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

Area of Science:

• Polymer Chemistry
• Materials Science

Background:

• Triblock copolymers like polystyrene-polyolefin-polystyrene (PS-PO-PS) are valuable thermoplastic elastomers.
• Commercial production of SEBS involves a costly two-step hydrogenation process.

Purpose of the Study:

• To develop a one-pot synthesis for PS-PO-PS triblock copolymers directly from monomers.
• To create a cost-effective alternative to existing thermoplastic elastomers.

Main Methods:

• Synthesized a dialkylzinc compound with styrene moieties.
• Grew poly(ethylene-co-propylene) chains using coordinative chain transfer polymerization with a hafnium catalyst.
• Attached polystyrene chains via anionic polymerization initiated by Me₃SiCH₂Li·(pmdeta).

Main Results:

• Achieved a low PS homopolymer fraction (~20%) and increased molecular weights (27-54 kDa).
• Observed spherical and wormlike PS domains (tens of nm) within the PO matrix via TEM.
• Found optimal tensile properties at 0.25 propylene mole fraction and 33% styrene content.

Conclusions:

• The one-pot synthesis successfully produced PS-PO-PS triblock copolymers with desirable thermoplastic elastomeric properties.
• The synthesized copolymers demonstrated performance comparable to commercial SEBS, showing no breakage over 10 cycles.
• This method offers a more efficient and potentially less expensive route to thermoplastic elastomers.