Macromolecules· 2026Q1
Order–Disorder Tricriticality in Symmetric A n B n Star Polymer Melts
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- 2026year
Short summary
Symmetric AnBn star polymer melts exhibit tricriticality driven by the arm number 'n', which itself acts as a thermodynamic parameter to shift the order-disorder transition from second to first order at n_tc ≈ 5.4475.
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Key points
- Arm number 'n' in symmetric AnBn star polymers acts as a thermodynamic parameter to induce tricriticality.
- A tricritical arm number (n_tc ≈ 5.4475) was analytically identified, separating second-order (n < n_tc) from first-order (n > n_tc) order-disorder transitions.
- For n > n_tc, the order-disorder transition shifts below the spinodal point, confirmed by SCFT calculations.
- Inter-arm correlations at the common junction are the origin of this behavior.
AI-generated from the title and abstract; the full text is not read.
Abstract
Abstract Tricriticality usually requires tuning an additional thermodynamic parameter. Here, we show that, in symmetric AnBn star polymer melts, the arm number n itself plays this role and drives the order–disorder transition (ODT) from second order to first order. By developing a sixth-order free-energy expansion within the random phase approximation and comparing it with self-consistent field theory (SCFT) calculations, we analytically identify a tricritical arm number, ntc ≈ 5.4475. For n < ntc, the lamellar ordering transition remains continuous and occurs at the spinodal point, (χN)s ≈ 10.495. For n > ntc, the transition becomes first order, and (χN)ODT shifts below (χN)s with a quadratic dependence near the tricritical point. SCFT calculations confirm the predicted transition character and phase-boundary shift. The origin of this behavior is traced to inter-arm correlations generated by the common junction. We further show that the noninteger tricritical arm number can be effectively realized in binary mixtures of star polymers. This provides a rare analytically tractable example of architecture-induced tricriticality in a microphase-separating polymer system.
The authors' abstract, as published at the source. Macromolecules, 2026 · DOI ↗
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Field: Materials Chemistry
Materials ChemistryMaterials Science