A review of molecular arrangement orientation detection technology for polymers and composites: principles, research, and application

During the molding process of polymers and composites, the application of shear and flow forces induces orientation behaviors in polymer molecular chains and composite fillers, predominantly governed by shear or flow directionality. This alignment leads to anisotropic mechanical, thermal, and optical properties in molded products. Strategic regulation (suppression or enhancement) of molecular orientation is essential to meet application-specific performance requirements. Precise detection and control of orientation are therefore critical for optimizing manufacturing processes and ensuring product quality. This review systematically summarizes recent advances in orientation detection technologies for polymers and composites, with a focus on the fundamental principles of characterization methodologies supported by experimental and computational case studies. A critical evaluation of each technique is provided, emphasizing their advantages, limitations, and applicability across different material systems. Furthermore, this work identifies key challenges in current detection technologies and proposes future research directions integrating artificial intelligence with surface/interface science and multiscale modeling. The insights presented herein aim to inspire innovative approaches for advancing polymer characterization and contribute to intelligent manufacturing paradigms.