Authors: S. N. PRAJAPATI | Prasanta Kumar Sinha
Source: ChemRxiv (article, 2026-03-31)
Field: Chemistry — Physical and Theoretical Chemistry

Fractal-Memory Polymers: A New Universality Class with 𝝂 =𝟏/𝟏. 𝟕𝟓 For fifty years, the Flory scaling exponent 𝜈 = 3/5 ≈ 0.588 for polymers in good solvents has stood as a cornerstone of polymer physics. This prediction, refined by renormalization group calculations to 𝜈 = 0.588 ± 0.001 (Le Guillou & Zinn-Justin, 1977), appears in every textbook and is taught to every student. Yet a systematic examination of experimental measurements from multiple independent laboratories reveals a persistent and statistically significant discrepancy: the weighted mean exponent across ten polymer-solvent systems is 𝜈exp = 0.5708 ± 0.0023( 𝑁 = 10independent measurements, 𝑝 < 10−12 ). This paradox has remained unresolved since the first accurate measurements by Daoud et al. (1975). Here we demonstrate that the discrepancy originates from a hidden assumption in classical theory: the Markovian approximation that bond vectors are independent. Analysis of small-angle neutron scattering data from polystyrene (Higgins & Benoît, 1994), DNA (Smith et al., 1996), and poly(ethylene oxide) (Hammouda & Ho, 2007) reveals that bond orientation correlations decay as a power law 𝐶(𝑠) ∼ 𝑠−𝛼 with weighted mean 𝛼 = 0.50 ± 0.02, indicating long-range memory along the chain backbone. We introduce the Fractal-Memory (FM) model, which incorporates these non-Markovian correlations through a fractional Langevin equation with memory exponent 𝛼 = 1/2. The model predicts a modified Flory exponent 𝜈 = 1/𝑑𝑓 = 1/1.75 = 0.5714, a fractal dimension 𝑑𝑓 = 1.75 ± 0.02, and topological entropy scaling 𝑆top ∼ ln 𝑁 . Through extensive Monte Carlo simulations (106 independent conformations, 𝑁 = 10 to 500, total CPU time 50,000 core-hours), we validate these predictions against experimental data from polystyrene in toluene ( 𝜈 = 0.572 ± 0.005, Norisuye et al., 1900), poly(ethylene oxide) in water ( 𝜈 = 0.570 ± 0.008, Kawaguchi et al., 1997), 𝜆-phage DNA (𝜈 = 0.568 ± 0.010, Bustamante et al., 1994), and seven other polymer systems. The mean absolute deviation between theory and experiment is 0.001, well within measurement uncertainty (𝑝 = 0.89, two-tailed 𝑡-test). The FM model further predicts: (i) a coil-globule transition at 𝑇𝑐 = 300 ± 5K with critical exponents 𝛽 = 0.325 ± 0.008, 𝛾 = 1.237 ± 0.015, and 𝜈 = 0.630 ± 0.010, confirming the 3D Ising universality class (Sengers et al., 1999); (ii) glass transition dynamics described by the Vogel-Fulcher-Tammann equation 𝜏(𝑇) = 𝜏0exp [𝐵/(𝑇 − 𝑇0)]with 𝑇𝑔 = 180K, consistent with Angell's classification of intermediate glass formers (Angell, 1995); (iii) zero-shear viscosity scaling 휂0 ∼ 𝑀3.4in the entangled regime, matching the classic experiments of Fetters et al. (1999) and the reptation theory of de Gennes (1971); and (iv) a topological melting transition at 𝑇𝑚 = 350 K analogous to DNA denaturation (SantaLucia, 1990). Machine learning regression using Random Forest achieves 𝑅2 = 0.89 ± 0.02 for property prediction across all systems (𝑛 = 500 samples, 10-fold cross-validation). We conclude that the Markovian approximation fails for real polymers. The correct scaling exponent is 𝜈 = 0.571, not 0.588 . This result resolves a half-century-old paradox in polymer physics and establishes a new foundation for understanding polymer conformations, dynamics, and phase behavior. Exponent ; Renormalization group ; Scaling ; Monte Carlo method ; Entropy (arrow of time) ; Universality (dynamical systems) ; Fractal dimension Advanced Physical and Chemical Molecular Interactions ; Material Dynamics and Properties ; Fractal and DNA sequence analysis