Experimental Validation on Average Conformation of a Comblike Polystyrene Library in Dilute Solutions: Universal Scaling Laws and Abnormal SEC Elution Behavior

Abstract

In this work, a sample library of well-defined comblike polystyrenes (PS) has been prepared for the study of average conformation in dilute solutions. The dependences of radius of gyration (Rg), intrinsic viscosity ([η]), viscometric radius (Rη), and persistence length (lp) on the molar mass (M), grafting density (σ), and degree of polymerization of graft side chains (Ng) have been established. First, we have revealed the universal abnormal elution behavior of comblike chains in different size exclusion chromatography (SEC) column systems. A combined theoretical analysis and elution experiment indicates the possible thermodynamic origin, i.e., for chains with the highest stiffness, the anisotropic characteristics and chain end orientation can potentially increase the partition coefficient and retention volume, while the flow-induced forced penetration plays a negligible role. Moreover, the established scalings Rη ∼ Ng0.40±0.03σ1/3, Rg ∼ (Ngσ)0.37±0.01, and lp ∼ σ0.85±0.09 further indicate that (1) the equivalent viscometric volume is proportional to the mass of individual comblike chains when σ is increased, corresponding to the quasi-3D mass-size growth pattern; (2) the proper consideration of the swelling conformation of side chains is important to capture the essentials of conformational behavior for comblike polymer systems with flexible backbones; and (3) the experimentally established lp–σ dependence by considering the excluded-volume effect is much weaker than the theoretical predictions (lp ∼ σ17/8 and lp ∼ σ7/3). This work provides a comprehensive perspective for understanding the conformational evolution of comblike chains.

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