Proposal of Pseudo‐Capping Effects by Polymer–Polymer Interaction through Preparation of Stereocomplex Pseudo‐Polyrotaxane with Cyclodextrin and PEG‐PLA Triblock Copolymers

Abstract

ABA types triblock copolymers, specifically poly(L‐lactide)‐co‐poly(ethylene glycol)‐co‐poly(L‐lactide) (PLLA‐PEG‐PLLA) and poly(D‐lactide)‐co‐poly(ethylene glycol)‐co‐poly(D‐lactide) (PDLA‐PEG‐PDLA), are employed for stereocomplexes (SCs) formation. These SCs are subsequently utilized as axles, in conjunction with various cyclodextrins (CDs) as ring moieties to create pseudo‐polyrotaxane (PPRX). The authors referred to this new construct as “SC PPRX”, to distinguish it from the earlier study, denoted as “PPRX SC”, which primarily focuses on SC within the PPRX. When attempting to form PPRXs in aqueous solutions, the authors encountered challenges related to the inclusion of CDs due to the robust presence of the SC structure. However, by using mixed solvents, such as water/acetone (10/1, v/v), a partial relaxation of the SC structure is observed. This allows for the successful inclusion of CDs, thereby facilitating the PPRX formation. These observations highlight the significance of axle–axle interaction, which, in this case, prevailed over axle–ring interactions in determining the outcome of the formation process. The authors propose the term, ‘SC pseudo‐capping effect’ to describe this unique phenomenon, underscoring the role of interactions among polymer chains, including polymer–polymer and axle–axle interactions, in shaping the architecture of rotaxanes. This study thus unveils a novel dimension of polymer‐polymer interactions within the realm of rotaxane.