Stereocomplexed and Homochiral Polyurethane Elastomers with Tunable Crystallizability and Multishape Memory Effects

Area of Science:

• Polymer Chemistry
• Materials Science
• Materials Engineering

Background:

• Developing polymer networks with tunable mechanical properties and multi-shape memory effects (multi-SMEs) is crucial for engineering applications.
• Polyurethane (PU) elastomers are versatile materials, but achieving controlled multi-SME behavior requires advanced network design.

Purpose of the Study:

• To synthesize stereocomplexed and homochiral polyurethane elastomers with tunable multi-SMEs.
• To investigate the relationship between polymer structure, stereocomplexation, and multi-SME performance.
• To explore the potential for manipulating crystallizability and mechanical properties through enantiomeric segment control.

Main Methods:

• Cross-linking triblock prepolymers containing poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) enantiomeric segments.
• Synthesizing homochiral and stereocomplexed polyurethane elastomers.
• Characterizing the crystalline structure, thermal transitions (glass and melting), and mechanical properties of the synthesized PUs.
• Evaluating the thermally induced triple- and quadruple-SMEs.

Main Results:

• Homochiral PU elastomers were found to be nearly amorphous.
• Stereocomplexed PU elastomers exhibited high crystallinity due to the stereocomplexation of PLLA and PDLA segments.
• Integration of distinct thermal transitions of PLLA/PDLA segments enabled triple- and quadruple-SMEs.
• Enantiomeric segmental ratios effectively controlled crystallizability, mechanical properties, and multi-SME behavior.

Conclusions:

• Stereocomplexation of enantiomeric poly(lactic acid) segments in polyurethanes is an effective strategy for creating crystalline networks with tunable multi-shape memory effects.
• The developed polyurethane elastomers offer a promising platform for advanced engineering applications requiring sophisticated shape memory functionalities.
• Precise control over enantiomeric ratios provides a pathway for tailoring material properties and multi-SME performance.