Order-Disorder Tricriticality in $\mathrm{A}_n \mathrm{B}_n$ Star Polymer Melts
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866914592599310336 |
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| author | Kim, Minhoon Kang, Wonjun Yong, Daeseong Cho, Junhan Kim, Jaeup U. |
| author_facet | Kim, Minhoon Kang, Wonjun Yong, Daeseong Cho, Junhan Kim, Jaeup U. |
| contents | Tricriticality usually requires tuning an additional thermodynamic parameter. Here we show that, in symmetric $\mathrm{A}_n\mathrm{B}_n$ 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, $n_{\mathrm{tc}}\approx 5.4475$. For $n<n_{\mathrm{tc}}$, the lamellar ordering transition remains continuous and occurs at the spinodal point, $(χN)_{\mathrm{s}}\approx 10.495$. For $n>n_{\mathrm{tc}}$, the transition becomes first order, and $(χN)_{\mathrm{ODT}}$ shifts below $(χN)_{\mathrm{s}}$ 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_23758 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Order-Disorder Tricriticality in $\mathrm{A}_n \mathrm{B}_n$ Star Polymer Melts Kim, Minhoon Kang, Wonjun Yong, Daeseong Cho, Junhan Kim, Jaeup U. Statistical Mechanics Soft Condensed Matter Tricriticality usually requires tuning an additional thermodynamic parameter. Here we show that, in symmetric $\mathrm{A}_n\mathrm{B}_n$ 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, $n_{\mathrm{tc}}\approx 5.4475$. For $n<n_{\mathrm{tc}}$, the lamellar ordering transition remains continuous and occurs at the spinodal point, $(χN)_{\mathrm{s}}\approx 10.495$. For $n>n_{\mathrm{tc}}$, the transition becomes first order, and $(χN)_{\mathrm{ODT}}$ shifts below $(χN)_{\mathrm{s}}$ 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. |
| title | Order-Disorder Tricriticality in $\mathrm{A}_n \mathrm{B}_n$ Star Polymer Melts |
| topic | Statistical Mechanics Soft Condensed Matter |
| url | https://arxiv.org/abs/2605.23758 |