Observing Nucleation Transition in Stretched Natural Rubber through Self-Seeding.

Area of Science:

• Polymer Science
• Materials Science
• Crystallization Phenomena

Background:

• Strain-induced crystallization (SIC) in polymers involves competition between fringed-micelle (N1) and folded-chain (N2) nucleation.
• Observing a transition from N2 to N1 nucleation during uniaxial deformation in natural rubber (NR) via in situ methods has been challenging.

Purpose of the Study:

• To provide the first in situ observational evidence of a nucleation transition from N2 to N1 in natural rubber during strain-induced crystallization.
• To investigate the effect of self-seeding on the nucleation mechanisms in natural rubber under deformation.

Main Methods:

• Utilized self-seeding by introducing residual temperature-induced crystallization (TIC)-melting crystallites into pure NR.
• Employed in situ synchronic Wide-Angle X-ray Diffraction (WAXD) to monitor crystal evolution during uniaxial deformation.
• Performed theoretical computations of nucleation barriers.

Main Results:

• Observed the formation of low-oriented crystals (N2 nucleation on self-seeds) evolving into highly oriented crystals (N1 nucleation).
• Demonstrated that self-seeding enables the observation of a clear nucleation transition phenomenon in NR's SIC.
• Theoretical calculations confirmed self-seeding increases critical strain for transition and decreases onset strain for SIC.

Conclusions:

• Self-seeding is an effective strategy to observe nucleation transition from N2 to N1 in natural rubber SIC.
• The study provides the first in situ evidence of this nucleation transition under uniaxial deformation.
• Self-seeding plays a crucial role in modulating the nucleation pathway and onset of crystallization in NR.