The Influence of the Hydroxyl Type on Crosslinking Process in Cyclodextrin Based Polyurethane Networks
The influence of the hydroxyl groups (OH) type on the polyaddition processes of isocyanates represents a critical approach for the design of multicomponent polyurethane systems. Herein, to prove the effect of hydroxyl nature on both the isocyanate-OH polyaddition reactions and the structure/properties of the resulting networks, two structurally different cyclodextrins in terms of the primary and secondary groups’ ratio were analyzed, namely native β-cyclodextrin (CD) and its derivative esterified to the primary hydroxyl groups with oligolactide chains (CDLA). Thus, polyurethane hydrogels were prepared via the polyaddition of CD or CDLA to isophorone diisocyanate polyethylene glycol-based prepolymers (PEG-(NCO)2). The degradable character of the materials was induced by intercalating oligolactide short sequences into the polymer chains composing the polymer network. In order to establish the influence of the OH type, the synthesis of polyurethane hydrogels was analyzed by a rheological investigation of the overall system reactivity. Materials properties such as swelling behavior, thermal properties and hydrolytic degradation were influenced by the reaction feed. Specifically, the presence of primary OH groups leads to more compact networks with similar water uptake, disregarding the CD content, while the predominance of secondary OH groups together with the presence of oligolactide spacers leads to the fine tuning of the water swelling properties.
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About this article: Peptu, Cristian, Alexandra-Diana Diaconu, Maricel Danu, Catalina A. Peptu, Mariana Cristea, and Valeria Harabagiu. 2022. “The Influence of the Hydroxyl Type on Crosslinking Process in Cyclodextrin Based Polyurethane Networks” Gels 8, no. 6: 348. https://doi.org/10.3390/gels8060348
Materials
D,L-lactide (LA—Purac, Gorkum, The Netherlands) was recrystallized from toluene, vacuum dried and stored under an Ar atmosphere in a desiccator on P2O5. β-cyclodextrin (CD—Cyclolab, Budapest, Hungary) was vacuum dried at 80 °C (0.01 mbar) for 72 h and stored in a desiccator under an Ar atmosphere on P2O5. N,N-dimethylformamide (DMF) was dried over activated 3Å molecular sieves and freshly distilled before use, isophorone diisocyanate (IPDI) and dibutyltin dilaurate (DBTL) were acquired from Sigma Aldrich (Saint Louis, MO, USA) and used as received. Polyethylene glycol (PEG, Mn = 2000 g/mol) from Sigma Aldrich (Saint Louis, MO, USA) was vacuum dried at 100 °C (10−2 mbar) for 3 h prior use to remove water traces. All other solvents, of chromatographic purity, were used as received.