Morphology-conductivity relationship in crystalline and amorphous sequence-defined peptoid block copolymer...

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Polymers conducting lithium ions are crucial for rechargeable lithium batteries.
• Ion transport is typically attributed to segmental motion in amorphous, rubbery polymers.

Purpose of the Study:

• To investigate lithium ion conductivity in both amorphous and crystalline polymer domains.
• To compare ion transport in chemically similar polymer blocks with different states of matter.

Main Methods:

• Synthesis of sequence-defined diblock copolypeptoids using submonomer solid-phase synthesis.
• Preparation of two analogous copolypeptoids with identical conducting blocks but different amorphous (pNeh) and crystalline (pNdc) nonconducting blocks.
• Self-assembly into lamellar morphology to create distinct amorphous and crystalline conducting domains.

Main Results:

• Ethyleneoxy-containing domains exhibited comparable lithium ion conductivities regardless of being amorphous or crystalline.
• The conducting block (pNte) was amorphous in one copolypeptoid and crystalline in the other, enabling direct comparison.
• The study successfully created a platform to study ion transport in similar polymer domains with differing crystallinity.

Conclusions:

• The state of matter (amorphous vs. crystalline) of polymer domains does not significantly impact lithium ion conductivity.
• This finding challenges the conventional understanding of ion transport mechanisms in polymer electrolytes for lithium batteries.