jin Kim,Pyung Cheon Lee,Sung Moon Bae,Jun Won Baek,Kyung Lee Park,Jong Chul Lee,Bun Yeoul Lee,Hyun Ju Lee,Seung Hyun Moon

doi:10.3390/polym12030537

Abstract

Polyolefins (POs) are the most abundant polymers. However, synthesis of PO-based block copolymers has only rarely been achieved. We aimed to synthesize various PO-based block copolymers by coordinative chain transfer polymerization (CCTP) followed by anionic polymerization in one-pot via conversion of the CCTP product (polyolefinyl)2Zn to polyolefinyl-Li. The addition of 2 equiv t-BuLi to (1-octyl)2Zn (a model compound of (polyolefinyl)2Zn) and selective removal or decomposition of (tBu)2Zn by evacuation or heating at 130 °C afforded 1-octyl-Li. Attempts to convert (polyolefinyl)2Zn to polyolefinyl-Li were unsuccessful. However, polystyrene (PS) chains were efficiently grown from (polyolefinyl)2Zn; the addition of styrene monomers after treatment with t-BuLi and pentamethyldiethylenetriamine (PMDTA) in the presence of residual olefin monomers afforded PO-block-PSs. Organolithium species that might be generated in the pot of t-BuLi, PMDTA, and olefin monomers, i.e., [Me2NCH2CH2N(Me)CH2CH2N(Me)CH2Li, Me2NCH2CH2N(Me)Li·(PMDTA), pentylallyl-Li⋅(PMDTA)], as well as PhLi⋅(PMDTA), were screened as initiators to grow PS chains from (1-hexyl)2Zn, as well as from (polyolefinyl)2Zn. Pentylallyl-Li⋅(PMDTA) was the best initiator. The Mn values increased substantially after the styrene polymerization with some generation of homo-PSs (27–29%). The Mn values of the extracted homo-PS suggested that PS chains were grown mainly from polyolefinyl groups in [(polyolefinyl)2(pentylallyl)Zn]−[Li⋅(PMDTA)]+ formed by pentylallyl-Li⋅(PMDTA) acting onto (polyolefinyl)2Zn.

Highlights

The synthesis of block copolymers has been a topical issue in the field of polymer science and chemistry [1]
We discovered a method to grow polystyrene (PS) chains initiating from2 Zn were recorded on a JEOL ECZ600 instrument
We eventually found that t-BuLi reacted with olefin monomers; we attempted to convert the coordinative chain transfer polymerization (CCTP) product2 Zn to polyolefinyl-Li by thoroughly flushing ethylene/propylene residual gases before adding t-BuLi

Summary

Introduction

The synthesis of block copolymers has been a topical issue in the field of polymer science and chemistry [1]. Block copolymers are synthesized by controlled living anionic or radical polymerizations [2,3]. A typical example is polystyrene-block-polybutadiene-block-polystyrene (SBS), which is industrially produced by controlled living anionic polymerization at a large scale. Polyolefins (POs) are the most abundant polymers, produced with ethylene and α-olefins, at a scale of more than 120 million metric tons per year worldwide. PO-based block copolymers have rarely been synthesized because α-olefins cannot be polymerized by either anionic or radical initiators [4,5,6]. The lack of versatile synthetic tools has promoted the development of multistep routes for the syntheses of PO-based block copolymers [7,8,9,10,11,12,13,14,15]. Polystyrene-block-poly(ethylene-co-1-butene)-block-polystyrene is produced industrially via a two-step

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