Polystyrene Chain Growth from Di-End-Functional Polyolefins for Polystyrene-Polyolefin-Polystyrene Block Copolymers.

Chung Kim,Bun Lee,Sung Kim,Jun Baek,Su Kwon,Seung Park

doi:10.3390/polym9100481

Abstract

Triblock copolymers of polystyrene (PS) and a polyolefin (PO), e.g., PS-block-poly(ethylene-co-1-butene)-block-PS (SEBS), are attractive materials for use as thermoplastic elastomers and are produced commercially by a two-step process that involves the costly hydrogenation of PS-block-polybutadiene-block-PS. We herein report a one-pot strategy for attaching PS chains to both ends of PO chains to construct PS-block-PO-block-PS directly from olefin and styrene monomers. Dialkylzinc compound containing styrene moieties ((CH2=CHC6H4CH2CH2)2Zn) was prepared, from which poly(ethylene-co-propylene) chains were grown via “coordinative chain transfer polymerization” using the pyridylaminohafnium catalyst to afford di-end functional PO chains functionalized with styrene and Zn moieties. Subsequently, PS chains were attached at both ends of the PO chains by introduction of styrene monomers in addition to the anionic initiator Me3SiCH2Li·(pmdeta) (pmdeta = pentamethyldiethylenetriamine). We found that the fraction of the extracted PS homopolymer was low (~20%) and that molecular weights were evidently increased after the styrene polymerization (ΔMn = 27–54 kDa). Transmission electron microscopy showed spherical and wormlike PS domains measuring several tens of nm segregated within the PO matrix. Optimal tensile properties were observed for the sample containing a propylene mole fraction of 0.25 and a styrene content of 33%. Finally, in the cyclic tensile test, the prepared copolymers exhibited thermoplastic elastomeric properties with no breakage up over 10 cycles, which is comparable to the behavior of commercial-grade SEBS.

Highlights

Polyolefins (POs), including polyethylene (PE) and polypropylene (PP), are the most abundantly produced polymers worldwide, with annual production of ~120 million metric tons.The subtle architecture of the PO chains is of particular interest in the bulk polyolefin industry.For example, sequence control to form olefin block copolymers (OBCs) is a formidable task in olefin polymerizations [1,2,3,4,5]
The strategy employed for preparation of the PS-block-PO-block-PS is similar to that attempted using the dialkylzinc species bearing the α-methylstyrene moiety (Scheme 1b versus Scheme 2)
The α-methylstyrene moiety remained intact during the CCTP performed using rac-[Me2 Si(2-methylindenyl)2 ]ZrCl2, it was sluggishly involved in the subsequent anionic styrene polymerization

Summary

Introduction

Polyolefins (POs), including polyethylene (PE) and polypropylene (PP), are the most abundantly produced polymers worldwide, with annual production of ~120 million metric tons.The subtle architecture of the PO chains is of particular interest in the bulk polyolefin industry.For example, sequence control to form olefin block copolymers (OBCs) is a formidable task in olefin polymerizations [1,2,3,4,5]. Due to its thermoplastic elastomer properties, SEBS is commonly employed in commodities such as rubbers and plastics [18,19,20,21,22], and its use in new specialized areas is receiving growing interest [23,24,25,26,27,28,29]. SEBS is not thermoplastic elastomer properties, SEBS is commonly employed in commodities such as rubbers produced directly from olefin and styrene monomers, but instead by a two-step process that involves and plastics [18,19,20,21,22], and its use in new specialized areas is receiving growing interest [23,24,25,26,27,28,29]

Methods

Results

Conclusion