A variety of biobased polymers have been derived from diverse natural resources. However, the mechanical properties of some of these polymers are inferior due to low chain entanglement. We report a facile strategy termed "supramolecular chain entanglement", which utilizes supramolecular interactions to create physical cross-linking and entanglements for polymers with long pendent fatty chains. The ensuing bioplastics-prepared by mixing copolymers, composed of a plant oil-derived methacrylate with an acid-containing comonomer as a hydrogen-bonding donor-and poly(4-vinylpyridine) as an entangling chain with a hydrogen-bonding acceptor show tunable mechanical strength and toughness. These polymer blends, consisting of >= 90 wt % sustainable sources, exhibit marked improvement in thermomechanical properties compared with the viscoelastic nature of the biobased homopolymers. Spectroscopic evidence and X-ray scattering substantiated the hydrogen-bonding interaction within the copolymers, while morphological and thermal characterization was performed to elucidate microstructures of biobased polymers.