Transforming Amorphous Atactic Polystyrene into a High-Strength Semicrystalline Material: Defying Stereoregularity for Mechanical Reinforcement

Abstract

Crystallizing atactic polystyrene (a-PS), the archetypal amorphous polymer, has remained a long-standing challenge in polymer science. Here, we demonstrate the formation of one-dimensional (1-D) extended-chain crystals from a-PS via a rapid thermal quenching (RTQ) process using benzoic acid (BA) as an entropy diluent. Spectroscopic and structural analyses reveal that these crystals are dominated by a β-like zigzag conformation, a highly extended ordered structure previously considered inaccessible for atactic chains. This unique molecular architecture translates into a dramatic enhancement in mechanical properties. The resulting a-PSRTQ films exhibit a storage modulus approximately three times higher than that of pristine a-PS, a level of reinforcement that far surpasses the modest improvements seen in conventionally crystallized syndiotactic polystyrene (s-PS). This exceptional performance is attributed to the high fraction of load-bearing, extended-chain structures. Furthermore, the induced crystals exhibit unique metastable thermal behavior, including a reversible β-to-α solid-state transition not observed in conventional s-PS. This study challenges the long-held paradigm that stereoregularity is a prerequisite for polymer crystallization, demonstrating that kinetic control via polymer-diluent interactions can effectively guide atactic chains into high-performance, ordered structures. Our findings open a new pathway for transforming low-cost, commodity amorphous polymers into high-strength, semicrystalline materials with tailored properties.