Fully bio-based poly(ɛ-capolactone)/poly(lactide) alternating multiblock supramolecular polymers: Synthesis, crystallization behavior, and properties

Supramolecular poly(ɛ-capolactone)/poly(lactide) alternating multiblock copolymers were prepared by UPy-functionalized poly(lactide)-b-poly(ɛ-capolactone)-b-poly(lactide) copolymers. The prepared supramolecular polymers (SMPs) exhibit the characteristic properties of thermoplastic elastomers. The stereo multiblock SMPs (sc-SMPs) were formed by blending UPy-functionalized poly(l-lactide)-b-PCL-b-poly(l-lactide) (l-SMPs) and UPy-functionalized poly(d-lactide)-b-PCL-b-poly(d-lactide) (d-SMPs) due to stereocomplexation of the PLLA and PDLA blocks. Sc-SMPs with low content of d-SMPs (≤20%) are transparent, elastic solids, while those having high d-SMPs content are opaque, brittle solids. The effects of l-SMPs/d-SMPs mixing ratios on thermal, crystallization behaviors, crystal structure, mechanical and hydrophilic properties of sc-SMPs were deeply investigated. The incorporation of UPy groups depresses the crystallization of polymer, and the stereocomplex formation accelerates the crystallization rate. The used initiator functionalized polyhedral oligomeric silsesquioxanes causes a different effect on the crystallization of PLA and PCL blocks. The tensile strength and elongation at break of l_d/d_d-SMPs (d represents the initiator diethylene glycol) are significantly larger than that of l_p/d_p-SMPs (p represents the initiator polyhedral oligomeric silsesquioxanes), and their heat resistance and hydrophilicity can be also modulated by the l-SMPs/d-SMPs mixing ratios and the different initiators.